An altitude-dependent spacecraft charging model

A model for the altitude dependence of the hot plasma parameters responsible for the electrostatic charging of spacecraft was developed. Based upon plasma orbit theory, the directed velocity is a function of the ambient magnetic field flux density. A consequence of this approach is that while the thermal velocity distributions (assumed to be Maxwellian) of the plasma particles are independent of the magnetic field strength (and hence altitude), the particle densities increase with magnetic field strength. Thus, according to this model, while the equilibrium voltage is independent of altitude, the charging current density increases with decreasing altitude. However, the probability of such spacecraft charging decreases with decreasing altitude

Environmental effects on spacecraft materials

The effects on the natural space environments on materials are presented, which may be used for SDI applications. The current state-of-the-art knowledge of those effects was studied, and a literature search, a questionnaire mailing, and some visits to NASA and Air Force research facilities were performed. Phase 2 will be a study of what materials may be used for SDI applications and to what natural space environments they may be vulnerable. Deficiencies in knowledge of the effects of the natural space environments on these materials are to be identified and recommendations are to be made to eliminate these knowledge deficiencies

Statistical evaluation of proton radiation from solar flares Final technical report

Statistical evaluation of proton radiation from solar flare

Spleen findings in drowning

A retrospective study of spleen findings in 42 victims of drowning and a comparison group of 42 cases of asphyxiation due to other causes (hanging, ligature strangulation and manual strangulation), that were matched for sex, age, body weight and build, was performed. Significantly smaller spleen weights (P < 0.05), spleen weight:body weight ratios (P < 0.01) and spleen weight:liver weight ratios (P < 0.01) were found in the victims of drowning. The difference in weight was 18%. A significant negative correlation between spleen weight and blood alcohol concentration was found in the study group (r = −0.44; P < 0.01), but not in the control group. The possibility that the findings are due to a stress reaction caused by hypoxia in the presence of cooling and an influence of alcohol on reflex mechanisms is discussed

A flight experiment to determine GPS photochemical contamination accumulation rates

It was recently suggested that photochemically deposited contamination, originating from volatiles outgassed by a spacecraft, may be responsible for the anomalous degradation in power seen on the GPS Block 1 vehicles. In an attempt to confirm, or deny, the photochemical deposition rates predicted, a study was undertaken to design a flight experiment to be incorporated on the GPS vehicles currently in production. The objective was to develop an inexpensive, light weight instrument package that would give information on the contamination levels within a few months of launch. Three types of apparatus were studied, Quartz Crystal Microbalances, (QCM's), modified solar cells, and calorimeters. A calorimeter was selected due primarily to its impact on the production schedule of the GPS vehicles. An analysis of the sensitivity of the final design is compared to the predicted contamination accumulation rates in order to determine how long after launch it will take the experiment to show the effects of photochemical contamination