[haunter]

Q: 'How many Starship launches are needed to execute the Artemis III lunar landing?'

NASA: 'We don't know but at least 15'

Video: 'Oh well that's a huge problem to have a complex project like this and we don't even have an exact answer'

[marcusverus]

Isn’t this disingenuous? As far as I can tell, Starship can make it to the lunar surface with a significant payload without refueling. The refueling launches are only required if you want to maximize the payload per lunar trip.

[avmich]

BOTE calculations, approximate numbers:

    - delta-V for LEO-to-the-Moon flight - 3100 m/s
    - delta-V to get to low Moon orbit (a-la Apollo) - 1000 m/s
    - delta-V to land on the Moon from low orbit - 1700 m/s
    - extra delta-V during landing like with Apollo LEM for
      emergencies - 700 m/s
    - delta-V to get back to the Moon orbit - 1700 m/s
    - extra delta-V during lift-off like with Apollo - 500 m/s

Total - 3100 + 1000 + 1700 + 700 + 1700 + 500 = 8700 m/s, that's a pretty large delta-V, almost like an Earth SSTO.

Raptor Isp - 3500 m/s, fueled mass - 1320 tons, empty mass - 120 tons, mass ratio - 1320 / 120 = 11. Tsiolkovsky formula:

    exp(8700 / 3500) = m_fueled / m_empty = 12

that is, we need Starship HLS to be somewhat lighter to get to the Moon surface and back to low Moon orbit from LEO than the current numbers for Starship, and that is without any payload.

It's definitely not the final numbers, so the results will change, but

> Starship can make it to the lunar surface with a significant payload without refueling

is questionable at the moment.

If you mean cargo flights with no return to the Moon orbit - rather than crewed flights as agreed with NASA today for Starship HLS - then of course the numbers are better.

[marcusverus]

Thanks for this!

[ianburrell]

The Artemis mission involves landing astronauts on the Moon and bringing them back to Earth. Not landing an empty Starship on the Moon. Maximizing the payload is really important when need to carry humans, and launch a whole large spacecraft off the Moon.