The Artemis 1 mission is going to do a wet dress rehearsal where the rocket will be filled with propellant and the launch sequence will continue until almost the last second. The launch sequence will then end. What happens to the propellant? Is it a universal procedure for all rockets? If not, what happens to their propellant?

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    $\begingroup$ Related: space.stackexchange.com/q/17272/6944 "More importantly, for either Apollo or Shuttle, if the spacecraft had to be de-fueled, where did all that propellant go?" $\endgroup$ Commented Mar 21, 2022 at 14:07
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    $\begingroup$ Given the amount, there isn't anything you could do with it except put it back in the tanks it came from. Pouring it down the drain would be an environmental disaster. Burning it off would not be much better. $\endgroup$
    – rghome
    Commented Mar 22, 2022 at 16:25
  • $\begingroup$ @rghome It's cryogenic. No environmental disaster but it could make an awfully big boom if it wasn't dumped carefully. $\endgroup$ Commented Mar 29, 2022 at 3:41
  • $\begingroup$ @Loren Pechtel Ah yes. Hydrogen and oxygen won't do much harm in this case. $\endgroup$
    – rghome
    Commented Mar 29, 2022 at 13:02
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    $\begingroup$ The relevant search term you're looking for is detanking. $\endgroup$
    – Wyck
    Commented Mar 30, 2022 at 13:45

1 Answer 1


A reputable blog, Spaceflight Now, says that

...culminating in a hold at T-minus 9.34 seconds, just prior to ignition of the main engines.
Then the core stage and upper stage will be drained of cryogenic propellants, and NASA engineers will evaluate the rocket’s performance during the dress rehearsal, before eventually rolling the rocket back to the Vehicle Assembly Building.

NASA agrees that the wet dress rehearsal includes

...practice the launch countdown and then recycle [sic: rewind?] back to T-10 minutes to demonstrate the ability to scrub a launch and de-tank.

NASA terminology for tanking and detanking mentions, e.g., a "LOX fill and drain line". For LH2, liquid is similarly drained; any remaining gas ("GH2") might be "vented to a burn pond".

Organic Marble's answer, that detanking returned as much propellant as possible to off-vehicle storage tanks, applies to large rockets more recent than the Space Shuttle if for no other reason than ground crew safety, as that answer's source says. Indiscriminately dumping onto the ground that much LOX or LH2, or both, is asking for all kinds of trouble.

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    $\begingroup$ "recycle" is the correct terminology i.imgur.com/ZLQDt6x.png from shuttle launch countdown $\endgroup$ Commented Apr 5, 2022 at 22:17
  • $\begingroup$ ?! Now there's a question! $\endgroup$ Commented Apr 6, 2022 at 1:08

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