Military needs for orbital power

Results of the DoD/ERDA (now Department of Energy) Space Power Study completed in October 1977 are presented. The major new thrust of Air Force Advanced Technology Plans center on the development of military solar power systems which will extend capabilities to the 10 - 50 KW sub e power range for new classes of missions while maintaining technology applicability to the 0.5 - 10 KW sub e present mission class. The status of FY78 efforts for Project 682J (Air Force Space Power Advanced Development Program) are reported. Project 682J is divided into the following tasks: (1) high efficiency solar panel; (2) nickel-hydrogen battery; (3) gallium arsenide solar concentrator hardness study; and (4) new-start nuclear dynamic power system applications/integration study

Radioisotope Power Subsystems for Space Applications

Many future space power requirements in the low power regime (watts to a few kilowatts) 9 with durations of a few months to years 9 are potentially satisfied by utilization of radioisotope power subsystems. The isotope power subsystems of today , essentially first generation devices, do not provide a direct basis for extrapolation to future performance capabilities. Many development problems must be solved before isotope power subsystems realize their full potential. The currently operational isotope powered I!SNAP I! units for space application are characterized by high specific weight (l watt/lb), low power output (\u3c=25 watts) , low heat source temperature (~1000°F)^ and low conversion efficiency (\u3c=5%). Future capabilities promise 10 to 20 watts/lb, 2000°C heat source operation ^ and conversion efficiencies approaching 20%. This paper examines the technical advancements necessary to attain these performance capabilities

Encapsulated sink-side thermal energy storage for pulsed space power systems

In sprint mode space applications, which require high power for relatively short durations, energy storage devices may be employed to reduce the size and mass of the thermal management system. This is accomplished by placing the reject heat in the thermal store during the sprint mode. During the remaining nonoperational portion of the orbit the stored heat is dissipated to space. The heat rejection rate is thus reduced, and this results in a smaller radiator being required. Lithium hydride (LiH) has been identfied as the best candidate for use in power system sink-side thermal energy storage applications due to its superior heat storage properties and suitable melt temperature (T/sub m/ = 962K). To maximize storage density, both sensible and latent modes of heat storage are used. This paper focuses on the use of encapsulated lithium hydride shapes in a packed bed storage unit with lithium or NaK as the heat transport fluid. Analytical and experimental development work associated with the concept is described. Since the program is in its early stages, emphasis thus far has been on feasibility issues associated with encapsulating lithium hydride spheres. These issues include shell stress induced by phase-change during heating, hydrogen diffusion through the encapsulating shell, heat transfer limitations due to poor conductivity of the salt, void behavior, and material constraints. The impact of these issues on the design of encapsulated lithium hydride spheres has been evaluated, and design alternatives have been identified for circumventing key problem areas

The Drag Coefficient of a Sphere in a Square Channel

The drag coefficient of a sphere in unconfined flow is given in most fluid mechanics texts, for example, Massey (1979). The drag coefficient, CD, is determined by measuring the force exerted on the sphere by the fluid when the relative velocity between the sphere And the oncoming fluid is known. Fluid flow over a sphere located inside a tapered tube has been studied because of application to flowmeter design (Blevins, 1984). … The purpose of this note is to present the drag coefficient of a sphere in a square channel at low Reynolds number (Re \u3c 1800). For smooth spheres, the drag coefficient depends on Re and the ratio d/W. This information is lacking in the literature