Engineering topics

Murphy, Gerald B.

Publications and source records attributed to Murphy, Gerald B..

4 records

NASA NTRS2001

Using a delta-doped CCD to determine the energy of a low-energy particle

The back surface of a thinned charged-coupled device (CCD) is treated to eliminate the backside potential well that appears in a conventional thinned CCD during backside illumination. The backside of the CCD includes a delta layer of high-concentration dopant confined to less than one monolayer of the crystal semiconductor. The thinned, delta-doped CCD is used to determine the energy of a very low-energy particle that penetrates less than 1.0 nm into the CCD, such as a proton having energy less than 10 keV.

Nikzad, Shouleh↗

NASA NTRS1990

Environmental interactions on Space Station

This paper describes the key environment/system interactions associated with the Space Station and its companion polar platform and defines the range of test environments that will need to be simulated. These environments include the neutral atmosphere, the ionospheric plasma, natural and man-made particulates, the ambient magnetic field, the South Atlantic Anomaly, and the ram/wake environment. The system/environment interactions include glow, oxygen erosion, drag, radiation effects, induced electric fields, high-voltage solar-array effects, and EMC/EMI associated with plasma/neutral gas operations. The Space Station and its associated systems pose unique demands on the ability to simulate these effects; synergistic effects require multiple environments to be simulated simultaneously, and the long life requirements require proper scaling of the exposure time. The analysis of specific effects and the calibration or improvement of ground test techniques will likely require in situ evaluation. Qualification and acceptance testing, because of cost and the impractically of extensive on-orbit analysis/modification, will likely remain ground test objectives except in very rare cases.

Garrett, Henry B.↗

NASA NTRS1988

Gaseous environment of the Shuttle early in the Spacelab 2 mission

A cold-cathode ionization gage was flown on Space Shuttle flight STS-5IF as part of the Spacelab 2 payload. Neutral pressure data that were taken in the payload bay during the first few hours on orbit are presented. These data show that when the payload bay is oriented such that the atmospheric gases are ramming into it, the pressure rises to a peak of 4 x 10 to the -6th Torr. Pressure is also slightly higher during the sunlit portion of each orbit. Outgassing of the payload bay causes the pressure to be elevated to a few times 10 to the -6th Torr early in the mission. In addition, several effects on pressure have been identified that are due to chemical releases. Substantial increases (50-150 percent) are seen during another experiment's gas purge. Orbiter chemical-release effects include: pressure increases of 200 percent up to 7 x 10 to the -6th Torr due to Orbital Maneuvering System burns, minor perturbations in pressure due to vernier thruster firings and little or no increase in pressure due to water dumps. In the case of vernier thruster firings, effects are seen only from down-firing thrusters in the back of the Orbiter, which are probably due to reflection of thruster gases off Orbiter surfaces.

Pickett, Jolene S.↗

NASA NTRS1986

A review of the findings of the plasma diagnostic package and associated laboratory experiments: Implications of large body/plasma interactions for future space technology

The discoveries and experiments of the Plasma Diagnostic Package (PDP) on the OSS 1 and Spacelab 2 missions are reviewed, these results are compared with those of other space and laboratory experiments, and the implications for the understanding of large body interactions in a low Earth orbit (LEO) plasma environment are discussed. First a brief review of the PDP investigation, its instrumentation and experiments is presented. Next a summary of PDP results along with a comparison of those results with similar space or laboratory experiments is given. Last of all the implications of these results in terms of understanding fundamental physical processes that take place with large bodies in LEO is discussed and experiments to deal with these vital questions are suggested.

Murphy, Gerald B.↗