In addition to the benefits of smaller and more frequent launches (and perhaps other benefits), could fuel depots also provide a modest benefit in reducing the mass of fuel tanks for vehicles leaving LEO?

This assumes that stresses on fuel tanks during the trip to LEO would be reduced by not being loaded with fuel, that stresses from LEO outward are lower, and that support for any inflation or other reconstruction in LEO would not add mass that must be carried out of LEO. (Any extra mass that is left in LEO would still be an issue.)

  • $\begingroup$ Created (possibly not useful) tag "fuel-depots". (Tag edits are welcome!) I have not researched this--not knowing where to begin--, but it seems likely to be not entirely a useless question. $\endgroup$ Aug 8 '13 at 19:24
  • $\begingroup$ If you could only broaden the question a bit, it would be a great one (advantages of orbital/L2 fuel depots). Structurally speaking, sloshing propellants are a pain. Mass-wise, docking nodes are an overhead. $\endgroup$ Aug 8 '13 at 19:32
  • $\begingroup$ @DeerHunter I considered also asking what the advantages would be of orbital fuel depots, but this particular possibility came to mind. The idea was for an empty tank (possibly "deflated")--no sloshing at lift-off. If fuel depots are used for other reasons, lightening fuel tanks might be icing on the cake. This question also includes whether the fuel tanks could be made lighter, so it would not be answered by a "why fuel depots" question. Perhaps the question is "too localized"? $\endgroup$ Aug 8 '13 at 19:47
  • $\begingroup$ It is localized only in the sense of not looking at the whole picture. Mission-wise, fuel depots may be a hindrance, a risk, a blessing. People reading the answers may become politicians and their pre-conceived notions will some day hamper space agencies' work :) $\endgroup$ Aug 8 '13 at 19:51

Any fuel sent to a depot has to be launched, and so needs to be in a sufficiently anti-slosh container.

Sending up deflated tankage to be filled from depots presumes inflatable tankage capable of handling the fuels; the most common space fuels use cryogenic fluids, and the others tend to be corrosives. (Hydrazine, monomethylhydrazine and nitrogen tetroxide are all hazardous fuels; Liquid Hydrogen and Oxygen are cryogenic fluids.)

Since any spacecraft going anywhere of note at present is likely to be using a high thrust short burst to accumulate the needed vector to go wherever, and another at the far end, the need to stress the fuel tankage remains; the use of separately launched tanks being thus preferable to inflation from a depot in orbit.


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