Three months after the Columbia shuttle disaster, NASA is still trying to decide how to keep humans flying in space. Officials are weighing different options, ranging from building a fourth, replacement shuttle to bringing back a version of the Apollo spacecraft that carried astronauts to the moon three decades ago.
None of the proposals appears to satisfy the conflicting demands of safety, cost, timeliness and practicality. "I'm very disappointed," Rep. Dana Rohrabacher, the California Republican who is chairwoman of the House Space Subcommittee, said at a recent hearing on the National Aeronautics and Space Administration's problem.
Although no final decision has been made, NASA's tentative plan is to fix the remaining three shuttles so they can continue flying until at least 2015, while building a smaller, safer Orbital Space Plane to take over the task of human flight by 2010.
Officials have yet to choose a design for such a plane, which could carry at least four people into orbit and back again. It might be winged, like the shuttle, or wingless, like the three-person Russian Soyuz spacecraft that now is Earth's only way to boost people into space.
The orbital plane is estimated to cost from $9 billion to $13 billion just for development, and it wouldn't completely fill the need for a way to rescue the space station crew in an emergency because it would carry only four members of a crew that could number as many as seven. The astronauts still would have to depend on the Soyuz, which docks at the station, if an emergency occurred.
Meanwhile, the remaining three shuttles will have to be modified to minimize the risk of another disaster if they return to flight. Operating shuttles and space planes at the same time for a number of years would be a substantial expense. "It is unclear whether NASA can afford to operate both at the same time," Rohrabacher said.
The Soyuz would be the only way to get people to and from the space station if the shuttle remained grounded. Russia has agreed to do this until only 2006, leaving a four-year gap before the space plane would be ready.
Other ideas being considered for space flight include:
Risk no more human lives on the remaining shuttles, and use them only to ferry cargo to and from the half-finished international space station or to service robotic science missions, such as the Hubble Space Telescope. "We can't make the existing orbiter as safe as it needs to be," said Rep. Joe Barton, a Texas Republican and a key member of the Space Subcommittee. "I think we ought to scrap that program."
This plan would require NASA to convert the shuttles to operate autonomously, using advanced video guidance and computer controls. A test version of such a system is to be demonstrated later this year. The Russian Progress supply spaceships use automated docking, and Russian cosmonauts formerly landed under robotic control.
NASA Administrator Sean O'Keefe said unmanned shuttles might be useful eventually, "but for the foreseeable future, human involvement will be required."
Park a shuttle at the space station for four months at a time so it could serve as an emergency escape vehicle for up to 10 people. This would allow a larger crew to live and work at the station, so more science could be done. A drawback is this plan would keep a third of the remaining shuttle fleet inactive for long periods.
Redesign the flight deck, where the pilot and three other crew members sit, to be used as an escape capsule in case of emergency. This would require the shuttle crew to be reduced from seven to four people.
Create an updated version of the old Apollo spacecraft, flown from 1968 to 1972 during the moon-landing program. The cone-shaped Apollo command module could be used for crew rescue and transport, and the larger cylindrical service module could handle cargo.