Mars has 1/3rd of the gravity and 0.6% of the pressure.
Those 2 factors make them very similar to each other and the distance makes the moon the clear candidate for a first step.
Earth LEO 9.3 km/s
LEO escape 3.22 km/s
escape MTO 0.6 km/s
MTO MCO 0.9 km/s
MCO LMO 1.4 km/s
LMO Mars 4.1 km/s
-----
19.5
Earth LEO 9.3 km/s
LEO LLO 4.04 km/s
LLO Moon 1.87 km/s
-----
15.2
Moon LLO 1.87 km/s
LLO escape 1.40 km/s
escape MTO 0.6 km/s
MTO MCO 0.9 km/s
MCO LMO 1.4 km/s
LMO Mars 4.1 km/s
-----
10.3
(Earth -> Moon -> Mars = 25.5 km/s)
30% of delta-V but much more than 30% more fuel used (etc) since "compound interest" applies as you're using fuel to ship fuel out of orbit and then much of that fuel again to change your orbit to mars, etc.
Similarly, Napoleon came up against the limits of using horses to pack hay for horses invading Russia - compound interest; you can only do so much.
PS - that 30% assumes a path that I don't, and no solar power used to catapult oxygen off the moon. I'd go for a Lagrange point you're ignoring.
PPS - you've assumed Mars, not, say, near-earth asteroids or trojans with a very different, far lower delta-V. Vastly different problem.
I didn't forget the Lagrange libration points, but decided not to include them because they were not relevant to the parent comment, and they would still require some mechanism to get propellant mass up to them. They're currently almost empty, and won't be very useful until the Moon itself has launch capacity to get water up there. Again, I was mainly responding to the parent post.
The rocket equation is indeed a bear. As delta-V scales linearly, fuel requirements scale up exponentially. One way to manage it is to use stages. Another is to refuel and assemble vehicles higher up in the gravity well. As it happens, shipping tanks of fuel and propellant up to LEO separately means that missions to Mars starting fully fueled from LEO would require only 0.9 km/s more than missions starting from the lunar surface. Measuring by delta-V, LEO is at about the halfway point for an Earth-Mars mission.
But it's also worth noting that the surface of the Moon is closer to LEO than the surface of the Earth. Shipping fuel and propellant from the Moon to LEO, to rendezvous with and refuel a vehicle coming up from Earth, is even cheaper than shipping up the resupply mass from Earth.
The Moon is not practice for Mars. It's a waste of time for political posturing.
Some of the most difficult challenges have to do with maintaining life support long term. The Moon isn't a bad place for that. If we're able to deal with operations in conditions dealing with vacuum, that experience is still applicable. Also, the human side of the procedures for preventing lunar dust and grit from entering the living space will be important and applicable to Mars. Mars soil isn't as bad, but some of it you don't want in your living space either.
Ah jeez. That's what I get for commenting right after rolling out of bed.
> ... the most difficult challenges have to do with maintaining life support long term. The Moon isn't a bad place for that.
The moon is a bad place for that because now you have to carry all that extra fuel for landing/etc. Low earth orbit is just fine for figuring out life support as has been done on the ISS already. Why do it again in some place there's no reason to go to? There's no nitrogen available on the moon.
The dust thing is applicable but minor.
I think that might be outweighed by the fact that the transit time is a few days compared to months, and launch windows are plentiful. It's better to test with all the benefits we can initially, IMO, as failure has such a high cost (in all aspects. How long do you think it would take for the public to get over their distaste of manned missions or colinization efforts after a big failure?).
Entirely false. On the Moon, we can exploit in-situ resources for life support. Regolith can be used for radiation shielding and the extraction of oxygen. We can even harvest water in certain locations. Crops can be grown using hydroponics. Doing these things while maintaining a spaceport on another world isn't going to be nothing. Getting experience doing ground based operations is going to be valuable. It's not just "dust." It's probably literally tens of thousands of things we will have to learn through hard won experience.
Ground-based operations. Better to get the experience where help is only 3 days away.
It's probably worse, since Martian soil has perchlorates, which are toxic and cause thyroid problems at low concentrations.
There is also something to be said for sending humans to a place where humans have never been able to go before. To many people, that's an end goal in and of itself.