Bob Zubrin has a different idea.
Elon chose methane because he was thinking Mars, but absent finding significant deposits of lunar carbon, LOX/Hydrogen is probably a better propellant for lunar ops.
9 thoughts on “Starship On The Moon”
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Why?
It is still cheaper than SLS.
He has some interesting ideas on alternate uses for Starship and the work that needs be done prior to using Starship.
Surely the problem with LOX/LH2 is that you’d need to build an entirely new engine and vehicle? Which would cost a lot more than a few extra tanker flights per lunar trip.
Eventually those costs would add up enough that it would make sense to think about building something new, but right now it seems to make more sense to use what you’ve got (or will hopefully soon have).
I’d like to point out that a Starship could do a round trip to the Moon in about 11 days whereas the Earth-Mars launch winduw opens up only every 26 month. So, the same Starship could make about 71 round trips to the Moon for every launch to Mars. SpaceX could sell at least 71 X more tickets to the Moon than Mars for each Starship. It stokes me that Starship is likely going to primarily be a Moonship in the early years and that it will grow a population on the Moon much faster than on Mars.
The point that the Starship is awful big is well taken. It would be sort of like using a 747 to explore Africa. It’s not like the only possible plan is the first thing off the top of Elon’s mind.
The Gateway is little more than an orbiting tank, It wouldn’t hurt to have engines and the ability to bring it back to the shop if you needed to.
I’m sure NASA could come up with something that won’t take more than 20 years and a trillion dollars.
Handling hundreds of tons of propellant in zero g will take a lot of work. It still is something we need to do to succeed in space.
Almost 80% of starship propellant is LOX, which can be made on the moon. Once we got LOX production going, there is plenty of time to build a LOX/LH2 variant of starship. But for now, keeping a common propulsion system for LEO, GEO, Moon and Mars is better than optimizing for every use case.
Bob Zubrin does some brilliant work, but NASA beat that expedable idea into his head. Elon didn’t drink that kool-aid. He plans on building about 1000 starships. I’m sure he will part with 20 of them for a small fee so NASA can say they accomplished something.
Zubrin always had some better or different idea based on some reconfiguration of whatever technology was available (or that he thought could be made available) at a given time. This used to be my stock in trade too (though more often disguised as science fiction), as with my 1989 Ad Astra article “Harvesting the Near-Earthers” (basically, what could you do with Soviet technology demonstrated in 1988) right on up to “Off the Shelf and On to Mars” ina 2004 issue of “Spaceflight.” I even did one featuring SpaceX, a short story called “The Rocket into Planetary Space” in a 2007 issue of Asimov’s.
It’s all OldSpace thinking now, and time to give it up. Musk is building us an interplanetary “tramp steamer” (like the one in “King Kong,’ for example). It won’t be the biggest or best interplanetary rocket ship, but it’ll be the first, and trying to think of ways it could support OldSpace technologies from the sidelines is ridiculous. It’s the spaceship we will have, barring catastrophe, and any attempt to dilute it with “different ideas,” especially different ideas that are not actually better ideas, can only delay the coming new era.
Remember what I said in an earlier thread about this stuff. SuperHeavy with an expendable Starkicker upper stage can deliver a complete Orion/Blue Moon-based lander fully fuelled to low-lunar orbit for around one percent of the cost of deliver same to NRHO via SLS.
I ran some Starship numbers last year and found that Falcon 9 could put more more payload to GTO than Starship, which sounds odd but is due to the staging point and dry mass. The problem isn’t that Starship is too heavy, it’s that it burns the vast majority of its fuel to get into LEO because it stages early, because Superheavy is undersized. If they used three Superheavies (ala Falcon 9 Heavy), Starship would arrive in orbit with almost full tanks. For some mission architectures, this greatly reduces the total number of Superheavy stages that are required to fulfill deep-space mission requirements.
Perhaps the real lesson in the exercise is that we shouldn’t base mission plans on what Elon is building now, but on what he’ll be building a year from now to better meet a new requirement.
We’ve talked about this before and I’m still certain you’re wrong. Here’s why:
Falcon 9 to Starship is an inapt comparison. Falcon 9 has an expendable upper stage, which you’re comparing to Starship, with a reusable upper stage. If Falcon had a reusable upper stage it’d would have essentially zero payload to GTO. By the same token, if you replace Starship with an expendable upper stage for SuperHeavy (which Musk has called Starkicker) you get a minimum of 220 metric tons to LEO, which translates to around 70 metric tons to GTO, many multiples of what Falcon 9 can do.
Secondarily, the SuperHeavy-Heavy you describe would either have to expend its center core, or provide it with considerable thermal protection to survive a hot reentry, or, more likely, reserve a lot of fuel for hypersonic retrothrust. The second two options will const considerable payload. The odds are high that in-space refueling will be cheaper and more flexible than any of those choices. (Musk seems to think so anyway.)
Your final paragraph is closer to the mark, though I think the follow-on to the 9 meter Starship is more likely 10 years away. Musk has said repeatedly that once Starship is proved out, he intends to go to 18 meters. We’ll see (and I hope I’m still alive then).
I think by the second half of this century, we’ll see NautilusX-style interplanetary liners (only much larger) using Starship-like vehicles as tenders. And, no, I don’t think they’ll be “cyclers,” whose economics is dubious.