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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS2007

Advanced Optical Technologies for Space Exploration

NASA Langley Research Center is involved in the development of photonic devices and systems for space exploration missions. Photonic technologies of particular interest are those that can be utilized for in-space communication, remote sensing, guidance navigation and control, lunar descent and landing, and rendezvous and docking. NASA Langley has recently established a class-100 clean-room which serves as a Photonics Fabrication Facility for development of prototype optoelectronic devices for aerospace applications. In this paper we discuss our design, fabrication, and testing of novel active pixels, deformable mirrors, and liquid crystal spatial light modulators. Successful implementation of these intelligent optical devices and systems in space, requires careful consideration of temperature and space radiation effects in inorganic and electronic materials. Applications including high bandwidth inertial reference units, lightweight, high precision star trackers for guidance, navigation, and control, deformable mirrors, wavefront sensing, and beam steering technologies are discussed. In addition, experimental results are presented which characterize their performance in space exploration systems.

Clark, Natalie↗
NASA NTRS2024

The NASA Radiation Hardness Assurance (RHA) Process Standard

This paper presents status on the upcoming NASA Agency-level RHA Process Standard. Based on recommendations provided by the NASA Engineering and Safety Center (NESC), the NASA Electronic Parts and Packaging (NEPP) Program has led development of an agency-level standard for space flight avionics and electronics RHA. The standard introduces a novel RHA taxonomy and prescribes the process required by NASA programs and projects to baseline their RHA programs consistent with the MEAL (Mission, Environment, Application, and Lifetime) criteria including the risk tolerance posture. The standard also provides requirements for the RHA schedule integration in the program or project lifecycle and requirements for data deliverables content. Additional non-prescriptive technical content is provided in the standard appendices to guide development of RHA programs for NASA missions.

Avionics↗
NASA NTRS1998

Design of the Experimental Exposure Conditions to Simulate Ionizing Radiation Effects on Candidate Replacement Materials for the Hubble Space Telescope

In this effort, experimental exposure times for monoenergetic electrons and protons were determined to simulate the space radiation environment effects on Teflon components of the Hubble Space Telescope. Although the energy range of the available laboratory particle accelerators was limited, optimal exposure times for 50 keV, 220 keV, 350 keV, and 500 KeV electrons were calculated that produced a dose-versus-depth profile that approximated the full spectrum profile, and were realizable with existing equipment. For the case of proton exposure, the limited energy range of the laboratory accelerator restricted simulation of the dose to a depth of .5 mil. Also, while optimal exposure times were found for 200 keV, 500 keV and 700 keV protons that simulated the full spectrum dose-versus-depth profile to this depth, they were of such short duration that the existing laboratory could not be controlled to within the required accuracy. In addition to the obvious experimental issues, other areas exist in which the analytical work could be advanced. Improved computer codes for the dose prediction- along with improved methodology for data input and output- would accelerate and make more accurate the calculational aspects. This is particularly true in the case of proton fluxes where a paucity of available predictive software appears to exist. The dated nature of many of the existing Monte Carlo particle/radiation transport codes raises the issue as to whether existing codes are sufficient for this type of analysis. Other areas that would result in greater fidelity of laboratory exposure effects to the space environment is the use of a larger number of monoenergetic particle fluxes and improved optimization algorithms to determine the weighting values.

Smith, L. Montgomery↗
NASA NTRS1974

Effect of inelastic electron-atom collisions on the Balmer decrement

Calculation of the Balmer decrement in radiatively ionized hydrogen gas as a function of temperature and density, taking into account the effect of electron-atom collisions. It is found that once the electron density exceeds 10 to the 10th power per cu cm significant deviations from the normal radiative recombination decrement begin to occur. Implications of these results for the physical conditions in the line-emitting region of the Seyfert galaxy NGC 4151 are discussed briefly.

Adams, W. M.↗
NASA NTRS2012

Radiation and Thermal Cycling Effects on EPC1001 Gallium Nitride Power Transistors

Electronics designed for use in NASA space missions are required to work efficiently and reliably under harsh environment conditions. These include radiation, extreme temperatures, and thermal cycling, to name a few. Information pertaining to performance of electronic parts and systems under hostile environments is very scarce, especially for new devices. Such data is very critical so that proper design is implemented in order to ensure mission success and to mitigate risks associated with exposure of on-board systems to the operational environment. In this work, newly-developed enhancement-mode field effect transistors (FET) based on gallium nitride (GaN) technology were exposed to various particles of ionizing radiation and to long-term thermal cycling over a wide temperature range. Data obtained on control (un-irradiated) and irradiated samples of these power transistors are presented and the results are discussed.

Patterson, Richard L.↗
NASA NTRS1970

The effects of nuclear power generators upon electronic instrumentation

Radiation sensitivity of electronic instruments susceptible to neutron and gamma radiation is evaluated by means of a radioisotope thermoelectric generator /RTG/. The gamma field of the RTG affects instrument operation and requires shielding, the neutron field does not affect operation via secondary capture-gamma production.

Miller, C. G.↗
NASA NTRS1997

Thermal motion of the STIS optical bench

Various tests have been done of the Space Telescope Imaging Spectrograph (STIS) using internal wavecals to measure thermal motion of the spectral format on the detectors. In most cases, the spectral format moves less than the specification not to exceed 0.2 pixels per hour. Primary causes of the motion are (1) changes to the thermal design dictated by the warmer Aft Shroud environment and (2) on-orbit power cycling of Multi-Anode Microchannel Arrays (MAMA) electronics to minimize the effects of radiation hits on the MAMA detectors. The rear portion of the STIS optical bench is too warm to be held at a constant temperature by internal heaters. Electronics swing in temperature with an orbital and daily frequency. The thermal drift of the optical formats is not negligible, but is well behaved in most circumstances. The observer is advised to examine the trade-off between the most accurate wavelengths with best spectral/spatial resolutions versus increased overheads that directly affect the observing times. A long term concern is that the Aft Shroud thermal environment is predicted to heat up as much as one Centigrade degree per year. Progressively more of the bench would move out of thermal control. Thus the external cooler for STIS, being considered for the Third Servicing Mission is of major importance to the long term operation of STIS.

Gull, Theodore R.↗
NASA NTRS1994

Simultaneous measurements of waves and precipitating electrons near the equator in the outer radiation belt

An investigation of wave-particle interactions is made using several simultaneous electron and wave measurements performed at near-equatorial positions from the Combined Release and Radiation Effects Satellite (CRRES) satellite. Bursts of electron precipitation were observed, most frequently at local times near dawn. Examples of bursts are presented in which the fluxes of the precipitating electrons and the wave intensities are correlated with coefficients as high as 0.7. During bursts the frequencies of the enhanced waves spanned a wide range from 311 Hz to 3.11 kHz, and the energies of the enhanced electrons were in the range 1.7 keV to 288 keV. The changes of the precipitating fluxes were generally less pronounced at the lowest energies. On the basis of electron-cyclotron resonant calculations using the cold plasma densities and ambient magnetic fields taken from the CRRES measurements it was found that the wave frequencies and precipitating electron energies were generally consistent with those expected from electron resonance with parallel propagating whistler waves. The electron data of principal concern here were acquired in and about the loss cone with narrow angular resolution spectrometers covering the energy range 340 eV to 5 MeV. The wave data included electric field measurements spanning frequencies from 5 Hz to 400 kHz and magnetic field measurements from 5 Hz to 10 kHz.

Imhof, W. L.↗
NASA NTRS2024

Revisiting High-Energy Polarization from Leptonic and Hadronic Blazar Scenarios

X-ray and MeV polarization can be powerful diagnostics for leptonic and hadronic blazar models. Previous predictions are mostly based on a one-zone framework. However, recent IXPE observations of Mrk 421 and 501 strongly favor a multizone framework. Thus, the leptonic and hadronic polarization predictions need to be revisited. Here we identify two generic radiation transfer effects, namely, double depolarization and energy stratification, that can have an impact on the leptonic and hadronic polarization. We show how they are generalized from previously known multizone effects of the primary electron synchrotron radiation. Under our generic multizone model, the leptonic polarization degree is expected to be much lower than the one-zone prediction, unlikely detectable in most cases. The hadronic polarization degree can reach a value as high as the primary electron synchrotron polarization during simultaneous multiwavelength flares, consistent with the one-zone prediction. Therefore, IXPE and future X-ray and MeV polarimeters such as eXTP, COSI, and AMEGO-X, have good chances to detect hadronic polarization during flares. However, the hadronic polarization cannot be well constrained during the quiescent state. Nonetheless, if some blazar jets possess relatively stable large-scale magnetic structures, as suggested by radio observations, a nontrivial polarization degree may show up for the hadronic model after a very long exposure time (≳1 yr).

Haocheng Zhang↗
NASA NTRS2001

Radiation dose from reentrant electrons

In estimating the crew exposures during an extra vehicular activity (EVA), the contribution of reentrant electrons has always been neglected. Although the flux of these electrons is small compared to the flux of trapped electrons, their energy spectrum extends to several GeV compared to about 7 MeV for trapped electrons. This is also true of splash electrons. Using the measured reentrant electron energy spectra, it is shown that the dose contribution of these electrons to the blood forming organs (BFO) is more that 10 times greater than that from the trapped electrons. The calculations also show that the dose-depth response is a very slowly changing function of depth, and thus adding reasonable amounts of additional shielding would not significantly lower the dose to BFO. Published by Elsevier Science Ltd.

NASA Center JSC↗
NASA NTRS2002

The action of a dietary retinoid on gene expression and cancer induction in electron-irradiated rat skin

Current models of radiation carcinogenesis generally assume that the DNA is damaged in a variety of ways by the radiation and that subsequent cell divisions contribute to the conversion of the damage to heritable mutations. Cancer may seem complex and intractable, but its complexity provides multiple opportunities for preventive interventions. Mitotic inhibitors are among the strongest cancer preventive agents, not only slowing the growth rate of preneoplasias but also increasing the fidelity of DNA repair processes. Ionizing radiation, including electrons, is a strong inducer of cancer in rat skin, and dietary retinoids have shown potent cancer preventive activity in the same system. A non-toxic dietary dose of retinyl acetate altered gene expression levels 24 hours after electron irradiation of rat skin. Of the 8740 genes on an Affymetrix rat expression array, the radiation significantly (5 fold or higher) altered 188, while the retinoid altered 231, including 16 radiation-altered genes that were reversely altered. While radiation strongly affected the expression of stress response, immune/inflammation and nucleic acid metabolism genes, the retinoid most strongly affected proliferation-related genes, including some significant reversals, such as, keratin 14, retinol binding protein, and calcium binding proteins. These results point to reversal of proliferation-relevant genes as a likely basis for the anti-radiogenic effects of dietary retinyl acetate.

Non-NASA Center↗