As the Space Shuttle Atlantis prepares to launch this afternoon at 1 PM, a curious sight has unfolded at the Cape that will be the last such sight during the shuttle program - there are two shuttles on their respective pads at the same time. It’s a sight that has occurred before, but never under these circumstances.
The second shuttle, Endeavor, is on the pad not just for its upcoming trip to the ISS, but it is also serving as a potential rescue ship for Atlantis should the ship be irreparably damaged while on orbit. The risks are slightly hightened for the STS-125 mission as it visits the Hubble Space Telescope for the last time as it is in a higher orbit with more debris. As the Columbia tragedy taught us, it doesn’t take much for the shuttle to be damaged in the wrong place for the whole mission to be compromised.
Other shuttle missions since the accident have all visited the station which can act as a save haven if something were to happen to a shuttle. There, the astronauts have enough resources to survive for months while a rescue mission could be mounted. At Hubble, the time is measured in weeks, far too short for a rescue shuttle to not be on the launch pad.
If the rescue mission needs to be mounted, it will be called STS-400 and will involve a skeleton crew being launched on Endeavor to rondezvous with Atlantis in orbit in a matter of a few days following the discovery of any damage. Once near each other, their robotic arms would interlock and a tether strung between the two airlocks. A series of three spacewalks would then transfer the 7 astronauts on Atlantis to Endeavor to join the 4 astronauts on board there. The crews would return to earth on Endeavor and Atlantis would be ditched over the Pacific Ocean where the debris could fall away from population centers. If STS-400 does happen, it would be one of the riskiest missions in NASA history, rivaling the Apollo 13 mission. Space shuttles have never flown simultaneously and a rondezvous would be unprecedented.
My thoughts and prayers are with STS-125 and that STS-400 never has to happen.
God Speed Atlantis!