[Isinlor]

It's not really the life support. It's the lower risk tolerance, the need to bring people back and the tyranny of the rocket equation.

You can just abandon a robot on Mars. But if you want to send people to the Moon or Mars you will need to send them with a spacecraft and fuel that will allow them to return. The tyranny of the rocket equation then forces you to build extra large rockets like Saturn V, SLS or Super Heavy Starship. You need exponentially more fuel as you increase payload mass in order to have the same capability.

SpaceX solves that with refueling in low Earth orbit, that allows to scale rocket fuel needs linearly with regard to payload instead of exponentially. And with refueling at the destination in case of Mars. But the need to bring fuel with you is still a big limitation for the Moon missions.

[avian]

> SpaceX solves that with refueling in low Earth orbit, that allows to scale rocket fuel needs linearly with regard to payload instead of exponentially.

I don't think that's the case. The rocket equation has the delta-v under exponent, not the mass ratio. Fuel mass scales linearly with payload in any case.

I don't think orbital refueling changes any scaling laws. It just means you can launch several small rockets instead of one huge one. Total mass launched stays approximately the same.

[dotancohen]

  > But if you want to send people to the Moon or Mars you
  > will need to send them with a spacecraft and fuel that
  > will allow them to return.

Though you are correct for political reasons, there are more than enough people willing to take a one-way trip to Mars. I'm one of them. I love my family, but they know that if Patrick Forester calls me one day because he has only enough O2 for a one-way mission, I'm going.

I'd even go if the mission was to see which of the radiation, CO2, microgravity, nutrition, heat, or isolation kills me first, to improve that for the next bunch. I feel that the goal is that important. Lots of others feel as I do.