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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

Test and Analysis of a Hyper-X Carbon-Carbon Leading Edge Chine

During parts production for the X43A Mach 10 hypersonic vehicle nondestructive evaluation (NDE) of a leading edge chine detected on imbedded delamination near the lower surface of the part. An ultimate proof test was conducted to verify the ultimate strength of this leading edge chine part. The ultimate proof test setup used a pressure bladder design to impose a uniform distributed pressure field over the bi-planar surface of the chine test article. A detailed description of the chine test article and experimental test setup is presented. Analysis results from a linear status model of the test article are also presented and discussed. Post-test inspection of the specimen revealed no visible failures or areas of delamination.

Smith, Russell W.↗
NASA NTRS2006

Inflatable Structures: Test Results and Development Progress Since TransHab

JSC's TransHab project was the first successful development program to prove the viability of inflatable habitats for space applications. Although TransHab was cancelled in 2000, significant progress has been made this past year by JSC engineers. Since February 2005, the following test articles have been manufactured and tested: 1 - An 88-in diameter restraint layer was pressure-tested to failure and reached an ultimate pressure of 197psi. This test article demonstrated the ability to build a 35- foot diameter inflatable with a factor of safety of 4.0 at 10.2 psi. 2 - An 88-in diameter restraint layer with a window frame incorporated into the restraint layer was tested to failure and reached an ultimate pressure of 197 psi. This test article demonstrated the ability to incorporate windows and other structural penetrations in the woven restraint layer without reducing its strength. 3 - An 88-inch diameter folding demonstrator that includes a bladder, restraint layer, and all of the MMOD shell layers was manufactured and assembled. This test article demonstrated an improved and simplified shell assembly and folding technique which installs pre-folded shell sections in a controlled manner. 4 - Fifth-scale MMOD hypervelocity test articles have demonstrated fiberglass as a viable material for a MMOD bumper shield which is cheaper and more readily available than previously used materials. In addition, four different full-scale advanced shape inflatable mockups have been manufactured and evaluated for applications such as lunar habitats, airlocks, and transfer tunnels.

Johnson, Chris↗
NASA NTRS2006

Studying Host-Pathogen Interactions In 3-D: Organotypic Models For Infectious Disease And Drug Development

Representative, reproducible and high-throughput models of human cells and tissues are critical for a meaningful evaluation of host-pathogen interactions and are an essential component of the research developmental pipeline. The most informative infection models - animals, organ explants and human trials - are not suited for extensive evaluation of pathogenesis mechanisms and screening of candidate drugs. At the other extreme, more cost effective and accessible infection models such as conventional cell culture and static co-culture may not capture physiological and three-dimensional aspects of tissue biology that are important in assessing pathogenesis, and effectiveness and cytotoxicity of therapeutics. Our lab has used innovative bioengineering technology to establish biologically meaningful 3-D models of human tissues that recapitulate many aspects of the differentiated structure and function of the parental tissue in vivo, and we have applied these models to study infectious disease. We have established a variety of different 3-D models that are currently being used in infection studies - including small intestine, colon, lung, placenta, bladder, periodontal ligament, and neuronal models. Published work from our lab has shown that our 3-D models respond to infection with bacterial and viral pathogens in ways that reflect the infection process in vivo. By virtue of their physiological relevance, 3-D cell cultures may also hold significant potential as models to provide insight into the neuropathogenesis of HIV infection. Furthermore, the experimental flexibility, reproducibility, cost-efficiency, and high throughput platform afforded by these 3-D models may have important implications for the design and development of drugs with which to effectively treat neurological complications of HIV infection.

Nickerson, Cheryl A.↗
NASA NTRS2006

Robots in Space -Psychological Aspects

A viewgraph presentation on the psychological aspects of developing robots to perform routine operations associated with monitoring, inspection, maintenance and repair in space is shown. The topics include: 1) Purpose; 2) Vision; 3) Current Robots in Space; 4) Ground Based Robots; 5) AERCam; 6) Rotating Bladder Robot (ROBLR); 7) DART; 8) Robonaut; 9) Full Immersion Telepresence Testbed; 10) ERA; and 11) Psychological Aspects

Sipes, Walter E.↗
NASA NTRS1978

Oil Saving Seal

Driven under difficult field conditions, the Army Jeep shown went more than 22,000 miles without an oil change in a test conducted by the U.S. Army Mobility Equipment Research and Development Command. Key to this exceptionally long oil life was a set of piston ring seals made of a new synthetic rubber formula called RC-34; the seal pictured, photographed after its arduous Army trial, shows no signs of deterioration. The seal and the RC-34 material, which may soon be available for use in the family auto, were developed by Ramsey Corporation, St. Louis, Missouri, a division of TRW Automotive Worldwide. The oil in an automobile engine must be I replaced every few thousand miles not because it wears out but because it becomes contaminated. The contamination sources are gasoline and combustion gases which blow by the piston rings to mix with the oil, reducing the oil's ability to lubricate properly. Seeking to prolong oil life by eliminating "blowby," Ramsey Corporation looked for a better way to seal piston rings and used NASA technology as a departure point. The parent company TRW, under contract to NASA's Jet Propulsion Laboratory, had developed seals and bladders from a type of material called elastomers which where designed to withstand the environmental extremes of interplanetary flight. That effort formed a knowledge base for research which culminated in Ramsey's RC-34 elastomer.

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NASA NTRS2007

Extravehicular Mobility Unit Penetration Probability from Micrometeoroids and Orbital Debris: Revised Analytical Model and Potential Space Suit Improvements

The NASA Extravehicular Mobility Unit (EMU) micrometeoroid and orbital debris protection ability has recently been assessed against an updated, higher threat space environment model. The new environment was analyzed in conjunction with a revised EMU solid model using a NASA computer code. Results showed that the EMU exceeds the required mathematical Probability of having No Penetrations (PNP) of any suit pressure bladder over the remaining life of the program (2,700 projected hours of 2 person spacewalks). The success probability was calculated to be 0.94, versus a requirement of >0.91, for the current spacesuit s outer protective garment. In parallel to the probability assessment, potential improvements to the current spacesuit s outer protective garment were built and impact tested. A NASA light gas gun was used to launch projectiles at test items, at speeds of approximately 7 km per second. Test results showed that substantial garment improvements could be made, with mild material enhancements and moderate assembly development. The spacesuit s PNP would improve marginally with the tested enhancements, if they were available for immediate incorporation. This paper discusses the results of the model assessment process and test program. These findings add confidence to the continued use of the existing NASA EMU during International Space Station (ISS) assembly and Shuttle Operations. They provide a viable avenue for improved hypervelocity impact protection for the EMU, or for future space suits.

Chase, Thomas D.↗
NASA NTRS2006

Novel Thermal Powered Technology for UUV Persistent Surveillance

Buoyancy Generation: Various technology attempts include melting a wax, which pushes directly against a piston (U.S. Patent 5,291,847) or against a bladder (Webb Research), using ammonia or Freon 21 (U.S. Patent 5,303,552), and using solar heat to expand an oil (www.space.com, April, 10, 2002). All these heat-activated buoyancy control designs have thus far proved impractical and have ultimately failed during repeated cycling in ocean testing. JPL has demonstrated fully reversible 10 C encapsulated wax phase change, which can be used to change buoyancy without electrical hydraulic pumps. This technique has greatly improved heat transfer and much better reversibility than previous designs. Power Generation: Ocean Thermal Energy Conversion (OTEC) systems have been designed that transfer deep, cold sea water to the surface to generate electricity using turbine cycles with ammonia or water as the working fluid. JPL has designed several UUV systems: 1) Using a propeller water turbine to generate power on a gliding submersible; 2) Employing a compact CO2 turbine cycle powered by moving through thermoclines; and 3) Using melted wax to directly produce power through a piston-geared generator.

submersible↗
NASA NTRS1989

Lightweight device to stimulate and monitor human vestibulo-ocular reflex

A helmet formed of a rigid shell is disclosed. The shell is lined with several air filled bladders to contact firmly the head of a user. The shell has a rigid chin bar supporting a bite bar connected fixedly to a mouthpiece bearing against the teeth and hard palate to firmly anchor the helmet without movement. The outer shell surface supports various air pumping bulbs and accelerometers. Separate left and right visor pivot on the side guided in a central tongue and groove track to move optical lens mounts into the user's field of vision. The chin bar is connected to the shell by a pair of releasable clasps. A safety lanyard connects to the clasps to quickly pull pins from the clasps to enable quick release in case of motion sickness.

McStravick, M. Catherine↗
NASA NTRS2008

Graded Compression Stockings Prevent Post-spaceflight Orthostatic Hypotension

Post-spaceflight orthostatic intolerance is characterized by hypotension and presyncope in 20-30% of returning astronauts. Previous data from our laboratory suggests that this is largely a result of decreased venous return. Currently, NASA astronauts wear an anti-gravity suit (AGS) which consists of inflatable air bladders over the calves, thighs and abdomen, which are typically pressurized from 0.5 to 1.5 PSI (~27 to 78 mmHg). ISS crew members sometimes wear Russian Kentavr suits which consist of laced compression shorts and gaiters, providing ~30 mmHg nominally. While these garments are effective during reentry, there are a number of drawbacks that make them impractical for postflight use. We studied the ability of commercially available, custom fit, graded compression stockings (Jobst, 55 mmHg at ankle to 6 mmHg at top of thigh, 25 mmHg mean compression) to prevent postflight orthostatic intolerance, hypothesizing that these garments would prevent orthostatic intolerance following short duration space flight. Crew members from a single Space Shuttle flight were tilted to 80 degrees for 10 min while wearing the stockings (n=5 males) upon arrival at the clinic (~2 hrs after landing). Hemodynamic data were compared to data from all crewmembers tilted (without countermeasures) since return to flight (n=9). Two-way, repeated measures ANOVA, using the entire tilt time curve (0-10 min) show that systolic blood pressure (SBP, group effect p=0.008), stroke volume (SV, group effect p=0.003), and cardiac output (CO, group effect p=0.004) were higher in crewmembers who wore the Jobst stockings. A one-way ANOVA comparing the last minute standing also showed that SV (p=0.001) and CO (p less than 0.001) were higher and SBP tended to be higher (p=0.06) in Jobst subjects compared to controls. Control subjects had a higher rate of presyncope than Jobst subjects (3/9 vs 0/5) during the tilt on landing day. Orthostatic hypotension continues to present following spaceflight, despite fluid loading and other countermeasures. This preliminary study shows that commercially available compression stockings may ameliorate this problem. These stockings are readily available, inexpensive, and can be worn for days following landing. We have observed similar protection against orthostatic intolerance in ground-based studies of hypovolemic test subjects. Further refinements to the design and compression of the stockings are in progress.

Platts, S. H.↗
NASA NTRS2009

Utilizing Ocean Thermal Energy in a Submarine Robot

A proposed system would exploit the ocean thermal gradient for recharging the batteries in a battery-powered unmanned underwater vehicle [UUV (essentially, a small exploratory submarine robot)] of a type that has been deployed in large numbers in research pertaining to global warming. A UUV of this type travels between the ocean surface and depths, measuring temperature and salinity. The proposed system is related to, but not the same as, previously reported ocean thermal energy conversion (OTEC) systems that exploit the ocean thermal gradient but consist of stationary apparatuses that span large depth ranges. The system would include a turbine driven by working fluid subjected to a thermodynamic cycle. CO2 has been provisionally chosen as the working fluid because it has the requisite physical properties for use in the range of temperatures expected to be encountered in operation, is not flammable, and is much less toxic than are many other commercially available refrigerant fluids. The system would be housed in a pressurized central compartment in a UUV equipped with a double hull (see figure). The thermodynamic cycle would begin when the UUV was at maximum depth, where some of the CO2 would condense and be stored, at relatively low temperature and pressure, in the annular volume between the inner and outer hulls. The cycle would resume once the UUV had ascended to near the surface, where the ocean temperature is typically greater than or equals 20 C. At this temperature, the CO2 previously stored at depth in the annular volume between the inner and outer hulls would be pressurized to approx. equals 57 bar (5.7 MPa). The pressurized gaseous CO2 would flow through a check valve into a bladder inside the pressurized compartment, thereby storing energy of the relatively warm, pressurized CO2 for subsequent use after the next descent to maximum depth.

Jones, Jack↗
NASA NTRS2009

Hypervelocity Impacts on ISS Handrails and Evaluation of Alternative Materials to Prevent Extravehicular Mobility Unit (EMU) Glove Damage During EVA

During post-flight processing of STS-116, damage to crewmember Robert Curbeam's Phase VI Glove Thermal Micrometeoroid Garment was discovered. This damage consisted of: loss of RTV-157 palm pads on the thumb area on the right glove, a 0.75 inch cut in the Vectran adjacent to the seam and thumb pad (single event cut), constituting the worst glove damage ever recorded for the U.S. space program. The underlying bladder and restraint were found not be damaged by this event. Evaluation of glove damage found that the outer Vectran fibers were sliced as a result of contact with a sharp edge or pinch point rather than general wear or abrasion (commonly observed on the RTV pads). Damage to gloves was also noted on STS-118 and STS-120. One potential source of EMU glove damages are sharp crater lips on external handrails, generated by micrometeoroid and orbital debris (MMOD) impacts. In this paper, the results of a hypervelocity impact (HVI) test program on representative and actual ISS handrails are presented. These tests were performed in order to characterize impact damage profiles on ISS handrails and evaluate alternatives for limiting risk to future missions. It was determined that both penetrating and non-penetrating MMOD impacts on aluminum and steel ISS handrails are capable of generating protruding crater profiles which exceed the heights required for EMU glove abrasion risk by an order of magnitude. Testing demonstrated that flexible overwraps attached to the outside of existing handrails are capable of limiting contact between hazardous crater formations and crewmember gloves during extravehicular activity (EVA). Additionally, replacing metallic handrails with high strength, low ductility, fiber reinforced composite materials would limit the formation of protruding crater lips on new ISS modules.

Ryan, Shannon↗
NASA NTRS2009

Water Vapor Permeability of the Advanced Crew Escape Suit

Crew Exploration Vehicle (CEV) crewmembers are expected to return to earth wearing a suit similar to the current Advanced Crew Escape Suit (ACES). To ensure optimum cognitive performance, suited crewmembers must maintain their core body temperature within acceptable limits. There are currently several options for thermal maintenance in the post-landing phase. These include the current baseline, which uses an ammonia boiler, purge flow using oxygen in the suit, accessing sea water for liquid cooling garment (LCG) cooling and/or relying on the evaporative cooling capacity of the suit. These options vary significantly in mass, power, engineering and safety factors, with relying on the evaporative cooling capacity of the suit being the least difficult to implement. Data from previous studies indicates that the evaporative cooling capacity of the ACES was much higher than previously expected, but subsequent tests were performed for longer duration and higher metabolic rates to better define the water vapor permeability of the ACES. In these tests five subjects completed a series of tests performing low to moderate level exercise in order to control for a target metabolic rate while wearing the ACES in an environmentally controlled thermal chamber. Four different metabolic profiles at a constant temperature of 95 F and relative humidity of 50% were evaluated. These tests showed subjects were able to reject about twice as much heat in the permeable ACES as they were in an impermeable suit that had less thermal insulation. All of the heat rejection differential is attributed to the increased evaporation capability through the Gortex bladder of the suit.

Bue, Grant↗
NASA NTRS2009

Splanchnic Compression Improves the Efficacy of Compression Stockings to Prevent Orthostatic Intolerance

Purpose: Post-spaceflight orthostatic intolerance (OI) is observed in 20-30% of astronauts. Previous data from our laboratory suggests that this is largely a result of decreased venous return. Currently, NASA astronauts wear an anti-gravity suit (AGS) which consists of inflatable air bladders over the calves, thighs and abdomen, typically pressurized from 26 to 78 mmHg. We recently determined that, thigh-high graded compression stockings (JOBST , 55 mmHg at ankle, 6 mmHg at top of thigh) were effective, though to a lesser degree than the AGS. The purpose of this study was to evaluate the addition of splanchnic compression to prevent orthostatic intolerance. Methods: Ten healthy volunteers (6M, 4F) participated in three 80 head-up tilts on separate days while (1) normovolemic (2) hypovolemic w/ breast-high compression stockings (BS)(JOBST(R), 55 mmHg at the ankle, 6 mmHg at top of thigh, 12 mmHg over abdomen) (3) hypovolemic w/o stockings. Hypovolemia was induced by IV infusion of furosemide (0.5 mg/kg) and 48 hrs of a low salt diet to simulate plasma volume loss following space flight. Hypovolemic testing occurred 24 and 48 hrs after furosemide. One-way repeated measures ANOVA, with Bonferroni corrections, was used to test for differences in blood pressure and heart rate responses to head-up tilt, stand times were compared using a Kaplan-Meyer survival analysis. Results: BS were effective in preventing OI and presyncope in hypovolemic test subjects ( p = 0.015). BS prevented the decrease in systolic blood pressure seen during tilt in normovolemia (p < 0.001) and hypovolemia w/o countermeasure (p = 0.005). BS also prevented the decrease in diastolic blood pressure seen during tilt in normovolemia (p = 0.006) and hypovolemia w/o countermeasure (p = 0.041). Hypovolemia w/o countermeasure showed a higher tilt-induced heart rate increase (p = 0.022) than seen in normovolemia; heart rate while wearing BS was not different than normovolemia (p = 0.353). Conclusion: BS may be an effective countermeasure to post-space flight OI. The addition of splanchnic compression is more effective than the previous thigh-high garments. These stockings are readily available, inexpensive, and can be worn for days following landing as astronauts re-adapt to Earth gravity.

Platts, Steven H.↗
NASA NTRS2009

NASA Tech Briefs, December 2009

Topics include: A Deep Space Network Portable Radio Science Receiver; Detecting Phase Boundaries in Hard-Sphere Suspensions; Low-Complexity Lossless and Near-Lossless Data Compression Technique for Multispectral Imagery; Very-Long-Distance Remote Hearing and Vibrometry; Using GPS to Detect Imminent Tsunamis; Stream Flow Prediction by Remote Sensing and Genetic Programming; Pilotless Frame Synchronization Using LDPC Code Constraints; Radiometer on a Chip; Measuring Luminescence Lifetime With Help of a DSP; Modulation Based on Probability Density Functions; Ku Telemetry Modulator for Suborbital Vehicles; Photonic Links for High-Performance Arraying of Antennas; Reconfigurable, Bi-Directional Flexfet Level Shifter for Low-Power, Rad-Hard Integration; Hardware-Efficient Monitoring of I/O Signals; Video System for Viewing From a Remote or Windowless Cockpit; Spacesuit Data Display and Management System; IEEE 1394 Hub With Fault Containment; Compact, Miniature MMIC Receiver Modules for an MMIC Array Spectrograph; Waveguide Transition for Submillimeter-Wave MMICs; Magnetic-Field-Tunable Superconducting Rectifier; Bonded Invar Clip Removal Using Foil Heaters; Fabricating Radial Groove Gratings Using Projection Photolithography; Gratings Fabricated on Flat Surfaces and Reproduced on Non-Flat Substrates; Method for Measuring the Volume-Scattering Function of Water; Method of Heating a Foam-Based Catalyst Bed; Small Deflection Energy Analyzer for Energy and Angular Distributions; Polymeric Bladder for Storing Liquid Oxygen; Pyrotechnic Simulator/Stray-Voltage Detector; Inventions Utilizing Microfluidics and Colloidal Particles; RuO2 Thermometer for Ultra-Low Temperatures; Ultra-Compact, High-Resolution LADAR System for 3D Imaging; Dual-Channel Multi-Purpose Telescope; Objective Lens Optimized for Wavefront Delivery, Pupil Imaging, and Pupil Ghosting; CMOS Camera Array With Onboard Memory; Quickly Approximating the Distance Between Two Objects; Processing Images of Craters for Spacecraft Navigation; Adaptive Morphological Feature-Based Object Classifier for a Color Imaging System; Rover Slip Validation and Prediction Algorithm; Safety and Quality Training Simulator; Supply-Chain Optimization Template; Algorithm for Computing Particle/Surface Interactions; Cryogenic Pupil Alignment Test Architecture for Aberrated Pupil Images; and Thermal Transport Model for Heat Sink Design.

Source record↗
NASA NTRS2010

Improved Attachment in a Hybrid Inflatable Pressure Vessel

The vessel is a hybrid that comprises an inflatable shell attached to a rigid structure. The inflatable shell is, itself, a hybrid that comprises (1) a pressure bladder restrained against expansion by (2) a restraint layer that comprises a web of straps made from high-strength polymeric fabrics. The present improvements are intended to overcome deficiencies in those aspects of the original design that pertain to attachment of the inflatable shell to the rigid structure. In a typical intended application, such attachment(s) would be made at one or more window or hatch frames to incorporate the windows or hatches as integral parts of the overall vessel.

Johnson, Christopher J.↗
NASA NTRS2010

Intelligent Flexible Materials for Space Structures: Expandable Habitat Engineering Development Unit

Expandable habitable elements are an enabling technology for human exploration in space and on planetary surfaces. Large geometries can be deployed from a small launch volume, allowing greater mission capability while reducing mass and improving robustness over traditional rigid shells. This report describes research performed by ILC Dover under the Intelligent Flexible Materials for Space Structures program on the design and manufacture of softgoods for LaRC's Expandable Habitat Engineering Development Unit (EDU). The EDU is a full-scale structural test article of an expandable hybrid habitat, integrating an expandable softgoods center section with two rigid end caps. The design of the bladder, restraint layer and a mock-up Thermal Micrometeoroid Cover is detailed together with the design of the interface hardware used to attach them to the end caps. The integration and design of two windows and a floor are also covered. Analysis was performed to study the effects of the open weave design, and to determine the correct webbing and fabric configuration. Stress analyses were also carried out on the interfaces between the softgoods and the end caps and windows. Testing experimentally determined the strength of the fabric and straps, and component testing was used to proof several critical parts of the design. This program established new manufacturing and design techniques that can be applied to future applications in expandable structures.

Hinkle, Jon↗
NASA NTRS2009

A New View of Radiation-Induced Cancer: Integrating Short- and Long-Term Processes. Part II: Second Cancer Risk Estimation

As the number of cancer survivors grows, prediction of radiotherapy-induced second cancer risks becomes increasingly important. Because the latency period for solid tumors is long, the risks of recently introduced radiotherapy protocols are not yet directly measurable. In the accompanying article, we presented a new biologically based mathematical model, which, in principle, can estimate second cancer risks for any protocol. The novelty of the model is that it integrates, into a single formalism, mechanistic analyses of pre-malignant cell dynamics on two different time scales: short-term during radiotherapy and recovery; long-term during the entire life span. Here, we apply the model to nine solid cancer types (stomach, lung, colon, rectal, pancreatic, bladder, breast, central nervous system, and thyroid) using data on radiotherapy-induced second malignancies, on Japanese atomic bomb survivors, and on background US cancer incidence. Potentially, the model can be incorporated into radiotherapy treatment planning algorithms, adding second cancer risk as an optimization criterion.

Shuryak, Igor↗
NASA NTRS2011

Comparison of Organ Dosimetry for Astronaut Phantoms: Earth-Based vs. Microgravity-Based Anthropometry and Body Positioning

The purpose of this study is to use NASA radiation transport codes to compare astronaut organ dose equivalents resulting from solar particle events (SPE), geomagnetically trapped protons, and free-space galactic cosmic rays (GCR) using phantom models representing Earth-based and microgravity-based anthropometry and positioning. Methods: The Univer sity of Florida hybrid adult phantoms were scaled to represent male and female astronauts with 5th, 50th, and 95th percentile heights and weights as measured on Earth. Another set of scaled phantoms, incorporating microgravity-induced changes, such as spinal lengthening, leg volume loss, and the assumption of the neutral body position, was also created. A ray-tracer was created and used to generate body self-shielding distributions for dose points within a voxelized phantom under isotropic irradiation conditions, which closely approximates the free-space radiation environment. Simplified external shielding consisting of an aluminum spherical shell was used to consider the influence of a spacesuit or shielding of a hull. These distributions were combined with depth dose distributions generated from the NASA radiation transport codes BRYNTRN (SPE and trapped protons) and HZETRN (GCR) to yield dose equivalent. Many points were sampled per organ. Results: The organ dos e equivalent rates were on the order of 1.5-2.5 mSv per day for GCR (1977 solar minimum) and 0.4-0.8 mSv per day for trapped proton irradiation with shielding of 2 g cm-2 aluminum equivalent. The organ dose equivalents for SPE irradiation varied considerably, with the skin and eye lens having the highest organ dose equivalents and deep-seated organs, such as the bladder, liver, and stomach having the lowest. Conclus ions: The greatest differences between the Earth-based and microgravity-based phantoms are observed for smaller ray thicknesses, since the most drastic changes involved limb repositioning and not overall phantom size. Improved self-shielding models reduce the overall uncertainty in organ dosimetry for mission-risk projections and assessments for astronauts

VanBaalen, Mary↗