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NASA NTRS2024

Final Report on Radiation Measurements Performed Inside of the BEAM Module

Measurements of the radiation environment inside of the Bigelow Expandable Activity Module (BEAM) have been made on a pseudo-continuous basis since June 6, 2016 using both passive and active instrumentation. Passive detectors yield a single cumulative dose value (or average daily dose) over the measurement period from deploy to return to ground. Active Radiation Environment Monitor (REM) sensors yield dose rate, Linear Energy Transfer (LET) spectra, and particle-specific dose, all on a 1-minute cadence. From the initial install in 2016 until early 2018, BEAM was an empty module. In 2018, further testing was approved and stowage began to be moved into BEAM. As a result, it was decided to stop measurements with RAM detectors to avoid potential difficulties with access after stowage was added. The REM sensors remained however in the original deploy locations.

radiation exposure↗

NASA NTRS1934

Maneuverability Investigation of an O3U-1 Observation Airplane

This report presents the results of maneuverability tests of an O3U-1 observation airplane. This investigation is the third in a series of similar investigations requested by the Bureau of Aeronautics (Navy) for the purpose of comparing the maneuverability of different airplane types and to provide quantitative data for use in establishing a criterion or method for rating the maneuverability of an airplane. The two former investigations were conducted with the fighter types designated F6C-3 and F6C-4 and have been reported previously. Measurement of the air speed, the angular velocity, the linear acceleration, and positions of the controls were made during abrupt single-control maneuvers with three stop positions for each control, during steady horizontal turns for the determination of minimum radius, and during 180 degree turns by various methods. Flight-path coordinates in two dimensions were determined for the 180 degree turns by means of a special camera obscura designed for the previous investigation of the F6C-4 airplane. All maneuvers were performed at an altitude of approximately 3,000 feet.

Thompson, F L↗

NASA NTRS1971

The characterization of facsimile camera systems for lunar and planetary surface exploration

Advantages of facsimile camera systems are reviewed for imagery of lunar and planetary surfaces from stationary or stopped remotely controlled vehicles. They include: better geometric fidelity than television systems, more picture elements per frame, ability to take single frame panoramic pictures, a very high contrast ratio within a picture, a choice of one or more narrow-band spectral responses over a wide possible range, image transmission over a low bit-rate communications channel without storage, very low power, small size, low weight, and ruggedizability to meet space flight requirements. Systems of this kind are under development for the 1975 Viking Martian lander, and have been used by the Soviets on Lunas and Lunokhod laboratory and field evaluation of a completed facsimile camera system is presented. The applicability of facsimile cameras to lunar and planetary rovers is demonstrated.

Eisenman, A.↗

NASA NTRS1984

Erosion and modification of SO2 ice by ion bombardment of the surface of Io

New measurements on the effect of slow ion bombardment of SO2 ice using Ar(+) in the 15-45 keV range are presented. Total yields for loss of SO2 are given along with the energy spectra of the ejected molecules and molecular fragments and information on the chemical changes induced by the ion bombardment. These data are used to estimate that the direct sputter ejection rate of sulfur into the Jovian plasma is of the order of 10 billion atoms/sq cm/s, that the erosion rate of fresh SO2 deposits due to sputtering is of the order of 0.001 cm/yr, and that a significant and possibly observable column density of SO3 can be produced in an SO2 front only for penetrating ion bombardment. Chemical activity occurs even in rather low-temperature SO2 ice bombardment by ions in the nuclear stopping region, and this activity is likely to increase with increasing temperature.

Johnson, R. E.↗

NASA NTRS2001

Formation and Early Evolution of Solar and Extra-Solar Giant Planets

This project investigates the origin of giant planets, both in the Solar System and around other stars. It is assumed that the planets form by the core accretion process: small solid particles in a disk surrounding a young star gradually coagulate into objects of a few kilometers in size, known as planetesimals, which then accumulate into solid protoplanetary cores. Once the cores have become large enough, they are able to attract gas from the surrounding disk to form the deep gaseous envelope of the giant planet. Our code simulates giant planet growth in a spherical approximation, and it has been quite successful in addressing a number of basic planetary properties. Further improvements to the code have been made to achieve a more realistic understanding of planetary formation. The computations of the models were based on an earlier version of our code and were stopped at the onset of runaway gas accretion. Now, improved boundary conditions have been incorporated into the code to allow for hydrodynamic inflow of gas and to handle the late stages of evolution when the planet evolves at constant mass. These changes were made to the version of the code that uses a constant accretion rate and to the version that uses a self-consistent method for calculating both the solid and gas accretion rates. The equation of state has been updated to incorporate the detailed tables of Saumon, Chabrier, and Van Horn. The opacities were updated to include the results of Alexander and Ferguson. The outer boundary conditions were modified. During the accretion phase when the planet's radius is between the accretion radius and the tidal radius, we set the outer boundary at a 'modified' accretion radius, which is the point where thermal energy is enough to bring gas to the edge of the Hill sphere.

Bodenheimer, P. H.↗

NASA NTRS2007

Optical Observations of GEO Debris with Two Telescopes

For several years, the Michigan Orbital DEbris Survey Telescope (MODEST), the University of Michigan s 0.6/0.9-m Schmidt telescope on Cerro Tololo Inter-American Observatory in Chile has been used to survey the debris population at GEO in the visible regime. Magnitudes, positions, and angular rates are determined for GEO objects as they move across the telescope s field-of-view (FOV) during a 5-minute window. This short window of time is not long enough to determine a full six parameter orbit so usually a circular orbit is assumed. A longer arc of time is necessary to determine eccentricity and to look for changes in the orbit with time. MODEST can follow objects in real-time, but only at the price of stopping survey operations. A second telescope would allow for longer arcs of orbit to obtain the full six orbital parameters, as well as assess the changes over time. An additional benefit of having a second telescope is the capability of obtaining BVRI colors of the faint targets, aiding efforts to determine the material type of faint debris. For 14 nights in March 2007, two telescopes were used simultaneously to observe the GEO debris field. MODEST was used exclusively in survey mode. As objects were detected, they were handed off in near real-time to the Cerro Tololo 0.9-m telescope for follow-up observations. The goal was to determine orbits and colors for all objects fainter than R = 15th magnitude (corresponds to 1 meter in size assuming a 0.2 albedo) detected by MODEST. The hand-off process was completely functional during the final eight nights and follow-ups for objects from night-to-night were possible. The cutoff magnitude level of 15th was selected on the basis of an abrupt change in the observed angular rate distribution in the MODEST surveys. Objects brighter than 15th magnitude tend to lie on a well defined locus in the angular rate plane (and have orbits in the catalog), while fainter objects fill the plane almost uniformly. We need to determine full six-parameter orbits to investigate what causes this change in observed angular rates. Are these faint objects either the same population of high area-to-mass (A/M) objects on eccentric orbits as discovered by the ESA Space Debris Telescope (Schildknecht, et al. 2004), or are they just normal debris from breakups in GEO?

Seitzer, P.↗

NASA NTRS1999

GCR Transport in the Brain: Assessment of Self-Shielding, Columnar Damage, and Nuclear Reactions on Cell Inactivation Rates

Radiation shield design is driven by the need to limit radiation risks while optimizing risk reduction with launch mass/expense penalties. Both limitation and optimization objectives require the development of accurate and complete means for evaluating the effectiveness of various shield materials and body-self shielding. For galactic cosmic rays (GCR), biophysical response models indicate that track structure effects lead to substantially different assessments of shielding effectiveness relative to assessments based on LET-dependent quality factors. Methods for assessing risk to the central nervous system (CNS) from heavy ions are poorly understood at this time. High-energy and charge (HZE) ion can produce tissue events resulting in damage to clusters of cells in a columnar fashion, especially for stopping heavy ions. Grahn (1973) and Todd (1986) have discussed a microlesion concept or model of stochastic tissue events in analyzing damage from HZE's. Some tissues, including the CNS, maybe sensitive to microlesion's or stochastic tissue events in a manner not illuminated by either conventional dosimetry or fluence-based risk factors. HZE ions may also produce important lateral damage to adjacent cells. Fluences of high-energy proton and alpha particles in the GCR are many times higher than HZE ions. Behind spacecraft and body self-shielding the ratio of protons, alpha particles, and neutrons to HZE ions increases several-fold from free-space values. Models of GCR damage behind shielding have placed large concern on the role of target fragments produced from tissue atoms. The self-shielding of the brain reduces the number of heavy ions reaching the interior regions by a large amount and the remaining light particle environment (protons, neutrons, deuterons. and alpha particles) may be the greatest concern. Tracks of high-energy proton produce nuclear reactions in tissue, which can deposit doses of more than 1 Gv within 5 - 10 cell layers. Information on rates of cell killing from GCR, including patterns of cell killing from single particle tracks. can provide useful information on expected differences between proton and HZE tracks and clinical experiences with photon irradiation. To model effects on cells in the brain, it is important that transport models accurately describe changes in the GCR due to interactions in the cranium and proximate tissues. We describe calculations of the attenuated GCR particle fluxes at three dose-points in the brain and associated patterns of cell killing using biophysical models. The effects of the brain self-shielding and bone-tissue interface of the skull in modulating the GCR environment are considered. For each brain dose-point, the mass distribution in the surrounding 4(pi) solid angle is characterized using the CAM model to trace 512 rays. The CAM model describes the self-shielding by converting the tissue distribution to mass-equivalent aluminum, and nominal values of spacecraft shielding is considered. Particle transport is performed with the proton, neutron, and heavy-ion transport code HZETRN with the nuclear fragmentation model QMSFRG. The distribution of cells killed along the path of individual GCR ions is modeled using in vitro cell inactivation data for cells with varying sensitivity. Monte Carlo simulations of arrays of inactivated cells are considered for protons and heavy ions and used to describe the absolute number of cell killing events of various magnitude in the brain from the GCR. Included are simulations of positions of inactivated cells from stopping heavy ions and nuclear stars produced by high-energy ions most importantly, protons and neutrons.

Shavers, M. R.↗

NASA NTRS2016

Holodeck Testbed Project

The main objective of the Holodeck Testbed is to create a cost effective, realistic, and highly immersive environment that can be used to train astronauts, carry out engineering analysis, develop procedures, and support various operations tasks. Currently, the Holodeck testbed allows to step into a simulated ISS (International Space Station) and interact with objects; as well as, perform Extra Vehicular Activities (EVA) on the surface of the Moon or Mars. The Holodeck Testbed is using the products being developed in the Hybrid Reality Lab (HRL). The HRL is combining technologies related to merging physical models with photo-realistic visuals to create a realistic and highly immersive environment. The lab also investigates technologies and concepts that are needed to allow it to be integrated with other testbeds; such as, the gravity offload capability provided by the Active Response Gravity Offload System (ARGOS). My main two duties were to develop and animate models for use in the HRL environments and work on a new way to interface with computers using Brain Computer Interface (BCI) technology. On my first task, I was able to create precise computer virtual tool models (accurate down to the thousandths or hundredths of an inch). To make these tools even more realistic, I produced animations for these tools so they would have the same mechanical features as the tools in real life. The computer models were also used to create 3D printed replicas that will be outfitted with tracking sensors. The sensor will allow the 3D printed models to align precisely with the computer models in the physical world and provide people with haptic/tactile feedback while wearing a VR (Virtual Reality) headset and interacting with the tools. Getting close to the end of my internship the lab bought a professional grade 3D Scanner. With this, I was able to replicate more intricate tools at a much more time-effective rate. The second task was to investigate the use of BCI to control objects inside the hybrid reality ISS environment. This task looked at using an Electroencephalogram (EEG) headset to collect brain state data that could be mapped to commands that a computer could execute. On this Task, I had a setback with the hardware, which stopped working and was returned to the vendor for repair. However, I was still able to collect some data, was able to process it, and started to create correlation algorithms between the electrical patterns in the brain and the commands we wanted the computer to carry out. I also carried out a test to investigate the comfort of the headset if it is worn for a long time. The knowledge gained will benefit me in my future career. I learned how to use various modeling and programming tools that included Blender, Maya, Substance Painter, Artec Studio, Github, and Unreal Engine 4. I learned how to use a professional grade 3D scanner and 3D printer. On the BCI Project I learned about data mining and how to create correlation algorithms. I also supported various demos including a live demo of the hybrid reality lab capabilities at ComicPalooza. This internship has given me a good look into engineering at NASA. I developed a more thorough understanding of engineering and my overall confidence has grown. I have also realized that any problem can be fixed, if you try hard enough, and as an engineer it is your job to not only fix problems but to embrace coming up with solutions to those problems.

Arias, Adriel↗

NASA NTRS1998

Gravitoinertial force background level affects adaptation to coriolis force perturbations of reaching movements

We evaluated the combined effects on reaching movements of the transient, movement-dependent Coriolis forces and the static centrifugal forces generated in a rotating environment. Specifically, we assessed the effects of comparable Coriolis force perturbations in different static force backgrounds. Two groups of subjects made reaching movements toward a just-extinguished visual target before rotation began, during 10 rpm counterclockwise rotation, and after rotation ceased. One group was seated on the axis of rotation, the other 2.23 m away. The resultant of gravity and centrifugal force on the hand was 1.0 g for the on-center group during 10 rpm rotation, and 1.031 g for the off-center group because of the 0.25 g centrifugal force present. For both groups, rightward Coriolis forces, approximately 0.2 g peak, were generated during voluntary arm movements. The endpoints and paths of the initial per-rotation movements were deviated rightward for both groups by comparable amounts. Within 10 subsequent reaches, the on-center group regained baseline accuracy and straight-line paths; however, even after 40 movements the off-center group had not resumed baseline endpoint accuracy. Mirror-image aftereffects occurred when rotation stopped. These findings demonstrate that manual control is disrupted by transient Coriolis force perturbations and that adaptation can occur even in the absence of visual feedback. An increase, even a small one, in background force level above normal gravity does not affect the size of the reaching errors induced by Coriolis forces nor does it affect the rate of reacquiring straight reaching paths; however, it does hinder restoration of reaching accuracy.

NASA Discipline Neuroscience↗

NASA NTRS2008

Prioritized LT Codes

It is common in data transmissions that some information is more important than others. This is especially true in space communications where mission critical information or science data are high priority. In this work, we propose a simple yet constructive scheme to send high priority data reliably and efficiently using Luby Transform (LT) codes. The new proposed scheme modifies the conventional LT encoder to send high priority data as a degree 1 and 2 so that high priority data can be quickly resolved and very likely recovered before a decoder stops. Preliminary results show that a carefully designed degree distribution of high priority data increases the likelihood of receiving high priority information while having negligible performance impact on data with lower priority. The performance of the proposed scheme is evaluated and compared with the conventional LT approach with the same parameters under a range of erasure error rates.

priority coding↗

NASA NTRS2016

Pilot Field Test: Use of a Compression Garment During a Stand Test After Long-Duration Space Flight

Orthostatic intolerance (OI) is a concern for astronauts returning from long-duration space flight. One countermeasure that has been used to protect against OI after short-duration bed rest and space flight is the use of lower body and abdominal compression garments. However, since the end of the Space Shuttle era we have not been able to test crewmembers during the first 24 hours after landing on Earth. NASA's Pilot Field Test provided us the opportunity to test cardiovascular responses of crewmembers wearing the Russian Kentavr compression garment during a stand test at multiple time points throughout the first 24 hours after landing. HYPOTHESIS We hypothesized that the Kentavr compression garment would prevent an increase in heart rate (HR) >15 bpm during a 3.5-min stand test. METHODS: The Pilot Field Test was conducted up to 3 times during the first 24 hours after crewmembers returned to Earth: (1) either in a tent adjacent to the Soyuz landing site in Kazakhstan (approx.1 hr) or after transportation to the Karaganda airport (approx. 4 hr); (2) during a refueling stop in Scotland (approx.12 hr); and (3) upon return to NASA Johnson Space Center (JSC) (approx.24 hr). We measured HR and arterial pressure (finger photoplethysmography) for 2 min while the crewmember was prone and throughout 3.5 min of quiet standing. Eleven crewmembers consented to participate; however, 2 felt too ill to start the test and 1 stopped 30 sec into the stand portion of the test. Of the remaining 8 crewmembers, 2 did not wear the Russian Kentavr compression garment. Because of inclement weather at the landing site, 5 crewmembers were flown by helicopter to the Karaganda airport before initial testing and received intravenous saline before completing the stand test. One of these crewmembers wore only the portion of the Russian Kentavr compression garment that covered the lower leg and thus lacked thigh and abdominal compression. All crewmembers continued wearing the Russian Kentavr compression garment during the second testing session in Scotland, but none wore it during testing at JSC. RESULTS: The mean Delta HR from the supine to standing position in the 8 crewmembers measured pre-flight or 60 days after return from long-duration space flight was 9.8 bpm. During the first few hours after landing from long-duration space flight, the mean Delta HR of the 6 crewmembers who wore the Russian Kentavr compression garment in Kazakhstan or Karaganda was +14 bpm and the change in mean arterial pressure (Delta MAP) was +0.8 mmHg, while the 2 crewmembers who did not wear the Russian Kentavr compression garment had a Delta HR of +38 bpm and a Delta MAP of +1.1 mmHg. In Scotland, 4 crewmembers wore the Russian Kentavr compression garment and had a Delta HR of +7.4 bpm while the 3 crewmembers who did not wear it had a Delta HR of +25.0 bpm. Seven crewmembers were tested upon return to JSC approx. 24 hr after landing, but none wore the Russian Kentavr compression garment and their Delta HR was 16.0 bpm. CONCLUSIONS: These are the first stand-test data to be collected from long-duration crewmembers during the first 24 hr of re-adaptation to gravity on Earth. The Delta HR measured in crewmembers who completed the stand-test while wearing Kentavr within the first approx.4 hours after returning to Earth was only slightly elevated from pre-flight Delta HR, while the few subjects who did not wear the Russian Kentavr compression garment had a much larger increase in HR in order to maintain arterial pressure throughout 3.5-min of standing. These data demonstrate the effectiveness of a compression garment in preventing large increases in HR during a 3.5 min stand test after long-duration space flight. However, the fact that three crewmembers were too ill to complete the test or was not able to complete 3.5 min of standing despite wearing the Russian Kentavr compression garment indicates that wearing a compression garment does not resolve all problems crewmembers face during the period of re-adaptation immediately after return to Earth's gravity.

Laurie, S. S.↗

NASA NTRS1983

Constraints on rift thermal processes from heat flow and uplift

The implications of heat flow data available from five major Cenozoic continental rift systems for the processes of continental rifting are discussed, and simple thermal models of lithospheric thinning which predict uplift are used to further constrain the thermal processes in the lithosphere during rifting. Compilations of the heat flow data are summarized and the salient results of these compilations are briefly discussed. The uplift predictions of the slow and rapid thinning models, in which thinning is assumed to occur at a respectively slower and faster rate than heat can be conducted into the lithosphere, are presented. Comparison of uplift rates with model results indicates that the lithosphere is in a state between the two models. While uplift is predicted to continue after thinning has ceased due to thermal relaxation of the lithosphere, the rapid thinning model is always predicted to apply to surface heat flow, and an anomaly in this flow is not predicted to develop until after thinning has stopped.

Morgan, P.↗

NASA NTRS1999

Aircraft and Ground Vehicle Winter Runway Friction Assessment

Some background information is given together with the scope and objectives of a 5-year, Joint Winter Runway Friction Measurement Program between the National Aeronautics & Space Administration (NASA), Transport Canada (TC), and the Federal Aviation Administration (FAA). Participants recently completed the fourth winter season of testing. The primary objective of this effort is to perform instrumented aircraft and ground vehicle tests aimed at identifying a common number that all the different ground vehicle devices would report. This number, denoted the International Runway Friction Index (IRFI) will be related to all types of aircraft stopping performance. The range of test equipment, the test sites, test results and accomplishments, the extent of the substantial friction database compiled, and future test plans will be described. Several related studies have also been implemented including the effects of contaminant type on aircraft impingement drag and the effectiveness of various runway and aircraft de-icing chemical types and application rates. New equipment and techniques to measure surface frictional properties are also described. The status of an international friction index calibration device for use in ensuring accuracy of ground vehicle friction measurements will also be discussed. NASA considers the success of this joint program critical in terms of ensuring adequate ground handling capability in adverse weather conditions for future aircraft being designed and developed as well as improving the safety of current aircraft ground operations.

Yager, Thomas J.↗

NASA NTRS1999

Aircraft and Ground Vehicle Winter Runway Friction Assessment

Yager, Thomas J.↗

NASA NTRS1994

Development of a Rotating Human Research Facility

A unique facility has been developed at the NASA Ames Research Center to provide scientists with unusual research opportunities at greater than Earth's gravity. In addition to its use for basic research, this facility will help provide answers to many of the questions posed by proponents of rotating human space vehicles. This paper describes the design and planned use of this facility, the Spaceflight Environmental Simulator. Using an existing 52-foot diameter cylindrical rotating platform design centrifuge, the revised facility design includes the provision of two human habitats for long duration studies of the effects of hypergravity. Up to four humans (per habitat) will be able to live at up to 2 G for as long as one month without stopping the centrifuge. Each habitat, constructed of lightweight honeycomb sandwich panels, is nominally 9 ft high x 11 ft wide x 25 1/2 ft long. A radial positioning system provides for positioning each habitat at a distance of 15 to 21 feet from the centrifuge's axis of rotation to the midpoint of the habitat's interior floor. As centrifugal acceleration changes with rotation rate, a habitat floor-mounted accelerometer signal provides automatic servo controlled adjustment of each habitat's angle of inclination to provide an environment for the habitat's crew and cargo in which the resultant gravity vector is normal to the habitat floor at all times. Design of the habitats and modifications to the centrifuge are complete, and are currently under construction. Design philosophy and operational rationale are presented along with complete descriptions of the facility and its systems.

Mulenburg, Gerald M.↗

NASA NTRS1981

On the injection and scattering of protons in Jupiter's magnetosphere

The interaction, scattering, and acceleration of Jovian ions through magnetohydrodynamic waves are investigated. A model of the Alfven speed in the plasma sheet for both inbound and outbound legs of the Voyager 1 encounter is presented, and underlying assumptions are discussed. Theoretical ingredients of a rotationally driven Jovian substorm are defined, and the convective growth rate of the fast wave for both a warm and a cold beam is derived. The mean-free path for scattering based on in situ measurements of magnetic fluctuations in the plasma sheet is estimated, and the results indicate that scattering of super-Alfvenic ions occurs on a regular basis throughout the plasma sheet, and the observed level of magnetic fluctuations is sufficiently high to stop ionospheric protons.

Barbosa, D. D.↗

NASA NTRS2016

Field Test: Results of Tandem Walk Performance Following Long-Duration Spaceflight

BACKGROUND: Coordinated locomotion has proven to be challenging for many astronauts following long duration spaceflight. As NASA's vision for spaceflight points toward interplanetary travel, we must prepare for unassisted landings, where crewmembers may need to perform mission critical tasks within minutes of landing. Thus, it is vital to develop a knowledge base from which operational guidelines can be written that define when astronauts can be expected to safely perform certain tasks. Data obtained during the Field Test experiment (FT) will add important insight to this knowledge base. Specifically, we aim to develop a recovery timeline of functional sensorimotor performance during the first 24 hours and several days after landing. METHODS: FT is an ongoing study of 30 long-duration ISS crewmembers. Thus far, 9 have completed the full FT (5 U.S. Orbital Segment [USOS] astronauts and 4 Russian cosmonauts) and 4 more consented and launching within the next year. This is in addition to the eighteen crewmembers that participated in the pilot FT (11 USOS and 7 Russian crewmembers). The FT is conducted three times preflight and three times during the first 24 hours after landing. All crewmembers were tested in Kazakhstan in either the medical tent at the Soyuz landing site (~one hour post-landing), or at the airport (~four hours post-landing). The USOS crewmembers were also tested at the refueling stop (~12 hours post-landing) and at the NASA Johnson Space Center (~24 hours post-landing) and a final session 7 days post-landing. Crewmembers are instrumented with 9 inertial measurement unit sensors that measure acceleration and angular displacement (APDM's Emerald Sensors) and foot pressure-sensing insoles that measure force, acceleration, and center of pressure (Moticon GmbH, Munich, Germany) along with heart rate and blood pressure recording instrumentation. The FT consists of 12 tasks, but here we will focus on the most challenging task, the Tandem Walk, which was also performed as part of pilot FT. To perform the Tandem Walk, subjects begin with their feet together, their arms crossed at their chest and eyes closed. When ready, they brought one foot forward and touched the heel of their foot to their toe, repeating with the other foot, and continuing for about 10 steps. Three trials were collected with the eyes closed and a fourth trial was collected with eyes open. There are four metrics which are used to determine the performance level of the Tandem Walk. The first is percent correct steps. For a step to be counted as correct, the foot could not touch the ground while bringing it forward (no side stepping), eyes must stay closed during the eyes closed trials, the heel and toe should be touching, or almost touching (no large gaps) and there shouldn't be more than a three second pause between steps. Three judges score each step and the median of the three scores is kept. The second metric is the average step speed, or the number of steps/time to complete them. Thirdly, the root mean squared (RMS) error in the resultant trunk acceleration is used to determine the amount of upper body instability observed during the task. Finally, the RMS error of the mediolateral center of pressure as measured by the Moticon insoles is used to determine the mediolateral instability at the foot level. These four parameters are combined into a new overall Tandem Walk Parameter. RESULTS: Preliminary results show that crewmembers perform the Tandem Walk significantly worse the first 24 hours after landing as compared to their baseline performance. We find that each of the four performance metrics is significantly worse immediately after landing. We will present the results of tandem walk performance during the FT thus far. We will also combine these with the 18 crewmembers that participated in the pilot FT, concentrating on the level of performance and recovery rate. CONCLUSION: The Tandem Walk data collected as part of the FT experiment will provide invaluable information on the performance capabilities of astronauts during the first 24 hours after returning from long-duration spaceflight that can be used in planning future Mars, or other deep-space missions with unassisted landings. FT will determine the average sensorimotor recovery timeline and inform return-to-duty guidelines for unassisted landings.

Rosenberg, M. J. F.↗

NASA NTRS2001

The Runaway Greenhouse Effect on Earth and other Planets

Water vapor is an efficient absorber of outgoing longwave infrared radiation on Earth and is the primary greenhouse gas. Since evaporation increases with increasing sea surface temperature, and the increase in water vapor further increases greenhouse warming, there is a positive feedback. The runaway greenhouse effect occurs if this feedback continues unchecked until all the water has left the surface and enters the atmosphere. For Mars and the Earth the runaway greenhouse was halted when water vapor became saturated with respect to ice or liquid water respectively. However, Venus is considered to be an example of a planet where the runaway greenhouse effect did occur, and it has been speculated that if the solar luminosity were to increase above a certain limit, it would also occur on the Earth. Satellite data acquired during the Earth Radiation Budget Experiment (ERBE) under clear sky conditions shows that as the sea surface temperature (SST) increases, the rate of outgoing infrared radiation at the top of the atmosphere also increases, as expected. Over the pacific warm pool where the SST exceeds 300 K the outgoing radiation emitted to space actually decreases with increasing SST, leading to a potentially unstable system. This behavior is a signature of the runaway greenhouse effect on Earth. However, the SST never exceeds 303K, thus the system has a natural cap which stops the runaway. According to Stefan-Boltzmann's law the amount of heat energy radiated by the Earth's surface is proportional to (T(sup 4)). However, if the planet has a substantial atmosphere, it can absorb all infrared radiation from the lower surface before the radiation penetrates into outer space. Thus, an instrument in space looking at the planet does not detect radiation from the surface. The radiation it sees comes from some level higher up. For the earth#s atmosphere the effective temperature (T(sub e)) has a value of 255 K corresponding to the middle troposphere, above most of the water vapor and clouds. "Additional information is contained in the original extended abstract."

Rabbette, Maura↗