Engineering topics

Schwartz, D. S.

Publications and source records attributed to Schwartz, D. S..

5 records

NASA NTRS1994

Influence of high pressure hydrogen environment on creep deformation of Mo-Re, Haynes 188, and NARloy-Z alloys

The present study focuses on the investigation of the influence of hydrogen on the mechanical properties of three types of alloys at elevated temperatures. The reasons for the consideration of hydrogen effects are the potential use of hydrogen as a coolant in gas-cooled reactors and fuel in advanced hypersonic vehicles. The materials used in hydrogen atmosphere must not be embrittled by hydrogen at ambient temperature and should have good strength in hydrogen atmosphere at elevated temperature. The paucity of information concerning the mechanical performance in hydrogen atmosphere at elevated temperature has been a limiting factor in the selection and design of structural components for operation in hydrogen environment.

Sastry, S. M. L.↗

NASA NTRS1991

A novel hydride phase in hydrogen charged Ti3Al

The effect of internal hydrogen on the microstructural modification of Ti3Al (alpha-2) compound was studied by large-angle neutron scattering and TEM. Ti-25 at. pct Al (Ti3Al) specimens were exposed to gaseous hydrogen atmosphere at 600 C that resulted in internal hydrogen concentration of 2000 ppm. The hydrogen-charged alloy consisted of a mixture of alpha-2 phase and a novel Ti3AlH phase with the E2(1), (Pm3m) crystal structure. The lattice parameters and atomic arrangement of the Ti3AlH phase were determined.

Schwartz, D. S.↗

NASA NTRS1975

In orbit sun calibration performance of Landsat-2

Sun calibration data from Landsat-2 are presented and compared with those from Landsat-1 (ERTS-1). The data support the hypothesis that organic contamination caused the poor performance of the Landsat-1 sun calibration mirror, since extra cleanliness precautions were taken with the Landsat-2 mirror. These precautions are described; of particular importance was the aluminum foil covering kept close to the reflective surfaces of the second mirror during the prelaunch period.

Horan, J. J.↗

NASA NTRS1974

Partial performance degradation of a remote sensor in a space environment, and some probable causes

The Multispectral Scanner (MSS) was launched on the Earth Resources Technology Satellite (ERTS-1) on July 23, 1972. The MSS has two calibration systems, one internal and one external. Both calibration systems have shown strong, spectrally dependent performance degradation since launch. This paper presents details on the optical system of the MSS and data on the performance degradation as a function of both spectral interval and time in orbit. The history of the MSS during tests is traced, and it is shown that hydrocarbons from an external source may have been deposited on optical surfaces in the instrument. It is postulated that these contaminant coatings may have polymerized as a result of the exposure to UV light from the sun, increasing their blue absorbtion and accounting for the observed performance degradation.

Horan, J. J.↗

NASA NTRS1973

Performance of optical surfaces in space.

The Multispectral Scanner carried by the ERTS-1 satellite (launched on July 23, 1972) is a very high resolution line scanning imaging radiometer operating in the visible and near infrared spectral regions. The instrument contains optical surfaces that are exposed to both direct and reflected sunlight, and the reflectivity and transmission of some of these surfaces have decreased in orbit. Details of the optical system are explained, and data on the degradation are reviewed as a function of both spectral interval and time in orbit. The history of the scanner during testing (when hydrocarbons from an external source may have been deposited on the optical surfaces) is also examined, and a mechanism is postulated for the observed degradation in orbit.

Horan, J. J.↗