In article , says...

On Mar/18/2018 at 2:32 PM, Niklas Holsti wrote :
Hmm. In his "Making Life Multiplanetary" address in September 2017, Musk
showed a simulation of a BFS Mars landing with text saying "over 99% of
energy removed aerodynamically". If less than 1% of the orbital energy
remains for rocket braking, is that really a significant difference
between Mars and Earth?


One percent of the energy of Mars' escape velocity (escape not
orbital energy, I think that is the relevant value to use here)
means one tenth its speed. That's about 503 m/s. According to
https://www.reddit.com/r/spacex/comm...tegy_analysed/
or https://tinyurl.com/hk252mj
the falcon 9 first stage inbound at 1.1 km travels at 105 m/s.
So 5 times the speed, 23 times the energy on Mars vs Earth.

I'd say it is significant but not a big problem. Of course, less
than 1% leaves plenty of room, 0.1% is less than 1%. But I would
think that it would be close to 1%, 5 times the speed seems
reasonable to me.

That looks like a pretty good first approximation. But secondary
effects like gravity losses will be different because the two planets
have different gravity.

Jeff

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