My understanding is that the "lunar gateway" is a politically expedient chance to get an ISS replacement on the budget ledgers. It has good technical reason to exist just as an ISS replacement (which must deorbit a lot sooner than we'd all like; some of its warranties are "coming due" as they say).
> And stopping there on the way to another planet would be hugely wasteful.
My understanding is that the scientific missions are less what they'd "stop there on the way" and more what they could eventually consider to "start there". At least some of the "lunar gateway" plans I heard had some complex "fabricator" goals, to assemble and build bigger modules in a "cheaper" in orbit than if they built it on the ground and shipped it all at once straight to the moon. I don't know how many of such plans remain on the books and I don't know enough of the science behind some of the proposals to know how viable they are (I do know that the growing body of inflatable modules research on ISS was pretty neat and supposedly related).
There is literally nothing that could done in high moon orbit that would not be overwhelmingly better done in low earth orbit.
The only reason to even consider using the high moon orbit is to have something, anything for SLS to do. Every conceivable mission scenario is better staged from low earth orbit, but they wouldn't need SLS for that.
And the whole point of SLS is so they can hand out $2B in plums to mil contractors for every mission, that they couldn't for a measly LEO launch.
I'm very willing to believe SLS itself is mostly a political boondog, but I'm also still willing to give Nasa the benefit of the doubt that they're trying their best to get useful science/engineering out of projects like the Lunar Gateway. My understanding is that the lunar orbit they want would give a lot of interesting science opportunities and technical opportunities (simpler communications versus the "tin can on a string that blacks out for worryingly large periods of time" of Apollo communications).
If anything the Lunar Gateway sounds to me a lot like "classic" Nasa risk aversion and over-preparedness. It isn't strictly necessary, probably, but it sounds like it makes lunar projects overall safer (in communications access at the very least, but also reusing ascent stages, and providing more backup habitat space in cases of disaster readiness) and that's still good science to prepare for risk. (They don't want a second Apollo 13, and who can blame them for that?)
> The only reason to even consider using the high moon orbit is to have something, anything for SLS to do.
It seems like that is already disproven. The first few missions to setup Lunar Gateway modules have already been scheduled on SpaceX Falcon Heavy launches (in 2024) so clearly even Nasa understands they may have to rely on SpaceX even for access to Lunar Gateway orbits because the SLS has already missed deadlines. The "traditional" flipside to political boondoggle politics is "standard" commercial bids and contracts, and Nasa is far too pragmatic to rest important pieces of a scientific mission waiting for the SLS as the "only option".
They solved the comms problem on Mars with relay satellites. Would those be harder to use, around the moon? "Habitat space" is useless unless you can get there, and if you can get there, you can get back to Earth.
To disprove it, you would need to find something useful for SLS to do.
NASA, of course, has no say in whether to use SLS. Congress decides that. The best NASA can do is have it not ready to fly. The longer it takes to fly, the fewer flights they will end up forced to do.
> And stopping there on the way to another planet would be hugely wasteful.
My understanding is that the scientific missions are less what they'd "stop there on the way" and more what they could eventually consider to "start there". At least some of the "lunar gateway" plans I heard had some complex "fabricator" goals, to assemble and build bigger modules in a "cheaper" in orbit than if they built it on the ground and shipped it all at once straight to the moon. I don't know how many of such plans remain on the books and I don't know enough of the science behind some of the proposals to know how viable they are (I do know that the growing body of inflatable modules research on ISS was pretty neat and supposedly related).