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NASA NTRSDate not supplied

Effects of Mild Hypobaric Hypoxia on Visual Field Impairment

INTRODUCTION: The primary objective of the Exploration Atmosphere (EA) study is to validate a new prebreathe protocol necessary before exposure to a suited hypobaric environment during extravehicular activity (EVA) from a habitat ‘exploration atmosphere’ of 56.5kPa (8.2 psia), 34% O2, 66% N2. Prebreathe protocols must be time and resource efficient while also controlling Decompression Sickness (DCS) risk to within acceptable limits. The habitat hypobaric exploration atmosphere also results in a mildly hypoxic environment (piO2 = 128mmHg). As a secondary objective of the EA study, we characterized the effects of 11-day exposure to a mild hypobaric hypoxic environment on visual performance. METHODS: Two, 11-day hypobaric chamber tests were performed (EA-1and EA-2, n=8 each) in NASA’s 20-foot chamber at Johnson Space Center where subjects lived in the exploration atmosphere. Subjects also underwent simulated 6-hour EVAs at 85% O2 and 29.6 kPa during EVA on days 3, 5, 7, 9, and 11. Visual acuity (VA), a measure of spatial resolution, and contrast sensitivity (CS), a measure of ability to distinguish ever finer increments of brightness, were assessed on non-EVA days by using gapped Landolt C testing. The luminance was controlled by using a booth, a light monitor, and a lighting rheostat. EA-1 data had revealed problems in lighting control impacting consistency of the data. Procedures were subsequently updated for the EA-2 test. RESULTS: EA-1 data revealed large variance and data recording errors and was removed from the analysis. One participant left the study at Test Day 3 during EA-2. EA-2 ANOVA results showed CS (mean change=0.010 logCSWeber) and VA (mean change, -0.016 logMAR) between pre-test and 11-day test phases; however, neither VA nor CS changes were statistically significant. There were non-statistically significant declines in VA across test phases. DISCUSSION: Overall, visual field performance did not exhibit clinically significant changes (3 lines or greater change in LogMar chart) during exposure to the mild hypoxic exploration atmosphere environment compared to pre-test baseline. The consistency and stability of VA data during EA-2 suggests that the mild hypobaric hypoxic environment did not cause clinically significant negative impacts to participants’ visual field performance.

Visual Acuity↗
NASA NTRS2008

Effects of Varying Surface Inclines and Suit Pressure: Implications on Space Suit Design

Suited human performance studies in reduced gravity environments to date include limited observations from Apollo Lunar surface Extravehicular Activities (EVA) and from previous studies conducted in partial gravity simulation environments. The Constellation Program EVA Systems Project office has initiated tests to develop design requirements for the next generation Lunar EVA suit. Theses studies were conducted in the Space Vehicle Mock-Up Facility (SVMF) at Johnson Space Center from which the results provided recommendations for suit weight, mass, center of gravity, pressure, and suit kinematic constraints that optimize human performance in partial gravity environments.

Clowers, Kurt↗
NASA NTRS2010

Constellation's First Flight Test: Ares I-X

On October 28, 2009, NASA launched Ares I-X, the first flight test of the Constellation Program that will send human beings to the Moon and beyond. This successful test is the culmination of a three-and-a-half-year, multi-center effort to design, build, and fly the first demonstration vehicle of the Ares I crew launch vehicle, the successor vehicle to the Space Shuttle. The suborbital mission was designed to evaluate the atmospheric flight characteristics of a vehicle dynamically similar to Ares I; perform a first stage separation and evaluate its effects; characterize and control roll torque; stack, fly, and recover a solid-motor first stage testing the Ares I parachutes; characterize ground, flight, and reentry environments; and develop and execute new ground hardware and procedures. Built from existing flight and new simulator hardware, Ares I-X integrated a Shuttle-heritage four-segment solid rocket booster for first stage propulsion, a spacer segment to simulate a five-segment booster, Peacekeeper axial engines for roll control, and Atlas V avionics, as well as simulators for the upper stage, crew module, and launch abort system. The mission leveraged existing logistical and ground support equipment while also developing new ones to accommodate the first in-line rocket for flying astronauts since the Saturn IB last flew from Kennedy Space Center (KSC) in 1975. This paper will describe the development and integration of the various vehicle and ground elements, from conception to stacking in KSC s Vehicle Assembly Building; hardware performance prior to, during, and after the launch; and preliminary lessons and data gathered from the flight. While the Constellation Program is currently under review, Ares I-X has and will continue to provide vital lessons for NASA personnel in taking a vehicle concept from design to flight.

Davis, Stephan R.↗
NASA NTRS2006

Mechanism Development, Testing, and Lessons Learned for the Advanced Resistive Exercise Device

The Advanced Resistive Exercise Device (ARED) has been developed at NASA Johnson Space Center, for the International Space Station (ISS) program. ARED is a multi-exercise, high-load resistive exercise device, designed for long duration, human space missions. ARED will enable astronauts to effectively maintain their muscle strength and bone mass in the micro-gravity environment more effectively than any other existing devices. ARED's resistance is provided via two, 20.3 cm (8 in) diameter vacuum cylinders, which provide a nearly constant resistance source. ARED also has a means to simulate the inertia that is felt during a 1-G exercise routine via the flywheel subassembly, which is directly tied to the motion of the ARED cylinders. ARED is scheduled to fly on flight ULF 2 to the ISS and will be located in Node 1. Presently, ARED is in the middle of its qualification and acceptance test program. An extensive testing program and engineering evaluation has increased the reliability of ARED by bringing potential design issues to light before flight production. Some of those design issues, resolutions, and design details will be discussed in this paper.

Lamoreaux, Christopher D.↗
NASA NTRS1988

Space Station-based deep-space optical communication experiments

A series of three experiments proposed for advanced optical deep-space communications is described. These proposed experiments would be carried out aboard the Space Station to test and evaluate the capability of optical instruments to conduct data communication and spacecraft navigation for deep-space missions. Techniques for effective data communication, precision spacecraft ranging, and accurate angular measurements will be developed and evaluated in a spaceborne environment.

Chen, Chien-Chung↗
NASA NTRS1992

Thermal control surfaces on the MSFC LDEF experiments

There were five Marshall Space Flight Center (MSFC) experiments on the LDEF. Each of those experiments carried thermal control surfaces either as test samples or as operational surfaces. These materials experienced varying degrees of mechanical and optical damage. Some materials were virtually unchanged by the extended exposure while others suffered extensive degradation. The synergistic effects due to the constituents of the space environment are evident in the diversity of these material changes. The sample complement for the MSFC experiments is described along with results of the continuing analyses efforts.

Wilkes, Donald R.↗
NASA NTRS1995

A Materials Exposure Facility

The objective of the Materials Exposure Facility (MEF) is to provide a test bed in space for conducting long-term (greater than one year) materials experiments which require exposure to the low Earth orbit (LEO) space environment. The proposed MEF is planned to be an integral part of the agency's Space Environments and Effects Research Program. The facility will provide experiment trays similar to the Long Duration Exposure Facility (LDEF). Each tray location is planned to have a power and data interface and robotic installation and removal provisions. Space environmental monitoring for each side of the MEF will also be provided. Since routine access to MEF for specimen retrieval is extremely important to the materials research, Space Station Freedom has been chosen as the preferred MEF carrier.

Slemp, Wayne S.↗
NASA NTRS2012

Single Event Rates for Devices Sensitive to Particle Energy

Single event rates (SER) can include contributions from low-energy particles such that the linear energy transfer (LET) is not constant. Previous work found that the environmental description that is most relevant to the low-energy contribution to the rate is a "stopping rate per unit volume" even when the physical mechanisms for a single-event effect do not require an ion to stop in some device region. Stopping rate tables are presented for four heavy-ion environments that are commonly used to assess device suitability for space applications. A conservative rate estimate utilizing limited test data is derived, and the example of SEGR rate in a power MOSFET is presented.

conservative rate↗
NASA NTRS1972

In-flight aeroacoustic environments on prospective space shuttle vehicles

The problem of in-flight aerodynamic noise has been studied by reliable estimates of full scale surface-pressure fluctuations from scale model tests in wind tunnels. Scaling relationships have been verified, and many details of the fluctuating pressure characteristics such as spatial correlation and convection velocities are understood. The effects of the wind tunnel environmental turbulence and noise have also been investigated sufficiently so that threshold levels of usable data are known.

Dods, J. B., Jr.↗
NASA NTRS1995

Gravitropic responses of the Avena coleoptile in space and on clinostats. I. Gravitropic response thresholds

We conducted a series of gravitropic experiments on Avena coleoptiles in the weightlessness environment of Spacelab. The purpose was to test the threshold stimulus, reciprocity rule and autotropic reactions to a range of g-force stimulations of different intensities and durations The tests avoided the potentially complicating effects of earth's gravity and the interference from clinostat ambiguities. Using slow-speed centrifuges, coleoptiles received transversal accelerations in the hypogravity range between 0.l and 1.0 g over periods that ranged from 2 to 130 min. All responses that occurred in weightlessness were compared to clinostat experiments on earth using the same apparatus. Characteristic gravitropistic response patterns of Atuena were not substantially different from those observed in ground-based experiments. Gravitropic presentation times were extrapolated. The threshold at 1.0 g was less than 1 min (shortest stimulation time 2 min), in agreement with values obtained on the ground. The least stimulus tested, 0.1 g for 130 min, produced a significant response. Therefore the absolute threshold for a gravitropic response is less than 0.1 g.

Flight Experiment↗
NASA NTRS2009

Freezable Radiator Coupon Testing and Full Scale Radiator Design

Freezable radiators offer an attractive solution to the issue of thermal control system scalability. As thermal environments change, a freezable radiator will effectively scale the total heat rejection it is capable of as a function of the thermal environment and flow rate through the radiator. Scalable thermal control systems are a critical technology for spacecraft that will endure missions with widely varying thermal requirements. These changing requirements are a result of the space craft s surroundings and because of different thermal loads during different mission phases. However, freezing and thawing (recovering) a radiator is a process that has historically proven very difficult to predict through modeling, resulting in highly inaccurate predictions of recovery time. This paper summarizes tests on three test articles that were performed to further empirically quantify the behavior of a simple freezable radiator, and the culmination of those tests into a full scale design. Each test article explored the bounds of freezing and recovery behavior, as well as providing thermo-physical data of the working fluid, a 50-50 mixture of DowFrost HD and water. These results were then used as a tool for developing correlated thermal model in Thermal Desktop which could be used for modeling the behavior of a full scale thermal control system for a lunar mission. The final design of a thermal control system for a lunar mission is also documented in this paper.

Lillibridge, Sean T.↗
NASA NTRS2004

Effects of Heat Flux, Oxygen Concentration and Glass Fiber Volume Fraction on Pyrolysate Mass Flux from Composite Solids

Experimental work on the effects of heat flux, oxygen concentration and glass fiber volume fraction on pyrolysate mass flux from samples of polypropylene/glass fiber composite (PP/G) is underway. The research is conducted as part of a larger project to develop a test methodology for flammability of materials, particularly composites, in the microgravity and variable oxygen concentration environment of spacecraft and space structures. Samples of PP/G sized at 30x30x10 mm are flush mounted in a flow tunnel, which provides a flow of oxidizer over the surface of the samples at a fixed value of 1 m/s and oxygen concentrations varying between 18 and 30%. Each sample is exposed to a constant external radiant heat flux at a given value, which varies between tests from 10 to 24 kW/m2. Continuous sample mass loss and surface temperature measurements are recorded for each test. Some tests are conducted with an igniter and some are not. In the former case, the research goal is to quantify the critical mass flux at ignition for the various environmental and material conditions described above. The later case generates a wider range of mass flux rates than those seen prior to ignition, providing an opportunity to examine the protective effects of blowing on oxidative pyrolysis and heating of the surface. Graphs of surface temperature and sample mass loss vs. time for samples of 30% PPG at oxygen concentrations of 18 and 21% are presented in the figures below. These figures give a clear indication of the lower pyrolysis rate and extended time to ignition that accompany a lower oxygen concentration. Analysis of the mass flux rate at the time of ignition gives good repeatability but requires further work to provide a clear indication of mass flux trends accompanying changes in environmental and material properties.

Rich, D. B.↗
NASA NTRS1991

Microgravity two-phase flow experiment and test results

A two-phase flow system was tested in the NASA KC-135 reduced gravity test facility. Its innovative flow configuration results in an unusual ease of control and significantly reduced power and heat rejection requirements, while permitting flow regimes, pressure drops, and boiling and condensing heat transfer to be examined. Numerous design features were incorporated that minimize the impact of the KC-135 environment on system condition. Among other results, flight testing indicates no significant effect of gravity on pressure drop for the conditions examined, and that many conditions can be examined definitively only in the long-term reduced gravity afforded by a space experiment.

Hill, Wayne S.↗
NASA NTRS1986

Biological and Medical Experiments on the Space Shuttle, 1981 - 1985

This volume is the first in a planned series of reports intended to provide a comprehensive record of all the biological and medical experiments and samples flown on the Space Shuttle. Experiments described have been conducted over a five-year period, beginning with the first plant studies conducted on STS-2 in November 1981, and extending through STS 61-C, the last mission to fly before the tragic Challenger accident of January 1986. Experiments were sponsored within NASA not only by the Life Sciences Division of the Office of Space Science and Applications, but also by the Shuttle Student Involvement Program (SSIP) and the Get Away Special (GAS) Program. Independent medical studies were conducted as well on the Shuttle crew under the auspices of the Space Biomedical Research Institute at Johnson Space Center. In addition, cooperative agreements between NASA and foreign government agencies led to a number of independent experiments and also paved the way for the joint US/ESA Spacelab 1 mission and the German (DFVLR) Spacelab D-1. Experiments included: (1) medically oriented studies of the crew aimed at identifying, preventing, or treating health problems due to space travel; (2) projects to study morphological, physiological, or behavioral effects of microgravity on animals and plants; (3) studies of the effects of microgravity on cells and tissues; and (4) radiation experiments monitoring the spacecraft environment with chemical or biological dosimeters or testing radiation effects on simple organisms and seeds.

Halstead, Thora W.↗
NASA NTRS1998

STS-90 Day 08 Highlights

On this eighth day of the STS-90 mission, the flight crew, Cmdr. Richard A. Searfoss, Pilot Scott D. Altman, and Mission Specialists Richard M. Linnehan, Dafydd Rhys Williams and Kathryn P. Hire, and Payload Specialists Jay C. Buckey and James A. Pawelczyk continue to operate the 26 individual experiments designed to provide insight into the operation of the nervous system, the most complex and least well-known part of the human body. The STS-90 crew members have used themselves as test subjects in a variety of experiments associated with studying functions such as blood pressure regulation , balance, coordination and sleep patterns. They also have studied a variety of animals to gain additional insight into the effects of the weightless environment of space on the development and performance of the nervous system.

Source record↗
NASA NTRS2015

Packaging Technologies for 500 C SiC Electronics and Sensors: Challenges in Material Science and Technology

This paper presents ceramic substrates and thick-film metallization based packaging technologies in development for 500C silicon carbide (SiC) electronics and sensors. Prototype high temperature ceramic chip-level packages and printed circuit boards (PCBs) based on ceramic substrates of aluminum oxide (Al2O3) and aluminum nitride (AlN) have been designed and fabricated. These ceramic substrate-based chip-level packages with gold (Au) thick-film metallization have been electrically characterized at temperatures up to 550C. The 96 alumina packaging system composed of chip-level packages and PCBs has been successfully tested with high temperature SiC discrete transistor devices at 500C for over 10,000 hours. In addition to tests in a laboratory environment, a SiC junction field-effect-transistor (JFET) with a packaging system composed of a 96 alumina chip-level package and an alumina printed circuit board was tested on low earth orbit for eighteen months via a NASA International Space Station experiment. In addition to packaging systems for electronics, a spark-plug type sensor package based on this high temperature interconnection system for high temperature SiC capacitive pressure sensors was also developed and tested. In order to further significantly improve the performance of packaging system for higher packaging density, higher operation frequency, power rating, and even higher temperatures, some fundamental material challenges must be addressed. This presentation will discuss previous development and some of the challenges in material science (technology) to improve high temperature dielectrics for packaging applications.

dielectric properties↗
NASA NTRS2015

Flying Through the Ages: Rodent Research for Human Health

As humans, we evolved, developed, grew, and now function in a continuous 1-gravity environment. Habitation in space poses unique challenges to human cells and organ systems. Biomedical research with rodents (primarily mice and rats) can help to both unravel molecular, cellular and physiologic mechanisms relevant to humans and test candidate interventions that mitigate adverse effects of space on humans, such as muscle atrophy, bone loss and cardiovascular deconditioning. One favored hypothesis that may explain the detrimental effects of spaceflight on humans is that reduced mechanical loading in microgravity accelerates aging. Rodents provide a relevant model system to study this problem as they age 40 times faster than humans. Now scientists from both public and commercial sectors conduct rodent experiments on the ISS using a new capability developed primarily at ARC. Results from the maiden voyage of the Rodent Research Project on the ISS reveal that long duration effects of spaceflight appear far different than short duration effects. Thus, Rodent Research missions on the ISS usher in a new era for exploration and biological discovery in space.

Globus, Ruth↗
NASA NTRSDate not supplied

The Integrated Impact of Diet on Human Immune Response, the Gut Microbiota, and Nutritional Status During Adaptation to Spaceflight

Long-duration spaceflight impacts human physiology, including well documented immune system dysregulation. Diet, the microbiome, and immune system function are interlinked, but diet is the only one of these factors that we have the ability to easily, and significantly, alter on Earth or during flight. As we better understand dietary impacts on physiology, we may then improve the spaceflight diet to improve crew health and potentially reduce spaceflight-associated physiological decrements. Increasing the consumption of fruits and vegetables and bioactive compounds (e.g., omega-3 fatty acids, lycopene, flavonoids) and therefore enhancing overall nutritional intake from the nominal shelf-stable, fully-processed, space food system is expected to serve as a countermeasure to detrimental impacts to human physiology, including dysregulation in immunological profiles, the taxonomic profile of the gut microbiota, and nutritional status during spaceflight. In this study, first we sought to determine the effect of the nominal shelf-stable spaceflight diet compared to an "enhanced" shelf-stable spaceflight diet on human biochemistry, immunology, and the microbiome in a ground-based, simulated space mission. The ground analog portion of this study was conducted in the NASA Human Exploration Research Analog (HERA) Campaign 4 missions, which consisted of four 45-day missions with closed chamber confinement and realistic mission simulation to study effects on crew health and performance. As reported previously, analyses indicate beneficial associations between diet and markers of nutritional status, stress, the microbiome, and cognitive performance. Intake and beneficial associations varied by subject. This data will be used as a ground-based control for spaceflight, where the spaceflight environment (e.g., radiation, microgravity) will have additional impacts and the potential to evaluate effects of the diet will be greater. The second phase of this study is to occur on the International Space Station, where it is currently being implemented. The test plan is similar to that used in the HERA missions. The enhanced diet is intended to provide 25% of the crews’ diet with foods rich in omega-3 fatty acids, lycopene, and flavonoids, along with more fruits and vegetables in general (the other 75% of the diet will be obtained from standard and crew preference items available on the ISS). Biological samples (blood, urine, stool, and saliva) are being collected from participants at selected time points before, during, and after the mission. Data collection also includes dietary intake recording and body mass measurement. Currently, 6 of 9 planned astronauts have completed data collection. Analysis of immune markers, latent herpes virus reactivation, the taxonomic and metatranscriptomic profile of the gut microbiome, and nutritional status biomarkers and biochemical metabolites will occur in batch to minimize sample handling variations. Mixed models statistical analyses will be used, incorporating random effects to account for repeated measures within individuals to assess the impact of diet on physiological outcomes. We expect this study to provide evidence of beneficial impact of this enhanced diet on crew health and adaptation to spaceflight. These data will aid in evidence-based mass-risk trades for food system design and development of targeted dietary interventions for future exploration-class space missions.

Grace L. Douglas↗