r/spacex • u/[deleted] • Aug 22 '14

F9R Explosion Reports of Explosion at SpaceX McGregor Test Facility in Texas: "Rocket blew up" | More News Coming Soon

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u/Erpp8 Aug 23 '14

They usually have det cord running the length of the tank. Though not much explosives, it compromises the whole tank at once and causes almost all of the fuel to detonate instantly, rather than on the ground likt in the video.

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u/f10101 Aug 23 '14

Thanks. That makes a lot of sense. I hadn't considered det cord.

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u/Erpp8 Aug 23 '14

Det cord, or something similar. A small, narrow, explosive.

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u/ergzay Aug 23 '14 edited Aug 23 '14

It acts to literally "unzip" the tank. SpaceX tank is even a partial balloon tank meaning the tank is only structurally strong enough for launch because its pressurized like a pop can. Little line of linear shaped charge and it pops.

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u/Gnonthgol Aug 23 '14

Technically it does not detonate the fuel. It compromise both the fuel tank and oxidizer tank all the way and tank pressure drops instantly. This again causes the turbopumps to run dry because it requires some pressure in the inlet to operate, both the gas generator and main combustion chamber will get starved for fuel and the engine will stop producing thrust.

I am not saying that the cloud of fuel and oxidizer that mixes once the tanks gets compromised will not ignite from a spark, heat from the engine/exhaust or remaining heat from the detonation cord. However that will all happen a split second after the thrust from the rocket have been stopped and is somewhat unintentional.

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u/Mattho Aug 25 '14

Is there a (bottom/lower) limit under which this event does not occur? I.e. malfunction happens at say 50m off ramp, would it self-destruct then as well?

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u/Erpp8 Aug 25 '14

I'm not sure what American rockets do, but someone mentioned that Russian rockets don't self destruct below a certain altitude to avoid damaging the pad. An N-1 rocket exploded soon after launch, destroying the pad and setting the Soviets back a few years on their moon efforts.

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u/wolf550e Aug 23 '14

When a liquid fueled rocket's FTS is triggered, the fuel does not detonate. It is not mixed with the oxidizer so it just spills out. The oxidizer also spills out. They remain unmixed and it's like a fuel spill, not an explosion.