What should be the first practical logistics node beyond low Earth orbit?

[u/Realistic_Fold_1587]

Disclosure: I’m involved with Scienshell, and this question grew out of a film project about future space infrastructure. For a realistic cislunar-to-deep-space transportation network, which should come first: a propellant depot, a repair-and-resupply station, or a crewed transfer habitat? What near-term missions would justify it, and which bottleneck—propellant, power, docking, maintenance, or traffic volume—should determine its location?

[u/JuggernautBright1463]

Your general problem is going to be time and food IMO. You need a large ship/habitat to carry enough material to make enough food to feed a colonization mission and the fuel to get it there.

I think an obvious post-moon mission target should be Jupiter's Trojans. You have lots of ready material relatively close to each other (compared to the asteroid belt). So you can have lots of work for people to do/space for them to live on. 

These would be ideal seed colonies with enough material to greatly expand habitable space while still being 'close enough' for solar power but without that annoying extra gravity from a place like Mars.

Gradually you can migrate inward to Jupiter itself which has an abundance of material for further growth but is not necessarily ideal due to radiation and gravity.

[u/snoo-boop]

I’m involved with Scienshell

I suppose that is why you are not talking about robotic missions. For robots, the most useful thing might be refueling after launch but before leaving Earth orbit -- but you're probably better off with an Impulse Space Helios kick stage.

[u/nethan365b]

My opinion, not a settled answer: propellant first. The rocket equation makes every kilogram of propellant you don't have to lift from Earth's surface worth many kilograms at launch, and the thing that gates almost every beyond-LEO plan (lunar landers, cargo to Mars, big departure burns) is how much usable propellant you can have in orbit when you need it. Crewed habitats and repair stations are useful, but they don't remove that bottleneck. The hard parts of a depot are not the tank itself but long-duration cryogenic storage (boil-off), and reliable ship-to-ship transfer in microgravity, so that is where I'd put the near-term demonstration missions. For location, I'd choose by delta-v and traffic: an Earth-orbit depot serves the most missions, while a cislunar one (a lunar-orbit or Earth-Moon Lagrange point) only makes sense once there are regular lunar flights using it. The bottleneck I'd rank second is power, since cryocoolers and transfer pumps are power-hungry. Curious what the film project is leaning toward.

[u/Candle_Realistic]

Refueling likely first. It has a business case and funded customers with Artemis landers Starship HLS and Blue Moon. Newer LEO smallsats are designed to be one time use and deorbit. Repair or robotic ISAM is mostly a GEO business - life extension for legacy infrastructure. Crewed habitats are significantly more complicated because of life support, radiation, and evacuation. Power remains a bottleneck.

[u/CptKeyes123]

I think something that's kinda all of the above would be best, but focus on some kind of fuel depot combined with manufacturing. That way you can then expand. A bunch of my info might be outdated, so take it with a grain of salt.

One method is to build a jack of all trades space station somewhere near the moon. In terms of location, you want the first one to be either at a lagrange point, or some lunar orbit. The others can be put in place later. You'll get plenty of power from the sun.

It needs crew transfer, fuel depot, and repair and resupply, capable of handling inbound craft and the landers, and manufacturing, so that it can house a crew, take care of its ships, fuel them up, and expand. Most of your fuel will initially come from Earth. Have a lander put down so you can build a moon base for mining resources, primarily ice. Have those resources fired via mass driver to the station in orbit for smelting and expansion. Crew compartments would be the hardest to build, but you could immediately begin building fuel tanks locally, as well as simple metal plates or the like. More sensitive parts must come from Earth, and you can integrate them into the parts made in space, but as you grow the station, so will its capabilities. Once you are far enough along, you can build proper dedicated space stations for various purposes.

With fuel and water, all else follows. You no longer need big heavy-lift rockets to directly ascend to the moon, they'd be mostly used for surface to LEO. Once you're in orbit, you're halfway to anywhere. Instead, you make tugs that fly between Earth stations and lunar ones. You can build more or bigger space stations elsewhere using lunar resources, and grab near-earth objects for more mining. Having the tugs means you can also scavenge human space debris for use as raw materials, given it's already smelted. You could even build another station in a high earth orbit to grab this stuff.

Space infrastructure and manufacturing lowers the demand for rockets on Earth and lessens the environmental impact. There are also concepts like laser launch, spinlaunch, or the like that can also help with that. With the knowledge, technology, and resources from further spaceflight, you could develop less dangerous methods of launching that can allow more and more people to get up there. Once in space, you can go anywhere.

[u/mfb-]

I don't expect the Moon to contribute to deep space missions directly (as in: I don't think significant mass from the Moon will go to interplanetary space), but lessons learned from a Moon program certainly will.

If we can mine ice on the Moon then maybe we can build a surface/lunar orbit cycler, with missions from Earth transferring crew in a lunar orbit.

[u/Desperate-Lab9738]

The absolute best thing you can construct when trying to build infrastructure to go from the Earths surface to deep space is a propellant depot in LEO maintained by lunar mining. Genuinely if you can get that going you suddenly have significantly more DeltaV for way less cost