STS-51-L

We are in the midst of a lot of reminiscing about the moon landings, particularly Apollo 11. So much is being said that anything I could add here would be pointless.

But in the middle of all this moonshot coverage, a short blurb about the Challenger destruction was aired. Challenger mission STS-51-L was the flight in which frozen o-rings could not function as designed, allowing a jet of flame to burn through to the main fuel tank, causing the explosion we all remember.

I am greatly dismayed to see that today's common conclusion about the cause of the disaster was the faulty design of the solid booster o-rings.

This is not true. The o-ring design was quite sufficient to maintain the integrity of the booster joints. Two o-rings were designed into each joint because it was expected that one could burn through during the two+ minutes of burn, so the second was there for back-up.

In fact, there were several shuttle missions where the primary o-ring did actually burn through, but the back-up o-ring did it's job and protected the joint.

Understand... the back-up o-ring would have burned through also, if the burn time was significantly longer. The design engineers knew this, that one o-ring could fail during the two minute burn, but the second would not, there was not enough time for that to happen. The first o-ring had to fail before the second one could be exposed to any heat or flame. The time needed for the second o-ring to face sufficient heat or fire to fail would never be reached, since the boosters would have already burned out and separated.

Did the o-rings fail? Yes and no. Since the launch of STS-51-L was conducted shortly after a hard freeze, the o-rings had not thawed out. Frozen o-rings will not work. As a result, at the instant of booster ignition, the still frozen o-rings were unable to function as designed, allowing the blow-by seen in photos as a "puff of smoke".

The Challenger was doomed at the instant of liftoff, not because of faulty o-ring design, but because of political pressure to put a teacher into space, one that had a timetable of non-mission related events that would be difficult to modify. Had the shuttle crew been just the trained NASA astronauts, there is no doubt the shuttle would not have launched that day.

So we lost a multi-billion-dollar shuttle.

The new three-o-ring joints are more complex, harder to install and face a higher risk of being damaged (nicked, shaved, pinched or cut) during installation. We are fortunate that we have not had a second failure.

The thing that riles me is that the designers and engineers have been blamed for a failure not caused by them, but caused by decision makers more concerned with outside pressures than they were the safety and integrity of the shuttle program. They were warned by the engineers. The engineers almost begged them not to launch in such cold weather, telling them the o-rings were - without doubt - compromised.

But now history says it was the o-rings. Yes, frozen o-rings that could not function as designed was the cause of the explosion. No mention of the lousy decision to launch - even with repeated warnings that the o-rings could fail catastrophically.

Forty years. It's been forty years since we landed on the moon. What do we have to show for that forty years? Pretty photographs made by robots.

Sad.