[TMWNN]

>Would a manned Mars mission really have been feasible? Is it feasible now? I have no idea, myself.

No less than Michael Griffith, *the NASA Administrator*, said in 2007 that the shuttle was a mistake (<https://aviationweek.typepad.com/space/2007/03/human_space_e...>), and that NASA should have instead continuing launching Saturn rockets:

>If we had done all this, we would be on Mars today, not writing about it as a subject for "the next 50 years." We would have decades of experience operating long-duration space systems in Earth orbit, and similar decades of experience in exploring and learning to utilize the Moon.

[TheOtherHobbes]

I don't think we would be on Mars. The hard part isn't getting there, it's creating a sustainable semi-independent habitat that will get you there and keep you alive there between resupply runs.

This is not a "Oh, we'll just deal with that when we need to" problem. It's absolutely critical for long-term missions. And there's been shockingly little research done on it.

The ISS is trivial in comparison because you can send up stuff and take stuff down almost instantly with relative ease. Mars is seven months away. So your mission has to be self-sustaining for at least that long. And it's going to need a steady stream of resupply runs - with a seventh month lead time if have an accident or start running out of stuff.

And all of that - for what? Mars is not a pleasant or easy environment. Aside from unpleasant, difficult, and hostile living space it has no obvious resources.

"Because we can" is a good enough reason for an initial exploration, but it's not a sustainable project without a long-term goal.

[JPLeRouzic]

Thanks for your link about a NASA administrator saying "the shuttle was a mistake". As someone who was a pre-teen during the Apollo area, this warms my heart.

However, even is Saturn V was an extraordinary engineering feat, to explore space we needed something much less expensive, much less polluting, much more secure.

Perhaps SpaceX fills better this niche, but I hope that we simply become a space species with most jobs and people at least in orbit around Earth or Moon.

[Tabular-Iceberg]

> much less polluting

Isn't the SpaceX Merlin a fuel-rich RP-1 engine too, just like the Rocketdyne F-1? Or is it another source of pollution that you have in mind?

[JPLeRouzic]

RP-1 is much less toxic than Hydrazine, but toxicity is not the same thing than pollution. One is qualitative, the other both qualitative and quantitative. Burning a huge amount of kerosene is polluting. For comparison a Boeing 747 (4 engines) consume 2,8 kg per second, while a Saturn V 1 first stage burns 13,600 kg per second, nearly 5000 times the amount of the Boeing 747.

I hope for a breakthrough in rocket engines, but I am quite sure it will not happen. We need something new.

[Tabular-Iceberg]

Yes, but the Merlin engine doesn’t burn hydrazine, it burns RP-1 just like the F-1. I fail to see the environmental benefit.

Also, how energy efficient is the production of hydrazine? Non-fossil processes for making fuels tend to be pretty wasteful, take hydrogen from methane compared to hydrogen from electrolysis for instance.

[messe]

SpaceX’s starship and superheavy are planned to use Methane rather than RP-1. The exhaust is much cleaner. It’s not as clean as just using Hydrogen, but that’s quite difficult to store at cryogenic temperatures, far less dense, and not as suited to long duration missions.

[_joel]

Yes, this is the whole reason they designed Raptor and get methane via the Sabatier reaction [1]. If you want to get back from Mars, you won't find tanks of RP-1 but you can make methane from abumdant CO2 and water (with solar arrays) which is available on Mars

[1] https://en.wikipedia.org/wiki/Sabatier_reaction

[nasmorn]

Why would we ever put most people in orbit? Of the sun sure but then it is just called a planet.

[JPLeRouzic]

Hilton's plan was for an hotel in orbit. It's a nice idea, but it means it would have been for a short stay, assuming some space tourism.

It would be better if we have several good reasons to stay permanently in orbit.