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February 22, 2003

My Nickle's Worth On The Shutle

Since a Lot of People Have Asked

I had decided I wasn't going to post anything on the Shuttle accident. In fact, to be honest, I didn't follow it in a lot of detail. At times like this, everyone becomes an overnight expert and it's difficult to sort out the worthwhile information from all the noise. But a lot of people have been in touch to ask for my take, so here it is, to save more answering of individual e-mails.

Pioneering fundamentally new technologies in a little-known, hostile environment is an inherently dangerous business regardless of the friendly-fuzzy images that NASA puts out, and every once in a while you are going to lose one. The engineers said that back in the 70s, when they put the probability of such an accident at 1 in a 100 launches. NASA management turned it into 1 in 100,000 when selling the package to Congress and the nation. Comparing the program to the history of such activities as quarrying and mining; tunneling, the building of bridges, dams, and other structures, steel making, ocean navigating, manned flight, to name a few examples, I think the record has been amazingly good. The brief that was finally handed down after the political compromises and budget cuts of various committees may have been questionable in it wisdom, but the engineering of the goals set out in that brief was superb. Consider just some of the problems that were taken on:

  • The violence of firing a rocket engine and the forces of space flight twist and warp the structure to the degree that everything in the past had been one-shot, throwaway ventures. The shuttle's main engines were designed to be reusable 55 times before overhaul, with internal pressures three times greater than that of any prior large engine.
  • Ascent involves 3 g's of stress, meaning that the structure is subject to an inertial drag of 3 times its own weight, with all five engines producing 167 decibels of acoustic vibration -- enough to kill an unprotected person.
  • In orbit, the craft drifts in hard vacuum at -250o F, rapidly changing to 2,700o F skin temperature on reentry -- enough to turn most metals into Silly Putty.
  • Descent is at Mach 25, 3 times faster than any other piloted craft previously flown, finally landing without power at a thumping 220 m.p.h. The similar-size DC-9 lands at 130 m.p.h. with power. No rocket built in history was required to endure such a wild variation of conditions. The shuttle's design aim was to take this nightmare roller-coaster ride 100 times.

Now, you'd think that when a nation pits its best before the world to take on a challenge like that, all the departments and agencies of its government would be solidly on the same side, backing the team. In an earlier posting, I described how EPA fanaticism in the unwarranted hysteria over asbestos led to replacement of the original O-ring sealant putty that had never given problems before by an inferior substitute that was implicated in the Challenger disaster 17 years ago. Well, it seems that little was learned, and the institutions that control much of what passes for science these days are driven by ideology, not facts or common sense.

In 1997, NASA was forced to switch to a "new method" of foam heat insulation for the external tank for the Columbia, using a compound that doesn't involve the use of freon. Freon, of course, being the culprit fingered for the ozone depletion hysteria of recent years, which for my money was as baseless as the nonsense over asbestos. And even if it were real, the contribution from shuttle insulation would have been utterly immeasurable and insignificant compared to other sources. The replacement insulation was more prone to fragility and flaking off on launch. At ascent velocities of Mach 2 to Mach 4, even flakes of foam insulation become transformed into damaging projectiles. Rob Rackansky drew my attention to a NASA page reporting instances from as far back as 1997 of "significant damage" to the orbiter protective tiles caused by reformulated freon-free insulation separating and flaking during launch.

So the current tally for the Shuttle part of the space program could well be: Space Hazards, 0; EPA 2.

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