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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 considered much easier with almost the same benefit to launch an entire fueled stage with engines instead of just the tanks with propellant. The only penalty is that you have the mass and cost of some engines attached to the bottom of the tanks that you were going to transfer propellentpropellant from, which is a relatively small fraction of the mass. The benefit is that a) you don't have to transfer propellant between tanks -- you just dock with the stage, and b) you can now design the stage for its interplanetary mission instead of having to modify an upper stage for two different missions (that and getting to orbit). For example you may want to keep cryogens from boiling off in a long cruise, which is never a concern for a launch vehicle.

In any case, there is research in both preventing cryogen boil off and in the transfer of propellants in space.

The International Space Station is regularly refueled in orbit. Though it's not so that it can depart Earth orbit.

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 considered much easier with almost the same benefit to launch an entire fueled stage with engines instead of just the tanks with propellant. The only penalty is that you have the mass and cost of some engines attached to the bottom of the tanks that you were going to transfer propellent from, which is a relatively small fraction of the mass. The benefit is that a) you don't have to transfer propellant between tanks -- you just dock with the stage, and b) you can now design the stage for its interplanetary mission instead of having to modify an upper stage for two different missions (that and getting to orbit). For example you may want to keep cryogens from boiling off in a long cruise, which is never a concern for a launch vehicle.

In any case, there is research in both preventing cryogen boil off and in the transfer of propellants in space.

The International Space Station is regularly refueled in orbit. Though it's not so that it can depart Earth orbit.

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 considered much easier with almost the same benefit to launch an entire fueled stage with engines instead of just the tanks with propellant. The only penalty is that you have the mass and cost of some engines attached to the bottom of the tanks that you were going to transfer propellant from, which is a relatively small fraction of the mass. The benefit is that a) you don't have to transfer propellant between tanks -- you just dock with the stage, and b) you can now design the stage for its interplanetary mission instead of having to modify an upper stage for two different missions (that and getting to orbit). For example you may want to keep cryogens from boiling off in a long cruise, which is never a concern for a launch vehicle.

In any case, there is research in both preventing cryogen boil off and in the transfer of propellants in space.

The International Space Station is regularly refueled in orbit. Though it's not so that it can depart Earth orbit.

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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 considered much easier with almost the same benefit to launch an entire fueled stage with engines instead of just the tanks with propellant. The only penalty is that you have the mass and cost of some engines attached to the bottom of the tanks that you were going to transfer propellent from, which is a relatively small fraction of the mass. The benefit is that a) you don't have to transfer propellant between tanks -- you just dock with the stage, and b) you can now design the stage for its interplanetary mission instead of having to modify an upper stage for two different missions (that and getting to orbit). For example you may want to keep cryogens from boiling off in a long cruise, which is never a concern for a launch vehicle.

In any case, there is research in both preventing cryogen boil off and in the transfer of propellants in space.

The International Space Station is regularly refueled in orbit. Though it's not so that it can depart Earth orbit.