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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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We propose a method for the application of single event upset (SEU) data towards the analysis of complex systems using transformed reliability models (from the time domain to the particle fluence domain) and space environment data.
A power management and distribution direct current (PMAD DC) test bed was set up at the NASA Lewis Research Center to investigate Space Station Freedom Electric Power Systems issues. Efficiency of test bed operation significantly improves with a computer simulation model of the test bed as an adjunct tool of investigation. Such a model is developed using the Electromagnetic Transients Program (EMTP) and is available to the test bed developers and experimenters. The computer model is assembled on a modular basis. Device models of different types can be incorporated into the system model with only a few lines of code. A library of the various model types is created for this purpose. Simulation results and corresponding test bed results are presented to demonstrate model validity.
A power management and distribution direct current (PMAD DC) test bed was set up at the NASA Lewis Research Center to investigate Space Station Freedom Eelectric Power Systems issues. Efficiency of test bed operation significantly improves with a computer simulation model of the test bed as an adjunct tool of investigation. Such a model is developed using the Electromagnetic Transients Program (EMTP) and is available to the test bed developers and experimenters. The computer model is assembled on a modular basis. Device models of different types can be incorporated into the system model with only a few lines of code. A library of the various model types is created for this purpose. Simulation results and corresponding test bed results are presented to demonstrate model validity.
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Automation is the application of self-regulating mechanical and electronic devices to processes that can be accomplished with the human organs of perception, decision, and actuation. The successful application of automation to a system process should reduce man/system interaction and the perceived complexity of the system, or should increase affordability, productivity, quality control, and safety. The expense, time constraints, and risk factors associated with extravehicular activities have led the Automation Technology Branch (ATB), as part of the NASA Automation Research and Technology Program, to investigate the use of robots and teleoperators as automation aids in the context of space operations. The ATB program addresses three major areas: (1) basic research in autonomous operations, (2) human factors research on man-machine interfaces with remote systems, and (3) the integration and analysis of automated systems. This paper reviews the current ATB research in the area of robotics and teleoperators.
Project Galileo, the United States' next planetary mission, will be launched by the Shuttle/Centaur in May 1986. The Galileo spacecraft consists of both a planetary Orbiter and an atmospheric Probe. The spacecraft was environmentally tested as a system in the fall and winter of 1984/1985 at the Jet Propulsion Laboratory. The protoflight qualification program consisted of vibration, acoustics, pyrotechnic shock, Electromagnetic Compatibility (EMC) and Solar Thermal Vacuum (STV) tests. This test program was accomplished on a large, complex, dual-spin spacecraft without the benefit of precursor spacecraft prototype tests. This paper discusses the objectives of these tests and the implementation, and summarizes the results.
This paper describes the design of a watchdog coprocessor for detecting hardware and software errors. The watchdog executes assertions about the process running on the main computer. Both general purpose an special purpose (used to check systems such as digital signal processors, telephone switching systems, or digital flight controllers) watchdog designs are described. The improvement of error coverage by adding control flow checking facilities is discussed. The implementation of the watchdog as a software process is presented.
The design of a space probe to explore the atmosphere of the planet Jupiter is discussed. Five major areas were considered: (1) definition of science requirements, (2) mission evaluation, (3) definition of probe system, (4) definition of spacecraft support requirements, and (5) nonequilibrium flow field analysis for communications blackout evaluation. The overall mission and system design are emphasized. The integration of the various technologies into complete systems designs is described. Results showed that a nonsurvivable turbopause probe mission to Jupiter with adequate data return to meet the science objectives is feasible and practical.
Mars ISRU converts atmospheric CO2 to generate O2 and CH4. Reduces launch mass, thus mission cost. Increases mission duration and independence. CO2 acquisition system must: a) Reliably extract CO2 over the varying Martian environment. 1) approx. 0.67-0.93 kPa pressure and 2) 125 C to 40 C. b) Provide and compress high purity gas to chemical plants. 1) Separate N2, Ar2, etc. from approx. 95% CO2 atmosphere and 2) Current pressure targets: 50 kPa-500 kPa.
The higher power and higher voltage levels anticipated for future space missions have required a careful review of the techniques currently in use to preclude battery problems that are related to the dispersion characteristics of the individual cells. Not only are the out-of-balance problems accentuated in these larger systems, but the thermal management considerations also require a greater degree of accurate design. Newer concepts which employ active cooling techniques are being developed which permit higher rates of discharge and tighter packing densities for the electrochemical components. This paper will put forward six semi-independent principles relating to battery systems. These principles will progressively address cell, battery and finally system related aspects of large electrochemical storage systems.
A strategic focus area for NASA is to pursue the development of technologies which support exploration in space beyond the current inhabited region of low earth orbit. An unresolved issue for crewed deep space exploration involves limiting crew radiation exposure to below acceptable levels, considering both solar particle events and galactic cosmic ray contributions to dosage. Galactic cosmic ray mitigation is not addressed in this paper, but by addressing credible, easily implemented, and mass efficient solutions for the possibility of solar particle events, additional margin is provided that can be used for cosmic ray dose accumulation. As a result, NASA s Advanced Engineering Systems project office initiated this Radiation Storm Shelter design activity. This paper reports on the first year results of an expected 3 year Storm Shelter study effort which will mature concepts and operational scenarios that protect exploration astronauts from solar particle radiation events. Large trade space definition, candidate concept ranking, and a planned demonstration comprised the majority of FY12 activities. A system key performance parameter is minimization of the required increase in mass needed to provide a safe environment. Total system mass along with operational assessments and other defined protection system metrics provide the guiding metrics to proceed with concept developments. After a downselect to four primary methods, the concepts were analyzed for dosage severity and the amount of shielding mass necessary to bring dosage to acceptable values. Besides analytical assessments, subscale models of several concepts and one full scale concept demonstrator were created. FY12 work terminated with a plan to demonstrate test articles of two selected approaches. The process of arriving at these selections and their current envisioned implementation are presented in this paper.
Recent work has shown that human activities on the lunar surface have the potential to impact not only surface infrastructure, but also have long-term repercussions to lunar orbit infrastructure that is directly proportional to the frequency and scale of landings and impacts. Those assets that are present within the lunar environment, whether on the surface or in orbit, are thus not entirely isolated from one another but contribute to the overall induced environment. With that in mind, this project endeavors to model that system using Model Based Systems Engineering (MBSE), employing previously developed mathematical methodology. The product from this work is a flexible tool with which a user may model any number of assets or events and determine how the dust and debris generated by those events effects mission operations and overall projected.
In the present of declining Defense budgets, increased pressure has been placed on the DOD to utilize Commercial Off the Shelf (COTS) solutions to incrementally solve a wide variety of our computer processing requirements. With the rapid growth in processing power, significant expansion of high performance networking, and the increased complexity of applications data sets, the requirement for high performance, large capacity, reliable and secure, and most of all affordable robotic tape storage libraries has greatly increased. Additionally, the migration to a heterogeneous, distributed computing environment has further complicated the problem. With today's open system compute servers approaching yesterday's supercomputer capabilities, the need for affordable, reliable secure Mass Storage Systems (MSS) has taken on an ever increasing importance to our processing center's ability to satisfy operational mission requirements. To that end, NSA has established an in-house capability to acquire, test, and evaluate COTS products. Its goal is to qualify a set of COTS MSS libraries, thereby achieving a modicum of standardization for robotic tape libraries which can satisfy our low, medium, and high performance file and volume serving requirements. In addition, NSA has established relations with other Government Agencies to complete this in-house effort and to maximize our research, testing, and evaluation work. While the preponderance of the effort is focused at the high end of the storage ladder, considerable effort will be extended this year and next at the server class or mid range storage systems.
During United States Extravehicular Activity 80 (US EVA 80), water was observed in the helmet of an Extravehicular Mobility Unit (EMU) during cabin repressurization. Through a comparative analysis and Test, Teardown, and Evaluation (TT&E) of this EMU, the most likely cause of the US EVA 80 water failure was determined to be sublimator carryover caused by a comparatively high latent load (water vapor production by the crewmember). High latent load can be reduced by the crewmember adjusting the thermal control valve (TCV) setting on the EMU to prevent the onset of significant sweating. To reduce the risk of high latent load leading to water in the helmet, a potential warning system was developed using the Systems Improved Numerical Differencing Analyzer EMU model (SINDA EMU). The goal of this warning system is to alert the crewmember when they are producing a high latent load and recommend adjustment of the TCV to increase cooling. This warning system was designed to ensure high risk conditions are avoided while simultaneously preventing a system that warns the crewmember too frequently. Theoretical tests of the warning system through modeling calculated that if the warning system were used during US EVA 80, the total latent load could have been reduced by up to 33% which would have significantly reduced the risk of water in the helmet. This analysis also investigated the effectiveness of the warning system on EVAs that occurred after US EVA 80.
The prediction of the SRB and ET impact areas requires six separate processors. The SRB impact prediction processor computes the impact areas and related trajectory data for each SRB element. Output from this processor is stored on a secure file accessible by the SRB impact plot processor which generates the required plots. Similarly the ET RTLS impact prediction processor and the ET RTLS impact plot processor generates the ET impact footprints for return-to-launch-site (RTLS) profiles. The ET nominal/AOA/ATO impact prediction processor and the ET nominal/AOA/ATO impact plot processor generate the ET impact footprints for non-RTLS profiles. The SRB and ET impact processors compute the size and shape of the impact footprints by tabular lookup in a stored footprint dispersion data base. The location of each footprint is determined by simulating a reference trajectory and computing the reference impact point location. To insure consistency among all flight design system (FDS) users, much input required by these processors will be obtained from the FDS master data base.
This paper describes results of a numerical analysis evaluating the feasibility of high-temperature shape memory alloys (HTSMA) for active clearance control actuation in the high-pressure turbine section of a modern turbofan engine. The prototype actuator concept considered here consists of parallel HTSMA wires attached to the shroud that is located on the exterior of the turbine case. A transient model of an HTSMA actuator was used to evaluate active clearance control at various operating points in a test bed aircraft engine simulation. For the engine under consideration, each actuator must be designed to counteract loads from 380 to 2000 lbf and displace at least 0.033 inches. Design results show that an actuator comprised of 10 wires 2 inches in length is adequate for control at critical engine operating points and still exhibits acceptable failsafe operability and cycle life. A proportional-integral-derivative (PID) controller with integrator windup protection was implemented to control clearance amidst engine transients during a normal mission. Simulation results show that the control system exhibits minimal variability in clearance control performance across the operating envelope. The final actuator design is sufficiently small to fit within the limited space outside the high-pressure turbine case and is shown to consume only small amounts of bleed air to adequately regulate temperature.
In order to ensure that adequate water resources are available during a mission, any net water loss from the habitat must be balanced with an equivalent amount of required makeup water. Makeup water may come from a variety of sources, including water in shipped tanks, water stored in prepackaged food, product water from fuel cells, and in-situ water resources. This paper specifically addresses the issue of storing required makeup water in prepackaged food versus storing the water in shipped tanks for the Mars Dual Lander Transit Mission, one of the Advanced Life Support Reference Missions. In this paper, water mass balances have been performed for the Dual Lander Transit Mission, to determine the necessary requirement of makeup water under nominal operation (i.e. no consideration of contingency needs), on a daily basis. Contingency issues are briefly discussed with respect to impacts on makeup water storage (shipped tanks versus storage in prepackaged food). The Dual Lander Transit Mission was selected for study because it has been considered by the Johnson Space Center Exploration Office in enough detail to define a reasonable set of scenario options for nominal system operation and contingencies. This study also illustrates the concept that there are multiple, reasonable life support system scenarios for any one particular mission. Thus, the need for a particular commodity can depend upon many variables in the system. In this study, we examine the need for makeup water as it depends upon the configuration of the rest of the life support system.