Engineering topics

Jeffery, J. A.

Publications and source records attributed to Jeffery, J. A..

4 records

NASA NTRS1982

Assessment of contamination in the Shuttle bay

The results of an analytical study to determine the contamination potential of the Galileo probe instruments while in the STS bay are presented. The study covered conditions wherein the instruments weren't covered, covers were used with vent paths of varying sizes, and if the instruments were sealed and a nitrogen purge was employed. The contamination limits for each of the Galileo instruments are considered. Analytic approximations are devised for the diffusion of particles from surfaces and materials in the Shuttle bay during the ascent phase, using Fick's second law of diffusion. It is recommended that an instrument purge be implemented during the first 15 min of Shuttle flight in order to carry the contaminants from both the bay fixtures and from the instruments into space. Covers are suggested as necessary for the most sensitive instruments.

Jeffery, J. A.↗

NASA NTRS1981

Spacecraft contamination prediction and testing techniques

Techniques used in the prediction of spacecraft contamination for the Galileo Jupiter Orbiter and in the determination of the effects of such contamination are presented. Following a quick-look assessment of the contributions of ground-based initial contaminant loading, launch vehicle interface effects, vacuum-exposed outgassing deposition and attitude control thruster impingement and venting to the spacecraft contamination burden, the evaluations centered on the effects of the attitude control thruster on the scan platform optics, including calculations of thruster flowfields and a high-fidelity computer simulation of contaminant distribution. The evaluations revealed a considerable problem with thruster contamination, which could be solved by the use of a thrust shield and the avoidance of thruster operation at certain scan platform orientations. The effects of the various possible contaminants on spacecraft thermal and optical system performances were also investigated in studies of the optical transmittance of deposited monomethyl hydrazine nitrate, vacuum optical degradation due to contaminant outgassing and re-emission outgassing, and an operational satellite contaminant monitor on the NOAA-C satellite. It is concluded that with a good evaluation and testing program, contamination control may become a necessary portion of system design procedures, and recommendations for the implementation of various practices and tests to minimize contamination effects are presented.

Jeffery, J. A.↗

NASA NTRS1980

Effect of bipropellant plume exhaust effluents on spaceborne optical instruments

Analytical tools together with a good data base are necessary to predict the transport of plume contaminants and their effects on spacecraft surfaces. The present paper describes an assessment of bipropellant thrusters, the production and transport of plume contaminants from these thrusters, and the use of the JPL contamination analysis program to assess the effects of plume contamination on the Galileo spacecraft. It is shown that, in the case of the Galileo mission, contamination from the liquid engines has been effectively reduced to nothing by the use of predictive tools. Plume shields together with precise scan platform stowage have been designed to protect the optical instruments.

Maag, C. R.↗

NASA NTRS1979

Space station thermal control surfaces

Mission planning documents were used to analyze the radiator design and thermal control surface requirements for both space station and 25-kW power module, to analyze the missions, and to determine the thermal control technology needed to satisfy both sets of requirements. Parameters such as thermal control coating degradation, vehicle attitude, self eclipsing, variation in solar constant, albedo, and Earth emission are considered. Four computer programs were developed which provide a preliminary design and evaluation tool for active radiator systems in LEO and GEO. Two programs were developed as general programs for space station analysis. Both types of programs find the radiator-flow solution and evaluate external heat loads in the same way. Fortran listings are included.

Maag, C. R.↗