| No spacecraft will ever be perfectly safe. Consequently, engineers must strive to design, develop, and operate spacecraft that are safe enough. This thesis presents a conceptual framework for defining and characterizing "safe" and distinguishing "safe enough" from "not safe enough." Space Shuttle and Soyuz safety records are presented in the context of this framework, and compared to the safety records of various modes of transportation (automotive, rail, boating, general aviation, commercial aviation) and adventure sport activities (skydiving, mountaineering, SCUBA diving). From these comparisons, a heuristic method for predicting space flight risk is derived. This method, which is built upon the inverse correlation between risk and usage, can coarsely predict risk in the absence of detailed spacecraft data. Based on these predictions, spacecraft risk can either be accepted as "safe enough" or rejected as "not safe enough."... |
