a. Space Environment The special space environmental conditions that must be considered in assessing personnel risk are lengthy exposures to zero-gravity and space radiation (Ref. A9). The effects of zero-gravity are not mentioned beyond this, although the duration SPS workers would spend in 0-g would be for longer than has yet occurred. Ref. A9 indicates that for protection from radiation, assembly would utilize a high degree of remotely controlled activity from a protected environment, and that extravehicular activity would be restricted to special requirements. The radiation risk is indicated more quantitatively in Refs. A12 and A16. This is depicted in Exhibit 52. From the tabular data in the upper portion of Exhibit 52, it can be seen that SPS workers can receive greater radiation doses than the suggested limits. This can be countered to some extent by protective shielding, and the curves in the power portion of Exhibit 52 indicate the required shield mass. From these curves, it can 2 2 be seen that shield masses of 8 Ib/ft (40 kg/m ) are required to meet bone marrow radiation dose limits for a six month stay in low earth orbit, 2 2 and shield masses of 6 Ib/ft (30 kg/m ) are needed to meet comparable requirements in geosynchronous orbit. These standards were proposed originally by the National Academy of Science for astronauts and are probably not suitable for a commercial activity such as SSPS construction. Atomic workers exposure standards would seem to be more appropriate. These standards are also much lower. Thus, considerably more shielding or shorter heating cycles would be required if the atomic worker dose were used and this could adversely impact the feasibility of the SSPS. b. SPS Created Environment The factors of concern with respect to the environmental conditions created by the SPS stem chiefly from the high voltages and the microwave radiation that will be present. The risks to SPS workers associated with these factors has not been addressed. Ref. All states that potentially hazardous situations have been identified for virtually all phases of SPS assembly and operations, and concludes that further studies are required. It also points out, particularly with regard to the Power
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