The Legacy of the Challenger Disaster

Twenty-four years after the Challenger disaster, space analyst Rand Simberg reflects on the influence of that failed launch on the future of private and public space flight.

By Rand Simberg
Shuttle Challenger
January 28, 2010 12:00 AM Text Size: A . A . A
On January 28, 1986—Twenty-four years ago today—the space shuttle Challenger launched and was torn apart, killing the seven crew members on board less than two minutes after liftoff.

It was my birthday, and at the time I was working for Rockwell International, the company that developed the vehicle, in Downey, California, just east of Los Angeles. I was part of a team working on more advanced concepts, including follow-ons to the space shuttle.

I have some personal recollections of the event, originally posted eight years ago. Though it wasn't obvious at the time, it was the beginning of the end of the Shuttle program, less than five years after it started flying in 1981. It was certainly the end of the fantasy that it was going to fly many times a year, at low costs, and do everything for everyone. In that respect, it was a necessary wake-up call, and it provided the basis for today's commercial launch industry.

It was the end of another fantasy as well—that a shuttle was a safe enough vehicle on which to fly schoolteachers and congressmen. This was a fantasy of politicians and NASA and contractor upper management, not of those of us actually working on it in the trenches. In the days afterward, after reluctantly accepting a role in the accident investigation, the late famous physicist Richard Feynman told the story of his interviews with industry insiders to try to ascertain what went wrong (he was the one who did the experiment with the o-ring in the ice water to demonstrate its inflexibility at the cold temperatures of launch day). When he talked to upper-level managers, he was told that the odds of losing an orbiter were one in a hundred thousand, but that seemed extremely counterintuitive to him, when he saw how complex the vehicle was, and how many things could go wrong. His own estimate was three orders of magnitude less — one in a hundred. When he talked to the engineers who had developed the vehicle, they confirmed it.

So those of us working the program were saddened, but not as shocked as the rest of the nation and its leadership, when we lost a vehicle and crew. The only surprise to us was the failure mechanism — the smart money would have been on a main engine failure, or loss of tiles on entry, not a Solid Rocket Booster breach. In fact, one of the vital lessons of Challenger is that, as many postulated disasters as we had in our fault trees, nature could still play tricks on us and come up with a new one that we hadn't even anticipated. Which meant that flying the shuttle was even more hazardous than we had previously estimated. And note, like other such technological disasters, such as the Titanic, or Three-Mile Island (and later, the loss of Columbia), this wasn't a consequence of just one thing going wrong. It was a combination of events, the lack of any one of which would probably have resulted in an uneventful flight.

In order for that o-ring leak to destroy the vehicle, it had to not just occur, but occur in precisely the right (or wrong) place. Had it been a warmer day, it probably would have been fine. Had it been on the side of the SRB away from the ET attach strut, it would have vented hot gases harmlessly, with the worst effect being a slight loss of performance as the main engine had to gimbal more than usual to adjust for the sideways thrust. If the support strut that was burned off had held out for just another fifty seconds or so, the SRB would have been safely jettisoned, and the Challenger would have continued to orbit without further incident.

But it didn't. The burn-through occurred, it occurred in just the wrong place (though this location might have been a result of the structural stress caused by the strut itself), and it was sufficiently hot that it cut the strut like a blow torch, about halfway through the first-stage burn, causing the top of the SRB to collapse into the top of the external tank, resulting in the famous conflagration that was shown over and over for days.

Prior to January 28th, 1986, the national policy had been that all of the nation's orbital payloads — NASA, military, commercial — would fly on the space shuttle. There was no need for a commercial launch industry, because NASA could handle all the business. Fortunately, the Pentagon had never accepted the notion that it should have no backup launch system for its satellites, and had continued to support the Delta, Atlas and Titan vehicles, so they could continue to deliver defense satellites even while the Shuttle stood down for almost three years after Challenger disaster. In fact, the need for resilience in our launch architecture was driven home even more dramatically less than three months after the Challenger was lost, when a Titan 34D exploded just off the pad at Vandenberg Air Force Base in California, shutting down that program as well.

The shock of the Challenger loss, and a new reality that the Shuttle wasn't as safe as we thought it was, changed that policy, for the better. NASA would no longer be allowed to fly commercial payloads in it, unless there was no other vehicle available for them (Hughes had designed a communications satellite specifically for the payload bay). In addition, NASA wouldn't launch a payload in the Shuttle that didn't require astronauts to operate it. This, combined with a decision by the Air Force to get out of the launch business themselves, provided a market starting in the early nineties that has resulted in the robust commercial launch industry that we see today.

But Shuttle continued on, as the nation's only manned space vehicle, until complacency set in, and disaster struck again, exactly seven years ago this coming Monday, when the Columbia was torn apart in a hurricane of plasma over an early morning Texas sky, again losing all crew. Challenger began the end of Shuttle as The National Space Transportation System. Columbia began the end of the program itself. With only three vehicles left, the nation could no longer justify continuing the expense and danger of the system, except for its vital role in completing the International Space Station. A little less than a year after the second loss, a decision was made to retire shuttle this year, 2010. Because of delays in ISS completion, it's possible that it will be extended a few months, into next year, but there are no parts available to fly it much longer.

The Shuttle is and was a magnificent technological achievement, but it is not, and in retrospect, never was the key to opening up space, despite the hopes and hype of the seventies. If it makes it into next year, it will have flown for almost three decades, and for a quarter of a century, since early 1986, with the knowledge that it had failed the promises of cheap, safe access that had been made when the program was initiated almost four decades earlier. It will be the end of an era for NASA, from a naive assumption that there is a single government-operated solution to space transportation, to a more mature and robust future of a variety of space transports, for humans and cargo, in a thriving commercial sector. That is a future that will finally fulfill the failed promise of the Shuttle.

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