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Comment by protomyth | Hacker News Reader

So, SpaceX figured that the booster was actually a hazard and asked the Air Force to fix the problem. The Air Force is referring all questions to SpaceX and we really don't know what happened since there is no video or photographs of the strike.

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More likely it was a floating ITAR export risk than a major threat to marine safety.

Large pressure vessels are essentially bombs; in this case a very large bomb.

Hasn't most of the energy been spent at that point? I was under the impression space launches were miserly with fuel for weight reasons?

You’re right, but it’s still under incredible pressure. You’re talking about liquified cryogenic fuels, so the remainder has greatly expanded over time. Even a small amount of remaining fuel must be vented to render it safe. Volumetric expansion is a bitch!

Fuel in SpaceX rockets (and other working gases) are cryo-cooled, after tanks warm up, even small amount of liquid gas stored in a tank evaporates into a lot of gas which can create very high pressure.

Cryogenic oxygen has something like a 700:1 expansion ratio when it is warmed into a gas.

Take a look at all of the failed landings[1], even after they land on the barge they still go boom(or RUD if you prefer that term) when the structural integrity is lost.

[1] https://www.youtube.com/watch?v=bvim4rsNHkQ

> More likely it was a floating ITAR export risk

Indeed. Literally an ICBM.

They would have understood that it was a hazard from the get-go, but presumably believed that they could render it safe, destroy it themselves, or tow it back intact. It would seem that they realized how unfeasible civilian EOD would be, and that necessarily ruled out any option save destruction.

According to Musk, "This rocket was meant to test very high retrothrust landing in water so it didn’t hurt the droneship, but amazingly it has survived." I suspect they never really thought about what it would take to tow it back, and when they did realized they didn't really want to.

That sounds very likely, and having the USAF do the job right, while a bit of negative PR, is better than losing lives.

Edit: Good points about PR, I missed that.

I don't think it's negative PR at all. Blowing stuff up is cool as long as nobody gets hurt. Also, people understand that bits and pieces of rockets need recovering or destroying. There's a lot of precedence for this.

And, all in all, which negative PR ? This is more positive in the "wicked cool" sense, isn't it ?

Wait, are you saying the core wasn't intending to land on the barge? Why have the barge out there to begin with then?

They didn't have the barge out there.

Different launch. This wasn't the Falcon Heavy core, this was a previous rocket that was intended to crash (for testing purposes). There wasn't a barge out there to catch it (unlike the Heavy).

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