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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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Proposed heat switch transfers heat from source to sink in regular cycles. Self-sustaining; actuated by transferred heat, contains no moving parts, and needs no external heaters or electronic circuitry to synchronize heat-transfer periods or control heat-transfer rates. Intended for use in gas-sorption refrigerator.
Highly relativistic electron precipitation events (HRE's) can provide a major source of energy affecting mesospheric constituents and ionization. Based on satellite data, these events are most pronounced near the minimum of the solar sunspot cycle, increasing in intensity, spectral hardness, and frequency of occurrence as the solar cycle declines. Since such events can be sustained up to several days, their integrated effect in the mesosphere can dominate over those of other energy sources such as relativistic electron precipitation events (REP's) and auroral precipitation. The energy deposition data to be discussed and analyzed were obtained by rocket at Poker Flat, Alaska, in May 1990 during a modest HRE observed at midday near the peak of the sunspot cycle. Using a NASA two dimensional model, significant enhancement of OH and depletion of O3 at 75 +/- 10 km altitude from the measured radiation are found. Estimates of enhanced effects were made for more intense HRE events, as might be expected during solar minimum. By causing O3 depletion, the electron precipitation can also regulate the penetration of solar UV radiation, which could affect the thermal properties of the mesosphere.
Spherically accreting black holes may sustain strong collisionless shocks, downstream of which the fluid approximation is not valid. The proton-electron Coulomb exchange provides for the downstream matter diffusion into the hole. Energy conversion efficiencies upward of 10-30 percent are obtained, with most of the luminosity in hard X-rays and gamma-rays. The whole spectrum and its application for radio-quiet QSO's and galactic X- and gamma-ray sources are discussed.
As human spaceflight pushes beyond Low Earth Orbit (LEO), resupply of consumables becomes a significant challenge. One solution to this problem is In-Space Manufacturing (ISM), the capability to perform on-demand manufacturing and repair of consumables in an in-space environment. ISM offers significant flexibility to missions as it allows for a high degree of tailorability and reduction in launch mass. Leveraging advancements in fabrication, repair and recycling, ISM provides a highly sustainable and affordable solution to Exploration mission operations and logistics. In this talk, advances in printed electronics and sensors, ranging from nanomaterial ink development and hands-free fabrication methodologies to devices will be presented. Applications presented will include sensors for crew health monitoring, structural health monitoring and power generation.
As human spaceflight pushes beyond Low Earth Orbit (LEO), resupply of consumables becomes a significant challenge. One solution to this problem is In-Space Manufacturing (ISM), the capability to perform on-demand manufacturing and repair of consumables in an in-space environment. ISM offers significant flexibility to missions as it allows for a high degree of tailor ability and reduction in launch mass. Leveraging advancements in fabrication, repair and recycling, ISM provides a highly sustainable and affordable solution to exploration mission operations and logistics. In this talk, advances in printed electronics and sensors, ranging from nanomaterial ink development and hands-free fabrication methodologies to devices will be presented. Applications presented will include sensors for crew health monitoring along with supporting electronics. In the future, these devices will be fabricated and characterized on the International Space Station and the approach will be evaluated for future in-space manufacturing to support human spaceflight.
The development, design, and preliminary performance characteristics of a microwave plasma disk ion source are presented. Several important design concepts indigenous to microwave plasmas have been utilized in the development of this ion source: generation of a resonantly sustained microwave discharge inside a microwave/plasma coupler, probe and length tuning of the microwave/plasma coupler, and minimization of plasma volume. The experimental results for a 2.45 GHz, eight cm ion source excited in the TE(211) and TM(011) modes are described. Results are presented for electromagnetic mode excitation, electron density, coupling efficiency and loaded cavity Q, and I-V characteristics and efficiencies. It is preliminarily shown that a microwave disk-like plasma can be sustained adjacent to the grids with either TE or TM cavity modes at pressures below 2 x 10 to the -4th torr. Over 80% of the power absorbed in the cavity is coupled into the plasma.
The accretion-powered radiation from the X-ray pulsar system Her X-1 (McCray et al. 1982) is studied. The changes in the soft X-ray and gamma-ray flux and in the accompanying electron-positron wind are discussed. These are believed to be associated with the inward movement of the inner edge of the accretion disk corresponding to the boundary with the neutron star's corotating magnetosphere (Alfven radius). LMXB evolution which is self-sustained by secondary winds intercepting the radiation emitted near an LMXB neutron star is investigated as well.
The electron-beam welding process is well adapted to function in the environment of space. The Soviets were the first to demonstrate welding in space in the mid-1980's. Under the auspices of the International Space Welding Experiment (ISWE), an on-orbit test of a Ukrainian designed electron-beam welder (the Universal Hand Tool or 'UHT') is scheduled for October of 1997. The potential for sustained presence in space with the development of the international space station raises the possibility of the need for construction and repair in space. While welding is not scheduled to be used in the assembly of the space station, repair of damage from orbiting debris or meteorites is a potential need. Furthermore, safe and successful welding in the space environment may open new avenues for design and construction. The safety issue has been raised with regard to hot particle emissions (spatter) sometimes observed from the weld during operations. On earth the hot particles pose no particular hazard, but in space there exists the possibility for burn-through of the space suit which could be potentially lethal. Contamination of the payload bay by emitted particles could also be a problem.
One of the most intriguing planets in our solar system for both solar system and extra-solar system science is Venus. Venus is the planet most similar to Earth in several key ways and many believe Venus-like planets are more common around other suns than are Earth-like planets. Therefore scientific understanding of our sister planet is a high priority. However, the hostile environmental conditions at the surface coupled with thick acid clouds and dense atmosphere have made understanding this planet very challenging. Remote sensing of surface features and near surface environments is very limited. The hostile environment has also limited the ability of landers to survive, in fact the longest living asset survived just over two hours. Even after over 50 years of attempts to explore Venus, many key measurements, especially near the surface, are still in the future. NASA has begun to undertake steps to overcome the technical challenges and is developing the capability for sustained operations and science return from this important body. For example, recent technology advances in high temperature sensors, electronics, power, and other systems have been funded and this, combined with the new capabilities to replicate Venus conditions on Earth, are changing the outlook for Venus surface exploration.
This presentation provides an overview of the aerospace supply chain and how the AAM Supply Chain Working Group will help to make it more sustainable and resilient. The urgent needs are building a tiered system, a modeling and simulation platform, and an electronic exchange platform.
Ulysses observations at 2.5 AU of 38-315 keV electrons and 61-4752 keV ions during February-April 1991 suggest in several ways that, during periods of sustained high solar activity, the inner heliosphere serves as a 'reservoir' for low-energy solar particles. Particle increases were not associated one-to-one with large X-ray flares because of their poor magnetic connection, yet intensities in March-April remained well above their February levels. The rise phase of the particle event associated with the great flare of 2245UT March 22 lasted most of two days, while throughout the one-week decay phase, the lowest-energy ion fluxes were nearly equal at Ulysses and earth (IMP-8).
In order to sustain life on the moon, and especially on Mars, the inhabitants must be self-sufficient. As on Earth, electronic and mechanical systems will break down and must be repaired. It is not realistic to "send" parts to the moon or Mars in an effort to replace failed ones or have spares for all components. It will be important to have spares on hand and even better would be to have the capability to fabricate parts in situ. The In Situ Fabrication and Repair (ISFR) team is working to develop the Arcam Electron Beam Melting (EBM) machine as the manufacturing process that will have the capability to produce repair parts, as well as new designs, and tooling on the lunar surface and eventually on Mars. What materials will be available for the inhabitants to use? What materials would be most useful? The EBM process is versatile and can handle a multitude of materials. These include titanium, stainless steels, aluminums, inconels, and copper alloys. Research has shown what parts have failed during past space missions and this data has been compiled and assessed. The EBM machine is fully capable of processing these materials of choice. Additionally, the long-term goal is to use the lunar regolith as a viable feedstock. Preliminary work has been performed to assess the feasibility of using raw lunar regolith as a material source or use a binder combined with the regolith to achieve a good melt.
The electron diffusion region forms the inner core of the magnetic reconnection machine. In this region, physical processes act to sustain a reconnection electric field, they accelerate to provide current density, and the heat to provide particle pressure in the current layer. The relative roles of these processes depend on whether the overall geometry is anti-parallel or asymmetric, and whether a guide field is present of not, but the overall concept applies in each case. The EDR is embedded in successively larger regions, starting with the ion diffusion region to even larger scales, where the plasma increasingly behaves like an anisotropic MHD plasma. With our new understanding of how the EDR works, it is of great interest to study how EDR processes couple to the larger scale environment. The ultimate efficacy of the magnetic reconnection is shaped by this interesting example of micro-macro coupling. In this presentation, we present some thoughts pertaining to this topic. In particular, we will discuss how information transport between scales is mediated, and how the very small scales can reach balance with the larger, overall system. We will review any pertinent research and present a set of questions inviting future research.
NASA's materials processing in space- (MPS) program involves both ground and space-based research and looks to frequent and cost effective access to the space environment for necessary progress. The first generation payloads for research are under active design and development. They will be hosted by the Space Shuttle/Spacelab on Earth orbital flights in the early 1980's. hese missions will focus on the acquisition of materials behavior research data, the potential enhancement of Earth based technology, and the implementation of space based processing for specialized, high value materials. Some materials to be studied in these payloads may provide future breakthroughs for stronger alloys, ultrapure glasses, superior electronic components, and new or better chemicals. An operational 25 kW power system is expected to be operational to support sustained, systematic space processing activity beyond shuttle capability for second generation payload systems for SPACELAB and free flyer missions to study solidification and crystal growth and to process metal/alloys, glasses/ceramics, and chemicals and biologicals.
Implementation of challenging Exploration Systems Missions Directorate objectives and strategies can be constrained by onboard computing capabilities and power efficiencies. The Radiation Hardened Electronics for Space Environments (RHESE) High Performance Processors for Space Environments project will address this challenge by significantly advancing the sustained throughput and processing efficiency of high-per$ormance radiation-hardened processors, targeting delivery of products by the end of FY12.
Biological nitrogen fixation, the microbial reduction of atmospheric nitrogen to bioavailable ammonia, represents both a major limitation on biological productivity and a highly desirable engineering target for synthetic biology. However, the engineering of nitrogen fixation requires an integrated understanding of how the gene regulatory dynamics of host diazotrophs respond across sequence-function space of its central catalytic metalloenzyme, nitrogenase. Here, we interrogate this relationship by analyzing the transcriptome of Azotobacter vinelandii engineered with a phylogenetically inferred ancestral nitrogenase protein variant. The engineered strain exhibits reduced cellular nitrogenase activity but recovers wild-type growth rates following an extended lag period. We find that expression of genes within the immediate nitrogen fixation network is resilient to the introduced nitrogenase sequence-level perturbations. Rather the sustained physiological compatibility with the ancestral nitrogenase variant is accompanied by reduced expression of genes that support trace metal and electron resource allocation to nitrogenase. Our results spotlight gene expression changes in cellular processes adjacent to nitrogen fixation as productive engineering considerations to improve compatibility between remodeled nitrogenase proteins and engineered host diazotrophs.
We report on the linear relationship between the durations of two types of electromagnetic emissions associated with shocks driven by coronal mass ejections: sustained gamma-ray emission (SGRE) and interplanetary type II radio bursts. The relationship implies that shocks accelerate approximately 10 kiloelectronvolts electrons (for type II bursts) and more than 300 megaelectronvolts protons (for SGRE) roughly over the same duration. The SGRE events are from the Large Area Telescope (LAT) on board the Fermi satellite, while the type II bursts are from the Radio and Plasma Wave Experiment (WAVES) on board the Wind spacecraft. Here we consider five SGRE events that were not included in a previous study of events with longer duration (more than 5 hours). The five events are selected by relaxing the minimum duration to 3 hours. We found that some SGRE events had a tail that seems to last until the end of the associated type II burst. We pay special attention to the 2011 June 2 SGRE event that did not have a large solar energetic particle event at Earth or at the STEREO spacecraft that was well connected to the eruption. We suggest that the preceding CME (Coronal Mass Ejection) acted as a magnetic barrier that mirrored protons back to Sun.
LaRosa and Moore (1993) recently proposed that the bulk dissipation of magnetic field that is required for the electron energization in the explosive phase of solar flares occurs in a 'fat current sheet', a wall of cascading magnetohydrodynamic (MHD) turbulence sustained by highly disordered driven reconnection of opposing magnetic fields impacting at a turbulent boundary layer. Here, we use the well-observed great two-ribbon eruptive flare of 1984 April 24/25 to assess the feasibility of both (1) the standard model for the overall three-dimensional form and action of the magnetic field and (2) the turbulent reconnection wall within it. We find (1) that the morphology of this flare closely matched that of the standard model; (2) the preflare sheared core field had enough nonpotential magnetic energy to power the flare; (3) the model turbulent wall required to achieve the flare's peak dissipative power easily fit within the overall span of the flaring magnetic field; (4) this wall was thick enough to have turbulent eddies large enough (diameters approximately 10(exp 8 cm) to produce the approximately ergs energy release fragments typically observed in the explosive phase of flares; (5) the aspect ratio (thickness/vertical extent) of the turbulent reconnection wall was in the 0.1-1 range expected by (Parker 1973). We therefore conclude that the viability of our version of the standard model (i.e., having the magnetic field dissipation occur in our turbulent reconnection wall) is well confirmed by this typical great two-ribbon eruptive flare.