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mrgtiguy t1_ivwx1c4 wrote

Reply to comment by johnn48 in NASA leaders recently viewed footage of an underwater dive off the East coast of Florida, and they confirm it depicts an artifact from the space shuttle Challenger by marketrent

The know what went wrong. An o ring failed because of cold weather and pressure to launch a teacher, amongst other crap. Horrible design that set us back decades.

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Spaceguy5 t1_ivwy60i wrote

The design wasn't bad, if it was used properly in the correct environment. The way they were using it is what was bad, because it wasn't designed to be used at those temperatures and they knew it but ignored the spec. And using stuff outside of spec without any kind of analysis nor investigation to confirm it won't be a problem is a lesson they learned in blood. It's something still taught to the current NASA work force (which I'm part of).

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isanameaname t1_ivx9d88 wrote

They had been partially failing since early testing but that partial failure was deemed acceptable because they failed in a way which was thought to be within acceptable levels of risk:

https://en.wikipedia.org/wiki/Space_Shuttle_Challenger_disaster?wprov=sfla1

Fun fact: it wasn't.

> Evaluations of the proposed SRB design in the early 1970s and field joint testing showed that the wide tolerances between the mated parts allowed the O-rings to be extruded from their seats rather than compressed. This extrusion was judged to be acceptable by NASA and Morton Thiokol despite concerns of NASA's engineers. A 1977 test showed that up to .052 inches (1.3 mm) of joint rotation occurred during the simulated internal pressure of a launch. Joint rotation, which occurred when the tang and clevis bent away from each other, reduced the pressure on the O-rings which weakened their seals and made it possible for combustion gases to erode the O-rings.

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intern_steve t1_ivy3wpw wrote

If you watch old slow motion footage of the boosters during launch you can actually see small puffs of smoke escaping from the seams between booster segments before the o rings extrude to fill the gap.

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wattatime t1_ivxhgju wrote

Studied this in a business class as an example of leadership making a poor decision. The engineers didn’t want to sign off on it and the pressure to lunch on that day led to a poor decision by leadership.

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SailboatAB t1_ivyjsyt wrote

It wasn't just pressure to launch a teacher. Part of the arguments NASA had made to secure funding for the shuttle program had hinged on the claim they could launch on reliable schedules. The military wanted more funding for unmanned rockets to launch satellites, but NASA had prevailed in Congress partly by asserting that the shuttles could put military hardware into space, replacing the need for more or newer unmanned boosters. The military was dubious they could maintain tight schedules and launch on short notice.

NASA felt pressure to prove their program could get into space regularly with minimal delays/cancellations in order to justify the spending and prove the military "wrong."

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92894952620273749383 t1_ivwzmzk wrote

Why did they need an oring? When other rockets don't need them. That is the real tragedy.

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Spaceguy5 t1_ivx0fes wrote

They need O-rings to seal the joints because the SRBs of that massive size are made by stacking multiple segments together and you need to be able to seal the hot gasses inside between the joints. There's no practical way to make SRBs that big without splitting them into segments

It wouldn't have been an issue if they used them at the correct temperatures. Though to be extra safe, they also redesigned the joints to be more robust and have a second layer after the failure. That redesign + more strict rules on launch temperatures led to there never being another issue with that part of the booster.

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ExecutiveAvenger t1_ivx90fo wrote

There certainly was also a design error with the joints since there really wasn't any redundancy. The new design solved this.

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Spaceguy5 t1_ivx9lvs wrote

I mean, redundancy and fault tolerance aren't absolutely mandatory for a design to be good, as long as it's a simple design used in design operating conditions with a low chance of failing. SRBs flown pre-STS-51L in design temps didn't have signs of burn through, only ones flown cold showed signs (which the fact those flown out of spec showed signs even before 51L should have set off alarm bells and gotten the situation resolved without loss of life)

But yes, it definitely was made a better design by adding that fault tolerance, and without adding too terribly much mass and complexity. And it makes sense that they'd add it in after experiencing that failure mode (even if it was caused by out of spec operation) just to give more peace of mind.

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SquiffSquiff t1_ivxdrlv wrote

Perfectly possible to make them that size, as discussed e.g. Here. It was because they wanted to manufacture them in Utah for I'm sure entirely sound technical reasons that had nothing whatsoever to do with politics

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Spaceguy5 t1_ivxea9z wrote

Can you not? Cut it out with the conspiracy crap. As someone who works on the space program, I'm tired of hearing all the anti NASA peanut gallery comments that just assume some weird political corruption is going on behind the scenes, and that that is the only reason the architecture was planned how it was. It's very far removed from reality but yet that conspiracy garbage is something me and my coworkers get spammed with practically every time we talk about work on social media.

Also you should read that r/science comment you linked as a source more closely because it mentions practical reasons why segmenting makes sense and actually supports what I said moreso than you.

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SquiffSquiff t1_ivxhbkb wrote

The point being that NASA could transport entire Saturn V rocket stages (by barge) and the shuttle orbiter (by plane) but for some reason there was 'no way' these boosters could be made in a single piece...

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theholyraptor t1_ivz9dxa wrote

You realize that, even if they built them next to the pad in Florida, that large assemblies are made up of smaller components for thousands of technical reasons, even if you rule out transport logistics.

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