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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS2009

Jet Propulsion Laboratory: Annual Report 2008

Nothing is more exciting than when science mines the far end of our knowledge for the new and the unexpected. In 2008, the world was taken by surprise when JPL astronomers announced the discovery of organic compounds on a planet orbiting another star. We were equally excited to learn from the Spitzer Space Telescope that many, if not most, sun-like stars have rocky planets roughly similar to Earth. Together these are very intriguing clues in our quest to learn if there is life elsewhere in the universe, which certainly has to be one of the most profound mysteries of our age.There are times when, dealing with unknowns, we are reminded to be humble. Very impressive progress is being made by the team developing our next flagship mission, Mars Science Laboratory. Ther conclusion, however, is that it would not be safe to try to fly during the Mars launch window in 2009, and reset for the next opportunity in 2011. We are lucky to have valuable assets that support us as we venture into the unknown. One is the global Deep Space Network, which functions both as our communication gateway to our spacecraft across the solar system as well as a research tool itself in conducting radar astronomy. Our successes depend on our entire team, administrators and business specialists as much as technical people. There are those who help share our missions with the public, finding imaginative venues such as sending out dispatches on the Internet's Twitter.com during the Phoenix mission. We also benefit greatly from the intellectual infusion that comes from our unique identity as a division of the California Institute of Technology and a member of the NASA family.

National Aeronautics and Space Administration (NAS↗
NASA NTRS1995

Experiments in Neural-Network Control of a Free-Flying Space Robot

Four important generic issues are identified and addressed in some depth in this thesis as part of the development of an adaptive neural network based control system for an experimental free flying space robot prototype. The first issue concerns the importance of true system level design of the control system. A new hybrid strategy is developed here, in depth, for the beneficial integration of neural networks into the total control system. A second important issue in neural network control concerns incorporating a priori knowledge into the neural network. In many applications, it is possible to get a reasonably accurate controller using conventional means. If this prior information is used purposefully to provide a starting point for the optimizing capabilities of the neural network, it can provide much faster initial learning. In a step towards addressing this issue, a new generic Fully Connected Architecture (FCA) is developed for use with backpropagation. A third issue is that neural networks are commonly trained using a gradient based optimization method such as backpropagation; but many real world systems have Discrete Valued Functions (DVFs) that do not permit gradient based optimization. One example is the on-off thrusters that are common on spacecraft. A new technique is developed here that now extends backpropagation learning for use with DVFs. The fourth issue is that the speed of adaptation is often a limiting factor in the implementation of a neural network control system. This issue has been strongly resolved in the research by drawing on the above new contributions.

NEURAL NETS↗
NASA NTRS1990

Space Station Freedom avionics technology

The Space Station Freedom Program (SSFP) encompasses the design, development, test, evaluation, verification, launch, assembly, and operation and utilization of a set of spacecraft in low earth orbit (LEO) and their supporting facilities. The spacecraft set includes: the Space Station Manned Base (SSMB), a European Space Agency (ESA) provided Man-Tended Free Flyer (MTFF) at an inclination of 28.5 degrees and nominal attitude of 410 km, a USA provided Polar Orbiting Platform (POP), and an ESA provided POP in sun-synchronous, near polar orbits at a nominal altitude of 822 km. The SSMB will be assembled using the National Space Transportation System (NSTS). The POPs and the MTFF will be launched by Expendable Launch Vehicles (ELVs): a Titan 4 for the US POP and an Ariane for the ESA POP and MTFF. The US POP will for the most part use derivatives of systems flown on unmanned LEO spacecraft. The SSMB portion of the overall program is presented.

Edwards, A.↗
NASA NTRS2011

Power and Propulsion System Design for Near-Earth Object Robotic Exploration

Near-Earth Objects (NEOs) are exciting targets for exploration; they are relatively easy to reach but relatively little is known about them. With solar electric propulsion, a vast number of interesting NEOs can be reached within a few years and with extensive flexibility in launch date. An additional advantage of electric propulsion for these missions is that a spacecraft can be small, enabling a fleet of explorers launched on a single vehicle or as secondary payloads. Commercial, flight-proven Hall thruster systems have great appeal based on their performance and low cost risk, but one issue with these systems is that the power processing units (PPUs) are designed for regulated spacecraft power architectures which are not attractive for small NEO missions. In this study we consider the integrated design of power and propulsion systems that utilize the capabilities of existing PPUs in an unregulated power architecture. Models for solar array and engine performance are combined with low-thrust trajectory analyses to bound spacecraft design parameters for a large class of NEO missions, then detailed array performance models are used to examine the array output voltage and current over a bounded mission set. Operational relationships between the power and electric propulsion systems are discussed, and it is shown that both the SPT-100 and BPT-4000 PPUs can perform missions over a solar range of 0.7 AU to 1.5 AU - encompassing NEOs, Venus, and Mars - within their operable input voltage ranges. A number of design trades to control the array voltage are available, including cell string layout, array offpointing during mission operations, and power draw by the Hall thruster system.

Near Earth Object (NEO)↗
NASA NTRS2000

A close-up look at Io from Galileo's near-infrared mapping spectrometer

Infrared spectral images of Jupiter's volcanic moon Io, acquired during the October and November 1999 and February 2000 flybys of the Galileo spacecraft, were used to study the thermal structure and sulfur dioxide distribution of active volcanoes. Loki Patera, the solar system's most powerful known volcano, exhibits large expanses of dark, cooling lava on its caldera floor. Prometheus, the site of long-lived plume activity, has two major areas of thermal emission, which support ideas of plume migration. Sulfur dioxide deposits were mapped at local scales and show a more complex relationship to surface colors than previously thought, indicating the presence of other sulfur compounds.

long duration↗