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The article introduces LOX - it's Liquid OXygen, the oxidizer for the Shuttle's main engine (with hydrogen as the fuel). The nozzle is the portion of the engine

The article introduces LOX - it's Liquid OXygen, the oxidizer for the Shuttle's main engine (with hydrogen as the fuel). The nozzle is the portion of the engine where the hot exhaust gas is allowed to explosively expand to provide thrust (what you probably think of as the "exit" of the engine). The pin caused two problems. First, the LOX itself was dangerous because if it had been released incorrectly, it could have caused an explosion. That, fortunately, did not happen. And second, the ejected pin severed several hydrogen pipes being used to cool the nozzle. I assume the cooling is to keep it from melting under the extreme temperatures of the launch - the article mentions "burn through", which I'm guessing is "the nozzle material melts and your rocket exhaust goes off in a random direction so you Will Not Go To Space Today". It severed three pipes; fortunately the shuttle was designed such that it could tolerate the failure of up to four, and the nozzle held. Wiki has a picture at [1] - the hydrogen leak from the severed pipes is in the engine on the right of the image, creating a white streak on the side of the nozzle and distorting the shape of the exhaust. [1] https://commons.wikimedia.org/wiki/File:STS-93_SSME_Hydrogen_Coolant_Nozzle_Leak_at_Liftoff.png https://commons.wikimedia.org/wiki/File:STS-93_SSME_Hydrogen...

plorg 2y ago
Ok, assume that I've also read the article. What does the "pin" part of "LOX pin" refer to?
- HPsquared 2y ago
  It's a plug that was inserted to block a damaged passageway. It fell out and hit the (fragile) wall of the nozzle which is hollow and itself full of tubes. Ironic really, that a leak prevention patch job ended up causing a different leak.
  - amelius 2y ago
    Conclusion: never trust a vehicle that was patched in any way.
    - mulmen 2y ago
      That leaves you with single use vehicles. You have never been on an airliner without a patch. SpaceX is famously making a business of operating rockets the same way.
      - amelius 2y ago
        Well, I hereby introduce "patch-only manufacturing", where every vehicle is patched, even new ones. That way, you reduce variations between vehicles, hopefully making them more reliable. If every vehicle is patched and it is part of normal manufacturing, then you could say that none of them are patched.
        mulmen 2y ago
        > If every vehicle is patched and it is part of normal manufacturing, then you could say that none of them are patched. This is only true if they are all patched in exactly the same way and if you patch existing examples in the field. In the real world patches are applied as repairs to incidents that are unique to each example. Airliners are too expensive to throw away because of minor flaws and damage.
marcosdumay 2y ago
> I assume the cooling is to keep it from melting under the extreme temperatures of the launch Yep, rocket nozzles and combustion chambers must be cooled down while they work. This is usually done by passing the fuel through their outer walls before it burns.

plorg 2y ago

Ok, assume that I've also read the article. What does the "pin" part of "LOX pin" refer to?

HPsquared 2y ago
It's a plug that was inserted to block a damaged passageway. It fell out and hit the (fragile) wall of the nozzle which is hollow and itself full of tubes. Ironic really, that a leak prevention patch job ended up causing a different leak.
- amelius 2y ago
  Conclusion: never trust a vehicle that was patched in any way.
  - mulmen 2y ago
    That leaves you with single use vehicles. You have never been on an airliner without a patch. SpaceX is famously making a business of operating rockets the same way.
    - amelius 2y ago
      Well, I hereby introduce "patch-only manufacturing", where every vehicle is patched, even new ones. That way, you reduce variations between vehicles, hopefully making them more reliable. If every vehicle is patched and it is part of normal manufacturing, then you could say that none of them are patched.
      - mulmen 2y ago
        > If every vehicle is patched and it is part of normal manufacturing, then you could say that none of them are patched. This is only true if they are all patched in exactly the same way and if you patch existing examples in the field. In the real world patches are applied as repairs to incidents that are unique to each example. Airliners are too expensive to throw away because of minor flaws and damage.

marcosdumay 2y ago

> I assume the cooling is to keep it from melting under the extreme temperatures of the launch Yep, rocket nozzles and combustion chambers must be cooled down while they work. This is usually done by passing the fuel through their outer walls before it burns.