EVA Controls for a Partially Captured Payload After Two Simultaneous System Failures During Payload Berthing Operations 2000-01-2443
The viability and long term success of the International Space Station (ISS) is at least partially dependent on the effective use of the six attached payload sites provided on its truss structure. These sites, two on the port end and four on the starboard end of the truss, provide locations for scientific and commercial payloads that require direct access to the space environment. These sites have been designed to accommodate external payloads that are nominally attached using the Space Station Robotic Manipulator System (SSRMS). Although certain redundancies have been designed into the berthing system used at each site, a potentially catastrophic hazard has been identified in the unlikely event that the berthing system and its redundancies fail when a payload is partially captured but not fully berthed to the site. Under this scenario, it is imperative that the payload be fully disengaged from the site before posing a catastrophic risk to the crew or the space station.
Failure of the primary (robotic) berthing system requires EVA operation of a back-up manual override. In the event that the manual override mechanism also fails, provisions must be made to permit separation of the payload from the site. This paper examines the EVA controls developed to effectively separate a partially captured payload from the attached payload site when the robotic berthing system fails. The solution developed by Boeing-HB is to provide an EVA removable capture latch on the attach site and an EVA releasable capture bar on the payload itself. Included in this paper are descriptions of the EVA analysis methodology used to arrive at a system solution to this scenario and a description of the relevant hardware. This paper also presents safety and EVA requirements that influenced the final solution and how those requirements are flowed down to potential payload users.