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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 199 records · Page 11
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NASA NTRS1984

Summary of current radiation dosimetry results on manned spacecraft

It is pointed out that the experimental data existing on radiation levels inside orbiting spacecraft are currently limited. However, it is recognized that perhaps the single most important constraint to long-term manned space activity may be related to the complex space radiation environment. For this reason, it is important to know the radiological parameters which determine the biological effects of space radiation on humans. Attention is given to radiation dose measurements, LET (linear energy transfer) spectra for HZE particles, and dosimetry data from U.S. manned spaceflights. In particular, data are now available on dose rates in spacecraft at low altitudes (less than 300 km), while insufficient measurements exist for high altitude and high inclination orbits, geostationary orbits, and many orbits in between. Very little data exist on neutron dose and spectra.

Benton, E. V.↗
NASA NTRS1999

Spacecraft Environments Interactive: Space Radiation and Its Effects on Electronic System

The natural space environment is characterized by complex and subtle phenomena hostile to spacecraft. Effects of these phenomena impact spacecraft design, development, and operation. Space systems become increasingly susceptible to the space environment as use of composite materials and smaller, faster electronics increases. This trend makes an understanding of space radiation and its effects on electronic systems essential to accomplish overall mission objectives, especially in the current climate of smaller/better/cheaper faster. This primer outlines the radiation environments encountered in space, discusses regions and types of radiation, applies the information to effects that these environments have on electronic systems, addresses design guidelines and system reliability, and stresses the importance of early involvement of radiation specialists in mission planning, system design, and design review (part-by-part verification).

Howard, J. W., Jr.↗
NASA NTRS1987

Cascaded-Blackbody Heat Radiators

New class of heat radiators made of metal or other conductive fin stock, fins of which are textured or covered with smaller fins. Measured from outside, effective emissivity of projected radiator surface greater than, and somewhat independent of, emissivity of flat surface made of same material. Special coatings to enhance emissivity not required, and emissivity not degraded significantly in long term by environmental effects. Intended orginally to radiate excess heat away from spacecraft, new radiators also used on Earth to dissipate heat in vacuum systems.

Keddy, Michael D.↗
NASA NTRS2009

CERES FM-5 on the NPP Spacecraft: Continuing the Earth Radiation Budget Climate Data Record

The Clouds and the Earth's Radiant Energy System (CERES) Flight Model-5 (FM-5) instrument will fly on the NPOESS Preparatory Project (NPP) spacecraft, which has a launch-readiness date in June, 2010. This mission will continue the critical Earth Radiation Budget Climate Data Record (CDR) begun by the Earth Radiation Budget Experiment (ERBE) instruments in the mid 1980 s and continued by the CERES instruments currently flying on the EOS Terra and Aqua spacecraft. Ground calibrations have been completed for FM-5 and the instrument has been delivered for integration to the spacecraft Rigorous pre-launch ground calibration is performed on each CERES unit to achieve an accuracy goal of 1% for SW flux and 0.5% for outgoing LW flux. Any ground to flight or in-flight changes in radiometer response is monitored using a protocol employing both onboard and vicarious calibration sources and experiments. Recent studies of FM-1 through FM-4 data have shown that the SW response of space based broadband radiometers can change dramatically due to optical contamination. With these changes having most impact on optical response to blue-to UV radiance, where tungsten lamps are largely devoid of output, such changes are hard to monitor accurately using existing on-board sources. This paper outlines the lessons learned on the existing CERES sensors from 30+ years of flight experience and presents a radiometric protocol to be implemented on the FM-5 instrument to ensure that its performance exceeds the stated calibration and stability goals.

Priestly, Kory↗
NASA NTRS2016

Cryogenic Selective Surfaces

There are many challenges involved in deep-space exploration, but several of these can be mitigated, or even solved, by the development of a coating that can reject most of the Sun's energy and yet still provide some far-infrared heat emission. Such a coating would allow non-heat-generating objects in space to reach cryogenic temperatures without using an active cooling system. This would be a benefit to deep-space sensors that require low temperatures, such as the James Webb Telescope focal plane array. It would also allow the use of superconductors in deep space, which could lead to magnetic energy storage rings, lossless power delivery, or perhaps a large-volume magnetic shield against galactic cosmic radiation. But perhaps the most significant enablement achieved from such a coating would be the long-term storage in deep space of cryogenic liquids, such as liquid oxygen (LOX).In this report, we review the state of the art in low-temperature coatings and calculate the lowest temperatures each of these can achieve, demonstrating that cryogenic temperatures cannot be reached in deep space in this fashion. We then propose a new coating that does allow coated objects in deep space to achieve the very low temperatures required to store liquid oxygen or nitrogen. These new coatings consist of a moderately thick scattering layer (typically 5 mm) composed of a material transparent to most of the solar spectrum. This layer acts as a scatterer to the Sun's light, performing the same process as titanium dioxide in white paint in the visible. Under that layer, we place a metallic reflector, e.g. silver, to reflect long-wave radiation that is not well scattered. The result is a coating we call "Solar White," in that it scatters most of the solar spectrum just as white paint does for the visible. Our modeling of these coatings has shown that temperatures as low as 50 K can be reached for a coated object fully exposed to sunlight at 1 AU from the Sun and far from the Earth.In the second half of the report we explore a mission application of this coating in order to show that it allows LOX to be carried on a mission to Mars. Heat can reach a LOX tank in five ways: direct radiation from the Sun, scattered or reflected radiation from the Sun off of spacecraft components, radiation from nearby planets or the Moon, radiation from the infrared emission of other parts of the spacecraft, and conduction along support struts and flow lines. We discuss these and sum their total contribution when using a Solar White coating to demonstrate an architecture that allows the transportation of LOX to Mars. After this, other applications of Solar White are listed.

Cryogenic Materials↗
NASA NTRS1999

A Survey of Radiation Measurements Made Aboard Russian Spacecraft in Low-Earth Orbit

The accurate prediction of ionizing radiation exposure in low-Earth orbit is necessary in order to minimize risks to astronauts, spacecraft and instrumentation. To this end, models of the radiation environment, the AP-8 trapped proton model and the AE-8 trapped electron model, have been developed for use by spacecraft designers and mission planners. It has been widely acknowledged for some time now by the space radiation community that these models possess some major shortcomings. Both models cover only a limited trapped particle energy region and predictions at low altitudes are extrapolated from higher altitude data. With the launch of the first components of the International Space Station with numerous constellations of low-Earth orbit communications satellites now being planned and deployed, the inadequacies of these trapped particle models need to be addressed. Efforts are now underway both in the U.S. and in Europe to refine the AP-8 and AE-8 trapped particle models. This report is an attempt to collect a significant fraction of data for use in validation of trapped radiation models at low altitudes.

Benton, E. R.↗
NASA NTRS1972

Impact of Jovian radiation environmental hazard on spacecraft and mission development design

The environmental impact on the TOPS 12L configuration is discussed. The activities in system environmental design and testing are described, and radiation design restraints based on the upper limit model are given. Range energy cutoffs in aluminum are also presented and the effective shielding thicknesses for electrons and protons of different energies are included. Design integration problems and radiation testing aspects are considered. Data are given for selecting the parts which should be tested in a formal test program, and the piece-part radiation thresholds are tabulated for electrons and protons.

Divita, E.↗
NASA NTRS1975

Response of Doppler spacecraft tracking to gravitational radiation

A calculation is made of the effect of gravity waves on the observed Doppler shift of a sinusoidal electromagnetic signal transmitted to, and transponded from, a distant spacecraft. We find that the effect of plane gravity waves on such observations is not intuitively immediate and in fact can have surprisingly different spectral signatures for different spacecraft directions and distances. We suggest the possibility of detecting such plane waves by simultaneous coherent Doppler tracking of several spacecraft.

Estabrook, F. B.↗
NASA NTRS2002

The radiation effects on Galileo spacecraft systems at Jupiter

The Galileo spacecraft has been subjected to the charged particle environment around Jupiter since 1995. There have been numerous system failures attributable to radiation effects. We summarize those failures, their causes and any associated fixes.

Galileo↗
NASA NTRS1979

Predictions of induced background radiations at gamma/X-ray experiment envelopes in NASA spacecraft

This work seeks to predict secondary radiation levels induced in spacecraft structures by space protons. The radiations analyzed are secondary neutrons from spallation and evaporation reactions and gamma and beta rays from the decay of induced radioactivity, as sources of interfering background to spaceborne measurements of galactic and planetary gamma rays below 10 MeV. The spacecraft considered are the Multi-Mission Spacecraft (MMS) and the Space Shuttle, modeled as spherical shells. The proton environment is that of the South Atlantic Anomaly, as well as cosmic ray protons. The induced radioactivity is analyzed in terms of its interference with various gamma-ray lines of astrophysical interest, as well as its contribution to several spectral regions of the gamma-ray continuum. The buildup of the line and continuum radioactivity background is predicted for a period of nearly 9 months in orbit (approximately 4100 orbits). In addition, background contributions from cosmic ray electron bremsstrahlung and earth gamma-ray albedo are estimated.

Fischbein, W. L.↗