[lazide]

Sure, and I have a bridge to sell you.

The technology already exists. Fundamentally (damn laws of thermodynamics) it is also a energy negative process, and hence expensive. It is far cheaper to just frack and burn fossil fuels (where that energy expense was paid however many millions of years ago by someone else), than it is to expend the energy to reverse the process - even if they were getting nearly free energy.

[inglor_cz]

They will rely on the Sabatier process to produce fuel on other celestial bodies. And the corresponding technology must be tested first - why not in Boca Chica?

I don't think that anyone is trying to make the claim that SpaceX will use the Sabatier process to fuel Starships here on Earth right now routinely. As you say, gas is cheaper to buy here on Earth. But they still must have the technology mastered before they fly away from the low Earth orbit.

[lazide]

The process IS already mastered, depending on the bar you set?

This isn’t something unknown or theoretical.

[inglor_cz]

Yes, but you still need to design, assemble and test the particular equipment you want to use, unless you can do with off-the-shelf components.

And contemporary off-the-shelf components that perform the Sabatier process aren't probably meant to operate outside the Earth.

[SiempreViernes]

But this is merely testing, not any sort of large scale use of this equipment because, as you point out, they are not made to work on Earth.

[Fnords]

"you still need to design, assemble and test"

Not if NASA did that decades ago.

[gpm]

I certainly hope that there are technological improvements that we can take advantage of that have occurred in the past decades (in manufacturing, modeling of pressure vessels and chemical processes, etc).

Mass to mars is incredibly expensive, it's worth spending the time and money to optimize whatever equipment you are sending there.

[politician]

Under STP and 1G, yes. Mars isn't at STP or 1G, so they can't assume that the Earth-standard machinery will work without modifications. This is a reasonable thing to experiment with.

[lazide]

Which I was referencing with ‘depending on the bar’, though it’s a well understood enough process that those variables are generally well understood.

Yet they aren’t, correct?

[DennisP]

Of course it's energy-negative, nobody is claiming otherwise. Powering that from renewables will cost more. But the cost of fuel is a very small percentage of launch cost, and if they're doing a lot of launches then being able to say they're carbon-neutral would be pretty helpful for public acceptance. Politics and regulation are much more dangerous to them than a little extra cost in fuel.

[Denvercoder9]

SpaceX wants to make a roundtrip to Mars, though. There's no fossil fuels on Mars.

[elif]

Yup and musk also argues in favor of a carbon tax. He is openly hopeful that the fundamental economics will be changed to make producing their own methane via Sabatier economical.

It is up to the controllers of incentive structures to change the fundamentals of commerce/ecology.

[lazide]

Pretty sure that would require something like a 5x cost increase in carbon, though I can’t find hard numbers anywhere easily. Do you have any pointers?

[elif]

If musk followed strict economics as implied by your premise, he would be launching disposable rockets with Boeing.

who knows what expense space X would be willing to shoulder to be sustainable... We are fortunate that it is still privately owned, and isn't legally obligated to pursue the financial interests of shareholders like all the other players in aerospace.

[lazide]

Pretty sure what Musk has been doing is a reasonably common business case - generating demand with some impressive salesmanship to increase volume and disrupt a schlerotic market ripe for disruption by driving down unit costs - and eventually competitors out of business. With decreases in unit costs, it unlocks more uses, which is a positive cycle.

It’s not an unusual playbook at all, but it is unusual that it is done in the satellite launch space. Kudos to him for that.

All the other players are military industrial complex, and the reason they act the way they do is more about market capture than anything else - shareholders are of course a concern, but not a huge one.

It also doesn’t change thermodynamics or any of the energy gathering, chemical precursor gathering, infrastructure, or raw input gathering problems.

Mars gets very little insolation. Mars has no infrastructure. Mars has no breathable air. Mars has no known life or biological sources we could survive on. Mars is very cold. Mars has no raw materials (or useful environments we know of to process anything) that would justify the energy required to export it.

It’s literally more hospitable and more useful to be on the North Pole, and I don’t see anyone in a rush to build housing developments there.

[gpm]

> Pretty sure that would require something like a 5x cost increase in carbon

5x over what? The US doesn't have a carbon tax does it?

[lazide]

5x over the current baseline cost of fuel. The only studies I could find of doing this were using large scale bulk solar and not counting financing costs into the equation.

They found that if avoiding fossil fuel use (natural gas is the cheapest easily available Hydrogen source right now), and cracking water to get it, end to end energy efficiency is between 44-56% (as in electrical efficiency to theoretical available chemical energy in the fuel). Burning said fuel for energy (turbines being one of the most efficient ways) then varies from 40-63% efficiency, rockets can hit up to 70% efficiency (varies immensely by many factors).

So, getting what they need from a fossil fuel is up to 70% efficient. Getting what they need from a Sebatier process? 28-41% efficient (combined). Add in extra capital costs and maintenance of acquiring and running the equipment, about 5x more expensive fossil fuel evens out.

It’s potentially worse than that of course when you factor in potential increases in electrical rates if fossil fuels did get 5x, but there is nothing saying that would for sure happen. They presumably could run it during oversupply from a large solar plant, but that is already factored into those studies. If you’re doing it at scale, that ‘free energy’ won’t be free for long.

[lazide]

And if it doesn’t make any economic sense to do it here, where it is super convenient, shipping it to Mars (with nothing of known value there to return or any known economic model that could make it worthwhile) to do it there is going to be worth it?

Not saying all human endeavor needs to have a healthy profit margin. SpaceX is a business however and besides doing it for the lulz, or getting a government contract, it doesn’t make much sense to try to spin up colonies or the like there. Everyone will starve and/or their US backers will go bankrupt pretty quick.

[MPSimmons]

> SpaceX is a business however

SpaceX has been described as a company with a Mars cult inside of it.

I think it's more fair to say that it's a Mars cult that has organized a company.

If you think that SpaceX won't do hydrocarbon generation on Mars, then you don't understand why SpaceX exists.

[DennisP]

If you want to go to Mars, it's way cheaper to get your return fuel from Mars instead of carrying it all the way to Mars from Earth. If you want to get your return fuel from Mars, then you have to make it, there aren't any convenient natural gas deposits that we know of.

This isn't an original SpaceX idea. Robert Zubrin pointed it out back in 1990 with his Mars Direct plan.

https://en.wikipedia.org/wiki/Mars_Direct

[lazide]

For sure - my point is, that presumes there is enough volume or an economic need to make that sort of infrastructure investment worthwhile (not even dollars, but energetically). Getting the direct equipment let alone supporting equipment there is going to be very, very expensive in energy. For one trip back, or even 5, it’s unlikely to pay off unless there is some cool super miniaturization tech and we’re not in a hurry - and that assumes everything keeps working over multiple missions.

And if we have all that, getting a mobile lab there and sending back bits instead of physical chunks of things is even easier.

You’d also need to get chemical feedstocks and process them (namely to extract the hydrogen, which is not readily available in the Martian atmosphere but is in the soil in various amounts in minerals and small amounts of dispersed water and methane ice) which would be non-trivial and a huge hassle to get even on Earth where you can go outside and smack the machinery with a shovel or stick your arm in somewhere to unclog something.

The existing Mars rovers struggle sometimes with dust on solar panels, let alone a broken bolt in a crusher due to harder than expected rocks or the like.

Having done some basic mining and a lot of earth moving over the years, it’s an incredible pain in the ass.

It’s also rare you don’t periodically need a human getting hands on, and using every bit of dexterity and strength they have to fix something. Robotic tech is nowhere near good enough to do this remotely.

So at a small, very very very slow scale? Maybe?

There are a lot of cool thought problems from all this, and some cool potential solutions. My fav is Project Orion [https://en.m.wikipedia.org/wiki/Project_Orion_(nuclear_propu...]

And we’ll just have to see what happens.

[politician]

So you're just a typical No-Mars skeptic, got it.