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Where the shuttle went wrong

Click for slide show: See scenes from Columbia's last mission.

"Space Shuttle Disaster," a documentary premiering on public TV stations tonight, traces the bad decisions that led to the shuttle Columbia's fatal breakup in 2003. But this isn't just about a five-year-old tragedy: The show also demonstrates why the 27-year-old space shuttle program has turned into a dead end - and why investigators say NASA must resist the temptation to keep the space planes flying for any longer than absolutely necessary.

"Extending the shuttle is taking unnecessary risks that could doom the whole program if there were another shuttle accident," said John Logsdon, a space historian at the National Air and Space Museum who served on the Columbia Accident Investigation Board. "Even though the shuttle has been improved since its return to flight, it's still a risky vehicle."

If the shuttle is so risky, why was it built that way? Didn't NASA realize how risky it was? Such questions get a prime-time spotlight in "Space Shuttle Disaster," airing on PBS as part of the "Nova" documentary series.

Close observers of the shuttle program might not find all that much new in the program. In fact, Logsdon told me this week that developments since the Columbia tragedy have served only to confirm the conclusions reached by the accident investigation board, also known as the CAIB.

"It reflects what a comprehensive job CAIB did," Logsdon said. "I think we nailed the situation pretty well."

The show also nails the situation well, starting with its examination of the shuttle program's historical roots. Just after 1969's historic Apollo 11 moon landing, NASA and the Nixon White House settled on a plan to build a reusable shuttle fleet and an orbiting space station for the next phase of space exploration. The idea was that the shuttle would serve as a low-cost "space truck" to bring people as well as cargo into orbit on a weekly basis, with the station serving as a jumping-off point for further exploration.

But the development cost for the shuttle turned out to be so high that plans for the station had to be thrown into limbo. That served as an early indication that the shuttle concept wasn't as efficient or as elegant as NASA thought.

In 1986, the Challenger explosion showed that the shuttle wasn't as safe as NASA thought, either - due to a booster design flaw that had long been ignored. The shuttle and its seven crew members were lost as a result.

The space agency agonized over its "safety culture." It redesigned the booster O-rings and returned the shuttle fleet to service.

A similar set of warning signs was ignored in the run-up to the 2003 Columbia tragedy,. "Space Shuttle Disaster" focuses on the shuttle fleet's problems with foam insulation debris from the external fuel tank - which was a known issue well before Columbia's final launch. Investigators concluded that a chunk of flying foam, seen in close-up views of the shuttle's ascent, blew a hole in Columbia's left wing and set the stage for the shuttle's fiery, fatal breakup 16 days later.

During Columbia's flight, some engineers tried unsuccessfully to get a better fix on what the foam did to the shuttle. And even after Columbia's loss, some experts inside NASA didn't believe that a lightweight piece of foam could do such damage. "Space Shuttle Disaster" replays the actual tests that proved it could.

Once again, the space agency agonized over its "safety culture." It redesigned the external fuel tank and returned the remaining shuttles to service. But this time, it also decided to retire the fleet in 2010, once construction of the international space station is complete.

The designs for NASA's next generation of spaceships follow the safety recommendations made by the accident investigation board, Logsdon said.

"One of our recommendations was to be sure to separate the crew-carrying from the cargo-carrying function as you go to space," he said. "The approach that's being taken for the new Vision for Space Exploration does precisely that."

NASA's proposed Orion crew vehicle is meant to ride at the top of a rocket, where there's far less risk from flying debris. It will also have a built-in escape rocket system in case the launch goes awry. Once again, however, building the spaceship is turning out to be more expensive and time-consuming than NASA would like.

That has led some lawmakers - including Republican presidential candidate John McCain and his Democratic rival, Barack Obama - to call on NASA to consider the option of extending the shuttle's retirement date past 2010. Some would even like to keep the shuttles flying until the Orion is ready, in the 2015 time frame.

That would be a big mistake, Logsdon said. He pointed out that NASA has estimated the probability of losing the crew on any single post-Columbia shuttle mission at 1 in 80. Adding another 10 flights between 2010 and 2015 would obviously add to the risk of another disaster.

That caution doesn't rule out adding one or two flights to take care of some important unfinished business, such as the delivery of the $1.5 billion Alpha Magnetic Spectrometer to the station. Right now, there's no room on the schedule for an AMS delivery, but some lawmakers want to give NASA more money to cover the cost of an extra flight.

"Flying one or two more flights in 2011 would not bother me very much," Logsdon said.

Looking beyond the shuttle, some space activists have suggested that commercial spaceships such as the SpaceX Dragon could help NASA fill the spaceflight gap. Logsdon said SpaceX's launch system - or Orbital Sciences' alternative, or still more spacecraft from Europe or Japan - would do a fine job for delivering cargo to the space station. But he would see cause for concern if NASA turned too hastily to unproven spaceships for crew transport.

"There are lots of variables at play in this," he observed. "It's a wicked, complex problem, but you can't risk human lives on unproven systems."

The best option, or the "least bad" option, would be to use those other spacecraft for cargo but continue using Russian Soyuz spaceships for crew transport, Logsdon said. Even though U.S. and Russian leaders may not see eye to eye on earthly matters, and even though NASA may wish things were different, the two nations are bound together in space for the foreseeable future.

Would things have turned out differently if NASA had stuck with the Apollo-Saturn system for space exploration, instead of starting from scratch with the shuttle? That's a topic worth chewing on in the comments section below. Feel free also to weigh in on whether "Space Shuttle Disaster" makes an accurate diagnosis of the shuttle program's problems, and whether Dr. Logsdon's prescription is the right one. If you miss the show on TV, never fear: You can watch the whole program online starting Wednesday.

Update for 9 p.m. ET: And now for something completely different ... NASA will air a documentary titled "50 Years of Exploration: The Golden Anniversary of NASA" on the agency's Public and Education channels at 9 p.m. ET Wednesday. Host for the 90-minute documentary is Apollo 11 moonwalker Neil Armstrong.

The show features interviews with former senator-astronaut John Glenn, Apollo flight director Gene Kranz, science-fiction author Ray Bradbury, Nobel-winning physicist John Mather and former Presidents George H.W. Bush and Bill Clinton. "50 Years of Exploration" will be rebroadcast at 1, 5 and 9 p.m. ET on Thursday and Friday, NASA says in its TV listing. Some cable systems air NASA TV, but the most reliable way to find it is online.

NASA TV's YouTube channel offers what appears to be a sampling of the documentary for anytime viewing.

It's also worth mentioning that the Discovery Channel has served up some tasty footage in its documentary series "When We Left Earth: The NASA Missions." The series' six episodes, plus hours of extras, are now available on DVD.