Rocket Report: Russia’s rocket engine predicament; 300th launch to the ISS

North Korea test-fired a powerful new solid rocket motor for its next-generation ICBM.

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[Chuckgineer]

Just wondering if anyone has done the math on refueling a Falcon 9 second stage in orbit. If a Starship can carry 100 tons to orbit, that's about the propellant mass a Falcon 9 2nd stage can hold. I know that kerosene requires a separate tank as payload, but the size and mass fraction of the 2nd stage is seriously impressive. For a mission to the outer planets, one launch of Starship and one F9 launch could orbit a spacecraft, and provide a 4 ton dry mass "3rd stage", instead of refueling a 100 ton dry mass Starship.

 

[Chuckgineer]

Why wouldn't the starship just carry the f9 upper stage with it along with the payload. That's a heck of a lot more straight forward than trying to transfer kerosene on orbit. And it saves a pointless F9 launch.

The propellant mass itself is slightly more than the expected 100 ton payload of Starship, if Starship evolves to a heavier payload, your approach is obviously better.