As NASA marks 25 years of shuttle flight this week, the space agency is looking ahead to its next spaceship to reach for the orbit and the Moon.
The space shuttle Columbia ushered in NASA's shuttle era on April 12, 1981, when it launched spaceward with STS-1 astronauts John Young and Robert Crippen aboard.
A quarter century later, NASA's aging shuttle fleet is destined for retirement in 2010 as the space agency returns to a capsule-based spaceflight with its $104-billion Crew Exploration Vehicle (CEV) plan. The agency's new spaceship to is expected to debut no later than 2014 to serve the International Space Station (ISS) , and push towards the Moon and possibly on the Mars.
"The shuttle was a 'do everything for everybody' vehicle," Scott Horowitz, NASA's associate administrator for the agency's Exploration Systems Mission Directorate, told SPACE.com. "We built a reusable spacecraft, which had never been done before. But it was more difficult to do than many people imagined."
"The shuttle showed us how to operate routinely in space and reaffirmed that going into [orbit] is difficult," he added.
Crew safety and escape
NASA's biggest lesson from its 114 shuttle flights - which it learned the hard way through accidents and sacrifice - has been the need for a quick and dependable way out for astronauts in case of a launch or landing emergency.
"We learned we need to have a dedicated vehicle to launch crew with a robust escape system," Horowitz said.
During Columbia's STS-1 mission and three subsequent test flights, all of which were flown by two-astronaut crews, the orbiter carried ejection seats for commander and pilot should they need to bail out of the vehicle - after first blowing the roof off the cockpit - at key moments. A bail out escape system was installed on shuttle middecks following the Challenger accident.
"Truthfully, I'm not sure that they could have handled many contingencies," Crippen told SPACE.com of the ejection seats, adding that it's unlikely they could have handled extreme failures like the Columbia or Challenger incidents. "With this [new] vehicle, we'll be able to put in an escape system that we weren't able to do with shuttle."
The CEV is expected to boast escape rockets capable of wrenching the crew capsule away from its booster during launch. Its broad, stubby heat shield concept is reminiscent of NASA's Mercury, Gemini and Apollo programs, and still employed by Russian and Chinese reentry vehicles today.
"We do know that those launch escape systems work," said Roger Launius, a former NASA historian and chair of the Division of Space History at the Smithsonian Institution's National Air and Space Museum in Washington, D.C. "We tested them unmanned on Mercury and Apollo, and the Russians have aborted twice in launches and succeeded in bringing the crew back."
"We always worried most about those and blowing the back end off the ship," former astronaut Tom Jones, a four-flight shuttle veteran, told SPACE.com. "If you had an engine explode on the way to orbit, it would probably have damaged the orbiter to the point that it couldn't return safely, and then the crew is lost."
With the capsule on top, the astronauts need not worry about foam insulation or other debris striking their spacecraft during launch, Jones said.
"We can at least look at the way the shuttle was fatally flawed, and make the CEV bulletproof to those threats," he added.
More focused spaceflight
The shift back to an Apollo-like capsule spacecraft will borrow from NASA's shuttle experience, NASA officials said. The agency plans to draw on its shuttle solid rocket boosters and external tanks to construct separate CEV crew and cargo launchers, they added.
But in return for the new system, NASA is trading the substantial performance capabilities of its shuttles, which have allowed astronauts to assemble the ISS, as well as repair satellites and the Hubble Space Telescope in orbit. The shuttle is also able to return tons of hardware to Earth from the ISS, with much of its flexibility stemming from its catch-all design.
"It's a remarkable vehicle [and] it does things that no other vehicle has ever done, and may not do for awhile," NASA shuttle program manager Wayne Hale said in an interview. "It has its limitations and we, as a spacefaring people, should have been building the next generation shuttle long ago...I think it will be well past time for the shuttle to retire when we roll it into the Smithsonian."
Launius, however, said he is concerned that NASA may spend years developing the CEV, only to be stymied after the shuttle is retired and be effectively left without a dedicated human spaceflight capability.
"The landscape right now is littered with would-be shuttle replacement programs," Launius said, referring to past NASA projects like the National Aerospace Plane, the Orbital Space Plane, the X-34 and others. "Each of those projects ran aground for a variety of reasons, usually technological or financial...and in each of those terms they hit the reset button."
The challenges, Launius said, are very real for NASA's CEV, which the space agency hopes to launch no later than 2014.
"I hope they're able to move forward with CEV and bring it online," he said.