44 votes
Accepted

Has in-space refueling been done?

Short answer: Space stations have been refueled on orbit, as well as some small demonstration missions. Long answer: There is only a limited number of objects that this is even an option. There are ...
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  • 118k
30 votes

Refueling a Mars mission on the way

Unfortunately sending propellant ahead to pick up on route will not help. The same amount of propellant will be needed regardless if both are accelerated together or separately. Also if launched ...
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  • 5,901
19 votes

Viability of orbital refueling

This is basically the approach being considered for getting all of the hardware to Mars for a crewed mission. However instead of refueling an upper stage that was used to get you to orbit, it is ...
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  • 57.6k
19 votes

Refueling a Mars mission on the way

If you think less about fuel and more about the other amenities for a long distance mission, you are awfully close to the concept of a cycler. The basic idea is that you take a big vessel, on which ...
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  • 448
17 votes
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Is it possible to refuel the James Webb Space Telescope?

Theoretically possible, but not planned. Refuelling in the sense of replacing expended fuel in the propulsion system is possible in theory. This answer provides a nice schematic of the propulsion ...
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  • 12k
17 votes

Refueling a Mars mission on the way

The real problem is that, in space travel, your speed determines your trajectory, and therefore two objects can't follow the same trajectory at different velocities. Precisely, a faster interplanetary ...
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  • 559
14 votes

What is the extent of on-orbit refueling experience at the ISS? Which fuels? which spacecraft?

The propulsion system of the Service Module (public relations name: Zvezda), part of the Russian side of the ISS, is refueled by Russian Progress spacecraft, and formerly by European Automated/Ariane ...
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12 votes

Has in-space refueling been done?

The ISS is periodically refueled by its cargo supply ships. NASA's Robotic Refueling Mission has experimented with refueling satellites. DARPA's Orbital Express demonstrated hydrazine refueling (...
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11 votes
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VLEO - ion thrust using atmospheric molecules?

ESA is working on such an engine. an ESA-led team has built and fired an electric thruster to ingest scarce air molecules from the top of the atmosphere for propellant, opening the way to ...
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  • 121k
10 votes

What is the extent of on-orbit refueling experience at the ISS? Which fuels? which spacecraft?

In addition to the standard operational refueling missions that are part of normal station-keeping operations, there have also been experiments performed that studied in-space refueling. In particular,...
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9 votes
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Has on-orbit refueling ever been demonstrated with cryogenic fuels?

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 ...
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9 votes
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How can Northrop Grumman's Mission Extension Vehicle (MEV-1, 2) "dock with 80% of satellites currently in a geostationary orbit"?

There isn't much information publicly available, but the MEV appears to dock to the one component many satellites have in common: the rocket engine nozzle. An extensible probe from the MEV (on the ...
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8 votes

Is a Mars return mission by Starship possible without local propellant production, given the current specifications?

You can find most of the information you need on the picture below which comes from Reddit. Crucially, if you add up the relevant lines, delta-V from Mars to Earth-Mars transfer is about 5.92 km/s. ...
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8 votes
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Is BFR refilling in space purely milli-g "gravity" feed rather than using pumps and/or pressure?

The reason for the acceleration is not so much to cause the transfer of the liquids, but to get the liquid to be at one end of the tank where the pump inlet is. Remember in zero-g, the liquid is not ...
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8 votes

Has in-space refueling been done?

I didn't see this referenced anywhere so I'm including it for completeness. Feel free to merge it in with another answer. STS-41G (launched October 5 1984) included a secondary payload called the ...
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8 votes
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Why we do not refuel and assemble in orbit?

Several things that KSP does not model: The challenges of actually docking two things mechanically together without a handy human such that the plumbing works (leaks have a tendency to go bang) The ...
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8 votes
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Which two spacecraft are being shown disconnecting here, and what was the connection for?

Looks like a demonstration program for robotic refueling that took place on ISS with Dextre in 2013. This was the Robotic Refueling Mission (RMM). A nasa page with several videos is at https://nexis....
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  • 5,762
7 votes
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Viability of orbital refueling

This is a short answer but in KSP pumping fuel is totally costless, whereas in reality pumping fuel between stages is difficult even in the case where the stages are mated together on the ground. This ...
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7 votes

Refueling a Mars mission on the way

Rather than having fuel tanks you meet on the way the better way would be preposition fuel tankers at the start and end of the trip i.e Earth and Mars orbit. You put fuel tankers in Earth's orbit as ...
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  • 200
6 votes

Liquid settling in tanks during orbital refueling

Shuttle orbital manuevering / attitude system tankage used screens to ensure that fluid always remained at the tank exit. Sufficient fluid would cling to the screens to get the engines started. The ...
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6 votes
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Could SpaceX Super Heavy (Starship) Booster reach Earth orbit without starship on top?

Have not attempted to math it out, but some rocket first stages can make orbit alone. The difficulty is that they have a payload of zero when doing so, because they are taking all the empty tank mass ...
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5 votes

Why do two Starships dock in such a manner their heat shields face opposite sides?

I think it’s because they want to use the same pipe work they use for tanking on the ground in orbit. I imagine the Starship will have an LOX inlet/outlet on one side and a Methane inlet/outlet on the ...
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  • 5,901
5 votes

Is it possible to refuel the James Webb Space Telescope?

Partial, sort of-answer, in addition to the above: Q: Is it possible to refuel the James Webb Space Telescope? A: That depends on the JWST having its tanks/plumbing/ports accessible to a robot. (not ...
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5 votes

How long does it take to refuel a rocket?

The difference in loading a flown booster and a brand new booster is the same. SpaceX starts loading RP1 and first stage LOX at T-35 min. RP1 fueling on the first stage finishes around the T-3 min and ...
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5 votes

Is Landsat-7's propellant resupply port "robot-ready"? (Restore-L mission)

My reading of the Aviation Week article on this seemed to suggest that while Landsat-7 was not designed to be refueled, when they looked at its design, they found a fuel line, they could patch into ...
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5 votes

Is an electric fuel tug from LEO to moon orbit economically feasible?

So the basic fact is that the delta-V from LEO to LLO (low lunar orbit) using a high-thrust system is about 4 km/s and using a low thrust system it's about 8. source So, using something like a vacuum ...
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  • 18.9k
4 votes

Liquid settling in tanks during orbital refueling

For the Salyut 6 space station, both Progress cargos and the station used bladder tanks. The tanks were pressurised using nitrogen. The nitrogen could be recovered once the operation was done (at ...
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  • 12.2k
4 votes

Liquid settling in tanks during orbital refueling

Ullage (i.e. getting the fuel at the end the tank you want it to be at and the pressurant at the other end) for large rocket stages in free-fall is usually handled with small auxiliary thrusters. ...
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4 votes
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How to slow a spinning spacecraft externally?

So long as the object you wish to slow is made of metal you can slow it by putting a ring of magnets around it. How fast this will work depends on the metals involved. I do not believe this can ...
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4 votes

Capacity of the BFR tanker -- how many flights to fully refuel the spaceship?

The presentations Musk made at the IAC suggested 6 tankers to one spaceship, for a Mars mission. Two tankers to one spaceship for a lunar mission.
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