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Safety has always been an important issue in the United States space program. One area of particular concern, especially since the Challenger accident, is crew rescue. While much attention has been given to crew rescue during launch and landing, interest in rescuing a stranded EVA crewperson is only beginning to increase now. Although there were orbital EVAs in the Gemini and Apollo programs, they were of short duration, and total excursion ranges were small so reattachment of a safety tether was not required. With maintenance of a piece of real estate as large as space station Freedom, astronauts will have to undo and reattach their tethers to reach remote locations. The increasing number of EVAs in the future also elevates the probability of a tether breaking. A mechanism for recovering from a crew separation needs to be determined to prevent a life being lost on-orbit.

Due to an increase in spacecraft traffic forecasted for the space station era, researchers are investigating manual control and other aspects of docking operations with hopes of increasing safety, productivity, and likelihood of success while decreasing cost. Experiments have been performed which revealed the effect of approach velocity, in-flight anomalies, and control mode. Displays have been designed to enable flight planners to more easily overcome the difficulties presented by orbital mechanics. Improved understanding of human factors in the docking mission and other orbital maneuvers will play a significant role in design tradeoffs concerning thruster size, docking fixture style and mass, and on-board trajectory planning displays.