Using the same o-rings afterwards is surprising, I've heard that the manufacturer was surprised that they were being used for that purpose because they weren't rated for that.

Also I'm not sure the assertion is correct. If the sealant and O-Rings were adequate, the joint would not have failed. It was suboptimal, and increased risk, sure, but it in itself wasn't the reason for the accident. It was the joint and the o-rings in combination. The holes in the swiss cheese model lined up that day, and a lot of small problems combined into one big problem

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inaros 6 hours ago | parent | next [-]

>> Using the same o-rings afterwards is surprising, I've heard that the manufacturer was surprised that they were being used for that purpose because they weren't rated for that.

Not surprising if you understand what the real cause was: https://news.ycombinator.com/item?id=47585889

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sidewndr46 5 hours ago | parent | prev | next [-]

Surprised? One of the engineers was literally on the phone with NASA the morning of the disaster begging them not to launch. He was overruled by management.

	▲	randomNumber7 2 hours ago \| parent [-]
		Surprising for the management. If you are a spoiled brat who always got what it wanted if you just asked/cried you don't expect reality to come and hit you.

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Mikhail_K 8 hours ago | parent | prev [-]

> If the sealant and O-Rings were adequate, the joint would not have failed.

That assertion requires some reasoning and evidence to back it.

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voidUpdate 8 hours ago | parent [-]

The sealant and O-rings were meant to keep the hot gasses inside. Simply making a joint slightly wiggly will not keep hot gasses inside. The hot gasses did not stay inside. The sealant and O-rings did not succeed in keeping the hot gasses inside (evidence: Challenger). They were not adequate

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Mikhail_K 8 hours ago | parent [-]

> The sealant and O-rings did not succeed in keeping the hot gasses inside (evidence: Challenger). They were not adequate

No. The whole assembly --joint, sealant and O-rings, -- failed.

"They were not adequate" - yet, after the redesign, they kept those same O-rings and declared that boosters are safe to fly, in manifest contradiction to your assertion. So your reasoning is clearly flawed.

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john_strinlai 5 hours ago | parent [-]

>"They were not adequate" - yet, after the redesign, they kept those same O-rings

presumably "redesign" means some stuff changed. why is it not possible that the O-rings were inadequate for the old design, but adequate for the new design?

	▲	buildsjets 42 minutes ago \| parent [-]
		Exactly. They re-designed the tang and clevis joint so that the metal parts of the joint did not spread under gas pressure and the o-ring did not lose compression. They added a heater to ensure that the o-ring remained in it's usable temperature range. And added a superfluous third O-ring. Speaking of which, has anyone ever adequately explained why Challenger's Right SRB joint temperature was measured as -13 deg C using infrared pyrometers, when the lowest ambient temperature that night was -5.5C, and the Left SRB was measured -4 C? What subcooled the right SRB? Allan McDonald's "Truth, Lies, and O-Rings" is mandatory reading for anyone who wants to discuss the details of this particular bit of corporate and government malfeasance. It's 600 pages of technical detail and political intrigue. He suggests that a plume from a cryo vent could have impinged on the field joint and cooled the o-ring to lower than ambient temperatures. No proof though.