[godelski]

  > Even if the answer turns out to still be 10x more expensive than the ground

You're off by at least an order of magnitude.

Using Musk's optimistic numbers, to put things into LEO, it is >$1k/kg for single reuse, ~$100/kg with ~5 reuses, and <$50/kg with like 50 reuses. That's to LEO. Moon is way more expensive.

  >  I'd suggest sending up 1000 km of HVDC cable

I'm sorry, WHAT?

I'll let you do the math on that one, because that stuff is not light weight... We're talking several kg/m minimum... Then consider payload...

You're being pretty cavalier about all the hard things... You can't just hand wave away these details because these "details" are just a fraction of what makes all of this so difficult.

[ben_w]

> I'm sorry, WHAT?

> I'll let you do the math on that one, because that stuff is not light weight... We're talking several kg/m minimum... Then consider payload...

https://www.wolframalpha.com/input?i=%28%28%28resistivity+of...

If you're not willing to have 8 starship landings for power infrastructure, why even bother? Even with 8 landings and a magic power system, it would only be on the scale of one of the smaller Antarctic research bases.

(100 Ω is completely arbitrary, FWIW. It's a dry vacuum, so bare metal just lying on the surface could run at 1MV. Above 1.044 MV, you actually need to care about random photo-ionised electrons turning into a cascade of positron-electron pair creation events for at least part of the line, but do also consider that this is the potential at opposite ends of a loop rather than vs. ground).

> You're being pretty cavalier about all the hard things... You can't just hand wave away these details because these "details" are just a fraction of what makes all of this so difficult.

I think you misunderstood me. I'm absolutely not saying "this would be easy" (nothing in space is), I'm saying "this is what my sales pitch would be".

Consider this as what I think is the MVP of being serious about the moon, that anything less than this scale is just rah-rah flag-waving.

As an aside, I prefer the moon to mars as a "first attempt" target for this kind of thing, precisely because I expect all kinds of disasters. Toy example: Accident, hardware failure, or meteorite impact that kills the water supply? Dehydration would kill you in 3 days. Emergency return from the moon (or resupplying the moon from Earth) is fast enough to solve that; but if it happens during all but the most survivable 0.4% of a Mars mission, everyone dies.

[godelski]

  > If you're not willing to have 8 starship landings

Your math is WAY off.

You used LEO payload... Their GSO payload is 21tons[0] and the moon is a lot further than GEO. If you use the GSO numbers you get about 37 launches. But TLI (Trans Lunar Injection) is probably closer to 15% LEO payload capacity[0], if we estimate off of Atlas V, so let's say about 50.

Not 8, 50. You're off by 5x-10x.

  > I think you misunderstood me.

Look, I don't want to call you dumb, I actually think you're pretty smart. But rocket science is famously hard. Many things are non-intuitive (true for most hard subjects).

I also think you should take a step back here and think about what you're saying. Look at your number of lander estimates here and how far off you are by a simple naive assumption. I get why you made that assumption and I understand why the error was made, but also these are not the kinds of mistakes people make when they have expertise in the domain. I knew it was more than 8 before even running any numbers, I knew it was more than a few dozen. But I also know people frequently make the claim that getting to LEO is the hardest part and that this warps people's perceptions and makes for bad assumptions. You have passion and I don't want to kill that passion, but if you are this passionate then use that passion to drive you into diving deeper into the topic. Don't be satisfied with shallow knowledge, your passion is greater than that.

So I want to address the full

  > If you're not willing to have 8 starship landings for power infrastructure, why even bother? 

Because 100 launches is a non-starter. There were a little over 300 for all of 2025. It's a big improvement, since 5 years back we barely broke 100, but you're talking about way more. About 100 of those were from China and SpaceX hit 170 total. That's a wildly impressive number, mind you, but you're also talking about 10xing their Starship launches. These things are hard to scale. They've been doing about +30/yr since 2020 on their Falcon 9. Impressive numbers, but not fast enough and scaling Starship will be harder.

  > I'm absolutely not saying "this would be easy" (nothing in space is), I'm saying "this is what my sales pitch would be".

So this is why you misunderstand me, and, I think, the conversation. Maybe the "sales pitch" works for people who don't know any better, but it isn't going to work on those with even junior level experience in the industry. The numbers are so off they will set of alarms and you get dismissed. It only makes it worse when pressed that the numbers look even worse.

Because I don't think you're suggesting it would be easy, if you did I would have laughed in your face. But I think you've underestimated how hard it is, even though I think you think it is really hard. There's no limit to how difficult something can get so it becomes easy to underestimate the difficulty. This is just like it is easier to make bad estimates of distance when looking at something very far away, it is easy to think something is 5 miles away when it is 10. This doesn't make one dumb, but rather that we need to more accurately be aware of our level of uncertainty. And in this case, it is pretty high. Why wouldn't it be? There's literally no expectation for it to be unless you're an aerospace engineer working on lunar systems.

[0] https://web.mit.edu/2.70/Reading%20Materials/SpaceX%20%20Sta...

[1] The Wiki says 100k but with in-orbit refueling and there's even a note about needing a better source. So that doesn't really count for our estimates. Saturn V and SLS has a bit better, hence the range in the next line. But also remember Saturn and SLS don't have to do returns... You'll find this helpful: https://forum.nasaspaceflight.com/index.php?topic=49117.0

[2] https://spacestatsonline.com/launches/year/2025

[ben_w]

> So this is why you misunderstand me, and, I think, the conversation. Maybe the "sales pitch" works for people who don't know any better, but it isn't going to work on those with even junior level experience in the industry. The numbers are so off they will set of alarms and you get dismissed. It only makes it worse when pressed that the numbers look even worse.

Yes, absolutely this. I'm not even coming at it from the side of the conversation you're arguing here.

Again, I don't actually believe Musk, and all the stuff I'm saying absolutely should *not* be treated as a complete ready-to-go mission plan; it's nowhere near that detailed, and I know it.

None of this was intended to be a "he can do it!" cheerleader, because I don't believe Musk can even get close, I'm saying "As a less bad alternative to him talking about a million people on mars by 2100…" or perhaps "As a less bad alternative to waxing lyrical about something that would be within spitting distance of fundamental thermodynamic constraints even if we start by assuming we've tiled the entire surface of the Moon with theoretically perfect PV" (which is ball-park what I get for his 1000 TW/year number).

What I suggested was only "what I'd be talking about if I had what he's promising", not what I think Musk can actually deliver. Even where Musk has beaten incumbents, it's by being less bad at price-timeline estimates rather than actually good at them.

Also:

> Look, I don't want to call you dumb, I actually think you're pretty smart.

Thanks, but do feel free to call me an idiot on this. I mean it: it took what I now regard to be an embarrassingly long time before I became skeptical of Musk's claims.

And I am not, and do not claim to be, even a junior level experience in space. Well, except for processing data from earth observation satellites, where I can claim *exactly* junior level experience and no more than that.

> You used LEO payload.

As per your own references, landings, not launches. Yes, this may be over-optimistic, but hopefully I'm saying often enough in this comment that I don't take Musk seriously any more.

I absolutely agree SpaceX have not demonstrated what they need to demonstrate to actually pull off the orbital refuelling plan, but (and as per your [1]) the target payload *if* they could was still 100 tons last I checked… well, assuming Musk doesn't randomly change everything again, which at this point I expect him to do instead of delivering any of this.

I'd like to not be skeptical of Musk, but, well, he's repeatedly demonstrated reason to be skeptical of every claim he makes in every field, and unfortunately SpaceX is merely his least-wrong domain rather than one where he's close to correct.

Still, steel-man and all that. Given what he's saying he plans to do, what would I do with that? Not Mars, not space data centres.

> Because 100 launches is a non-starter.

I don't expect Musk to actually succeed with his prices, but *hypothetically* if he did, the target price per launch is order-of $10M (and if that target price sounds stupid, I'm more inclined to believe anyone on this forum dissenting than Musk's own claims on this), *if* then it would be lower than a Falcon 9's current price to launch. Again, I don't believe him, Cybertruck's launch spec was higher price for worse everything than he initially announced and that was something he should've been able to estimate better.

As someone who cares about the environment, I am not too happy about even the current rate of launches given the apparent lack of any of those Sabatier machines he kept saying would let them do ISRU for return trips from Mars. So I also kinda want him to fail here.

But if, *if* I was taking those numbers seriously, if I was worth a few hundred billion and wanted to demonstrate serious commitment to building up off-Earth infrastructure, *then*.