NASA's Final Shuttle: The End of an Error?

(2 of 2)

What makes this so-called single-stage-to-orbit (SSTO) concept so elusive is the stubborn, circular nature of the thrust and weight problem. Getting to orbit without shedding parts requires a very powerful engine and a lot of fuel. But a very powerful engine and a lot of fuel add extra weight that must be lifted — which requires an even more powerful engine and even more fuel and on and on. Light, composite materials, very efficient engines and highly energetic fuel bring the goal closer — indeed, they're part of the design of any good booster — but never quite within reach. In this case, the problem very much is rocket science — and it ain't easy to do.

The solution for the shuttle was to bolt the orange whale of the external tank onto the belly of the orbiter and tack two solid rockets onto the tank. That might have been the only way to get the 89-ton ship moving fast enough to achieve orbit, but it did present the inconvenient problem of positioning the crew directly next to three massive loads of compressed explosives instead of atop it as you would on a traditional rocket. If, say, an O-ring begins leaking superheated gas or a chunk of killer foam falls from the external tank, the astronauts and their spacecraft are directly in harm's way. That those two things both happened — with the most disastrous consequences possible — is a matter of historical record. That they were both precisely foreseeable is much less certain, but there's no doubt that smart people knew the ship presented a new portfolio of risks.

Then too there was the very idea of reusability. To hear the shuttle's most enthusiastic supporters tell it, turning the vehicle around between flights would mean little more than hosing it down, gassing it up and putting a little air in the tires — and if the reality had been anything like that, the economies of scale might have brought the price-per-pound of payload down to the one-tenth level Nixon promised. But a crewed vehicle requires complex life-support hardware, redundant safety systems and an overall degree of care that an unmanned booster can do without, and it takes a long time to get everything properly checked out between flights. Nixon might have foreseen a spacecraft that could fly to space 100 times, but the most well-traveled of the five shuttles was Discovery, which made only 38 trips in 28 years. Challenger, the least flown, managed just 10 before its destruction in 1986. The greatest number of missions ever flown in a single year was nine, in 1985.

As the lags between flights grew longer and longer and the cost of renting payload space remained high, customers fled back to the commercial boosters like the Atlas and Delta. That pushed NASA to cut corners and rush launches which, in the case of Challenger, was a proximate cause of the disaster, as the ship lifted off during a Florida freeze when its O-rings had become dangerously brittle. By the time the shuttles were certified to fly after all of the post-Challenger investigations were complete, they would be used largely as space trucks for the military or for NASA's own missions, such as space-station construction.

Now, with the space station built and the shuttles gone creaky (the first of them rolled off the assembly line in 1979), nothing will quite become the overall program like the ending of it. And yet it will be impossible not to miss the cursed vehicles at least a little. There was always a just-do-it-ness to the decision to fly the shuttles. Tiles fell from one ship and the next one was glued together better and rolled out to the pad. Launches were scrubbed for this or that glitch six or seven times in a row, and the astronauts would gamely suit up for try No. 8. Seven people died and the crews kept coming. Seven more were lost and still they came.

The astronauts and the flight controllers were, by any measure, better than the ships they were given to fly, but the shuttles we had were the shuttles we were capable of building at the time. Two of the missions may have ended in tragedy, but assuming Atlantis returns from its final flight safely, 133 will have concluded with a safe, rolling stop on a familiar earthly runway. We will never get back the billions we spent on the program, and the lives that were lost are lost forever. Still, when the ledger is tallied — when all of the technological, scientific, mortal and moral variables are factored together — we might, just might, end up on the plus side of the page. It's probably fair to give both Nixon and NASA a pass on this one — provided we all learn from the mistakes we've made.