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Below, explore peer-reviewed journal articles related to ISS National Lab investigations. For a more extensive list of spaceflight-related publications (not limited to ISS National Lab sponsorship), see the International Space Station Research Results Citations on the NASA website .

 A Microfluidic, High Throughput Protein Crystal Growth Method for Microgravity ⇥

Citation: Carruthers, Jr. CW, Gerdts C, Johnson MD, Webb P. A microfluidic, high throughput protein crystal growth method for microgravity. PLOS ONE. 201321;8(11):e82298.

The attenuation of sedimentation and convection in microgravity can sometimes decrease irregularities formed during macromolecular crystal growth. Current terrestrial protein crystal growth (PCG) capabilities are very different than those used during the Shuttle era and that are currently on the International Space Station (ISS). The focus of this experiment was to demonstrate the use of a commercial off-the-shelf, high throughput, PCG method in microgravity. Using Protein BioSolutions’ microfluidic Plug Maker™/CrystalCard™ system, we tested the ability to grow crystals of the regulator of glucose metabolism and adipogenesis: peroxisome proliferator-activated receptor gamma (apo-hPPAR-γ LBD), as well as several PCG standards. Overall, we sent 25 CrystalCards™ to the ISS, containing ~10,000 individual microgravity PCG experiments in a 3U NanoRacks NanoLab (1U = 103 cm.). After 70 days on the ISS, our samples were returned with 16 of 25 (64%) microgravity cards having crystals, compared to 12 of 25 (48%) of the ground controls. Encouragingly, there were more apo-hPPAR-γ LBD crystals in the microgravity PCG cards than the 1g controls. These positive results hope to introduce the use of the PCG standard of low sample volume and large experimental density to the microgravity environment and provide new opportunities for macromolecular samples that may crystallize poorly in standard laboratories.

“Musica Universalis” of the Cell: A Brief History of Biological 12-Hour Rhythms ⇥

Citation: Zhu B, Dacso CC, O'Malley BW. Unveiling "Musica Universalis" of the cell: A brief history of biological 12-hour rhythms. J Endocr Soc. 2018;2(7):727-752.

?Musica universalis? is an ancient philosophical concept claiming the movements of celestial bodies follow mathematical equations and resonate to produce an inaudible harmony of music, and the harmonious sounds that humans make were an approximation of this larger harmony of the universe. Besides music, electromagnetic waves such as light and electric signals also are presented as harmonic resonances. Despite the seemingly universal theme of harmonic resonance in various disciplines, it was not until recently that the same harmonic resonance was discovered also to exist in biological systems. Contrary to traditional belief that a biological system is either at stead-state or cycles with a single frequency, it is now appreciated that most biological systems have no homeostatic ?set point,? but rather oscillate as composite rhythms consisting of superimposed oscillations. These oscillations often cycle at different harmonics of the circadian rhythm, and among these, the ~12-hour oscillation is most prevalent. In this review, we focus on these 12-hour oscillations, with special attention to their evolutionary origin, regulation, and functions in mammals, as well as their relationship to the circadian rhythm. We further discuss the potential roles of the 12-hour clock in regulating hepatic steatosis, aging, and the possibility of 12-hour clock?based chronotherapy. Finally, we posit that biological rhythms are also musica universalis: whereas the circadian rhythm is synchronized to the 24-hour light/dark cycle coinciding with the Earth?s rotation, the mammalian 12-hour clock may have evolved from the circatidal clock, which is entrained by the 12-hour tidal cues orchestrated by the moon.

A Human Pluripotent Stem Cell Model of Catecholaminergic Polymoprhic Ventricular Tachyardia Recapitulates Patient-Specific Drug Responses ⇥

Citation: Preininger MK, Jha R, Maxwell JT, Wu Q, Singh M, Wang B, Dalal A, Mceachin Z, Rossoll W, Hales CM, Fischbach PS, Wagner MB, Xu C. A human pluripotent stem cell model of catecholaminergic polymorphic ventricular tachyardia recapitulates patient-specific drug responses. Dis Model Mech. 2016;9(9):927-939.

β-blockers are unsuccessful in eliminating stress-induced ventricular arrhythmias in approximately 25% of patients with catecholaminergic polymorphic ventricular tachycardia (CPVT). Induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) generated from these patients have potential for investigating the phenomenon, but it remains unknown whether they can recapitulate patient-specific drug responses to β-blockers. This study assessed whether the inadequacy of β-blocker therapy in an individual can be observed in vitro using patient-derived CPVT iPSC-CMs. A CPVT patient harboring a novel mutation in the type 2 cardiac ryanodine receptor (RyR2) was identified whose persistent ventricular arrhythmias during β-blockade with nadolol were abolished during flecainide treatment. iPSC-CMs generated from this patient and two control individuals expressed comparable levels of excitation-contraction genes, but assessment of the sarcoplasmic reticulum Ca2+ leak and load relationship revealed intracellular Ca2+ homeostasis was altered in CPVT iPSC-CMs. β-adrenergic stimulation potentiated spontaneous Ca2+ waves and unduly frequent, large, and prolonged Ca2+ sparks in CPVT compared to control iPSC-CMs, validating the disease phenotype. Pursuant to the patient's in vivo responses, nadolol treatment during β-adrenergic stimulation achieved negligible reduction of Ca2+ wave frequency and failed to rescue Ca2+ spark defects in CPVT iPSC-CMs. In contrast, flecainide reduced both frequency and amplitude of Ca2+ waves and restored the frequency, width, and duration of Ca2+ sparks to baseline levels. By recapitulating a CPVT patient's improved response to flecainide compared to β-blocker therapy in vitro, these data provide new evidence that iPSC-CMs can capture basic components of patient-specific drug responses.

A long non‐coding RNA GATA6‐AS1 adjacent to GATA6 is required for cardiomyocyte differentiation from human pluripotent stem cells ⇥

Citation: Jha R, Li D, Wu Q, Ferguson K, Forghani P, Gibson G, Xu C. A long non‐coding RNA GATA6‐AS1 adjacent to GATA6 is required for cardiomyocyte differentiation from human pluripotent stem cells. FASEB J. 2020;34(11):14336-14352.

Long noncoding RNAs (lncRNAs) are crucial in many cellular processes, yet relatively few have been shown to regulate human cardiomyocyte differentiation. Here, we demonstrate an essential role of GATA6 antisense RNA 1 (GATA6‐AS1) in cardiomyocyte differentiation from human pluripotent stem cells (hPSCs). GATA6‐AS1 is adjacent to cardiac transcription factor GATA6. We found that GATA6‐AS1 was nuclear‐localized and transiently upregulated along with GATA6 during the early stage of cardiomyocyte differentiation. The knockdown of GATA6‐AS1 did not affect undifferentiated cell pluripotency but inhibited cardiomyocyte differentiation, as indicated by no or few beating cardiomyocytes and reduced expression of cardiomyocyte‐specific proteins. Upon cardiac induction, the knockdown of GATA6‐AS1 decreased GATA6 expression, altered Wnt‐signaling gene expression, and reduced mesoderm development. Further characterization of the intergenic region between genomic regions of GATA6‐AS1 and GATA6 indicated that the expression of GATA6‐AS1 and GATA6 were regulated by a bidirectional promoter within the intergenic region. Consistently, GATA6‐AS1 and GATA6 were co‐expressed in several human tissues including the heart, similar to the mirror expression pattern of GATA6‐AS1 and GATA6 during cardiomyocyte differentiation. Overall, these findings reveal a previously unrecognized and functional role of lncRNA GATA6‐AS1 in controlling human cardiomyocyte differentiation.

A miniature microcontroller curve tracing circuit for space flight testing transistors ⇥

Citation: Prokop NF, Greer LC, Krasowski MJ, Flatico JM, Spina DC. A miniature microcontroller curve tracing circuit for space flight testing transistors. Review of Scientific Instruments. 2015; 86(2):024707.

This paper describes a novel miniature microcontroller based curve tracing circuit, which was designed to monitor the environmental effects on Silicon Carbide Junction Field Effect Transistor (SiC JFET) device performance, while exposed to the low earth orbit environment onboard the International Space Station (ISS) as a resident experiment on the 7th Materials on the International Space Station Experiment (MISSE7). Specifically, the microcontroller circuit was designed to operate autonomously and was flown on the external structure of the ISS for over a year. This curve tracing circuit is capable of measuring current vs. voltage (I-V) characteristics of transistors and diodes. The circuit is current limited for low current devices and is specifically designed to test high temperature, high drain-to-source resistance SiC JFETs. The results of each I-V data set are transmitted serially to an external telemetered communication interface. This paper discusses the circuit architecture, its design, and presents example results.

A Molecular Genetic Basis Explaining Altered Bacterial Behavior in Space ⇥

Citation: Zea L, Prasad N, Levy SE, Stodieck L, Jones A, Shrestha S, Klaus D. A molecular genetic basis explaining altered bacterial behavior in space. PLoS ONE. 2016;11(11): e0164359.

Bacteria behave differently in space, as indicated by reports of reduced lag phase, higher final cell counts, enhanced biofilm formation, increased virulence, and reduced susceptibility to antibiotics. These phenomena are theorized, at least in part, to result from reduced mass transport in the local extracellular environment, where movement of molecules consumed and excreted by the cell is limited to diffusion in the absence of gravity-dependent convection. However, to date neither empirical nor computational approaches have been able to provide sufficient evidence to confirm this explanation. Molecular genetic analysis findings, conducted as part of a recent spaceflight investigation, support the proposed model. This investigation indicated an overexpression of genes associated with starvation, the search for alternative energy sources, increased metabolism, enhanced acetate production, and other systematic responses to acidity all of which can be associated with reduced extracellular mass transport.

A New View of Coastal Oceans from the Space Station ⇥

Citation: Corson MR, Davis CO.  A new view of coastal oceans from the space station. Eos, Transactions American Geophysical Union. 2011;92(19):161-162.

Understanding and quantifying the natural processes that occur along coasts are critical components of managing environmental resources and planning and executing coastal operations, from humanitarian relief to military actions. However, the coastal ocean is complicated, with dissolved and suspended matter that hinders water transparency, phytoplankton blooms that can be toxic, and bathymetry and bottom types that vary over spatial scales of tens of meters, all of which affect processes in an area that spans millions of square kilometers. A hyperspectral imager collects the spectrum of the light received from each pixel in an image. For environmental characterization the wavelength range typically spans the visible and shortwave infrared wavelengths, and the spectrum is collected in contiguous spectral intervals 1–10 nanometers wide. This spectral information is exploited to provide significantly more information about vegetation, minerals, and other components in the scene than can be retrieved from panchromatic or even multispectral imagery, which rely primarily on the shape of the object for detection [Goetz et al., 1985]. Such technology can also work over shallow seas. Over the past 2 decades, experiments with hyperspectral imagers on airborne platforms have demonstrated the ability to characterize the coastal environment [Davis et al., 2002, Davis et al. 2006] and produce maps of coastal bathymetry, in‐water constituents, and bottom type.

A Spheroid Toxicity Assay Using Magnetic 3D Bioprinting & Realtime Mobile Device-based Imaging ⇥

Citation: Tseng H, Gage JA, Shen T, Haisler WL, Neeley SK, Shiao S, Chen J, Liao A, Hebel C, Raphael RM, Becker JL, Souza GR. A spheroid toxicity assay using magnetic 3D bioprinting and real-time mobile device-based imaging. Sci Rep. 2015;5:13987.

An ongoing challenge in biomedical research is the search for simple, yet robust assays using 3D cell cultures for toxicity screening. This study addresses that challenge with a novel spheroid assay, wherein spheroids, formed by magnetic 3D bioprinting, contract immediately as cells rearrange and compact the spheroid in relation to viability and cytoskeletal organization. Thus, spheroid size can be used as a simple metric for toxicity. The goal of this study was to validate spheroid contraction as a cytotoxic endpoint using 3T3 fibroblasts in response to 5 toxic compounds (all-trans retinoic acid, dexamethasone, doxorubicin, 5′-fluorouracil, forskolin), sodium dodecyl sulfate (+control), and penicillin-G (−control). Real-time imaging was performed with a mobile device to increase throughput and efficiency. All compounds but penicillin-G significantly slowed contraction in a dose-dependent manner (Z’ = 0.88). Cells in 3D were more resistant to toxicity than cells in 2D, whose toxicity was measured by the MTT assay. Fluorescent staining and gene expression profiling of spheroids confirmed these findings. The results of this study validate spheroid contraction within this assay as an easy, biologically relevant endpoint for high-throughput compound screening in representative 3D environments.

A Technique for Removing Second-order Light Effects from Hyperspectral Imaging Data ⇥

Citation: Li R, Lucke RL, Korwan DR, Gao BG. A technique for removing second-order light effects from hyperspectral imaging data. IEEE Transactions on Geoscience and Remote Sensing. 2012;50(3):824-830.

The Hyperspectral Imager for the Coastal Ocean (HICO) instrument currently on board the International Space Station is a new sensor designed specifically for the studies of turbid coastal waters and large inland lakes and rivers. It covers the wavelength range between 0.4 and 0.9 μm with a spectral resolution of 5.7 nm and a spatial resolution of approximately 90 m. The HICO sensor is not equipped with a second-order blocking filter in front of the focal plane array. As a result, the second-order light from the shorter visible spectral region falls onto the detectors covering the near-IR spectral region above 0.8 μm. In order to have accurate radiometric calibration of the near-IR channels, the second-order light contribution needs to be removed. The water-leaving radiances of these near-IR channels over clear ocean waters are close to zero because of strong liquid water absorption above 0.8 μm. Through analysis of HICO imaging data containing features of shallow underwater objects, such as coral reefs, we have developed an empirical technique to correct for the second-order light effects in near-IR channels. HICO data acquired over Midway Island in the Pacific Ocean and the Bahamas Banks in the Atlantic Ocean are used to demonstrate the effectiveness of the new technique.

An Improved Vascularized, Dual-Channel Microphysiological System Facilitates Modeling of Proximal Tubular Solute Secretion ⇥

Citation: Chapron A, Chapron BD, Hailey DW, Chang SY, Imaoka T, Thummel KE, Kelly E, Himmelfarb J, Shen D, Yeung CK. An Improved Vascularized, Dual-Channel Microphysiological System Facilitates Modeling of Proximal Tubular Solute Secretion. ACS Pharmacol Transl Sci. 2020 Jan 28;3(3):496-508.

A vascularized human proximal tubule model in a dual-channel microphysiological system (VPT-MPS) was developed, representing an advance over previous, single-cell-type kidney microphysiological systems. Human proximal tubule epithelial cells (PTECs) and human umbilical vein endothelial cells (HUVECs) were cocultured in side-by-side channels. Over 24 h of coculturing, PTECs maintained polarized expression of Na+/K+ ATPase, tight junctions (ZO-1), and OAT1. HUVECs showed the absence of ZO-1 but expressed endothelial cell marker (CD-31). In time-lapse imaging studies, fluorescein isothiocyanate (FITC)-dextran passed freely from the HUVEC vessel into the supporting extracellular matrix, confirming the leakiness of the endothelium (at 80 min, matrix/intravessel fluorescence ratio = 0.2). Dextran-associated fluorescence accumulated in the matrix adjacent to the basolateral aspect of the PTEC tubule with minimal passage of the compound into the tubule lumen observed (at 80 min, tubule lumen/matrix fluorescence ratio = 0.01). This demonstrates that the proximal tubule compartment is the rate-limiting step in the secretion of compounds in VPT-MPS. In kinetic studies with radiolabeled markers, p-aminohippuric acid (PAH) exhibited greater output into the tubule lumen than did paracellular markers mannitol and FITC-dextran (tubule outflow/vessel outflow concentration ratio of 7.7% vs 0.5 and 0.4%, respectively). A trend toward reduced PAH secretion by 45% was observed upon coadministration of probenecid. This signifies functional expression of renal transporters in PTECs that normally mediate the renal secretion of PAH. The VPT-MPS holds the promise of providing an in vitro platform for evaluating the renal secretion of new drug candidates and investigating the dysregulation of tubular drug secretion in chronic kidney disease.

An information-theoretic approach for measuring the distance of organ tissue samples using their transcriptomic signatures ⇥

Citation: Manatakis DV, VanDevender A, Manolakos ES. An information-theoretic approach for measuring the distance of organ tissue samples using their transcriptomic signatures [published online ahead of print July 19, 2020]. Bioinformatics. doi: 10.1093/bioinformatics/btaa654

Manatakis DV, VanDevender A, Manolakos ES. An information-theoretic approach for measuring the distance of organ tissue samples using their transcriptomic signatures [published online ahead of print July 19, 2020]. Bioinformatics. doi: 10.1093/bioinformatics/btaa654

An Integrated Omics Analysis: Impact of Microgravity on Host Response to Lipopolysaccharide in Vitro ⇥

Citation: Chakraborty NM, Gautam A, Muhie S, Miller S, Jett M, Hammamieh R.  An integrated omics analysis: impact of microgravity on host response to lipopolysaccharide in vitro. BMC Genomics. 2014;15(1):659.

Microgravity facilitates the opportunistic infections by augmenting the pathogenic virulence and suppressing the host resistance. Hence the extraterrestrial infections may activate potentially novel bionetworks different from the terrestrial equivalent, which could only be probed by investigating the host-pathogen relationship with a minimum of terrestrial bias.

Anti-PolyQ Antibodies Recognize a Short PolyQ Stretch in Both Normal and Mutant Huntingtin Exon 1 ⇥

Citation: Owens G, New D, West A, Bjorkman P. Anti-polyQ antibodies recognize a short polyQ stretch in both normal and mutant Huntingtin exon 1. J Mol Biol. 2015;427(15):2507-2519.

Huntington's disease is caused by expansion of a polyglutamine (polyQ) repeat in the huntingtin protein. A structural basis for the apparent transition between normal and disease-causing expanded polyQ repeats of huntingtin is unknown. The "linear lattice" model proposed random-coil structures for both normal and expanded polyQ in the preaggregation state. Consistent with this model, the affinity and stoichiometry of the anti-polyQ antibody MW1 increased with the number of glutamines. An opposing "structural toxic threshold" model proposed a conformational change above the pathogenic polyQ threshold resulting in a specific toxic conformation for expanded polyQ. Support for this model was provided by the anti-polyQ antibody 3B5H10, which was reported to specifically recognize a distinct pathologic conformation of soluble expanded polyQ. To distinguish between these models, we directly compared binding of MW1 and 3B5H10 to normal and expanded polyQ repeats within huntingtin exon 1 fusion proteins. We found similar binding characteristics for both antibodies. First, both antibodies bound to normal, as well as expanded, polyQ in huntingtin exon 1 fusion proteins. Second, an expanded polyQ tract contained multiple epitopes for fragments antigen-binding (Fabs) of both antibodies, demonstrating that 3B5H10 does not recognize a single epitope specific to expanded polyQ. Finally, small-angle X-ray scattering and dynamic light scattering revealed similar binding modes for MW1 and 3B5H10 Fab-huntingtin exon 1 complexes. Together, these results support the linear lattice model for polyQ binding proteins, suggesting that the hypothesized pathologic conformation of soluble expanded polyQ is not a valid target for drug design.

Antiproton flux, antiproton-to-proton flux ratio, and properties of elementary particle fluxes in primary cosmic rays measured with the Alpha Magnetic Spectrometer on the International Space Station ⇥

Citation: Aguilar-Benitez M, Cavasonza LA, Alpat B, Ambrosi G, Arruda MF, Attig N, Aupetit S. Antiproton flux, antiproton-to-proton flux ratio, and properties of elementary particle fluxes in primary cosmic rays measured with the Alpha Magnetic Spectrometer on the International Space Station. Physical Review Letters. 2016 117(9):091103.

A precision measurement by AMS of the antiproton flux and the antiproton-to-proton flux ratio in primary cosmic rays in the absolute rigidity range from 1 to 450 GV is presented based on 3.49×105 antiproton events and 2.42×109 proton events. The fluxes and flux ratios of charged elementary particles in cosmic rays are also presented. In the absolute rigidity range ∼60 to ∼500  GV, the antiproton ¯p, proton p, and positron e+ fluxes are found to have nearly identical rigidity dependence and the electron e− flux exhibits a different rigidity dependence. Below 60 GV, the (¯p/p), (¯p/e+), and (p/e+) flux ratios each reaches a maximum. From ∼60 to ∼500  GV, the (¯p/p), (¯p/e+), and (p/e+) flux ratios show no rigidity dependence. These are new observations of the properties of elementary particles in the cosmos.

Application of the Hyperspectral Imager for the Coastal Ocean to Phytoplankton Ecology Studies in Monterey Bay, CA, USA ⇥

Citation: Ryan JP, Davis CO, Tufillaro NB, Kudela RM, Gao BG. Application of the Hyperspectral Imager for the Coastal Ocean to Phytoplankton Ecology Studies in Monterey Bay, CA, USA. Remote Sensing. 2014;6(2):1007-1025.

As a demonstrator for technologies for the next generation of ocean color sensors, the Hyperspectral Imager for the Coastal Ocean (HICO) provides enhanced spatial and spectral resolution that is required to understand optically complex aquatic environments. In this study we apply HICO, along with satellite remote sensing and in situ observations, to studies of phytoplankton ecology in a dynamic coastal upwelling environment—Monterey Bay, CA, USA. From a spring 2011 study, we examine HICO-detected spatial patterns in phytoplankton optical properties along an environmental gradient defined by upwelling flow patterns and along a temporal gradient of upwelling intensification. From a fall 2011 study, we use HICO’s enhanced spatial and spectral resolution to distinguish a small-scale “red tide” bloom, and we examine bloom expansion and its supporting processes using other remote sensing and in situ data. From a spectacular HICO image of the Monterey Bay region acquired during fall of 2012, we present a suite of algorithm results for characterization of phytoplankton, and we examine the strengths, limitations, and distinctions of each algorithm in the context of the enhanced spatial and spectral resolution.

Assembly of Hepatocyte Spheroids Using Magnetic 3D Cell Culture for CYP450 Inhibition/Induction ⇥

Citation: Desai PK, Tseng H, Souza GR. Assembly of hepatocyte spheroids using magnetic 3D cell culture for CYP450 inhibition/induction. J Mol Sci. 2017;18(5):1085.

There is a significant need for in vitro methods to study drug-induced liver injury that are rapid, reproducible, and scalable for existing high-throughput systems. However, traditional monolayer and suspension cultures of hepatocytes are difficult to handle and risk the loss of phenotype. Generally, three-dimensional (3D) cell culture platforms help recapitulate native liver tissue phenotype, but suffer from technical limitations for high-throughput screening, including scalability, speed, and handling. Here, we developed a novel assay for cytochrome P450 (CYP450) induction/inhibition using magnetic 3D cell culture that overcomes the limitations of other platforms by aggregating magnetized cells with magnetic forces. With this platform, spheroids can be rapidly assembled and easily handled, while replicating native liver function. We assembled spheroids of primary human hepatocytes in a 384-well format and maintained this culture over five days, including a 72 h induction period with known CYP450 inducers/inhibitors. CYP450 activity and viability in the spheroids were assessed and compared in parallel with monolayers. CYP450 activity was induced/inhibited in spheroids as expected, separate from any toxic response. Spheroids showed a significantly higher baseline level of CYP450 activity and induction over monolayers. Positive staining in spheroids for albumin and multidrug resistance-associated protein (MRP2) indicates the preservation of hepatocyte function within spheroids. The study presents a proof-of-concept for the use of magnetic 3D cell culture for the assembly and handling of novel hepatic tissue models.

Assessing the Application of Cloud-Shadow Atmospheric Correction Algorithm on HICO ⇥

Citation: Amin R, Lewis D, Gould, Jr. RW, Hou W, Lawson A, Ondrusek M, Arnone RB. Assessing the application of cloud-shadow atmospheric correction algorithm on HICO. IEEE Transactions on Geoscience and Remote Sensing. 2014;52(2):2646-2653.

Several ocean color earth observation satellite sensors are presently collecting daily imagery, including the Hyperspectral Imager for the Coastal Ocean (HICO). HICO has been operating aboard the International Space Station since its installation on September 24, 2009. It provides high spatial resolution hyperspectral imagery optimized for the coastal ocean. Atmospheric correction, however, still remains a challenge for this sensor, particularly in optically complex coastal waters. In this paper, we assess the application of the cloud-shadow atmospheric correction approach on HICO data and validate the results with the in situ data. We also use multiple sets of cloud, shadow, and sunlit pixels to correct a single image multiple times and intercompare the results to assess variability in the retrieved reflectance spectra. Retrieved chlorophyll values from this intercomparison are similar and also agree well with the in situ chlorophyll measurements.

Assessing Water Quality in the Northern Adriatic Sea From HICO™ Data ⇥

Citation: Braga F, Giardino C, Bassani C, Matta E, Candiani G, Strombeck N, Adamo M, Bresciani M. Assessing water quality in the northern Adriatic Sea from HICO™ data. Remote Sensing Letters. 2013;4(10):1028-1037.

This letter focuses on water-quality estimation in the northern Adriatic Sea using physically-based methods applied to image obtained with the Hyperspectral Imager for the Coastal Ocean (HICO™). Optical properties of atmosphere and water were synchronously measured to parameterise such methods. HICO™-derived maps of chlorophyll-a (chl-a) and suspended particulate matter (SPM) indicated low values, in the range of 0-3 mg m-3 and 0-4 g m-3, respectively, correlating significantly with field data (R2 = 0.71 for chl-a and R2 = 0.85 for SPM). The results, on analysis, identify clear waters in the open sea and moderately turbid waters near the coast due to river sediment discharge and organic matter from coastal lagoons. These findings support the use of HICO™ data to assess water-quality parameters in coastal zones and suggest the feasibility of integrating them with future-generation space-borne hyperspectral images.

Ballistic Supercavitating Nanoparticles Driven by Single Gaussian Beam Optical Pushing and Pulling Forces ⇥

Citation: Lee E, Huang D, Luo, T. Ballistic Supercavitating Nanoparticles Driven by Single Gaussian Beam Optical Pushing and Pulling Forces. Nat Commun. 2020;11:2404.

Directed high-speed motion of nanoscale objects in fluids can have a wide range of applications like molecular machinery, nano robotics, and material assembly. Here, we report ballistic plasmonic Au nanoparticle (NP) swimmers with unprecedented speeds (~336,000 μm s-1) realized by not only optical pushing but also pulling forces from a single Gaussian laser beam. Both the optical pulling and high speeds are made possible by a unique NP-laser interaction. The Au NP excited by the laser at the surface plasmon resonance peak can generate a nanoscale bubble, which can encapsulate the NP (i.e., supercavitation) to create a virtually frictionless environment for it to move, like the Leidenfrost effect. Certain NP-in-bubble configurations can lead to the optical pulling of NP against the photon stream. The demonstrated ultra-fast, light-driven NP movement may benefit a wide range of nano- and bio-applications and provide new insights to the field of optical pulling force.

Behavior of mice aboard the International Space Station ⇥

Citation: Ronca AE, Moyer EL, Talyansky Y, Lowe M, Padmanabhan S, Choi S, Gong C, Cadena SM, Stodieck, L, Globus RK. Behavior of mice Aboard the International Space Station. Sci Rep. 2019;28;9(1),4717.

Interest in space habitation has grown dramatically with planning underway for the first human transit to Mars. Despite a robust history of domestic and international spaceflight research, understanding behavioral adaptation to the space environment for extended durations is scant. Here we report the first detailed behavioral analysis of mice flown in the NASA Rodent Habitat on the International Space Station (ISS). Following 4-day transit from Earth to ISS, video images were acquired on orbit from 16- and 32-week-old female mice. Spaceflown mice engaged in a full range of species-typical behaviors. Physical activity was greater in younger flight mice as compared to identically-housed ground controls, and followed the circadian cycle. Within 9–11 days after launch, younger (but not older), mice began to exhibit distinctive circling or ‘race-tracking’ behavior that evolved into a coordinated group activity. Organized group circling behavior unique to spaceflight may represent stereotyped motor behavior, rewarding effects of physical exercise, or vestibular sensation produced via self-motion. Affording mice the opportunity to grab and run in the RH resembles physical activities that the crew participate in routinely. Our approach yields a useful analog for better understanding human responses to spaceflight, providing the opportunity to assess how physical movement influences responses to microgravity.

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• v.180(12); 2009 Jun 9

The space-flight environment: the International Space Station and beyond

Human space exploration is dependent on robust spacecraft design and sophisticated life-support technologies, both of which are critical for working in the hostile space environment. This article focuses on the specific challenges of the space environment. In an upcoming issue, a Dispatch from Space provides a personal look at space travel, and 2 other articles address the acclimation necessary for people to travel and live in space and the technological advances that can be applied to health care on earth.

The early space program progressed from suborbital missions lasting minutes to orbital flights lasting days, demonstrating that people can both survive and work in space. Almost 50 years have elapsed since those initial flights, with remarkable progress in extending the duration of missions and the complexity of the objectives. The International Space Station circles the earth at an altitude of more than 300 km in an environment characterized by high vacuum, microgravity, extremes of temperature, meteoroids, space debris, ionospheric plasma, and ultraviolet and ionizing radiation. The development of new technologies to send people farther in space and keep them there longer is critical to the future of human space exploration.

During the first spacewalk of NASA mission STS-118, Canadian astronaut Dave Williams worked on the P6 module of the International Space Station.

There are different definitions for the boundary to space. National Aeronautics and Space Administration (NASA) uses flight above 80 km to designate individuals as astronauts, while the Fédération Aéronautique Internationale uses the 100 km Karman line as the internationally accepted boundary to space. Beyond this altitude, aerodynamic flight is not possible, and spacecraft must travel faster than orbital velocity to manoeuvre and remain in orbit.

Only about 350 people have flown in space over the last 4 decades, making it difficult to develop higher levels of clinical evidence to assess the efficacy of interventions in space medicine. Case series and descriptive studies represent the majority of the published literature in the field. 1 A review of technical and special publications from NASA and peer-reviewed literature was undertaken to complement our experiences. Each of us has experienced space first-hand, and, as a group, we have logged 2000 hours in space. One of the authors (D.W.) holds the Canadian record for spacewalking, with over 17 hours spent working outside of the space station.

Environmental characteristics

Research programs into bioastronautics and longitudinal studies of astronaut health have amassed considerable data that can help us to understand the environmental characteristics of orbital flight that present the greatest health and safety concerns to astronauts. The environmental factors of concern during long missions aboard the International Space Station are summarized in Table 1 , along with current mitigation measures developed by the Multilateral Medical Policy Board.

Characteristics of the space environment in the low earth orbit and measures to reduce the impact on crew health and safety

Temperature extremes

Spacecraft in low orbit of the earth travel at Mach 25, or about 8 km per second. These spacecraft orbit the earth once every 90 minutes. The crew controls the temperature in the crew compartment of the space shuttle and modules of the International Space Station, with an average temperature between 21 and 23°C. Much greater extremes occur outside the spacecraft. When on the sun-lit side of the earth, the temperature on the spacecraft or space station can reach over 100°C. Forty-five minutes later, during a night pass through earth’s dark shadow, temperatures can plunge to –100°C. 2

During spacewalks, the personal life-support system of the spacesuit provides active cooling to dissipate the heat generated by high-metabolic workloads. A manually controlled thermostat is used to control active cooling and regulate the temperature in the suit. Heating the suit is a passive process resulting from accumulated body heat in the absence of active cooling. Manually activated electric heaters in astronauts’ gloves may be used when the touch temperatures fall below –20°C. Thermal mittens can also be used to provide insulation from high touch temperatures.

During a spacewalk, it is easy to become focused on a task and lose awareness of an impending dusk or dawn, until surrounded by darkness or brilliant sunlight. Temperature is often the first cue that these transitions are imminent.

Circadian dyssynchrony

The light–dark transition that occurs every 45 minutes results in changes in the thermal properties of the spacecraft and in power generated from solar arrays. This transition is of interest as a potential source of circadian dyssynchrony.

Space Shuttle Endeavour ’s orbital manoeuvring system pods and vertical stabilizer are shown in this image while the shuttle was docked on the International Space Station during mission STS-118.

The irregular light pattern caused by the 16 daily sunsets and sunrises may disrupt the circadian rhythm of astronauts, leading to degradation of the quality of their sleep. Many studies have been undertaken to evaluate the sleep patterns of astronauts. Although the light–dark transitions are of interest, the greatest sleep disruption has resulted from timeline pressures or ambient noise. 3

High vacuum

A high vacuum exists outside the space shuttle and the International Space Station. 4 The pressure inside both spacecraft is regulated to 101.34 kPa (14.7 psi) and is equilibrated after docking and before hatch opening. NASA’s suit for space-walks (extravehicular mobility unit) is pressurized to 29.5 kPa with 100% oxygen. The Russian Orlan spacesuit is pressurized to 40 kPa. The transition from ambient pressure to vacuum during airlock depressurization causes considerable decompression stress to spacewalking astronauts. Thus, before spacewalks, astronauts perform an oxygen pre-breathe protocol that reduces the level of nitrogen in the tissues. Astronauts are trained to recognize the symptoms of decompression sickness. Treatment protocols involve re-pressurization, 100% oxygen therapy and, if necessary, over-pressurization of the spacesuit by use of a bends treatment adaptor.

The risks associated with depressurization of a suit or spacecraft are partially mitigated by micrometeoroid shielding in the suit and spacecraft modules. However, in June 1997, there was rapid depressurization of the Spektr module of the Mir space station following a collision with a supply vehicle. The hatch between the modules was quickly closed to prevent depressurization of the station. This episode was a reminder of the harsh reality of living in the vacuum of space.

Ionizing radiation

At an orbital altitude of 350 km, the International Space Station is above the earth’s magnetosphere. This results in exposure of astronauts to higher fluxes of ionizing radiation. The primary radiation sources are galactic cosmic rays (energetic particles from outside our solar system), particles trapped in the earth’s magnetic field (the Van Allen Belts) and solar energetic particle events (solar flares). 5 , 6 High-energy protons and heavy ions emanate from the Sun and elsewhere in the cosmos. Even higher energy secondary particles (protons, neutrons and heavy ions) are produced when the incoming radiation strikes the spacecraft hull.

The 52° orbital inclination of the International Space Station causes it to pass through the South Atlantic Anomaly daily. This region, located east of Argentina, is characterized by an anomalous perturbation in the earth’s geomagnetic field with trapped energetic particles found at lower altitudes. These pertubations briefly subject astronauts to higher fluxes of ionizing radiation.

The average total dose of radiation that a person on earth receives from natural land-based sources and medical procedures is less than 0.005 Sievert (Sv) per year. The standard radiation dose associated with a chest radiograph is 0.02 μSv, while commercial aircraft travel is associated with exposure to 0.3–5.7 μSv per hour. At orbital altitudes near that of the International Space Station, the dose-equivalent to the astronauts is about 0.3 Sv per year. 7

Astronaut who fly missions solely in low orbit around the earth are unlikely to receive a total dose of 1 Sv over their career. However, as the duration of space flights become longer and as destinations take us farther from earth, radiation doses will become higher. Astronauts participating in exploratory missions to Mars in the coming decades will receive an estimated round-trip dose of 1 Sv. 8 During these 2- to 3-year missions, there is a good chance that at least 1 solar flare will occur, which could drastically increase their exposure to 5 Sv.

Ionizing radiation can kill cells, damage genetic material and, in some instances, lead to cancer. The primary biologic effect of low and moderate doses of radiation is damage to DNA. The mechanisms that give rise to genetic mutation involve physical energy transfer, free radical formation and alteration of the molecular structure of DNA. 6

Health risks from radiation exposure may be described in terms of short-term effects and long-term risks. The extent and severity of short-term effects is determined by the type and amount of exposure to radiation. Dose-related short-term effects range from nausea and vomiting to central nervous system damage and even death. Long-term risks include cataracts with lens doses of > 8 mSv and potentially cancer. 9 This increased risk of cancer is the principal concern for astronauts exposed to space radiation. The risk decreases with increasing age at exposure 10 and persists after landing.

The goal of human space-flight programs is to continue the exploration and development of space while minimizing risks from exposure to ionizing radiation. Astronauts are regarded as radiation workers and follow the “as low as reasonably achievable” principles and guidelines, with radiation monitoring to document exposure. NASA and the other international partners have adopted the recommendations of the National Council on Radiation Protection about exposure to radiation during human space-flight activities. 8

Space debris

Space debris has become a greater risk for space flights in low orbit in recent years. Micrometeoroids exist naturally in the solar system from breakups of comets and asteroids, and space debris is associated with increased frequency of space flight. This debris includes leftover satellites, broken-up rocket stages and even paint flakes from deteriorating spacecraft. Today, there are more than 12 000 objects larger than 10 cm (softball size and larger) that are being tracked by ground-based sensors and catalogued. 11 Smaller objects probably number in the hundreds of thousands.

Robert Thirsk is pictured working in the spacelab during mission STS-78, his first flight, in 1996.

The consequences of collisions between spacecraft and a micrometeoroid or a piece of space debris can be catastrophic. Collisions take place at hyper-velocities of about 10 km/s with dissipation of huge kinetic energies for very small particles. The impact of a collision of a 1 kg piece of space debris with the International Space Station has the same energy as a collision involving a 35 000 kg tractor-trailer travelling at 190 km/h. 12 Metal shielding can protect vulnerable parts of the space station against objects that are smaller than 1 cm diameter, while collision-avoidance manoeuvres have been taken by the shuttle and may be taken by the International Space Station to prevent collisions with larger pieces of debris.

Suit penetration from a micrometeoroid strike or an inadvertent puncture from a tool, wire or sharp edge is a risk associated with spacewalks. The 14 layers of material that make up the spacesuit include a layer of Kevlar to reduce the probability of suit penetration. To date, there have been no recorded cases of suit penetration from micrometeoroids. However, a tear to the outermost layer of a spacesuit glove from a sharp edge was noted on mission STS-118 in August 2007, resulting in early termination of the spacewalk.

Ionospheric plasma

Spacecraft in low orbit around the earth have a complex interaction with ionospheric plasma. The solar arrays on the International Space Station operate at 160V, and the distribution system is at 120V DC. The negative side of the power system is grounded to the structure of the space station, resulting in a large amount of energy stored in the structure at –140V. High voltage solar arrays, coupled with the design and material properties of the International Space Station, can lead to detrimental interactions with the ionospheric plasma.

Two plasma contactor units have been placed on the International Space Station to provide a “ground wire” to prevent arc discharging. These devices emit a low-energy stream of electrons during spacewalks that reduces the buildup of electrical charge. 13 As long as the plasma contactor units are functional, an astronaut floating freely during a spacewalk has no risk of exposure to arcing. However, the steel tethers used by astronauts to attach themselves to the structure of the space station and the exposed metallic surfaces of the spacesuit or tools used during the spacewalk are potential sources for arcing if both of the plasma contactor units were to fail during a spacewalk.

Acoustic noise

Spacecraft systems and experiments include fans, pumps and motors, which generate continuous noise. Acoustic levels at most locations on the International Space Station are close to 60 dBA (A-weighted decibels; similar to normal conversation level); however, certain areas of the space station are particularly noisy and are a potential source of hearing loss for astronauts. 14

Elevated ambient noise can have a deleterious effect on communication between astronauts, and it may adversely affect performance through impaired concentration and distraction from tasks, in addition to disrupting sleep. Inadvertent alarms have woken astronauts from sleep, an issue of particular concern if it occurs before a critical task on the mission.

Dave Williams floats near the torso portions of 2 spacesuits in the Quest Airlock of the International Space Station.

Microgravity

The International Space Station is designed to serve as a research facility for low-gravity experimentation in fundamental science and technology development. Depending on which onboard systems are operating and the nature of crew activities, the acceleration environment on the station ranges from transient episodes of 0.01 g to quasi-steady levels below one-millionth of 1 g . 15

Perturbations in this environment occur during certain phases of orbital activity. Rendezvous and docking introduce transient accelerations that could be disruptive to certain experiments. In addition, on-board exercise devices could result in perturbations of the microgravity environment and are isolated (treadmill vibration isolation system) from adjacent structures. Rack isolation systems have also been developed to isolate critical experiments from transient vibrations and accelerations.

From a clinical perspective, the 2 major challenges associated with human space flight are the radiation effects and the physiologic consequences of living and working in a micro-gravity environment. All organ systems are affected in space to some degree where gravitational loading, hydrostatic pressure, convection, buoyancy and sedimentation do not exist. Consequently, microgravity is the most profound aspect of the space environment on human physiology.

A subsequent article in this series will provide an overview of the unique physiologic acclimations associated with human space flight and discuss the implications for the delivery of health care in partial and microgravitational environments.

• Because of the harsh environment in space, astronauts are at risk for both short- and long-term health risks.
• The 2 major challenges associated with spaceflight are radiation effects and the physiologic consequences of a microgravity environment.
• Many of the immediate risks (decompression, thermal injury, arcing injuries) are mitigated by the design of the spacecraft and spacesuits.
• The biologic effects of long-term exposure to space radiation are unclear but may include the development of cataracts and cancer.

While preparing this article, astronaut Dr. Robert Thirsk was getting ready for a 6-month stint on the International Space Station, the first long-duration mission by a Canadian. In addition to being the medical officer for the 6-member international crew, Dr. Thirsk will work as a robotics specialist, operating Canadarm2, and perform experiments on behalf of Canadian and international scientists. The launch was set for late May aboard a Russian Soyuz rocket from Baïkonur, Kazakhstan.

In 1996, Robert Thirsk wrote a Special Report for CMAJ prior to his flight aboard the space shuttle Columbia . This report is available at www.cmaj.ca/cgi/content/full/154/12/1884/DC1

This article has been peer reviewed.

Published at www.cmaj.ca on the day the Soyuz rocket left for the International Space Station.

Competing interests: David Williams was employed by the Canadian Space Agency from 1992 to 2008. During this time, he performed research into the space environment. None declared for Robert Thirsk, Andre Kuipers and Chiaki Mukai.

Contributors: All of the authors were involved in the drafting and revising of the article and approved the final version submitted for publication.

Life and Physical Sciences Research for a New Era of Space Exploration: An Interim Report (2010)

Chapter: 3 research on the international space station, 3 research on the international space station.

If the life of the ISS is extended, a more robust program of science, human research and technology development would significantly increase the return on investment from the Station and better prepare for human exploration beyond low-Earth orbit.

—Augustine Committee Final Report (Seeking a Human Spaceflight Program Worthy of a Great Nation), October 2009

The International Space Station (ISS) is an engineering marvel that is a testimony to human ingenuity and a sterling example of international cooperation for the purpose of conducting unique research in space. As the only existing and available platform of its kind, it is essential that its presence and dedication to research for the life and physical sciences be fully utilized in the decade ahead. Before the 2010 budget announcement, NASA’s research plan for ISS utilization was expected to focus on objectives required for lunar and Mars missions in support of Constellation timelines, and ISS participation by the United States was expected to end in 2016. There is now a de-emphasis on lunar missions along with the extension of the ISS mission to 2020. The change in focus strengthens rather than weakens the need for a permanent research laboratory in microgravity devoted to scientific research in space focused on both fundamental questions and questions posed in response to the envisioned needs of future space missions.

In accordance with the charge (see the appendix) for this interim report, this chapter identifies some of the broad research areas that represent near-term opportunities for ISS research. However, it should be understood that flight research is generally part of a continuum of research that extends from laboratories and analog environments on the ground, through other low-gravity platforms as needed and available, and eventually into extended-duration flight. Like any process of scientific discovery this process is iterative, and further cycles of integrated ground-based and flight research are likely to be warranted as understanding of the system under study evolves. Separating out a portion of the research continuum that would benefit from relatively near-term access to the ISS was therefore a significant challenge for the committee, which asks that readers keep the following in mind.

While the ISS is a key and unique component of research infrastructure that will need to be utilized by a life and physical sciences program, it is only one component of a robust program. Other platforms and elements of research infrastructure will be important, including those that are ground based.

Because of the limited amount of research time that will be available on the ISS even with an extended lifetime, most of the research that will be flown on the ISS will need to be supported by a very strong ground-based program to be scientifically credible.

The research discussed here includes both enabling research (associated with the development of new knowledge that could be applied to exploration mission needs) and enabled research (associated with the development of new knowledge that can be obtained only by using the unique microgravity environment of space).

The research discussed below is divided into general fields of life and physical sciences that are amenable to study on the ISS. These fields are not presented in any priority order.

PLANT AND MICROBIAL RESEARCH

Plant and microbial research on the ISS fulfills two major goals: (1) to increase basic knowledge of how these organisms sense and respond to their environment, especially gravity-related phenomena, and (2) to provide the underpinning for enabling sustained human habitation in space.

There has not been a comprehensive program dedicated to analyzing microbial populations and responses to spaceflight. This represents a critical gap in our knowledge because microbial populations play significant roles in positive and negative aspects of human health and in the degradation of their environment through, for example, food spoilage and biofouling of equipment. At present there is little information on how long-term contact with the combination of factors imposed during spaceflight, such as chronic exposure to cosmic radiation and altered physical parameters associated with microgravity such as reduced convection, could lead to changes in microbial populations or provide sufficient selective pressures to drive microbial evolutionary processes. Also, the degree to which such changes reflect physiological responses to the spaceflight environment versus genomic changes remains undefined. Continued access to the ISS coupled to the technological maturity, low cost, and speed of genomic analyses, plus the rapid generation time of microbes, makes monitoring of the evolution of microbial genomic changes induced by extended growth in space a highly feasible short-term goal. Since samples could be taken from the surfaces of the ISS and the crew on board and returned for analysis on the ground, the on-orbit portion of this research could largely be accomplished using the already-existing microbial air and surface sampler kits. This research would allow a comprehensive analysis of microbial population changes in response to the factors present in the spaceflight environment that impact the rates of reproduction or survival of microbes, using both experimentally established populations and samples of microbes colonizing the surfaces and the crew of the ISS.

In contrast, a series of experiments on the ISS with a focus on plants has provided an initial, limited characterization of plant responses ranging from the developmental and molecular changes elicited by spaceflight to changes in photosynthesis, phototropism, and gravisensing in this environment. 1 , 2

One aim of this research has been to acquire basic knowledge to enable the use of plants for long-term life support in extraterrestrial habitats by capitalizing on plants’ ability to provide fresh food and to aid in the recycling of air, water, and waste products. Establishing the robust elements of such a bioregenerative life support system, which will likely incorporate a combination of biological systems and physico-chemical technologies, requires extended research now that carefully integrates ground- and ISS-based work. Levels and quality of light, atmospheric composition, nutrient levels, and availability of water are all critical elements shaping plant growth in space, where each needs to be optimized in a rigorously tested technology platform designed to maximize plant performance during spaceflight. Although such a research program will be enabled by access to the unique environment of the ISS, it is fundamentally aimed at enabling the long-term human presence in space. Developing a sustained research program combining ground- and ISS-based design and validation of components will be critical to establishing the dynamic integrated intramural and extramural research community necessary to support this area. Food plants will be a cornerstone of this effort because they alone can synthesize nutritious, edible biomass from carbon dioxide (CO 2 ), inorganic nutrients, and water while revitalizing the atmosphere using the energy of light. However, microbial reactors will likewise require attention to ensure that they can reliably and efficiently process the solid, liquid, and gaseous wastes of habitation. The ISS provides a key enabling resource for beginning to test the efficacy of each component of a long-

term life support system in the spaceflight environment, with the long-term goal of facilitating translation from basic research to reliable, applied systems.

Inextricably linked to such a program oriented toward the development of bioregenerative life support technology is the need for research into the fundamental mechanisms behind plant and microbial responses to spaceflight. Despite identification of a range of molecular components linked to gravity perception in plants, currently still unknown are the precise molecular identities of the receptors that translate the physical force of gravity to cellular signal(s) and the immediate signals generated by this sensory system and the associated response components. Similarly, understanding how the often extreme environments of spaceflight—ranging from high ethylene levels in the local air to lack of surface gas exchange due to the absence of convection in microgravity—affect microbial and plant growth is a key gap in current knowledge. Research addressing these questions will contribute to advances in basic understanding of how plants and microbes perceive and respond to the many stimuli present in space. In addition, it will provide essential insight into how these organisms might be selected or engineered, or how their growth environment might be manipulated so as to better tailor them to support a safe, sustained human presence in space. Such a research program studying the sensing and responses of plants and microbes to individual components of the spaceflight environment such as altered gravity, radiation, and atmospheric composition, and to the integrated effects of these multiple factors, will need to combine a robust ground-based program with ISS-based experimentation.

Existing ISS facilities, such as the European Modular Cultivation System, should allow rapid implementation of initial elements of microbial and plant research programs. Extended access to the ISS is essential for the success of these programs because it is currently the sole facility available to test plant and microbial responses in the complex, unique environments presented by spaceflight and especially to test these responses against the background of microgravity.

It is also important to note that new analytical approaches developed over the past decade have redefined understanding of biology in terrestrial settings at the molecular, developmental, and cellular levels. The study of spaceflight biology is poised to take advantage of this new knowledge and the techniques such as genomics, transcriptomics, proteomics, and metabolomics that have enabled it. It is clear that the recent massive strides in genome sequencing, for example, could revolutionize the design of experiments that can be conducted in space by allowing scientists to answer fundamental questions about the role of gravity in transcriptional regulation in biological systems. In the near term, these analyses can be accomplished by sample return and analysis on the ground. However in order to maximize scientific return via on-orbit analyses, and so minimize the currently major limitation of sample return needed for subsequent analysis, a technology development program could be initiated to take advantage of these recently developed, systems-level analytical technologies for investigations associated with the ISS. Such on-orbit analyses would enable research with a wide range of biological specimens, greatly facilitating, for example, the continuous monitoring of microbial genomes described above. The requisite technology development program will need to be initiated in the near-term if such tools are to become available while the ISS is in operation. It will also need to apply modern cell and molecular approaches and integrate a vigorous spaceflight and ground-based research program aimed at assessing the feasibility of implementation and the subsequent development of automated technology to allow these kinds of state-of-the-art molecular analyses on orbit. The resulting extensive data sets will provide the basis for analysis by large numbers of researchers and interdisciplinary teams, thus adding significant value to the limited and costly access to the ISS.

BEHAVIOR AND MENTAL HEALTH RESEARCH

The Augustine Committee Final Report 3 pointed to the fact that future astronauts will face three unique stressors: (1) prolonged exposure to solar and galactic radiation; (2) prolonged periods of exposure to microgravity; and (3) confinement in close, relatively austere quarters along with a small number of other crewmembers with whom the astronaut will have to live and work effectively for many months, with limited contact with family and friends. All of these stressors are present in the ISS environment, although the level of radiation is likely to be lower there than on a space mission because the ISS flies under the Van Allen belts, which provide some protection against charged particle radiation. Accordingly, ISS research studies could profitably determine mission-specific effects of these and other relevant stressors, alone and in combination, on astronauts’ general psychological and physical well-being and their ability to perform mission-related tasks. In addition, the ISS platform provides an ideal laboratory for developing techniques to predict and/or monitor the psychological and behavioral status of astronauts, and to develop and test interventions to prevent and/or treat adverse behavioral responses during extended space missions.

There are three key program areas for behavioral mental health research on the ISS:

Individual and group functioning. Studies are needed to assess how psychological well-being impacts astronaut effectiveness and accomplishment of mission goals. Similar issues pertain to team cohesiveness and effectiveness, increased crewmember autonomy, and crew-groundcrew interactions. For instance, there is accumulating evidence that longer-duration missions are associated with unusual psychological morbidity (symptoms of fatigue and exhaustion, weakness, and emotional lability and irritability, as well as difficulties in concentrating). Careful characterization of such symptoms as well as development of effective interventions is crucial for longer-term missions. Clearly, this is a research area that can best be addressed with continued study on the ISS.

Cognitive functioning. Because space is a hostile and unforgiving environment, even small errors in judgment or coordination can produce potentially catastrophic effects. To the extent possible, it is important that the cognitive capacity of astronauts be monitored using “embedded” measures—e.g., reaction time when working at a computer monitor or efficiency in operating a robotic arm—typical mission-related duties from which data could be culled to determine the individual astronaut’s cognitive status, thereby reducing the need for more extensive cognitive testing. Future cognitive tests would need to be validated against specific, mission-relevant tasks.

Sleep. NASA has a long history of recognizing the importance of sleep and circadian rhythms in crew health and performance. This emphasis on sleep has been appropriate, since it is clear that adequate sleep is necessary for normal cognitive functioning and that individuals are poor at recognizing the extent of their decreased cognitive performance in the face of sleep loss. Studies are needed to measure the extent to which sleep plays a role in maintaining mental, physical, and cognitive resilience during space missions—and the extent to which sleep-enhancing interventions reverse stress-related symptoms and restore and sustain mental resilience.

The ISS offers a unique platform for this type of research. Whereas analog environments can advance knowledge in these areas, they are limited in terms of the duration of exposure, the crowdedness of the living situation, the implacable hostility of the isolated and confined environment, and loneliness juxtaposed with an excess of face-to-face crew interaction. Similarly, analog environments are limited in terms of their ability to provide crews with characteristics comparable to those likely for crews on the ISS. More fundamentally however, such analog environments are limited in terms of their ability to mimic long-term low gravity and constantly fluctuating circadian rhythms. Finally, the ISS also offers a

platform for facility design and habitability so that issues of crowdedness versus isolation can be optimally addressed.

The facilities needed to advance behavioral and mental health research on the ISS are relatively modest. The most crucial “facility” needed on the ISS to advance this field is the will and commitment to exploration of the effects of extended space missions on all aspects of human functioning. As summarized elsewhere in this report, there are substantial problems with translational research efforts in space. The major reason for having an ISS is to provide a research platform. One of the key pieces of “apparatus” on this platform is its human “cargo”; yet, there have been long-standing problems with obtaining research cooperation from astronauts as well as accessing data from prior missions. In terms of other facilities needed, the equipment needs for this research area are generally modest in terms of size or mass. Sleep-monitoring equipment, for instance, has become dramatically smaller in terms of its “footprint.” Most of the other behavior and mental health research topics are facilitated by virtue of a strong communications link between the ISS and Earth—a link that can be used for communicating important diagnostic information as well as providing therapeutic links with Earth.

HUMAN AND ANIMAL BIOLOGY

The National Aeronautics and Space Administration Act of 2005, e.g., Article 3 of Section 305, 4 directs the United States to have a national laboratory aboard the ISS to conduct animal and human space-directed research; hence the extension of the availability of the ISS to 2020 and beyond provides a platform to fulfill two major goals: (1) to increase both basic and translational knowledge of animals and humans on a variety of systems that are adversely affected by a microgravity environment and (2) to develop potential countermeasures to alleviate these deficiencies in physiological homeostasis.

A large body of previous research on both animals and humans has clearly established that microgravity and equivalent ground-based analogs induce deficits/alterations in cardiovascular homeostasis, bone mass and strength, muscle mass, strength and endurance, sensorimotor function, thermoregulation, and immune function. As a result, many gaps in knowledge have been defined across these systems that need to be explored to maintain the necessary functional homeostasis when humans are faced with altered gravitation on future missions. Although this section identifies some of the key research issues (most of which have been identified previously by NASA and in earlier studies), the large number of affected physiological systems precludes even a brief discussion of every system in this interim report. The committee’s final report will contain an extensive discussion of questions in animal and human biology.

The ISS provides the only opportunity to carry out both fundamental and translational research on organ and systemic function in the absence of the gravity variable. Moreover it provides the optimal environment to establish key countermeasures toward maintaining homeostasis across various organ systems and to initiate interventions that cannot be effectively duplicated by studies using ground-based analogs.

The ISS provides the only opportunity to probe fundamental questions about the role of gravity in developmental biology by examining how animals grow, develop, mature, and age over a large portion of their life span without the influences of gravity. The ISS provides the only means to study, without the stimulus of gravity, these fundamental questions by (1) raising multiple generations of living mammals in space and (2) utilizing transgenic animal models (e.g., overexpression and/or knock-down of transcription factors and altered gene function, including the evolving field of epigenetics) to understand gene regulation of fundamental cell processes. Ethically and practically, these types of experiments cannot be conducted on humans. Equally important is the opportunity to obtain key functional physiological measurements in microgravity that have been unobtainable in previous science missions. This unique

knowledge can be gained only via the inclusion of animal studies on the ISS. To carry out these novel animal experiments, an animal facility capable of housing rodents 5 is necessary to conduct current and future generational experiments that are essential to accomplishing these goals. Equipment-sharing agreements with international partners will be necessary for the successful completion of any centrifugation studies using rodents. In summary, the establishment of a rodent habitat on the ISS is a critical need.

As noted above, exposure to microgravity leads to homeostatic deficits across the key systems necessary for the maintenance of health, fitness, and performance. To date, however, none of the exercise countermeasure strategies have been successful in maintaining cardiovascular fitness, muscle mass, strength or endurance, and sensorimotor function, as well as bone mass and strength. For example, recent findings for ISS astronauts who have been in space for 6 months or longer and performing the recommended exercise countermeasures indicated that the countermeasures were unable to prevent the loss of muscle mass or the decrement in muscle performance. 6 Normal function of these systems is necessary for maintaining crew performance capability on return to Earth or entry into other gravitational environments. The ISS is the critical laboratory for conducting studies on countermeasures because this platform creates the capability for supporting long-term exposure in microgravity while testing whether a given countermeasure has the capability for maintaining normal function for long durations in microgravity. Success in maintaining approximately normal homeostasis on the ISS would benefit astronauts traveling to all currently proposed destinations (the Moon, asteroids, Mars, Lagrange points) with their different gravities. Hence, both basic and applied research is needed to integrate information on (1) the responsible mechanisms impacting structural and functional deficits and (2) the translational effectiveness of countermeasures for correcting them. For example, it is envisioned that integrated research teams will be assembled to simultaneously study the interactions between the skeletal muscle, bone, and sensorimotor systems and/or linkage between cardiovascular, sensorimotor, and skeletal muscle systems, as examples of crosscutting thematic research projects. Other studies could integrate pharmacological and mechanical stress investigating maintenance of bone homeostasis. The key is that multiple systems and paradigms would be investigated. Hence, a program is needed to test the effectiveness of (1) a variety of devices and (2) potential integrated exercise regimens, especially those that can impact multiple systems. It appears that mechanical loads during countermeasures have not been appropriate to provide 1- g -like loading. Studies to test appropriate countermeasures are urgently needed. Emerging pharmacological interventions to prevent bone and muscle loss also need to be explored.

These kinds of integrative studies can also lead to insights in several divergent areas that have not been explored extensively in the microgravity environment of the ISS. These include but are not limited to bone formation versus resorption processes; fracture repair; reduction of the risk factors for renal stones; net protein balance and contractile protein turnover in skeletal muscle; substrate and organism energy turnover capacity during exercise; the prevalence of cardiac atrophy; head-ward fluid shifts and visual acuity; the mismatch in functional integration of sensorimotor circuits; the verification of the hypothesis that vestibular dysfunction is the cause of motion sickness; the alteration of Starling forces in the microgravity environment; the deposition of different sized aerosols in lung tissue; altered thermoregulation during extravehicular activity (EVA); alterations in female reproductive function and human spermatogenesis; and T-cell activation in astronauts prior to and following re-entry as a result of spaceflight.

In summary, a strong rationale exists for evolving new directions in NASA’s approach to human and animal research. Studies on human countermeasures with new approaches to loading and pharmacological interventions in the context of thematic studies need to be considered, and animal studies can provide new insights concerning the mechanism of organ system alterations. Thus, the ISS has great

potential to provide new knowledge of the effects of gravity and of its absence on human and animal systems and to test countermeasures for these effects.

FUNDAMENTAL PHYSICAL SCIENCE

The goals of the fundamental physical sciences are (1) to explore the laws governing matter, space, and time and (2) to discover and understand the organizing principles of complex systems from which structure and dynamics emerge. To achieve these goals, fundamental physical sciences researchers have a well-established need for access to space. Specifically, use of the ISS for this research can support achieving groundbreaking results, and in fact the fundamental physical sciences community has had significant experience with space-based research that has produced some high-impact results aboard the ISS. This community has included some of the best scientists of our time—several Nobel laureates as well as principal investigators who have become leading national science policy makers. At present the highest-priority areas for a pioneering, next-generation ISS program are (1) soft condensed matter physics and complex fluids, (2) precision measurement of fundamental forces and symmetries, (3) quantum gases, and (4) condensed matter and critical phenomena. Fundamental physical science research in space is unique in that it is almost entirely “enabled by” exploration, although in the long term this work may enable NASA’s exploration mission through the development of new materials and energy sources, time and frequency standards for navigation, and technologies that help humans adapt to the hostile conditions in space.

Soft Condensed Matter and Complex Fluids

Soft condensed matter and complex fluids are materials with multiple levels of structure. Key systems for study include colloids, polymer and colloidal gels, foams, emulsions, soap solutions, and so on because of the gradients that are formed in their properties under gravity. The ISS provides a unique opportunity to remove these gradients and study long-time dynamics free from gravitational interference. Very similar issues exist for complex and dusty plasmas, where density and morphology are height dependent under gravity. Similarly, in granular materials, stress chains and yield properties are height dependent and sensitive to the magnitude of gravity. NASA realized the importance of microgravity research to this field from its infancy, and some of the most significant discoveries were reported at NASA meetings, including highly cited papers coauthored with astronauts. Looking ahead, one example of highly relevant research is the experimentally tested, constitutive equations that describe the strain-strain rate relationships for granular materials under reduced gravity. (It is noteworthy that the Mars Rover “Spirit” has been stuck in the martian soil, a granular material, since May.) In terms of broader impact, along with the fundamental importance of complex fluids/soft materials, their manipulation is a ubiquitous part of the food, chemical, petroleum, cosmetics, pharmaceutical, and plastics industries.

Precision Measurements of Fundamental Forces and Symmetries.

The ISS offers unique conditions to address important questions about the fundamental laws of nature. In particular, the ISS can support high-precision measurements that probe understanding of gravity as well as theories of high-energy physics in ways that are not practical on Earth. Consider some examples: (1) Atomic-physics-based tests of the equivalence principle can probe whether different kinds of matter interact with gravity in the same way. If a violation of this principle is observed, it could offer understanding of dark energy and evidence for quantization of gravity, some of the most important ideas of our time. (2) Since the time of Einstein, physicists have been seeking an “ultimate theory” that ties together gravity, particle physics, and quantum physics. Recently it has been realized that such a theory might involve violations of very fundamental symmetries (e.g., Lorentz symmetry—the idea that the fundamental laws of nature are the same in any inertial reference frame). ISS-based experiments could

provide a several-orders-of-magnitude improvement in our search for such violations. A typical experiment might consist of clock comparisons, in which two or more high-stability, ISS-based clocks are simultaneously operated and their timing compared and correlated with position and velocity in gravity.

Quantum Gases

When the temperature of a gas is decreased the quantum, wavelike properties of the constituent atoms or molecules can dominate the behavior of the gas, and remarkable cooperative behavior can emerge. For many gases this can represent the formation of a novel state of matter known as a Bose-Einstein condensate (BEC). A closely related state of a solid is the superconductor, and for a fluid it is the superfluid. In 2001, then NASA-supported fundamental physical scientist Wolfgang Ketterle shared the Nobel Prize in physics for realizing a BEC in his laboratory. The key to creating a BEC is to cool the gas to within nanokelvin temperatures above absolute zero. The lowest achievable temperature is currently limited by the effects of gravity; however, on board the ISS BEC temperatures on the order of a picokelvin (0.000000000001 degrees above absolute zero) should be achievable. A remarkable range of different physical phenomena can then be investigated. If the particles of the quantum gas are “fermions” (particles are classified as either “bosons” or “fermions”), then another class of physics can be investigated. Cold fermion research could address wide-ranging problems such as the unresolved mechanism of superconductivity in high-temperature superconductors. Overall, experiments with quantum gases on the ISS will allow the study of matter in regimes not achievable on Earth. This research will also support new futuristic devices such as the atom laser—a bright source of coherent matter waves analogous to coherent light waves of the familiar laser. Such devices form a basis for next-generation technologies and quantum sensors. An exciting example is the atom interferometer, which has already been tested as a rotation sensor and which can be used for the measurement of fundamental quantities such as the photon momentum and the local force of gravity. As rotational sensors for inertial navigation, these devices rival the best gyroscopes available and are potentially important for space navigation applications.

Condensed Matter and Critical Phenomena

One of the great scientific successes enabled by the microgravity environment over the past two decades concerns better understanding the nature of materials at a very special transition known as a critical point. At this critical point the distinction between the liquid and vapor phases disappears, creating a fog-like critical state that fluctuates wildly. Many other important materials, including superfluids, magnetic materials, and colloids, undergo similar transitions so that work on one system affects understanding of many different systems of recognized scientific and technological interest. Already, a new series of ISS-based experiments have been conceived and designed that will elucidate fundamentally new effects that can be observed when a system near its critical point is driven away from equilibrium, both in the bulk and near boundaries such as a container wall.

Fundamental Physical Science Facilities and Opportunities

In addition to having a track record of successful spaceflight experiments, the fundamental physical sciences community has already developed a portfolio of projects to a level of advanced flight readiness. With renewed NASA support and continued, successful peer review, these projects provide an opportunity to obtain a well-defined, rapid science return from the ISS national laboratory. In general ISS-based fundamental physical science experiments are not facility oriented, with one exception—the Low-Temperature Microgravity Physics Facility (LTMPF). A facility designed to attach to the ISS, LTMPF is engineered to support experiments on critical phenomena and precision measurement experiments as discussed above. It is approximately 70 percent complete, and once finished, it will enable deployment of the flight-ready experiments aboard the ISS.

APPLIED PHYSICAL SCIENCES AND TRANSLATIONAL RESEARCH

Applied physical sciences research on the ISS will accomplish two major goals: (1) to provide a foundation for the development of systems and technologies enabling human and robotic space exploration and (2) to enhance understanding of phenomena enabled by the reduced-gravity environment on the ISS. NASA’s future exploration missions will include long-duration, microgravity and partial gravity conditions as well as extreme thermal and radiation environments. Research on the ISS directed toward the first goal will contribute to the development of power generation and energy storage systems; space propulsion systems; systems for EVA; life support systems; fire prevention, mitigation, and recovery systems; materials production and storage; in situ resource utilization (ISRU); and habitat construction and maintenance. Research on the ISS directed toward the second goal could lead to new and fundamental discoveries that would advance exploration and also have beneficial terrestrial applications.

Applied and Translational Research on the ISS That Will Enable Exploration

Power generation and energy storage systems for NASA’s future missions will require power at a level ranging from a few watts (for microsatellites) to tens of kilowatts and perhaps megawatts. For low power requirements, systems based on technologies such as thermionics and thermoelectrics are preferred. For higher power, i.e., kilowatts per kilogram, Sterling, Brayton, and Rankine cycle technologies are more suitable. NASA’s power generation, storage, and heat rejection technology requirements in the coming decades will be driven by applications such as near-Earth science platforms, lunar and planetary surface missions, and deep-space exploration probes. Increasing the efficiency and lifetime of power generation and energy storage systems will reduce costs by reducing mass and redundancy. All of these systems will benefit from research, prototyping, and testing on the ISS.

Power generation systems include photovoltaic, solar thermal power, and nuclear power systems. For space power generation applications, concentrating solar-thermal power systems have the highest kilowatts-per-kilogram capability. In low gravity, such systems can be lightweight, self-erecting gossamer structures supplying both primary and secondary power. Research conducted on the ISS on materials and structures can enable higher-efficiency systems. The ISS also provides a platform for research on environmental effects on solar arrays, such as the effects of plasma arcing, radiation damage, and micrometeroid impact. For energy storage, regenerative fuel cells and lithium-ion and other advanced battery technologies face major development issues in the quest to provide safe, reliable, affordable, long-life solutions to NASA’s future energy storage needs. Since such systems are integral to major ISS systems, the ISS is an excellent developmental platform.

Key advantages of power systems based on the Rankine cycle are higher power and small component size because two-phase-flow and heat-transfer coefficients are much larger than those for gas in non-two-phase systems. Two-phase technology is intrinsic to power systems based on the Rankine cycle, as well as to the thermal management, storage, and handling of cryogenics and other liquids in life support and thermal control systems. Unfortunately, little is known at present about the behavior of two-phase flows and associated heat transfer in a reduced-gravity environment. To enable the design of systems utilizing two-phase technology, it is critical that microgravity research in this area be given very high priority for experiments on the ISS while being supported by a relevant ground-based program. Experimental studies of multiphase flow and heat transfer on the ISS will provide scaling of phenomena with respect to gravity, data for validation of analytical/numerical simulation models, and development of design tools for heat exchangers based on two-phase flow. Experiments on the ISS on pool boiling; forced flow boiling including phase separation and flow stability in single and multiple channels; closure relations for interfacial and wall heat; mass and momentum transfer; condensation; and capillary-driven flows would provide significant knowledge for validating computer models and designing systems. A deeper understanding of two-phase flows would impact a host of important technologies, from those for cryogenic fluid handling to nuclear and other high-power sources of energy.

The major design goals for any space-bound thermal management system in power generation and electronic cooling are performance, cost, physical size, and reliability. Earth-based system processes involving phase change and/or multiple phase flow have been shown to have the highest heat transfer coefficient. Testing on the ISS of a complete system including boilers, phase separators, condensers, and radiators would allow meaningful correlations and validations to be made among the Earth-based and reduced-gravity thermal management systems. Such a system testing under microgravity will allow the study of interactions among components and provide data for validation of system-level simulation tools.

A deeper understanding of capillary flow in, for example, plant nutrient transport can aid in the design of technologies for water-processing systems and fluids handling in propellant storage depots. Finally, the Microgravity Science Glovebox and the Fluids Integrated Rack are valuable facilities available on the ISS. It would be useful to consider the utility of developing a multipurpose, multiuser facility on the ISS for multiphase flow research. Such a facility would also act as a catalyst for bringing together national and international researchers to address the challenge in a cost-effective and comprehensive manner. The merits of single-purpose experiment packages would need to be weighed in such an assessment as well.

To support NASA’s exploration missions, an evolutionary space transportation architecture is needed for science discovery and technology demonstration. These space propulsion systems will support the large human and cargo missions envisioned as well as pico-spacecraft that capitalize on advances in micro- and nanotechnologies. Advances in propulsion performance (specific impulse, efficiency, thrust to weight, propellant bulk density), reliability, thermal management, power generation and handling, and propellant storage and handling are key drivers to dramatically reduce mass, cost, and mission risk. The ISS provides unique opportunities for research in a number of these areas.

The reduced-gravity environment on the ISS provides opportunities for research on cryogenic two-phase fluid management, propellant transfer, engine starts, flame stability, and active thermal control of injectors and combustors. In addition, the ISS can benefit non-cryogenic (Earth-storable) propulsion systems by providing research opportunities for mixing or separation, and tribology under reduced-gravity. Research conducted on the ISS on physical phenomena involved in heat exchangers, thermal control, Stirling and Brayton cycles, lightweight and high-temperature thermal structures, propellant transfer and management, and liquid metal or noble gas storage under reduced gravity will provide the opportunity for fundamental advances for solar electric, nuclear thermal, and nuclear electric propulsion options. Indeed, the ISS can be an ideal laboratory providing an infrastructure and space environment for the development and demonstration of these non-chemical propulsion options that have a potential to reduce the duration of trips to Mars. In addition, the emerging technology for inflatable and low-mass aerobraking for re-entry systems can benefit from small free-flyer aerothermochemistry experiments conducted from the ISS. Using inflatable structures in re-entry systems to transport laboratory specimens and products from the ISS to Earth can provide opportunities to characterize for prototype return systems such items as vibration and deceleration loads, minimum thermal protection, and costs for a range of cargo types, and to gain operational experience. Currently, the transport of such items is limited to the return capsules or the remaining and available shuttle flights, and so such a system might be useful for more timely return of samples for analyses.

Creation of propellant depots in space that are supplied from propellant sources on Earth (and eventually the Moon) will dramatically improve the architecture and economics of exploration activities beyond low Earth orbit. Supply depots in Earth orbit can utilize a wide range of new-era commercial launch systems. Key science issues that need to be understood to make such depots a reality can be advanced with research on the ISS on cryogenic fluid management, including zero boil-off working fluids, propellant storage, two-phase flows, contact line motion on a solid surface, adhesion forces under low temperatures, and fluid transfer.

For EVA, the ISS environment is ideal for testing and qualifying a wide range of spacesuit mobility and performance innovations, such as joint torque minimization, suit comfort and trauma/injury countermeasures, thermal control, and radiation protection. In addition, EVA innovations in areas such as more efficient power, communication, avionics, and informatics systems can be tested for endurance

during extended ISS missions. The ISS is also the ideal platform to investigate plasma interactions with astronauts during EVAs in proximity to space structures that have high-power, high-voltage solar arrays. Research could be performed to address dust and micrometeorite interactions with spacesuits.

Life support systems (LSS)—for pressure control; atmosphere revitalization: removal of carbon dioxide, water vapor, and trace contaminants; temperature and humidity control; and waste collection—are integral to spacecraft habitats, rovers, and EVA. ISS laboratories provide a microgravity environment and facilities to characterize and test such LSS functions as heat and mass transfer in porous media and monitoring to identify major atmosphere constituents and trace contaminants. Innovative approaches can be evaluated to perform closed-loop air revitalization with CO 2 removal, recovery, and reduction; oxygen generation via electrolysis with high-pressure capability; improved sorbents and catalysts for trace contaminant control; and atmosphere particulate control and monitoring. Experiments on the ISS can be conducted to study dust accumulation, particle deposition in lungs, and especially electrostatic effects. Many of these approaches remain undeveloped because of poor understanding of multiphase and capillary flow (for example, for passive solid separation technologies) in reduced-gravity environments.

Fire safety is critical to enabling human exploration of space because fires can have devastating consequences, including loss of life and loss of vehicle or habitat integrity. Historically, fire research has been treated as a subset of combustion research. Basic and applied combustion research using ground-based facilities and in the ISS (Combustion Integrated Rack) have made significant advances that support fire safety research. This research includes characterization of particulates and toxic gases, smoldering, ignition, extinction, and flame spread. Nevertheless, the timely attainment of fire safety substantially depends on an adequate and comprehensive strategy that does not necessarily require a full understanding of the underlying principles of combustion, but is based more on phenomenological models and empirical correlations. As a result, the research and development (R&D) needs for fire safety for human exploration of space relate more to the understanding of how the different components together deliver an adequate fire safety strategy. The critical components are (1) a material’s response to fires, (2) fire detection, (3) fire suppression, and (4) recovery from fire (and explosions). The limited facilities, size constraints, and manpower limitations on the ISS restrict progress on the main areas of fire safety research necessary for application to space exploration. Thus, the use of ground-based facilities is particularly critical for a comprehensive fire safety program and will be detailed in the committee’s final report.

The link between ISRU on the Moon, Mars, and small bodies (asteroids or planetary moons) and the ISS is indirect. Research aimed at better understanding multiphase fluid flow on the ISS will be helpful for the design of systems for handling fluids in reduced-gravity environments. Also, research aimed at developing a capability for transferring propellant in space could play a part in a future lunar or Mars ISRU-based propellant production and utilization scenario. Research in the ISS relevant to excavation and material transport would also help in situ resource utilization in reduced-gravity environments.

Research activities that could be conducted on the ISS that will be beneficial, even critical, for any future planetary surface exploration involve materials and structural dynamics (self-deploying, inflatable, composite materials), as well as radiation protection systems. Testing on the ISS would benefit continuing development of food preparation, delivery, and storage systems, health maintenance equipment, radiation protection systems and materials, robotic systems, and human-machine interface systems.

Applied Research That Is Enabled by the ISS

Research enabled by the unique microgravity environment and facilities on the ISS can also address unexplored phenomena that have beneficial implications for exploration systems as well as many terrestrial technologies.

Gravity can mask the effects of many important fluid flow phenomena. Areas that can provide new and important insights via experiments on the ISS include flows driven by gradients of surface tension caused by temperature and concentration, solid-liquid adhesion forces, interfacial forces involving

shear and pressure forces, electric fields, magnetic fields, acoustic fields, and acceleration. Other examples are spreading, stability, and rupture of ultrathin liquid films. Much can be learned by considering granular materials at reduced-gravity. Key aspects concern effects such as particle clustering, self-assembly, and dissipation; the study of electrostatic effects and interstitial fluids; and the impact of having multiple particle sizes and/or shapes.

In the area of materials synthesis and processing, a microgravity environment can shed new light on the nucleation process because liquids can be suspended and solidified without a container, thus removing the effects of walls, as well as convection due to compositional inhomogeneities that accompany the formation of nuclei. Thus it is possible to study the formation of stable and metastable phases from undercooled melts, the formation of glasses, the relationship between liquid structure and the resulting crystal structure, and the thermophysical properties of deeply undercooled liquids. Understanding the processes leading to the production of materials composed of phases with much different densities, such as metallic and ceramic foams, can be improved by research on the ISS.

On Earth, during crystal growth the density differences between crystals and the parent fluid or vapor—as well as the temperature and composition dependence of the density of the parent phase and variations in the surface tension of a liquid-vapor—lead to convection. This convection results in nonuniform compositions as well as defects in the resulting crystal. The microgravity environment allows these crystal growth phenomena to be studied without the confounding effects of gravitationally induced convection. The Materials Science Research Rack (MSRR) available on the ISS is a very valuable asset.

Gravitationally induced convection or sedimentation makes it very difficult to study the physics that underlie processes such as dendritic and cellular solidification, liquid phase sintering, and phase separation. The effects of interactions between individual dendrites or cells on their spatial distribution and morphology, the evolution of dendrite morphology during transient heating or cooling, and the effects of noise and initial conditions on the resulting patterns remain unclear. The interactions between dendrites are particularly important in setting the properties of a solid-liquid mixture found in castings, called the mushy zone. Fluid flow within mushy zones can become unstable during solidification, resulting in deleterious casting defects. The nature of this instability and the properties of the mushy zone need further investigation.

Studies of combustion in a reduced-gravity environment would lead to a greater understanding of terrestrial combustion. On Earth, energy release, fluid dynamics, and gravity-induced buoyancy interact in a nonlinear fashion. By varying or eliminating the effects of gravity, researchers can extract fundamental data that are important for understanding combustion systems. Such data include parameters such as chemical reaction rates, diffusion coefficients, and radiation coefficients that strongly influence ignition, propagation, and extinction of combustion waves.

It is very rare, on Earth and in space, for an area, cabin, or room to be uniformly filled with a stoichiometric, homogeneous mix of fuel and oxidizer. Unfortunately, very little is known about the behavior of flames propagating through reactivity gradients. Reactivity gradients are important for all stages of a fire or explosion from ignition and propagation through to extinction. Reduced-gravity environments can be used to learn more about flame ignition, propagation, and extinction in reactivity gradients.

It is now speculated that gaseous flammability limits might not exist at all, or that a diffusive or hydrodynamic mechanism may cause extinction, or that flame balls or flame strings are themselves the limiting structure. Most combustors and unwanted fires involve diffusion flames. There remain significant gaps in the understanding of these flames, such as those associated with chemical kinetics, transport, radiation, soot formation, pollutant emissions, flame stability, and extinction. All of these areas will benefit from experiments performed on the ISS.

In response to requests from Congress, NASA asked the National Research Council to undertake a decadal survey of life and physical sciences in microgravity. Developed in consultation with members of the life and physical sciences communities, the guiding principle for the study is to set an agenda for research for the next decade that will allow the use of the space environment to solve complex problems in life and physical sciences so as to deliver both new knowledge and practical benefits for humankind as we become a spacefaring people.

The project's statement of task calls for delivery of two books--an interim report and a final survey report. Although the development of specific recommendations is deferred until the final book, this interim report does attempt to identify programmatic needs and issues to guide near-term decisions that are critical to strengthening the organization and management of life and physical sciences research at NASA.

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Collection  09 July 2018

Editor's choice: International Space Station science

Is colonisation of space feasible? The International Space Station (ISS) is the collaborative hub of research which aims to answer this question. Here, Editors from two open-access Nature Research journals, npj Microgravity   and Scientific Reports , have brought together more than 30 free-to-access papers describing data generated aboard the ISS. This Collection spans materials science, genetics, plant science, biology of fish and rodents, and human physiology.

• Collection content
• Participating journals

The effect of long-term exposure to microgravity on the perception of upright

• Laurence R. Harris
• Michael Jenkin
• Richard T. Dyde

“Cerebellar contribution to visuo-attentional alpha rhythm: insights from weightlessness”

• A. M. Cebolla

Brain structural plasticity with spaceflight

• Vincent Koppelmans
• Jacob J Bloomberg
• Rachael D Seidler

Spaceflight modulates gene expression in the whole blood of astronauts

• Jennifer Barrila
• Cheryl A Nickerson

Protein expression changes caused by spaceflight as measured for 18 Russian cosmonauts

• Irina M. Larina
• Andrew J. Percy
• Evgeny N. Nikolaev

Latent virus reactivation in astronauts on the international space station

• Satish K. Mehta
• Mark L. Laudenslager
• Duane L. Pierson

Changes in mitochondrial homeostasis and redox status in astronauts following long stays in space

• Hiroko P. Indo
• Hideyuki J. Majima
• Chiaki Mukai

Alterations in adaptive immunity persist during long-duration spaceflight

• Brian Crucian
• Raymond P Stowe
• Clarence Sams

Dichotomal effect of space flight-associated microgravity on stress-activated protein kinases in innate immunity

• Auke P. Verhaar
• Elmer Hoekstra
• Maikel P. Peppelenbosch

Impact of the Mk VI SkinSuit on skin microbiota of terrestrial volunteers and an International Space Station-bound astronaut

• Richard A. Stabler
• Helena Rosado
• Peter W. Taylor

An algorithm for the beat-to-beat assessment of cardiac mechanics during sleep on Earth and in microgravity from the seismocardiogram

• Marco Di Rienzo
• Emanuele Vaini
• Prospero Lombardi

Long-term exposure to microgravity impairs vestibulo-cardiovascular reflex

• Hironobu Morita
• Chikara Abe
• Kunihiko Tanaka

Dysfunctional vestibular system causes a blood pressure drop in astronauts returning from space

• Emma Hallgren
• Pierre-François Migeotte
• Floris L. Wuyts

Eye-Head Coordination in 31 Space Shuttle Astronauts during Visual Target Acquisition

• Millard F. Reschke
• Ognyan I. Kolev
• Gilles Clément

Circadian misalignment affects sleep and medication use before and during spaceflight

• Erin E Flynn-Evans
• Laura K Barger
• Charles A Czeisler

Fish & rodent

Evaluation of rodent spaceflight in the NASA animal enclosure module for an extended operational period (up to 35 days)

• Eric L Moyer
• Paula M Dumars
• Mike G Skidmore

Skin physiology in microgravity: a 3-month stay aboard ISS induces dermal atrophy and affects cutaneous muscle and hair follicles cycling in mice

• Thibaut Neutelings
• Betty V Nusgens
• Charles Lambert

Development of new experimental platform ‘MARS’—Multiple Artificial-gravity Research System—to elucidate the impacts of micro/partial gravity on mice

• Hiroyasu Mizuno
• Satoru Takahashi

Rapid adaptation to microgravity in mammalian macrophage cells

• Cora S. Thiel
• Diane de Zélicourt
• Oliver Ullrich

Microgravity promotes osteoclast activity in medaka fish reared at the international space station

• Masahiro Chatani
• Akiko Mantoku

Acute transcriptional up-regulation specific to osteoblasts/osteoclasts in medaka fish immediately after exposure to microgravity

• Hiroya Morimoto

Oscillations and accelerations of ice crystal growth rates in microgravity in presence of antifreeze glycoprotein impurity in supercooled water

• Yoshinori Furukawa
• Ken Nagashima

Other biology

From the bench to exploration medicine: NASA life sciences translational research for human exploration and habitation missions

• Joshua S. Alwood
• April E. Ronca
• Thomas J. Goodwin

Successful amplification of DNA aboard the International Space Station

• Anna-Sophia Boguraev
• Holly C. Christensen
• Ezequiel Alvarez Saavedra

Nanopore DNA Sequencing and Genome Assembly on the International Space Station

• Sarah L. Castro-Wallace
• Charles Y. Chiu
• Aaron S. Burton

Four-year bacterial monitoring in the International Space Station—Japanese Experiment Module “Kibo” with culture-independent approach

• Tomoaki Ichijo
• Nobuyasu Yamaguchi

Detection of antimicrobial resistance genes associated with the International Space Station environmental surfaces

• C. Urbaniak
• A. Checinska Sielaff
• K. Venkateswaran

Microgravity elicits reproducible alterations in cytoskeletal and metabolic gene and protein expression in space-flown Caenorhabditis elegans

• Akira Higashibata
• Toko Hashizume
• Atsushi Higashitani

Fluid dynamics alter Caenorhabditis elegans body length via TGF-β/DBL-1 neuromuscular signaling

• Shunsuke Harada

The effect of spaceflight on the gravity-sensing auxin gradient of roots: GFP reporter gene microscopy on orbit

• Robert J Ferl
• Anna-Lisa Paul

The gravity-induced re-localization of auxin efflux carrier CsPIN1 in cucumber seedlings: spaceflight experiments for immunohistochemical microscopy

• Chiaki Yamazaki
• Nobuharu Fujii
• Hideyuki Takahashi

Physical science

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Recapturing a Future for Space Exploration: Life and Physical Sciences Research for a New Era (2011)

Chapter: 11 the role of the international space station.

The Role of the International Space Station

UNIQUE STATUS AND CAPABILITIES

Spanning a construction period of more than a decade and involving the coordinated efforts of many nations, the International Space Station (ISS) represents a stunning achievement of human engineering. After years of continual redesign, development, and assembly, the ISS is poised to begin fulfilling its intended role as a world-class scientific laboratory for studying biological and physical processes in the near absence of gravity. However, the ISS of today lacks a number of important research facilities, such as the 3-meter centrifuge, planned during earlier stages of its design.

The assembly of major U.S., European, and Japanese components of the ISS will be completed in 2011—13 years after the launch of the first ISS component, the Russian Zarya module in 1998. (The Russians may launch their own pressurized laboratory to the station in the 2012-2013 time frame, but those plans are not yet finalized.) The ISS reached its full crew complement of six in May 2009 and should continue to hold that many until at least 2020, and perhaps beyond. Although limited by crew and equipment availability, significant science research was conducted during the construction phase of the ISS, with small observational experiments carried out shortly after the initial launch and more meaningful work beginning after the arrival of the Expedition 1 crew in late 2000.

Flight research is generally part of a continuum of efforts that extend from laboratories and analog environments on the ground, through other low-gravity platforms as needed and available, and eventually into extended-duration flight. Like any process of scientific discovery this effort is iterative, and further cycles of integrated ground-based and flight research are likely to be warranted as understanding of the system under study evolves. Although research on the ISS is only one component of this endeavor, the capabilities provided by the ISS are vital to answering many of the most important research questions detailed in this report. The ISS provides a unique platform for research, and past studies of the National Research Council (NRC) have noted the critical importance of the ISS’s capabilities to support the goal of long-term human exploration in space. * These capabilities include the ability to perform experiments of extended duration, the ability to continually revise experiment parameters on the basis of previous results, the flexibility in experimental design provided by human operators, and the availability of sophisticated experimental facilities with significant power and data resources. The ISS is the only

_____________

* See, for example, National Research Council, Review of NASA Plans for the International Space Station , The National Academies Press, Washington, D.C., 2006.

existing and available platform of its kind, and it is essential that its presence and dedication to research for the life and physical sciences be fully employed in the decade ahead.

Before the 2010 budget announcement, the research plan of the National Aeronautics and Space Administration (NASA) for ISS utilization was expected to focus on objectives required for lunar and Mars missions in support of Constellation program timelines. Participation by the United States in the ISS was expected to end in 2016. There is now a de-emphasis at NASA on lunar missions and an extension of the ISS mission to 2020. The change in focus strengthens the need for a permanent research laboratory in microgravity devoted to scientific research in space focused both on fundamental questions and on questions posed in response to the envisioned needs of future space missions.

AREAS OF RESEARCH ON THE INTERNATIONAL SPACE STATION

Each of the panel chapters (Chapters 4 through 10 ) in this report describes critical research questions, most of which will need to progress through the use of more than one research platform, including ground-based laboratories and facilities such as drop towers or parabolic flights, to use of the ISS. The platforms and facilities required for each research area are discussed in the individual chapters, but it can be noted that for the majority of investigations, the ISS will provide the most advantageous research platform once the investigations transition to flight. In many cases, the ISS will be the only platform capable of meeting the requirements of investigations, and the ISS is the only platform that can provide a very long duration microgravity environment. Summarized in the following sections are examples of areas of past and future life and physical sciences research benefiting from, or requiring, the capabilities of the ISS.

Life Sciences Research on the ISS

Although it is impossible to list all the various biological research projects that were conducted on the ISS prior to the current era, insights from a 2008 report from NASA indicate a spectrum that, for plants, ranges from investigating the influences of gravity on the molecular changes in Arabidopsis thaliana to studying the mechanisms of photosynthesis, phototropism, and gravity sensing. 1 Cellular biology studies included investigating gene expression changes in Streptococcus pneumonia and select microbes, exploring mechanisms of fungal pathogenesis and tumorgenesis, and observing changes in the responses of monocytes in cell culture, blood vessel development, and wound healing to the space environment. Also investigated were the chromosomal aberrations in the blood lymphocytes of astronauts and the effect of spaceflight on the reactivation of latent Epstein-Barr virus. Such analyses have revealed notable gaps in knowledge. For example, there has not been a comprehensive program dedicated to analyzing microbial populations and responses to spaceflight, yet microbes play significant roles in positive and negative aspects of human health and in the degradation of their environment through, for example, food spoilage and biofouling of equipment.

The final report of the Review of U.S. Human Spaceflight Plans Committee (also known as the Augustine Commission or Augustine Committee) 2 has emphasized that future astronauts will face three unique stressors: (1) prolonged exposure to solar and galactic radiation, (2) prolonged periods of exposure to microgravity, and (3) confinement in close, relatively austere quarters along with a small number of other crew members with whom the astronaut will have to live and work effectively for many months while having limited contact with family and friends. All of these stressors are present in the ISS environment. Accordingly, ISS research studies could profitably determine mission-specific effects of these and other relevant stressors, alone and in combination, on the general psychological and physical well-being of astronauts and on their ability to perform mission-related tasks. Aspects pertaining to crew member interactions and the behavioral aspects of isolation and confinement have been examined on the ISS, 3 but research with the full crew complement of six and prolonged mission durations is needed to address critical mission issues, such as the importance of sleep for astronaut performance and how best to maximize interpersonal behavior and maintain cognitive function so that the crew can function at its optimal level.

Experiments related to human physiology on the ISS have examined the effects of spaceflight on the central nervous system and spinal excitability, skeletal muscle, bone maintenance and loss, cardiovascular control, pulmo-

nary function, locomotor dysfunction, ground reaction forces, and nutritional status. Investigations have included the effects of radiation, the influence of light on the sleep-awake cycle, the risk of renal stones, and the advantages of select pharmaceutical drugs. 4 This research has revealed important limitations on the current understanding of how humans react to the spaceflight environment and so to current approaches to maintaining astronaut health under these conditions. For example, recent findings for ISS astronauts who have been in space for 6 months or longer and who performed the recommended exercise regimens indicated that these countermeasures were unable to prevent loss of muscle mass or decrement in muscle performance. 5

It is clear that further research is essential for attaining an understanding of how and why human physiology is altered in space and for the design of effective countermeasures that will help to maintain the necessary functional homeostasis when humans are faced with altered gravitation on future missions. The ISS provides a unique opportunity to carry out both fundamental and translational research on organ and systemic function in the absence of the gravity variable necessary to meet these goals. The presence of humans in the space laboratory for up to 6 months enables the development of the much-needed databases for the various physiological systems as well as a thorough evaluation of select countermeasures such as exercise and pharmacological agents. Insights can be gleaned, for example, concerning the effect of radiation on coronary heart disease and pharmacological interventions to reduce bone resorption within a given tour.

The prolonged access to space afforded by the ISS will also allow the probing of fundamental questions about animal biology not directly related to human health, such as the role of gravity in developmental biology, by examining how animals grow, develop, mature, and age. Notably absent from the 2008 report from NASA on ISS research accomplishments 6 and in subsequent reports were references to animal research being conducted in ISS modules, even though the capability exists. Because of budgetary constraints and policy decisions, this essential component of microgravity research has not been implemented. Also eliminated was a provision for a small-animal centrifuge that the Russians had previously demonstrated as an effective countermeasure to the effects of microgravity in Cosmos 936. 7 Thus, although there are some current facilities on the ISS to allow the inclusion of experiments on, for example, fruit flies or nematodes, the inclusion of an animal facility capable of housing rodents will be necessary. Without this capability, it will not be possible to conduct future experiments essential to advancing the basic understanding of animal physiology in space and to providing animal models for probing changes affecting the health of astronauts and for the development of suitable countermeasures. Thus, the availability of animals in the ISS National Laboratory would facilitate fundamental research on the effects of microgravity on inadequately studied systems, such as the immune, endocrine, reproductive, and nervous systems, while expanding knowledge of the mechanisms responsible for cellular and molecular changes in skeletal, muscular, and connective tissue systems. With the availability of “knock out” and “disease” animal models, new insights on how microgravity affects physiological mechanisms can be secured from space experiments. In addition, there is the potential to gain new data on tissue healing (especially fractures) and on the growth and development of animals over multiple generations.

One further element of research enabled by access to the ISS is its use as a test bed to facilitate studies on plant and microbial components of a bioregenerative life support system. Such research would allow exploration of the possibility of self-sufficiency for food production, water recycling, and regeneration of the craft’s atmosphere for extended crewed missions, obviating the need for costly resupply. Establishing the robust elements of such a bioregenerative life support system, which will likely incorporate a combination of biological systems and physico-chemical technologies, requires extended research now that carefully integrates ground- and ISS-based work. Levels and quality of light, atmospheric composition, nutrient levels, and availability of water are all critical elements shaping plant growth in space; each of the elements needs to be optimized in a rigorously tested technology platform designed to maximize performance during spaceflight. Although such a research program will be enabled by access to the unique environment of the ISS, it is fundamentally aimed at enabling a long-term human presence in space. Developing a sustained research program combining the ground- and ISS-based design and validation of components will be critical to establishing the dynamic, integrated intramural and extramural research community necessary to support this area.

These examples highlight the ISS as an essential and integral component of any implementation of the life sciences research outlined in this decadal survey.

Physical Sciences Research on the ISS

The reduced-gravity platforms currently available to researchers in the physical sciences are aircraft, drop towers, sounding rockets (in Europe and Japan), the space shuttle, and the ISS. Aircraft provide partial gravity for 20 to 25 s, with a g -jitter of 10 -2 g . Drop towers allow microgravity for a few seconds, and sounding rockets for a few minutes. In the space shuttle, gravity levels on the order of 10 -4 g can be sustained for long periods of time. However, the ISS is a very long duration experiment platform providing acceleration levels on the order of 10 -5 to 10 -6 g under the right conditions. 8 The premise of the ISS has been that it will serve as a laboratory for research and for the development and testing of technologies that facilitate space exploration. It also provides a platform for basic and applied research in biological and physical sciences aimed at enhancing a fundamental understanding of phenomena and processes with eventual space and terrestrial applications.

The facilities available on the ISS for U.S. researchers in the physical sciences include the Microgravity Science Glovebox, the Combustion Integrated Rack, the Fluids Integrated Rack, the Materials Science Research Rack, the Space Dynamically Responding Ultrasound Matrix System (Space DRUMS), and several multiuser EXPRESS Racks. 9 In addition, the European Space Agency has the Fluid Science Laboratory, and the Japanese Aerospace Exploration Agency has the Ryutai and Kobairo Racks for fluid physics and materials science research. Through international collaboration, all of these facilities can be used to advance research in the physical sciences.

As of 2009, NASA had carried out 20 expeditions to the ISS. These expeditions have led to 52 experiments in the physical sciences, and 15 more were planned for expeditions 21 and 22. Some of the recent experiments that have been conducted in the basic fluid physics area include gelation and phase separation in colloidal suspensions, critical phenomena, crystallization of glasses, growth of dendritic crystals, properties of magneto-rheological fluids, properties of particle growth in liquid-metal mixtures, and stress/strain response in polymeric liquids under shearing. In the area of combustion and fire safety, investigations have included smoke and aerosol measurements and the study of soot emission from gas-jet flames.

The fundamental and applied microgravity research in the physical sciences for which the ISS can serve as a laboratory is described in detail elsewhere in this report (see Chapters 8 , 9 , and 10 ). Here only a brief summary is presented. In the fundamental physics area, the topics of interest are soft matter and complex fluids (materials with multiple levels of structure), including colloids, polymer and colloidal gels, foams, emulsions, liquid crystals, dusty plasmas, and granular materials. Because of the gradients that develop in their properties under gravity, the microgravity environment provides ideal conditions for understanding the dynamic behavior of such materials, allowing the testing of ideas about fundamental physical processes—varying from examination of the constitutive equations that describe the strain-rate relationships for granular materials through to analysis of crystal growth—without the confounding effects of convection-based imperfections in material deposition. Precision measurements of fundamental forces and symmetries are another area that can benefit greatly from the microgravity environment of the ISS. Some of the subtopics of interest are the study of the equivalence principle and theories behind the standard model and general relativity to ask whether different kinds of matter interact with gravity in the same way. The study of quantum gases can lead to a range of new technologies and understanding, from developing ultraprecise atomic clocks and quantum sensors to resolving the mechanism of superconductivity in high-temperature superconductors. Major advances in the understanding of phenomena near the critical point can be achieved through well-conceived experiments conducted on the ISS. The completion of the Low Temperature Microgravity Physics Facility would significantly enhance the capability of the ISS to support experiments in fundamental physics.

Applied physical sciences include fluid physics and heat transfer, combustion, and materials science. In the fluid physics area, multiphase flow phenomena and associated heat transfer have been identified as a critical area that would benefit greatly from experiments in the long-duration microgravity environment of the ISS. Experiments on pool boiling; forced-flow boiling, including phase separation and flow stability; closure relations for interfacial and wall heat, mass and momentum transfer; condensation; and capillary-driven flows would provide significant knowledge and a database with which computer models could be validated and systems could be designed. In addition, research aimed at increasing the efficiency and lifetime of power-generation and energy-storage systems would reduce costs by reducing mass and redundancy. All of these systems would benefit from research, prototyping, and testing on the ISS. For example, key advantages of spaceborne power systems based on the Rankine

cycle are higher power and small component size, because two-phase-flow and heat-transfer coefficients are much larger than those for gas in non-two-phase systems. Unfortunately, little is known at present about the behavior of two-phase flows and associated heat transfer in a reduced-gravity environment. The possibility of developing a multipurpose, multiuser facility for multiphase flow research on the ISS should therefore be considered. Such a facility would also act as a catalyst for bringing together national and international researchers to address the problem in a cost-effective and comprehensive manner. Significant insights into the static and dynamic behavior of granular materials and dusts could be gained through experiments on the ISS. Such an understanding would be of value for applications on Earth and for human and robotic exploration of the Moon and Mars. (It is noteworthy that the Mars rover Spirit has been stuck in the martian soil, a granular material, since May 2009.)

Advances in propulsion performance (specific impulse, efficiency, thrust to weight, propellant bulk density), reliability, thermal management, power generation and handling, propellant storage and handling, and strategies for refueling on orbit are all key drivers for dramatically reducing mass, cost, and mission risk. The ISS provides unique opportunities for advances in a number of these areas through research on processes such as cryogenic two-phase fluid management, propellant transfer, engine starts, flame stability, active thermal control of injectors and combustors, and cryogenic fluid management.

In summary, the ISS platform is an essential and integral component of any implementation of the physical sciences research outlined in this decadal survey.

Utilizing the ISS for Research

The decadal survey committee strongly recommends that NASA intensify the utilization of the ISS as a world-class research laboratory engaged in both basic and applied research that enables space exploration and is enabled by the microgravity environment of the ISS. The goal should be to maximize the utilization of existing facilities and to engage world-class scientists and engineers to carry out research that leads to the development of space-related technologies. Ground-based experimental and theoretical work should form a significant component of the overall activity.

Cross-disciplinary research should be emphasized, and a research portfolio with prioritization should be developed and shared with the technical community. 10 To develop a vibrant research community that is committed to space-related research, NASA should have a firm plan for sustaining the research by providing adequate resources. Aside from benefiting directly from the research, NASA would be contributing to the creation of the workforce for the future. The process, from the acceptance of a proposal to preparation of the flight experiment to conduct of experiments on the ISS, should be streamlined, with a reduction in time from start to finish. This is essential to keep graduate students and other researchers engaged in the research activity. Some of the experimental rigs that have already been flown on the ISS can serve as facilities for future research investigations in the physical sciences. NASA should reconsider the placement of a centrifuge on the ISS so that long-duration partial-gravity experiments can be conducted. NASA should also strengthen and expand its collaborations with international partners. This would allow access to the facilities of the partner countries, avoid a duplication of research, and allow U.S. researchers to accomplish much more than they could otherwise.

Discussed throughout this report are various topics within each of the areas described above. The committee reiterates, however, that although the ISS is a key component of the research infrastructure to be utilized by a biological and physical sciences research program, it is only one component of a healthy program. Other platforms will play an important role and, in particular, research on the ISS will have to be supported by other platforms, including a parallel ground-based program, to be scientifically credible.

1 . Evans, C.A., Robinson, J.A., Tate-Brown, J., Thumm, T., Crespo-Richey, J., Baumann, D., and Rhatigan, J. 2009. International Space Station Science Research Accomplishments During the Assembly Years: An Analysis of Results from 2000-2008. NASA/TP-2009-23146-Revison A. NASA Johnson Space Center, Houston, Tex., p. 1.

2 . Review of U.S. Human Spaceflight Plans Committee. 2009. Seeking a Human Spaceflight Program Worthy of a Great Nation. Final Report. Available at http://www.nasa.gov/pdf/396093main_HSF_Cmte_FinalReport.pdf , p. 113.

3 . Evans, C.A., Robinson, J.A., Tate-Brown, J., Thumm, T., Crespo-Richey, J., Baumann, D., and Rhatigan, J. 2009. International Space Station Science Research Accomplishments During the Assembly Years: An Analysis of Results from 2000-2008. NASA/TP-2009-23146-Revison A. NASA Johnson Space Center, Houston, Tex., p. 1.

4 . Evans, C.A., Robinson, J.A., Tate-Brown, J., Thumm, T., Crespo-Richey, J., Baumann, D., and Rhatigan, J. 2009. International Space Station Science Research Accomplishments During the Assembly Years: An Analysis of Results from 2000-2008. NASA/TP-2009-23146-Revison A. NASA Johnson Space Center, Houston, Tex., p. 1.

5 . Trappe, S., Costill, D., Gallagher, C., Creer, A., Peters, J.R., Evans, H., Riley, D.A., and Fitts, R.H. 2009. Exercise in space: Human skeletal muscle after 6 months aboard the International Space Station. Journal of Applied Physiology 106:1159-1168.

6 . Evans, C.A., Robinson, J.A., Tate-Brown, J., Thumm, T., Crespo-Richey, J., Baumann, D., and Rhatigan, J. 2009. International Space Station Science Research Accomplishments During the Assembly Years: An Analysis of Results from 2000-2008. NASA/TP-2009-23146-Revison A. NASA Johnson Space Center, Houston, Tex., p. 1.

7 . Kotovskaya, A.R., Ilyin, E.A., Korolkov, V.I., and Shipov, A.A. 1980. Artificial gravity in spaceflight. Physiologist 23(Suppl. 6):S27-S29.

8 . DeLombard, R., Hrovat, K., Kelly, E., and McPherson, K. 2004. Microgravity environment on the International Space Station. AIAA Paper 2004-0125. NASA/TM-2004-213039. NASA Glenn Research Center, Cleveland, Ohio.

9 . Robinson, J.A., NASA. 2009. “International Space Station,” presentation to the Committee for the Decadal Survey on Biological and Physical Sciences in Space, August 19. National Research Council, Washington, D.C.

10 . National Research Council. 2003. Factors Affecting the Utilization of the International Space Station for Research in the Biological and Physical Sciences. The National Academies Press, Washington, D.C.

More than four decades have passed since a human first set foot on the Moon. Great strides have been made in our understanding of what is required to support an enduring human presence in space, as evidenced by progressively more advanced orbiting human outposts, culminating in the current International Space Station (ISS). However, of the more than 500 humans who have so far ventured into space, most have gone only as far as near-Earth orbit, and none have traveled beyond the orbit of the Moon. Achieving humans' further progress into the solar system had proved far more difficult than imagined in the heady days of the Apollo missions, but the potential rewards remain substantial.

During its more than 50-year history, NASA's success in human space exploration has depended on the agency's ability to effectively address a wide range of biomedical, engineering, physical science, and related obstacles—an achievement made possible by NASA's strong and productive commitments to life and physical sciences research for human space exploration, and by its use of human space exploration infrastructures for scientific discovery. The Committee for the Decadal Survey of Biological and Physical Sciences acknowledges the many achievements of NASA, which are all the more remarkable given budgetary challenges and changing directions within the agency. In the past decade, however, a consequence of those challenges has been a life and physical sciences research program that was dramatically reduced in both scale and scope, with the result that the agency is poorly positioned to take full advantage of the scientific opportunities offered by the now fully equipped and staffed ISS laboratory, or to effectively pursue the scientific research needed to support the development of advanced human exploration capabilities.

Although its review has left it deeply concerned about the current state of NASA's life and physical sciences research, the Committee for the Decadal Survey on Biological and Physical Sciences in Space is nevertheless convinced that a focused science and engineering program can achieve successes that will bring the space community, the U.S. public, and policymakers to an understanding that we are ready for the next significant phase of human space exploration. The goal of this report is to lay out steps and develop a forward-looking portfolio of research that will provide the basis for recapturing the excitement and value of human spaceflight—thereby enabling the U.S. space program to deliver on new exploration initiatives that serve the nation, excite the public, and place the United States again at the forefront of space exploration for the global good.

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