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Results for “shutdown dose rates”

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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NASA NTRS1991

Radiation dose estimates for typical piloted NTR lunar and Mars mission engine operations

The natural and manmade radiation environments to be encountered during lunar and Mars missions are qualitatively summarized. The computational methods available to characterize the radiation environment produced by an operating nuclear propulsion system are discussed. Mission profiles and vehicle configurations are presented for a typical all-propulsive, fully reusable lunar mission and for a typical all-propulsive Mars mission. Estimates of crew location biological doses are developed for all propulsive maneuvers. Post-shutdown dose rates near the nuclear engine are estimated at selected mission times.

Schnitzler, Bruce G.↗

NASA NTRS1991

Pellet bed reactor for nuclear propelled vehicles: Part 2: Missions and vehicle integration trades

Mission and vehicle integration tradeoffs involving the use of the pellet bed reactor (PBR) for nuclear powered vehicles is discussed, with much of the information being given in viewgraph form. Information is given on propellant tank geometries, shield weight requirements for conventional tank configurations, effective specific impulse, radiation mapping, radiation dose rate after shutdown, space transfer vehicle design data, a Mars mission summary, sample pellet bed nuclear orbit transfer vehicle mass breakdown, and payload fraction vs. velocity increment.

Haloulakos, V. E.↗

NASA NTRS1972

SNAP-8 post shutdown gamma radiation approximations

Detector responses were calculated for normalized sources in the Perkins and King energy group structure for a SNAP 8 power system on a NASA space station. Gamma decay rates were then calculated by using an expanded, updated list of isotopic decay data, and from these, actual detector responses were found for the SNAP 8 system. The results indicate that energy-dependent calculations must be made to determine decay gamma dose rates for actual reactor configurations. A simplified method for making these calculations has been devised.

Byrn, N. R.↗

NASA NTRS2004

Solar Variability and the Near-Earth Environment: Mining Enhanced Low Dose Rate Sensitivity Data From the Microelectronics and Photonics Test Bed Space Experiment

This effort is a detailed analysis of existing microelectronics and photonics test bed satellite data from one experiment, the bipolar test board, looking to improve our understanding of the enhanced low dose rate sensitivity (ELDRS) phenomenon. Over the past several years, extensive total dose irradiations of bipolar devices have demonstrated that many of these devices exhibited ELDRS. In sensitive bipolar transistors, ELDRS produced enhanced degradation of base current, resulting in enhanced gain degradation at dose rates <0.1 rd(Si)/s compared to similar transistors irradiated at dose rates >1 rd(Si)/s. This Technical Publication provides updated information about the test devices, the in-flight experiment, and both flight-and ground-based observations. Flight data are presented for the past 5 yr of the mission. These data are compared to ground-based data taken on devices from the same date code lots. Information about temperature fluctuations, power shutdowns, and other variables encountered during the space flight are documented.

Turflinger, T.↗

NASA NTRS1991

Nuclear safe orbit basing considerations

Consideration is given to one aspect of space nuclear power safety, namely, the radiation dose rate risk due to a reentered reactor. It is found that for nuclear-thermal propulsion NERVA vehicles, the minimum required altitude for initial basing and earth escape is 500 to 600 km; for final end-of-life storage, the required altitude is about 1000 km. For a 10-MWe nuclear-electric propulsion vehicle, the basing node is 800 km and the final end-of-life storage altitude is 1100 km. Radiation levels have been evaluated for both the SP-100 nuclear electric and the NERVA nuclear thermal reactors as a function of operating time, power level, and time after shutdown.

Frisbee, Robert H.↗