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Looking at the question Has in-space refueling been done?, it looks like all fuel transfer operations in orbit have been done with room-temperature hypergolics. Has on-orbit transfer of cryogenic fuels ever been demonstrated, even as an experiment?

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  • $\begingroup$ If refueling was done with cryogenic fuels in orbit, the fuel should have been used in the next hours or days. But there is the additional problem of pumping cryogenic fuels in zero gravity. Pumping and igniting hypergolics in zero gravity is much easier. If refueling with cryogenic fuel is not useful anyway, why should anyone experiment with it? $\endgroup$ – Uwe Aug 15 '17 at 12:13
  • $\begingroup$ @Uwe Well, it'll be useful for ACES and ITS; I'm curious whether ULA (or anyone else) has tried actually doing it in space instead of just in Earth-based experiments. $\endgroup$ – DylanSp Aug 15 '17 at 13:23
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    $\begingroup$ @Uwe et al, the question ULA: bringing propellants from Earth “Avoids Earth's Deep Gravity Well”? is an example of a plan to transfer cryogenic fuels in orbit. Clearly somebody thinks it's potentially useful! $\endgroup$ – uhoh Aug 15 '17 at 16:20
  • $\begingroup$ @Uwe: Refueling with cryofuels would make sense for heavyweight interplanetary mission. Bring payload to orbit together with second stage, using up last of second stage's cryofuel (and possibly with last stage empty). Bring cryofuel tank into orbit, rendezvous, refuel the second stage (possibly fuel up last stage with hypergolics too). Reuse the second stage as transfer stage for the escape/transfer burn. But since the heaviest interplanetary we've sent so far (Curiosity) wasn't nearly as heavy as to require that, there was no reason so far. Manned Mars may be one though. $\endgroup$ – SF. Aug 16 '17 at 10:03
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No. (Unless it has been done as part of a secret mission.) NASA's Space Technology Mission Directorate had plans for just that called Cryogenic Propellant Storage & Transfer (CPST), which would have launched a mission to demonstrate both the transfer of cryogenic propellent, and its storage in space for a long period of time.

Unfortunately it was cancelled for cost reasons, and replaced with a ground-based investigation.

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