Two space shuttles now sit out on the launch pads at Kennedy Space Center: Atlantis on 39A for the much anticipated Hubble Repair mission, scheduled to launch on May 12. Over on 39B sits Endeavour, which made the slow journey there early on Friday and she is now poised for the STS-400 LON (Launch On Need) Mission, a mission no one hopes will happen. This would be a mission to rescue the crew of Atlantis should the shuttle be struck by debris – either during launch or during the mission (read more about the risks of debris hit during the Hubble Mission). If STS-400 were necessary what would actually happen?
In the situation where Atlantis and the crew are not in immediate danger, but, for example, the shuttle’s thermal protection system (heat tiles) were compromised from debris hit (from insulating foam from the external tank like Columbia was, or space debris) and the shuttle would be unable to land safely, Endeavour would be launched at a specific time and inclination in order be able to rendezvous with Atlantis. The rescue flight would last 8 days and go as follows:
Once Endeavour and her four-person crew reaches orbit, the preparations for rendezvous with Atlantis would begin. Unlike all previous post-Return to Flight missions, the crew would not perform the standard Thermal Protection System inspection on Flight Day Two, but instead by done after the STS-125 crew was rescued.
Endeavour would rendezvous with Atlantis the day after launching from the Kennedy Space Center. The two space shuttles would then approach each other payload bay to payload bay, at a 90-degree angle, about 44 ft apart. Endeavour’s robotic arm would grapple the orbital boom system on Atlantis. After Endeavour successfully grapples Atlantis, Endeavour would take attitude control of the “stack” of the two shuttles.
Then, comes the most interesting – and dangerous – part. Spacewalkers from Endeavour would do one space walk on Flight Day 3 to string a tether between both shuttles. On Flight Day 4, they would conduct two spacewalks to retrieve their colleagues from Atlantis.
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Once Atlantis’ crew is safely aboard the rescue orbiter, Endeavour’s crew will maneuver the two vehicles to provide the right separation, which would occur during daylight so the crew could watch for any problems.
Atlantis would be released and be commanded from the ground to do deorbit and landing maneuvers and likely crash into the Pacific Ocean.
On Flight Day 5 the dual crew would inspect Endeavour for damage, and if all was well, land on Flight Day 8.
Astronaut John Grunsfeld, one of the four spacewalkers who will fly on Atlantis, says keeping the Hubble telescope flying is a mission worth the risk.
“When you think about risk, it is all relative to what is the reward, and I think in the big picture Hubble is something that I certainly feel is worth risking my life for because it is about something that is so much bigger than all of us,” Grunsfeld said. “It is about science, it is about inspiration, it is about discovery. It is about all the kids who will look at the Hubble images and dream.”
Source: NASA Spaceflight.com