[amitparikh]

Why are human missions so much more costly than robotic missions? Answer: Life Support.

If our (very) long-term goal is to stake humanity's claim on other planets/asteroids/etc., then it makes sense to work on improving and expanding Life Support capabilities in harsh environments. I see it as an investment in the future -- it may not seem to have immediate benefits, but these are key milestones and steps for reaching the ultimate goal.

[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.

[nicoburns]

> If our (very) long-term goal is to stake humanity's claim on other planets/asteroids/etc.

This doesn't seem realistic without revolutionary advances in Physics.

[kadoban]

What advances in physics are necessary? I understand it to be an engineering, economics and political question.

[dikei]

Well, if you want to colonized planets in other solar systems, FTL travel or Cryonics technology might be necessary.

[brohee]

People willing to breed and die during the trip would work too. At which point it's a pure engineering challenge, albeit a hard one...

Sending humans to outside the solar system doesn't mean they have to be the same humans that departed.

[hobofromabroad]

But then the question becomes what generation +1 wants?

This is probably going to be nearly as big a problem as the engineering one.