Test and space experience with protoflight spacecraft

Data are presented on environmental testing of protoflight spacecraft, which are defined as spacecraft designed in advance to serve as both a prototype and a flight model. Protoflight spacecraft discussed include DME-A, IMP-F, RAE-A, ISIS-A, TIROS-M, SAS-A, IMP-I, ISIS-B, SSS, ERTS-A, IMP-H, SAS-B, RAE-B, IMP-J, AE-C, and SMS-A. Comparative data on conventional and protoflight test programs are given together with results of the in-test performance of the 16 protoflight craft and a comparison of the space performance of 53 conventional flight spacecraft and the 16 protoflight ones. It is concluded that: (1) based on system-level test results, some additional risk of space failures appears to exist when a protoflight spacecraft is launched instead of a flight craft; (2) the space performance of all protoflight craft to date has been satisfactory, with failure rates slightly less than those for conventional flight craft; and (3) the results of the present study support the continued use of the protoflight concept.