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This is something that I'd seen in the BBC fictional documentary Voyage to the Planets. There, as the crew arrives in the orbit of Mars, there's a tank that has already been sent there so that the crew can refuel their spacecraft. Till today no space agency ever proposed this for crewed interplanetary travel or I dunno of any such concepts. Would it be a good idea for a manned mission to Mars and/or to other planets? The tank may not necessarily be in orbit around a body, it may also be landed on a celestial body near the spot where the crew is to land eventually.

Would it be efficient? Does it have disadvantages? Or doesn't it matter? I think it is good because you don't have to use a too heavy rocket for launch from Earth then.

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    $\begingroup$ uhoh, thank you for having improved my question, you did it very well, it's formulated better now by you $\endgroup$
    – LoveForChrist
    Jun 11, 2020 at 10:14
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    $\begingroup$ Welcome to Space! Nice question. You accepted an answer only a few hours after the question was posted. While it is a good answer, it is generally a good idea to wait 12 to 24 hours to accept an answer. This allows other persons (not me) in other time zones time to research and write an answer. Thanks! $\endgroup$
    – DrSheldon
    Jun 11, 2020 at 15:18
  • $\begingroup$ @DrSheldon I know but GdD's post really answers my question. It is enough to send the tank into lunar orbit or to be refueled at a fuel pod on the Lunar Gateway (similar to the Armageddon movie) rather than launching it to another planet's orbit or surface. However, users are free to add something we might have missed. $\endgroup$
    – LoveForChrist
    Jun 11, 2020 at 15:42

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The big problem with sending supplies and fuel ahead is that there's many ways it could go wrong which would end up with the crew being dead.

There's no major advantage to sending supplies ahead of the mission to orbit another body, and a lot of risk. The thought is that you can split the cargoes and launch them in smaller, cheap rockets rather than sending up one gigantic and expensive launcher. However, you don't gain anything by sending the cargoes ahead, and if the manned spacecraft cannot rendezvous with the cargo later then the crew are dead. Rendezvous in orbit around another planet is much riskier than around the Earth as there will be much more limited and less accurate position data, and limited help from mission control due to the distance. Rather than assembling the spacecraft around Mars it makes more sense to assemble it around the Earth or the Moon and send it complete on its mission as you get the same result with the same expenditure of energy.

There's more advantage to sending fuel ahead to a Mars landing site as you can reduce the weight of the lander when it enters the atmosphere as it doesn't have return fuel. Again it's very risky as there's no possibility of aborting, and if your lander doesn't come down in the right spot the crew is also dead.

The scenario where rendezvous with a fuel tank in orbit around another body really makes sense is where the fuel was produced on the other body and sent to orbit. That capability would significantly reduce overall mission costs as there would be a lot less weight to transport, again there's the risk of a failed rendezvous, which would have to be balanced against that benefit. Plus, we don't know how to do this yet, there's been work done on producing fuel on Mars but nothing has been proven to work.

Lastly there's a time penalty. If we are sending missions to Mars we want them to focus on science, not spending half their time resupplying.

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  • $\begingroup$ Thank you. You're right that to use the Lunar Gateway as fuel resupply for interplanetary missions is very good. However you're talking like if in my proposal the fuel tank and the crew would launch almost simultaneously. The thought is that the crew doesn't launch from Earth until the tank is at its planned position (in the orbit or on the ground of the planet in question) and I don't think refueling takes "half their time". Nonetheless, it's really a better idea to refuel the interplanetary spacecraft in Earth orbit, lunar orbit or the Earth-Moon libration point. $\endgroup$
    – LoveForChrist
    Jun 11, 2020 at 11:15
  • $\begingroup$ Possible advantages of sending fuel into orbit ahead would be (1) one could launch the fuel in a way which requires more time but less delta-V, and wait until it is successfully parked before sending humans; (2) sending e.g. ten shipments such that the probability of at least eight being successful would be acceptably high might be cheaper than sending one mission with that same probability of success. Further, it may be possible to plan the mission so that if a delivery failure is discovered while the crew is en route, the crew would have supplies for a safe return. $\endgroup$
    – supercat
    May 3, 2021 at 20:33

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