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.

See full article...

 

[Dtiffster]

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.

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.

 

[Dtiffster]

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.

We don't really know what the payload would be today, or even next year, but considering the lead time of missions to the outer planets and that starship hasn't any on the books neither particularly matter at the moment. But there's nothing to say they would necessarily need to completely fill the upperstage. A 90% load of propellant is still a good deal of impulse.

 

[Dtiffster]

How do they match up performance wise? The original Delta IV bases upper stage is comically undersized for something as big as the SLS core.

ICPS is big enough though, and centaur V is bigger with a better dry mass fraction. ULA has even talked about a stretched stage with more engines. As is I suspect centaur V is probably smack in the middle of ICPS and EUS in terms of payload to TLI, which is fine as the whole comanifesting payloads thing was just a thin excuse to justify continuing to develop EUS.

NG's upper stage is actually larger than EUS, and probably no worse on dry mass fraction. Isp is a bit lower, but a short version probably has pretty comparable performance to EUS.