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NASA NTRS1978

The prospects for composites based on boron fibers

The fabrication of boron filaments and the production of composite materials consisting of boron filaments and organic or metallic matrices are discussed. Problem involving the use of tungsten substrates in the filament fabrication process, the protection of boron fibers with diffusion barrier cladings, and the application of alloy additives in the matrix to lessen the effects of diffusion are considered. Data on the kinetics of the boron fiber/matrix interaction at high temperatures, and the influence of the fiber/matrix interaction on the mechanical properties of the composite are presented.

Naslain, R.↗

NASA NTRS1985

System technology analysis of aeroassisted orbital transfer vehicles. Moderate lift/drag (0.75-1.5). Volume 1A, part 1: Executive summary, phase 1

Activities and significant results of Phase 1 of a study to access aeroassisted orbit transfer vehicle (AOTV) system technology are summarized. Broad concept evaluations were performed and the technology requirements and sensitivities for ground based AOTV's over a range of vehicle hypersonic lift/drag (L/D) from 0.75 to 1.5 were systematically identified and assessed. The four major task areas included systems analysis, system/subsystem trades, technology payoff assessment and plan, and cost analysis. Findings indicate that substantial performance improvements and hence cost benefit can be obtained by developing enhanced technologies such as: (1) low thrust advanced expander LOX-hydrogen engines with specific impulse of 480 to 490 sec; (2) reducing the external thermal protection system weight and increasing the maximum allowable bond/structure temperature; and (3) reducing the structural shell weight by improving the quality of the design allowable data, or use of advanced structural materials. Results also show that use of mid L/D AOTV's provide significant aerodynamic plane change capability and control authority over trajectory dispersions and off-nominal atmospheres.

Source record↗

NASA NTRS1986

Finite-element reentry heat-transfer analysis of space shuttle Orbiter

A structural performance and resizing (SPAR) finite-element thermal analysis computer program was used in the heat-transfer analysis of the space shuttle orbiter subjected to reentry aerodynamic heating. Three wing cross sections and one midfuselage cross section were selected for the thermal analysis. The predicted thermal protection system temperatures were found to agree well with flight-measured temperatures. The calculated aluminum structural temperatures also agreed reasonably well with the flight data from reentry to touchdown. The effects of internal radiation and of internal convection were found to be significant. The SPAR finite-element solutions agreed reasonably well with those obtained from the conventional finite-difference method.

Ko, William L.↗

NASA NTRS1994

Oxidation performance of platinum-clad Mo-47Re alloy

The alloy Mo-47Re has favorable mechanical properties at temperatures above 1400 C, but it undergoes severe oxidation when used in air with no protective coating. To shield the alloy from oxidation, platinum cladding has been evaluated. The unprotected alloy undergoes catastrophic oxidation under static and dynamic oxidation conditions. The platinum cladding provides good protection from static and dynamic oxidation for moderate times at 1260 C. Samples tested for longer times under static oxidation conditions experienced severe oxidation. The data suggest that oxidation results from the transport of oxygen through the grain boundaries and through the pinhole defects of the platinum cladding.

Clark, Ronald K.↗

NASA NTRS1999

EXPRESS Rack Technology for Space Station

The EXPRESS rack provides accommodations for standard Mid-deck Locker and ISIS drawer payloads on the International Space Station. A design overview of the basic EXPRESS rack and two derivatives, the Human Research Facility and the Habitat Holding Rack, is given in Part I. In Part II, the design of the Solid State Power Control Module (SSPCM) is reviewed. The SSPCM is a programmable and remotely controllable power switching and voltage conversion unit which distributes and protects up to 3kW of 12OVDC and 28VDC power to payloads and rack subsystem components. Part III details the development and testing of a new data storage device, the BRP EXPRESS Memory Unit (BEMU). The BEMU is a conduction-cooled device which operates on 28VDC and is based on Boeing-modified 9GB commercial disk-drive technology. In Part IV results of a preliminary design effort for a rack Passive Damping System (PDS) are reported. The PDS is intended to isolate ISPR-based experiment racks from on-orbit vibration. System performance predictions based on component developmental testing indicate that such a system can provide effective isolation at frequencies of 1 Hz and above.

Davis, Ted B.↗

NASA NTRS2001

Measurement of Charged Particle Interactions in Spacecraft and Planetary Habitat Shielding Materials

The Microgravity Materials Program, through its 98-HEDS-04 Research Announcement, has called for research to support 'enhanced human radiation protection through the development of light weight soft goods with high radiation protection characteristics.' Given the nature of the particle flux from the Galactic Cosmic Radiation (GCR), and the many constraints on the depth and type of shielding in spacecraft and planetary habitats, it is clear that the health risks these particles present to astronauts in deep space cannot be entirely eliminated. It is the objective of this project to develop a highly accurate model of GCR transport so that NASA can develop and validate the properties of protective shielding materials with the best available information. The validity of the GCR transport model depends in large part on having accurate and precise input data in the form of the charge-changing and fragment production cross sections for the heavy ions of greatest biological significance. The accuracy of the transport model can be evaluated and enhanced by employing the following a three-step strategy: (1) New cross section data will be made available to the NASA-Langley scientists responsible for the transport codes, and will be used as inputs to the codes; (2) The codes will be used to predict additional cross sections and/or details of the radiation field behind realistic shielding arrangements, where the materials and configurations may be quite complex. Mock-ups of the shielding configurations suitable for use in accelerator experiments will obtained by the NASA-Langley co-investigators; and (3) The transport model predictions will be tested in accelerator-based experiments. The time scale for one pass through these steps is well-suited to a four-year schedule. Over a longer term, these steps may be repeated, leading to still further refinements of the transport code, new predictions, and an additional round of measurements, until the desired predictive accuracy is achieved. The focus of this work is primarily on the first of these steps, the determination of fragmentation cross sections, which will be the main task in years one and two. The detailed strategy for carrying out the remainder of the program is more difficult to specify, as it depends on unpredictable factors such as the extent to which the transport model must be modified, schedules for accelerator time, target fabrication, etc.

Zeitlin, C.↗

NASA NTRS2003

PAIRS, The GIS-Based Incident Response System for Pennsylvania, and NASA

Over the past several years the Pennsylvania Departments of Environmental Protection (DEP), Health (DOH), and Agriculture (PDA) built the GIs-based Pennsylvania West Nile Surveillance System. That system has become a model for collecting data that has a field component, laboratory component, reporting and mapping component, and a public information component. Given the success of the West Nile Virus System and the events of September 11, 2001, DEP then embarked on the development of the Pennsylvania Incident Response System, or PAIRS. PAIRS is an effective GIs-based approach to providing a system for response to incidents of any kind, including terrorism because it is building upon the existing experience, infrastructure and databases that were successfully developed to respond to the West Nile Virus by DEP, DOH, and PDA. The proposed system can be described as one that supports data acquisition, laboratory forensics, decision making/response, and communications. Decision makers will have tools to view and analyze data from various sources and, at the same time, to communicate with the large numbers of people responding to the same incident. Recent collaborations with NASA partners are creating mechanisms for the PAIRS system to incorporate space-based and other remote sensing geophysical parameters relevant to public health assessment and management, such as surface temperatures, precipitation, land cover/land use change, and humidity. This presentation will describe the PAIRS system and outline the Pennsylvania-NASA collaboration for integration of space-based data into the PAIRS system.

Conrad, Eric↗

NASA NTRS2006

Nutritional Status in Self-Neglecting Elderly

Elder self-neglect is the most common, and most compelling form of elder mistreatment. Individuals who cannot provide the basic needs for themselves may develop social, functional, and physical deficits. The CREST project has the goal of systematically characterizing these individuals, and the objective of the study reported here is to characterize aspects of their nutritional status. Self-neglect (SN) subjects referred from Adult Protective Services were recruited and consented. Control (CN) subjects were matched for age, gender, race, and socio-economic status when possible. Reported here are data on 47 SN subjects (age 77 +/- 7, mean +/- SD; body weight 76 kg +/- 26) and 40 CN subjects (77 +/- 7, 79 kg +/- 20). Blood samples were analyzed for indices of nutritional status. SN subjects had higher serum concentrations of homocysteine (p < 0.01) and methylmalonic acid (p < 0.05). Red blood cell folate levels were lower (p < 0.01) in the SN subjects and serum folate levels tended (p < 0.07) to be lower, also. C-reactive protein concentrations were higher than 10 mg/dL in 36% of SN subjects and 18% of CN subjects. Total cholesterol and triglyceride concentrations were similar in the two groups. These data demonstrate that the self-neglecting elderly population is at risk with respect to several markers of nutritional status.

Oliver, S. Mathews↗

NASA NTRS2006

Phase II Testing of Liquid Cooling Garments Using a Sweating Manikin, Controlled by a Human Physiological Model

An Advanced Automotive Manikin (ADAM) developed at the National Renewable Energy Laboratory (NREL) is used to evaluate NASA's liquid cooling garments (LCGs) used in advanced space suits for extravehicular applications. The manikin has 120 separate heated/sweating zones and is controlled by a finite element physiological model of the human thermoregulatory system. Previous testing showed the thermal sensation and comfort followed the expected trends as the LCG inlet fluid temperature was changed. The Phase II test data demonstrates the repeatability of ADAM by retesting the baseline LCG. Skin and core temperature predictions using ADAM in an LCG/Arctic suit combination are compared to NASA physiological data to validate the manikin/model. Additional LCG configurations are assessed using the manikin and compared to the baseline LCG. Results can extend to other personal protective clothing, including HAZMAT suits, nuclear/biological/chemical protective suits, and fire protection suits.

Paul, Heather↗

NASA NTRS2011

NASA Occupant Protection Standards Development

Current National Aeronautics and Space Administration (NASA) occupant protection standards and requirements are based on extrapolations of biodynamic models, which were based on human tests performed under pre-Space Shuttle human flight programs where the occupants were in different suit and seat configurations than is expected for the Multi Purpose Crew Vehicle (MPCV) and Commercial Crew programs. As a result, there is limited statistical validity to the occupant protection standards. Furthermore, the current standards and requirements have not been validated in relevant spaceflight suit, seat configurations or loading conditions. The objectives of this study were to develop new standards and requirements for occupant protection and rigorously validate these new standards with sub-injurious human testing. To accomplish these objectives we began by determining which critical injuries NASA would like to protect for. We then defined the anthropomorphic test device (ATD) and the associated injury metrics of interest. Finally, we conducted a literature review of available data for the Test Device for Human Occupant Restraint New Technology (THOR-NT) ATD to determine injury assessment reference values (IARV) to serve as a baseline for further development. To better understand NASA s environment, we propose conducting sub-injurious human testing in spaceflight seat and suit configurations with spaceflight dynamic loads, with a sufficiently high number of subjects to validate no injury during nominal landing loads. In addition to validate nominal loads, the THOR-NT ATD will be tested in the same conditions as the human volunteers, allowing correlation between human and ATD responses covering the Orion nominal landing environment and commercial vehicle expected nominal environments. All testing will be conducted without the suit and with the suit to ascertain the contribution of the suit to human and ATD responses. In addition to the testing campaign proposed, additional data analysis is proposed to mine existing human injury and response data from other sources, including military volunteer testing, automotive Crash Injury Research Engineering Network (CIREN), and IndyCar impact and injury data. These data sources can allow a better extrapolation of the ATD responses to off-nominal conditions above the nominal range that can safely be tested. These elements will be used to develop injury risk functions for each of the injury metrics measured from the ATD. These risk functions would serve as the basis for the NASA standards. Finally, we propose defining standard test methodology for evaluating future spacecraft designs against the IARVs, including developing a star-rating system to allow crew safety comparisons between vehicles.

Somers, Jeffrey T.↗

NASA NTRS2011

Solid Rocket Booster (SRB) - Evolution and Lessons Learned During the Shuttle Program

The Solid Rocket Booster (SRB) element integrates all the subsystems needed for ascent flight, entry, and recovery of the combined Booster and Motor system. These include the structures, avionics, thrust vector control, pyrotechnic, range safety, deceleration, thermal protection, and retrieval systems. This represents the only human-rated, recoverable and refurbishable solid rocket ever developed and flown. Challenges included subsystem integration, thermal environments and severe loads (including water impact), sometimes resulting in hardware attrition. Several of the subsystems evolved during the program through design changes. These included the thermal protection system, range safety system, parachute/recovery system, and others. Obsolescence issues occasionally required component recertification. Because the system was recovered, the SRB was ideal for data and imagery acquisition, which proved essential for understanding loads and system response. The three main parachutes that lower the SRBs to the ocean are the largest parachutes ever designed, and the SRBs are the largest structures ever to be lowered by parachutes. SRB recovery from the ocean was a unique process and represented a significant operational challenge; requiring personnel, facilities, transportation, and ground support equipment. The SRB element achieved reliability via extensive system testing and checkout, redundancy management, and a thorough postflight assessment process. Assembly and integration of the booster subsystems was a unique process and acceptance testing of reused hardware components was required for each build. Extensive testing was done to assure hardware functionality at each level of stage integration. Because the booster element is recoverable, subsystems were available for inspection and testing postflight, unique to the Shuttle launch vehicle. Problems were noted and corrective actions were implemented as needed. The postflight assessment process was quite detailed and a significant portion of flight operations. The SRBs provided fully redundant critical systems including thrust vector control, mission critical pyrotechnics, avionics, and parachute recovery system. The design intent was to lift off with full redundancy. On occasion, the redundancy management scheme was needed during flight operations. This paper describes some of the design challenges, how the design evolved with time, and key areas where hardware reusability contributed to improved system level understanding.

Kanner, Howard S.↗

NASA NTRS2013

Development of the Orion Crew-Service Module Umbilical Retention and Release Mechanism

The Orion CSM umbilical retention and release mechanism supports and protects all of the cross-module commodities between the spacecrafts crew and service modules. These commodities include explosive transfer lines, wiring for power and data, and flexible hoses for ground purge and life support systems. The mechanism employs a single separation interface which is retained with pyrotechnically actuated separation bolts and supports roughly two dozen electrical and fluid connectors. When module separation is commanded, either for nominal on-orbit CONOPS or in the event of an abort, the mechanism must release the separation interface and sever all commodity connections within milliseconds of command receipt. There are a number of unique and novel aspects of the design solution developed by the Orion mechanisms team. The design is highly modular and can easily be adapted to other vehiclesmodules and alternate commodity sets. It will be flight tested during Orions Exploration Flight Test 1 (EFT-1) in 2014, and the Orion team anticipates reuse of the design for all future missions. The design packages fluid, electrical, and ordnance disconnects in a single separation interface. It supports abort separations even in cases where aerodynamic loading prevents the deployment of the umbilical arm. Unlike the Apollo CSM umbilical which was a destructive separation device, the Orion design is resettable and flight units can be tested for separation performance prior to flight.Initial development testing of the mechanisms separation interface resulted in binding failures due to connector misalignments. The separation interface was redesigned with a robust linear guide system, and the connector separation and boom deployment were separated into two discretely sequenced events. These changes addressed the root cause of the binding failure by providing better control of connector alignment. The new design was tuned and validated analytically via Monte Carlo simulation. The analytical validation was followed by a repeat of the initial test suite plus test cases at thermal extremes and test cases with imposed mechanical failures demonstrating fault tolerance. The mechanism was then exposed to the qualification vibration environment. Finally, separation testing was performed at full speed with live ordnance.All tests of the redesigned mechanism resulted in successful separation of the umbilical interface with adequate force margins and timing. The test data showed good agreement with the predictions of the Monte Carlo simulation. The simulation proved invaluable due to the number of variables affecting the separation and the uncertainty associated with each. The simulation allowed for rapid assessment of numerous trades and contingency scenarios, and can be easily reconfigured for varying commodity sets and connector layouts.

Separation↗

NASA NTRS2015

Characterization of Encapsulated Corrosion Inhibitors Containing Microparticles for Environmentally Friendly Smart Coatings

This poster presents the results obtained from experiments designed to evaluate the release properties, as well as the corrosion inhibition effectiveness, of several encapsulated corrosion inhibitors. Microencapsulation has been used in the development of environmentally friendly multifunctional smart coatings. This technique enables the incorporation of autonomous corrosion detection, inhibition and self-healing functionalities into many commercially available coating systems. Select environmentally friendly corrosion inhibitors were encapsulated in organic and inorganic pH-sensitive microparticles and their release in basic solutions was studied. The release rate results showed that the encapsulation can be tailored from fast, for immediate corrosion protection, to slow, which will provide continued long-term corrosion protection. The incorporation of several corrosion inhibitor release profiles into a coating provides effective corrosion protection properties. To investigate the corrosion inhibition efficiency of the encapsulated inhibitors, electrochemical techniques were used to obtain corrosion potential, polarization curve and polarization resistance data. These measurements were performed using the free as well as the encapsulated inhibitors singly or in combinations. Results from these electrochemical tests will be compared to those obtained from weight loss and other accelerated corrosion experiments.

Coatings↗

NASA NTRS2016

Mars 2020 Entry, Descent and Landing Instrumentation 2 (MEDLI2)

The Mars Entry Descent and Landing Instrumentation 2 (MEDLI2) sensor suite will measure aerodynamic, aerothermodynamic, and TPS performance during the atmospheric entry, descent, and landing phases of the Mars 2020 mission. The key objectives are to reduce design margin and prediction uncertainties for the aerothermal environments and aerodynamic database. For MEDLI2, the sensors are installed on both the heatshield and backshell, and include 7 pressure transducers, 17 thermal plugs, and 3 heat flux sensors (including a radiometer). These sensors will expand the set of measurements collected by the highly successful MEDLI suite, collecting supersonic pressure measurements on the forebody, a pressure measurement on the aftbody, direct heat flux measurements on the aftbody, a radiative heating measurement on the aftbody, and multiple near-surface thermal measurements on the thermal protection system (TPS) materials on both the forebody and aftbody. To meet the science objectives, supersonic pressure transducers and heat flux sensors are currently being developed and their qualification and calibration plans are presented. Finally, the reconstruction targets for data accuracy are presented, along with the planned methodologies for achieving the targets.

Aerodynamics↗

NASA NTRS2014

Dissertation Defense: Computational Fluid Dynamics Uncertainty Analysis for Payload Fairing Spacecraft Environmental Control Systems

Spacecraft thermal protection systems are at risk of being damaged due to airflow produced from Environmental Control Systems. There are inherent uncertainties and errors associated with using Computational Fluid Dynamics to predict the airflow field around a spacecraft from the Environmental Control System. This paper describes an approach to quantify the uncertainty in using Computational Fluid Dynamics to predict airflow speeds around an encapsulated spacecraft without the use of test data. Quantifying the uncertainty in analytical predictions is imperative to the success of any simulation-based product. The method could provide an alternative to traditional validation by test only mentality. This method could be extended to other disciplines and has potential to provide uncertainty for any numerical simulation, thus lowering the cost of performing these verifications while increasing the confidence in those predictions.Spacecraft requirements can include a maximum airflow speed to protect delicate instruments during ground processing. Computational Fluid Dynamics can be used to verify these requirements; however, the model must be validated by test data. This research includes the following three objectives and methods. Objective one is develop, model, and perform a Computational Fluid Dynamics analysis of three (3) generic, non-proprietary, environmental control systems and spacecraft configurations. Several commercially available and open source solvers have the capability to model the turbulent, highly three-dimensional, incompressible flow regime. The proposed method uses FLUENT, STARCCM+, and OPENFOAM. Objective two is to perform an uncertainty analysis of the Computational Fluid Dynamics model using the methodology found in Comprehensive Approach to Verification and Validation of Computational Fluid Dynamics Simulations. This method requires three separate grids and solutions, which quantify the error bars around Computational Fluid Dynamics predictions. The method accounts for all uncertainty terms from both numerical and input variables. Objective three is to compile a table of uncertainty parameters that could be used to estimate the error in a Computational Fluid Dynamics model of the Environmental Control System spacecraft system.Previous studies have looked at the uncertainty in a Computational Fluid Dynamics model for a single output variable at a single point, for example the re-attachment length of a backward facing step. For the flow regime being analyzed (turbulent, three-dimensional, incompressible), the error at a single point can propagate into the solution both via flow physics and numerical methods. Calculating the uncertainty in using Computational Fluid Dynamics to accurately predict airflow speeds around encapsulated spacecraft in is imperative to the success of future missions.

Fluid Dynamics↗

NASA NTRS2015

Reducing the Effect of Transducer Mount Induced Noise on Aeroacoustic Wind Tunnel Testing Data with a New Transducer Mount Design

Characterization of launch vehicle unsteady aerodynamics is a field best studied through experimentation, which is often carried out in the form of large scale wind tunnel testing. Measurement of the fluctuating pressures induced by the boundary layer noise is customarily made with miniature pressure transducers installed into a model of the vehicle of interest. Literature shows that noise level increases between two to five decibels (dB referenced to 20 micropascal) can be induced when the transducer surface is not mounted perfectly flush with the model outer surface. To reduce this artificially induced noise, special transducer holders have been used for aeroacoustic wind tunnel testing by NASA. This holder is a sleeve into which the transducer fits, with a cap that allows it to be mounted in a recessed hole in the model. A single hole in the holder allows the transport of the tunnel medium so the transducer can discriminate the fluctuating pressure due to the turbulent boundary layer noise. The holder is first dry fitted into the model and any difference in height between the holder and the model surface can be sanded flush. The holder is then removed from the model, the transducer glued inside the holder, and the holder replaced in the model, secured also with glue, thus eliminating the problem of noise level increases due to lack of flushness. In order to work with this holder design, special transducers have been ordered with their standard screen removed and the diaphragm moved as close to the top of the casing as possible to minimize any cavity volume. Although this greatly reduces induced noise due to the transducers being out of flush, the holders can also induce a cavity resonance that is usually at a very high frequency. This noise is termed transducer mount induced noise (XMIN). The peak of the mode can vary with the cavity depth, boundary layer noise that can excite the mode, tunnel flow medium, and the build of the transducers. Because the boundary layer flow interaction with the microphone holder seems to have some effect on the cavity resonance response, the NASA/Marshall Space Flight Center (MSFC) aeroacoustic team postulated that changing the design of the holder might reduce the cavity resonance response. An experiment was performed at the MSFC Trisonic Wind Tunnel comparing a new holder design with the traditional MSFC holder. The new holder design is intended to mimic the Kulite Semiconductors, Inc. B-screen, where the single hole of the traditional MSFC holder is replaced by a series of ten 0.007 inch diameter holes. This particular design serves to protect the transducer diaphragm as in the manufacturer's B-screen, but also increases the frequency of the XMIN such that it is not apparent in the data collected from aeroacoustic wind tunnel tests. MSFC compared the two holder designs by installing two transducers in standard holders on one side of a ten inch long ten degree cone, and two transducers in B-screen holders on the opposite side for a series of runs at different conditions. Over 11-13 February, 2013, the model was run at Mach numbers between 0.80 and 1.96 at angles of attack at 0 deg, plus or minus 1 deg, plus or minus 2 deg, plus or minus 4 deg, and plus or minus 8 deg. Model roll attitudes at 0 deg, 90 deg, and 180 deg were tested to isolate potential tunnel bias. This paper presents results from the test showing that the proposed holder design significantly reduces the influence of XMIN on measured fluctuating pressure levels.

Herron, A. J.↗

NASA NTRS2005

Human Exploration of the Moon and Mars: Space Radiation Data, Modeling and Instrumentation Needs

On January 14, 2004 President Bush announced the Vision for Space Exploration, a program for long-term human and robotic exploration of the solar system which will include a return of humans to the moon not later than 2020, followed by human missions to Mars. Since this announcement, NASA has been developing plans and mission architectures for these human missions as well as robotic precursor missions. Among the critical needs for research and development in support of this Vision are investigations on the ionizing radiation environment and development of instrumentation to guide NASA in managing the radiation exposure of the crew during the manned missions. For mission planning, models are needed for a reference worst-case solar energetic particle event and a reference worst-case galactic cosmic ray environment. During Lunar missions it will be necessary to carefully manage the radiation exposure of the crew in real time because of the variability of the radiation environment due to solar activity. In particular, prompt warnings will be needed when large solar energetic particle events occur. Accurate predictions will also be needed of the particle flux and flux history at the moon to support critical mission management decisions. A new generation of dosimeters and radiation monitors will also be needed to accompany the crew. These instruments must return data in real time so that they can be used in the critical decisions that must be made if a large solar energetic particle event occurs. This is especially true if it occurs during a lunar excursion. A substantial radiation exposure on extended lunar missions and Mars missions comes from galactic cosmic rays. This exposure must be mitigated by radiation shielding and other measures. During Mars missions the galactic cosmic ray exposure occurs primarily during the cruse phase between the Earth and Mars. This is especially true for opposition class missions. These missions would typically last -430 days with only 30-90 days on Mars. Solar energetic particle events are less of a concern on Mars because of its greater distance from the Sun (approximately 1.5 AU) and the partial protection afforded by its atmosphere (approximately 20 grams per square centimeter). The talk will describe the current plans for future human missions to Earth orbit, the Moon and Mars. The needs for data and models of the radiation environment and radiation detectors to support these missions will be discussed.

Adams, James H.↗

NASA NTRS2014

Dissertation Defense Computational Fluid Dynamics Uncertainty Analysis for Payload Fairing Spacecraft Environmental Control Systems

Spacecraft thermal protection systems are at risk of being damaged due to airflow produced from Environmental Control Systems. There are inherent uncertainties and errors associated with using Computational Fluid Dynamics to predict the airflow field around a spacecraft from the Environmental Control System. This paper describes an approach to quantify the uncertainty in using Computational Fluid Dynamics to predict airflow speeds around an encapsulated spacecraft without the use of test data. Quantifying the uncertainty in analytical predictions is imperative to the success of any simulation-based product. The method could provide an alternative to traditional "validation by test only" mentality. This method could be extended to other disciplines and has potential to provide uncertainty for any numerical simulation, thus lowering the cost of performing these verifications while increasing the confidence in those predictions. Spacecraft requirements can include a maximum airflow speed to protect delicate instruments during ground processing. Computational Fluid Dynamics can be used to verify these requirements; however, the model must be validated by test data. This research includes the following three objectives and methods. Objective one is develop, model, and perform a Computational Fluid Dynamics analysis of three (3) generic, non-proprietary, environmental control systems and spacecraft configurations. Several commercially available and open source solvers have the capability to model the turbulent, highly three-dimensional, incompressible flow regime. The proposed method uses FLUENT, STARCCM+, and OPENFOAM. Objective two is to perform an uncertainty analysis of the Computational Fluid Dynamics model using the methodology found in "Comprehensive Approach to Verification and Validation of Computational Fluid Dynamics Simulations". This method requires three separate grids and solutions, which quantify the error bars around Computational Fluid Dynamics predictions. The method accounts for all uncertainty terms from both numerical and input variables. Objective three is to compile a table of uncertainty parameters that could be used to estimate the error in a Computational Fluid Dynamics model of the Environmental Control System /spacecraft system. Previous studies have looked at the uncertainty in a Computational Fluid Dynamics model for a single output variable at a single point, for example the re-attachment length of a backward facing step. For the flow regime being analyzed (turbulent, three-dimensional, incompressible), the error at a single point can propagate into the solution both via flow physics and numerical methods. Calculating the uncertainty in using Computational Fluid Dynamics to accurately predict airflow speeds around encapsulated spacecraft in is imperative to the success of future missions.

CFD↗