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On February 8, SpaceX had to scrub a launch due to an Air Force technical problem. What happens to the cryogenic fuels when such a launch is delayed? Are the tanks (LOx for the Falcon 9) drained? Are the cryogenics recovered or vented to atmosphere? How much does this cost the launch company, NASA, the insurance, and the launch customer?

I am interested in the specific case of the Falcon 9, and also the general case for other rockets with cryogenic fuels.

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Typically they drain the cryogenics back, if they can.

Now it depends on the cryogenic. Oxygen can be drained and reused. Hydrogen in liquid form is very hard to keep cool enough, and they will drain it, but they will lose lots of it to venting.

Liquid Nitrogen that they use for pressurization they may just let vent, since the quantities are pretty small (compared to fuel or oxidizer loads) and LN2 is amazingly cheap (Less than milk). Liquid Helium, even though it is very hard to keep cool enough is quite expensive, so even in small quantities they will likely try to recover it.

Wet dress rehearsals and hot fires are the perfect example of this. The vehicle is fully fueled in each case. In the first it is then fully drained. In the second, the engines ignite for a few seconds (less than 3 in the case of Falcon 9, since they ignite at T-3 and stop at T-0).

In the specific case of Falcon 9 and SpaceX, I was initially under the impression, that the tenth feed line in the Loxtopus image below was for cross feed (9 engines, 9 feed lines, plus one for drainage), but I was corrected, and it is in fact a drain line, for just such a case.enter image description here

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    $\begingroup$ Loxtopus? I love that word! $\endgroup$
    – dotancohen
    Mar 30, 2015 at 18:07
  • $\begingroup$ As a tangent regarding Helium, it's interesting that the planning document for LC-13 states that after landing, the stage will be vented of Helium, rather than planning to recover it. $\endgroup$
    – marked-down
    Mar 30, 2015 at 18:30
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    $\begingroup$ @EchoLogic That is interesting. But consider. They carry mostly enough Helium for the mission + margin. At the end of the mission all that is left is margin. Building infrastructure to safely and properly recover Helium may not be worth the cost of the marginal amount remaining. $\endgroup$
    – geoffc
    Mar 30, 2015 at 18:32
  • $\begingroup$ I wasn't aware it was expended at all! I know it's used to pressurize the legs for deployment, but where does the Helium go normally? $\endgroup$
    – marked-down
    Mar 30, 2015 at 18:33
  • $\begingroup$ @EchoLogic That looks like a different questioN! Go ask it! $\endgroup$
    – geoffc
    Mar 30, 2015 at 18:34

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