In the meantime, some small upgrades to astronaut flight suits and orbiter structure could improve escape procedures in the near term.
"Today's flight suits don't have a constant volume at the joints and elbows," explained aerospace engineer Bruce Hilty, of NASA's Johnson Space Center, during a summit here this week on the agency's shuttle life extension program. "When they inflate upon decompression, they can swell up like the Michelin tire man."
Getting unstrapped and out the shuttle door can then be so difficult that the entire crew would not make it to safety, he added.
Then and now
The first few shuttle missions had a pair of ejection seats for the mission commander and pilot, who were the only humans aboard the vehicles at the time. A larger scale escape system has been in place since 1986, following the 1986 Challenger accident that claimed the lives of seven astronauts when a solid rocket booster exploded shortly after launch. That system is designed to help astronauts bail out, using a pole track to pass over the shuttle wing and parachute to safety. But the system is only useful during the last stages of descent.
Additional hardening and thermal protection of the shuttle's crew compartment could also increase the survivability of the astronauts inside, giving them more time to make a safe egress, NASA officials said. Analysis of past shuttle accidents, such as the 2003 loss of Columbia and the Challenger explosion, showed that the pressurized crew cabin appears to stay relatively intact during a catastrophic break-up.
"We're looking to see if we can find a way to help that [process] along," Hilty said.
Improvements to search-and-rescue protocols, such as more advanced location beacons for astronauts and a broader, less U.S.-centric focus for rescue aircraft would shorten the time needed to locate shuttle crewmembers should they be forced to bail out over the ocean while approaching alternative landing sites in Europe.
"There are so many things that on the low-end that we can go for to improve crew survivability," said Bill Parsons, manager of the space shuttle program. ""Our main goal is to make sure the vehicle is safe for flight."
Future escape systems
NASA engineers evaluated a number of systems for future spacecraft, including personal ejection seats powered by rockets, pod-like encapsulated ejection seats and even a full separation of the nose and crew compartment from the rest of the space shuttle. Most of those options had long lead times to first flight, more than eight years -- and a cost of $4.2 billion in the nose-separation version.
"There's been a lot of discussion on crew escape systems, but if it takes eight years to develop something, we're not going to go down that path with the current shuttle," said Michael Kostelnik, NASA associate administrator of the shuttle and space station programs. The technology could, however, be folded into NASA's new focus on manned exploration of space further down the line, he added.
Higher up
Unlike the pole system aboard the shuttle, which is useful up to an altitude of about 60,000 feet, future escape systems must push to higher altitudes and speeds to stretch the egress windows of astronauts aboard.
Some of the options studied by engineers were thrown out because they failed to provide escape procedures for a total crew of seven astronauts, the standard expected to service the ISS, or were too heavy to meet shuttle weight requirements without cutting out valuable workspace in the rear of the spacecraft's flight deck.
The most desirable option for crew escape was a two tiered system that included two ejection seats in the cockpit for the pilot and commander. The rest of the seven-person crew would sit in a canister in the shuttle's payload bay with their own ejection seats. "It would be similar to a modified docking adapter for the ISS," Hilty explained.
That option, he said, could cost up to $2.2 billion and take 6.5 years to develop.
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