June 16, 2008 -- Trapped in space on a crippled shuttle — it's every astronaut's and NASA's worst nightmare. That's why, when the shuttle Atlantis goes to repair the Hubble space telescope this fall, NASA has a backup plan: STS-400, the ultimate "what if" scenario.
When NASA launches the Hubble repair mission, STS-125, astronauts won't come anywhere close to the safe haven the International Space Station provides if a shuttle cannot safely land. Instead, they'll be on their own in high Earth orbit.
Atlantis will be commanded by astronaut Scott Altman along with six crew mates. If they cannot get Atlantis down, a second shuttle — designated STS-400 — would have to go rescue them. It is the mission NASA hopes never to fly. And it would be a race against time.
ABC News has obtained the flight plan for STS 400, which reveals the details of what would be a daring, but carefully planned, rescue to transfer the Atlantis crew to another shuttle before sending the multibillion-dollar Atlantis crash landing into the ocean below.
Spacewalking to Safety
The mission to repair Hubble was planned for years but cancelled in 2003 after the Columbia accident. It was thought to be too dangerous because there would be no way to rescue the crew if Atlantis was damaged.
A visiting crew could stay on the space station for months, if necessary, until another space shuttle could come take them home. That would not be an option for the crew repairing the Hubble space telescope. Hubble and the space station are in very different orbits, and Atlantis could not get to the space station.
The STS-400 rescue flight plan outlines an eight-day mission that would be flown by four crew members on the shuttle Endeavour. Endeavour would be on its launch pad during Atlantis' flight and be ready to launch within days if needed.
The mission schedule would go like this:
Flight Day 1: Launch
Flight Day 2: Rendezvous and grapple Atlantis using both shuttles' robotic arms.
Flight Day 3: First spacewalk to string a tether between both shuttles.
Flight Day 4: Third and fourth spacewalks; release Atlantis, which would probably be sent to crash in the Pacific ocean.
Flight Day 5: Inspect Endeavour for damage
Flight Day 8: Deorbit and land
Weighing the Risks
NASA Administrator Mike Griffin made the decision to reinstate the Hubble mission after an 18-month study of its risks and rewards.
"The only way to get a rescue capability on the pad is to prepare two shuttles, have them ready to go. The second shuttle will be a normal space station mission shuttle, and we will use it for that if it is not needed for the rescue," Griffin said. "We think it won't. We think the odds are only one in 400 that we would need to launch a rescue shuttle."
Even with those odds, when Atlantis rolls out to the launch pad 39A, Endeavour will be close behind, headed to launch pad 39B. Atlantis could only stay aloft with extreme power conservation for 25 days. The rescue mission could launch as early as the fourth day of Hubble's mission.
Veteran astronaut Navy Capt. Christopher J. Ferguson would command Endeavour, with pilot Air Force Lt. Col. Eric A. Boe and two spacewalking astronauts from the Endeavour crew, who would go get their colleagues on Atlantis.
"We have put a plan together [so] we can get there as quickly as we can," said Tony Ceccacci, the lead flight director for the Hubble mission. "We have between 17 and 25 days that the 125 vehicle can stay on orbit, and we have very high confidence we can get a rescue vehicle to them in that time."
Getting Endeavour to Atlantis would only be half the battle. Atlantis' crew members would need to be transported across the gap between the two shuttles.
Endeavour would rendezvous with Atlantis the day after launching from the Kennedy Space Center. The two space shuttles would then orbit payload bay to payload bay, at a 90-degree angle. Endeavour's robotic arm would grapple the orbital boom system on Atlantis, and then the spacewalkers from Endeavour would retrieve their colleagues from Atlantis in a series of three spacewalks — including two on one day, something NASA has never done before.
Four of the astronauts on the Hubble crew are trained spacewalkers.
Altman, pilot Greg Johnson and robotics officer Megan McArthur are all training on spacewalks for this what-if scenario. The training also includes an intense multi-day simulation at the Johnson Space Center with Mission Control and all the flight support teams.
Astronaut John Grunsfeld is one of the four spacewalkers who will fly on Atlantis. This mission will be his fifth trip into space and his third trip to repair the Hubble. Grunsfeld is also an astronomer, who 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."