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Given that SpaceX have successfully landed several Falcon 9 boosters and that these vehicles use helium pressure-fed engines, when these vehicles land, their propellant tanks will presumably be mostly filled with a fairly large quantity of relatively lower pressure helium.

Is SpaceX able to recover and reuse this helium? Do they? Is it economically worth them doing so?

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As far as I know they vent any remaining propellants after landing for safety reasons so I would assume most of the helium would end up being vented along with that. So my assumption is no they don't recapture it.

Would it be worth it? I doubt it. 20k might sound like a lot but when you are talking about a 60M a mission it ends up being 0.03% of the cost of the mission. Add in the cost of actually capturing and separating back out the helium and your savings are even smaller.

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  • $\begingroup$ The LOX tanks have to be vented because the LOX will otherwise turn into GOX and likely make the LOX tanks explode. The RP-1 tanks would cause quite a bit of pollution if you were to just dump the kerosene into the ocean or on land. It is the RP-1 tanks that are pressurized with helium. $\endgroup$ – user8269 Feb 11 '18 at 8:24
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The helium would no longer be pure. Especially in the liquid oxygen tank, the helium would have significant quantities of other gases mixed in. Fractional distillation could be used to separate them out again, but that might require major machinery and significant time.

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    $\begingroup$ Considering how expensive helium is, it might be worthwhile... $\endgroup$ – PearsonArtPhoto Oct 23 '16 at 20:03
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    $\begingroup$ 180 kg of helium at 50 USD per kg would cost around 9000 USD, and that's approximately enough to fill the entire F9 first stage oxidizer tank to its operating pressure. The other tanks are all smaller in volume. So we're talking $20,000 per mission. $\endgroup$ – user2790167 Oct 23 '16 at 21:48
  • $\begingroup$ Impure helium would still be useful to pressurize the next mission. $\endgroup$ – Hobbes Oct 26 '16 at 6:45

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