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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Preliminary comparison of material charging properties using single-energy and multienergy electron beams

Results of tests designed to compare the charging properties of spacecraft material under a monoenergetic beam and under a continuously distributed beam are summarized. In the test setup the electron source was mounted in the top of a cylindrical vacuum chamber. A sheet of 5-mil-thick Kapton was placed on an insulated metal substrate at the bottom of the vacuum chamber. The dc current arriving on the substrate was measured and a field meter measured the potential of the test sample. A retarding potential analyzer measured the energy spectrum of the incident electron beam. With the monoenergetic beam, the sample charged to 12 kV and electrical discharges occurred. With the multi-energy spectra the samples charged to only 6 kV and 4 kV, and no discharger were observed. In these experiments, no effort was made to duplicate the spectra occurring in space. The tests were intended to simply to compare spacecraft material charging properties using monoenergetic and continuous multi-energy beams.

Adamo, R. C.↗
NASA NTRS1999

X-Raying Molecular Clouds

Dense interstellar clouds are known to consist almost entirely of molecular hydrogen gas which is, however, normally not observable directly. We have developed a new method for measuring gas column density through its X-ray absorption. The latest data analysis software has been implemented to correct for both exposure and flat- fielding and to subtract various non-cosmic background from individual images. The ROSAT PSPC observations on the R CrA cloud have been merged into maps in three broad energy bands, with corrections for residual differential background between the observations. Individual sources have been detected and removed from these maps. We have then applied the shadowing technique to derive the first column density map based on X-ray data alone. We have conducted various tests to access systematic errors, including possible background intensity variations. We have also proposed a NRAO 12m telescope mapping of the CO distribution in the R CrA cloud. This mapping will supplement our X-ray measurement to allow for a direct calibration of the Co-to-H2 conversion ratio. We use a multi-energy band X-ray shadowing technique to measure the total column density distribution of molecular clouds.

Wang, Q. Daniel↗
NASA NTRS2024

A Perspective on Multi-Source Energy Harvesting Technology Using Piezoelectric and Thermoelectric Materials

Energy harvesting using various locally available energy sources such as vibration energy, heat, sound, or magnetic field have become attractive topics for supplying power to modular electronic devices making them run independently in extreme environments. In this paper, we will be discussing the perspectives on thermoelectric (TE) and piezoelectric materials and devices, and then the concept of multi-source energy harvester using piezoelectric and thermoelectric devices and integration of them into a reliable and independent power source. TE materials having low thermal conductivity and high figure-of-merit ( zT ) are developed to convert even a small temperature gradient efficiently into electrical energy with the state-of-the-art conversion efficiency of ~15% and output power of ~56 W from single device. The piezoelectric device architecture is configured using high performance piezoelectric ceramics (Cu-Mn-PIN-PMN-PT). These ceramics exhibit high piezoelectric coefficient with high mechanical quality factor and low dielectric loss factor. Using these piezoelectric materials, power density as high a 2 mW/cm 2 is demonstrated in 1-1.5 g vibration environments. The piezoelectric device is attached on the surface of TE module to capture both the vibration and thermal energy sources to realize dual mode energy harvester. The multi-energy transfer strategy opens opportunities for a future generation of wireless and modular electronic devices. These devices would be useful in powering wearable electronic devices, micro sensor chargers, etc. in extreme environmental conditions using body heat/thermal sources and induced motion/vibrations.

Piezoelectric↗