1989-07-01

Development of an Extravehicular Activity Self Rescue Technique for Space Station 891594

An astronaut performing an extravehicular activity (EVA) exposes him/herself to many risks from which his colleagues inside the space vehicle are shielded. Among these are suit depressurization as a result of micrometeoroid impact and portable life support system (PLSS) failure. In addition, there is a risk of prolonged separation from the vehicle should a tether break or a manned maneuvering unit (MMU) run out of fuel. While it may be possible for the shuttle to retrieve and rescue a stranded crew member if necessary, the space station will not possess the required mobility to do so. In order to simplify contingency operations and to prepare for the situation when no other means is available, a self-rescue capability must be determined. A crew member working. on a remote area of the space station may become separated from his work site. S/he may depart with a substantial separation velocity and might also be tumbling around one or more principal axes, A design study was conducted to delineate potential failure modes and to evaluate various solutions.
Tens of thousands of hours of extravehicular activity (EVA) will be required for Space Station assembly and maintenance.(1) Experiments will have to be exchanged and repaired, and structural elements may have to be replaced as well. Although EVA crew will be required to be tethered to the station when they are not in an manned maneuvering unit (MMU), it is inevitable that a crew person will become untethered and separated from the station during the course of the station's 20-30 year lifetime. Once adrift,it matters not whether an individual is one centimeter or one kilometer away from the station,s/he has no means of returning to the station. Any form of rescue that is provided must be quick,reliable and cost effective. A solution for this failure was sought and is presented here.

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