[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?