densities and linear densities for these components were obtained from the SP-100 100 kWe reference design. (Note: Since OTRs do not have to control an active coolant loop, the components used for that function were omitted from the OTR estimates.) Mass estimates for all of the radiators include armor to protect them against micro-meteoroids. We assume that armoring is provided by simply increasing the thickness of the heat pipe radiator walls since these are near-term systems. If graphite armor were available, the associated mass could be reduced, lire armor is thick enough that the radiators have a 97.5% probability of being fully operational after ten years operation at the selected orbit altitude. Any penetration of the armor would cause only limited degradation due to redundancy of the heat pipes in each radiator. The specific masses used for the waste heat radiators are 6.8 kg/m2 for temperatures below 690 K and 8.2 kg/m2 for temperatures above 690 K. Micro-meteoroid protection was not included for any other components since we lack both the design detail and the time to do so. It is of interest to note that space debris is not yet a threat at the selected orbit altitude which is fortunate because it is impossible to protect against space debris without huge mass penalties. Mass estimates also include aluminum shielding around all electronics of sufficient thickness to limit the dose from protons and electrons in the Van Allen belt to 20% of the total dose that the electronics must survive. • Mass estimates for the radiation shields consider: • reactor control electronics which operate at 300 K and can withstand 1016 neutrons/cm2 and 0.5 Mrad of gamma radiation. • power conditioning electronics which operate at 425 K and can withstand 1013 neutrons/cm2 and 1 Mrad of gamma radiation. • satellite payload devices which operate at 300 K and can withstand 1013 neutrons/cm2 and 1 Mrad of gamma radiation. Since the power conditioning electronics are limited to 1013 neutrons/cm2, the payload need be no harder than that and we arbitrarily assume that all payload electronics, sensors, and other functions can meet or be locally shielded to survive the above payload environment. • that all components are shielded so that no more than 80% of the above specified doses comes from the reactor and no more than 20% from the natural environment. • a varying separation distance between the reactor and the satellite payload optimized to minimize total system mass (See Figure 4.4 for a typical example). Boom mass is assumed to be 9 kg/meter, which is typical of the beryllium design proposed for the SP-100 thermoelectric system. We calculate that a 20 m boom of this design cantilevered horizontally could support a 1100 kg load at 1 g without exceeding yield stresses in the materials. This assumes that the joints of the fully extended boom could be made as strong as the parent material. Such a boom could
RkJQdWJsaXNoZXIy MTU5NjU0Mg==