An Alternative Approach to Human Servicing of Crewed Earth Orbiting Spacecraft
As crewed spacecraft have grown larger and more complex, they have relied on spacewalks, or Extravehicular Activities (EVA), for assembly and to assure mission success. These spacecraft maintain all of the hardware and trained personnel needed to perform an EVA on-board at all times. Maintaining this capability requires up-mass, volume for storage of hardware, and crew time for on-orbit training and maintenance of hardware. This paper proposes utilizing launch-on-need hardware and crew, or regularly scheduled missions to provide EVA capability for space stations in low Earth orbit after assembly complete. For crew safety contingencies, it is assumed the station is designed such that the crew could either solve those issues from inside the spacecraft or use the docked Earth to Orbit vehicles as a return lifeboat, such as the International Space Station (ISS) which does not rely on EVA for crew safety related contingencies. This approach reduces ground training requirements for long duration crews, saves on-orbit crew time in the form of hardware maintenance and training, and leads to more efficient EVAs because they would be performed by specialists with detailed knowledge and training stemming from their direct involvement in the development of the EVA. The on-orbit crew would focus on the immediate response to failures such as systems reconfiguration or jumper installation as well as the day-to-day operations of the spacecraft and payloads. This paper offers an alternative to how current unplanned EVAs are conducted on ISS. Any space station that utilized this approach would need a robust transportation system. In addition, fault tolerance of the future space station would be an important consideration in how much time was available for EVA preparation after the failure. Future programs must weigh the risk of on-time launch against the increase in available crew time for the main objective of the spacecraft.
Brian Alpert, NASA Johnson Space Center (JSC), USA
ICES403: Extravehicular Activity: Operations
The 47th International Conference on Environmental Systems was held in South Carolina, USA on 16 July 2017 through 20 July 2017.