sevenperforce

With treads, probably yes.

A treaded octagrabber is actually a ridiculously good idea for this application.

If you have a pressurized (shirtsleeve-environment) rover to get from hab to hab, then you can make it work...at least for long enough until you eventually use a crane or whatever to put the habs closer together. You'd have dedicated installations...a multipurpose airlock, lab for science, a sleeping area, showers, a hab for food storage and prep, etc. Each manned landing adds a new component to the base.

Would need to get a landing pad in Tampa.

Possibly, but that does tend to make landing precision a bit hairy unless your flexible tube is really really long (which is its own issue anyway). Unless you have sintered landing pads across the board then you end up with touchdown debris potentially puncturing the tube. The disadvantage of a rover-based base (LOL) is that you are tied to the rovers to move around, and you are in a bad place if a rover dies, gets stuck, or the like. Can mitigate by having multiple pressurized rovers and by putting suitports in the rover (which you'd probably want anyway) with either a suitport entry or a standard airlock in the hab modules. NASA could order habitation modules from Bigelow or someone. The nice thing about having a permanent hab serving as the docking port connection to the ascent module is that you can "stretch out" into the hab during the flight to the lunar surface (though of course you'd close the hatch during descent in case you ran into a contingency abort situation). Your ascent capsule can be more of a taxi, which lowers the barrier for access. And there is no particular reason why anyone really needs the docking port on the ceiling; it's just sort of been standard over the years since most vehicles are earth-launched and have a single axial engine underneath.

As-depicted, the starboard aft fin would be inside the rightmost booster cap. But yeah, it's useless. Notional staging velocity for a single-stack Super Heavy is ~2 km/s. Going "Heavy Super Heavy" would put the center core at 3 km/s or more and so far downrange that it would need to reserve a prohibitive amount of fuel for boostback.

I see what you did there. (No pun, just funny.) Electric architecture is really very ideal for cislunar operation, since you need electrical storage anyway. I don't know if the batteries would be easy to rate for long-term exposure to space. NASA would still exist on hypergolics for ascent engines, obviously. Too bad kerosene is crappy for cislunar operations. SpaceX had notional plans for a Rutherford-class pressure-fed methane-oxygen thruster for Starship RCS, though Elon has since stated that they will use cold-gas only in initial flight articles. If they dusted this off and put a little R&D into electric pumps, it could make a hell of a good landing engine. If only Elon had connections to some kind of company that makes reliable electric motors and batteries.

I think I saw this proposed a while back in conjunction with a reusable heat shield (this is before Elon proposed it for Starship). Basically you would have lightweight stick-on tiles that could be placed edge to edge on any surface and assigned to bleed resources (fuel, ox, monoprop, even xenon or ore) as ablator. Such a part could also be used to dump resources.

This is possible, but unless the components get attached to each other, it's sort of pointless. Going outside uses expendables every single time, and it's a mess. Ideally a lunar base would have a large airlock, complete with showers in an lesser "airlock" to the hab so that they don't drag dust in (perhaps the airlock between the real airlock and the hab is a shower. Well, you don't need that at all if you have a pressurized rover. The more I think about the idea, the more I like it. Your reusable crew taxi has tanks above, engines on the sides, and a single docking port in the floor. Each mission carries a new surface hab which is left behind at the end of the mission. All hab modules have a docking port in the side for ingress/egress by pressurized rover. Move by rover to any previously-landed module, one of which would be your dedicated airlock.

If the crew/ascent vehicle is small, then it is basically a space taxi between LOP-G (or wherever) and the lunar surface, and you need existing infrastructure on the surface to support exploration and science activity. Suitable for a flags-and-footprints mission as a proof-of-concept and for regular exploration missions once the infrastructure is in place. I advanced a wet-workshop-airlock before, an idea I am definitely fond of...but an alternate approach is to have a descent stage which includes a ready-built airlock and permanent science/exploration/habitation modules already built in. So you're not expending the descent stage as much as you are using the descent stage for emplacement of base modules. Each new mission adds a new section of the base.

What kind of engines exist and are appropriate at this time? It makes no sense whatsoever to use an entire CPL logistics supply launch just to refuel the transfer element when you can simply re-launch a brand new transfer element.

Except for the station-keeping you need in LLO. Nothing can stay there very long. Doesn't matter how big you build the EUS if it can't burn beyond LEO. If a cryogenic upper stage can have persistence to cislunar space then you have something to work with.

They now have a proposed architecture: Three stage with two stages reused. Presumably subsequent missions would involve a new descent element launched commercially carrying fuel to refuel both the ascender and transfer vehicle...though that might require SLS. Wait, here are all three slides. https://cdn.geekwire.com/wp-content/uploads/2019/02/moonmissions.pdf Two commercial unmanned logistics-launch resupply missions to refuel the ascent and transfer vehicles; a third for a brand new descent module to deliver under its own power; an added SLS launch tho only to do another crew exchange. Wasteful.

Yeah, you could have a single central LH2 tank and carry nitrogen bottles for purging outside. Once purged, vent LOX from other tanks into the purged fuel tank to bring it up to breathable levels. Plenty of space underneath or along one side for a rover, etc.

Note that with the dual-engine configuration, the vehicle can also be used as a skycrane to lower cargo, supplies, or even an external hab to the lunar surface. The BE-3 (540 kN) might be overkill but a smaller engine like the Rutherford (26 kN) could be a solution, and an electric turbopump is perfect for cislunar activity.

Tracks provide better zero-turn capability, I bet.

Mocked up quickly in KSP: More images below. The reusable crew hab, with its tanks, would dock base-first to the Gateway using RCS. For each lunar sortie, a new descent-and-airlock module would be delivered under its own power to the gateway and dock port-to-port. The descent module would deliver the hab to the surface and then vent, and so forth.

Heyyyyyyyyyyyyyyy............ What about using a descent stage tank as the airlock?! Base building or no base building, you want an airlock if you're going to be able to spend any extended amount of time on the surface. But airlocks are basically just a big room. So have your reusable crew capsule establish a lower berth connection with a propellant tank. The tank would have a door cut into the side of it. Once on the surface, the tank is purged of its contents by valve and then you can lower a ladder into it. Open the door and walk out, and vice versa.

Can you take up multiple flatpacked/noodled items in a single launch as long as they are in separate chambers?

KSP obviously doesn't have near-rectilinear halo orbits. But if you want to simulate a lunar gateway in stock, you can do so by using the debug menu's "Set Orbit" function as follows: Semi-major axis to 12 million Eccentricity to 0.1 Inclination to 5 Vary your MNA (iteration necessary) so that you lead the Mun by as small an angle as possible without crossing its orbit. This orbit has the same period as the Mun, but the slight eccentricity and inclination means that the gateway will appear to orbit in a perpendicular corkscrew around the Mun's own orbital path, so it will always be nearby but never in exactly the same place. The dV required to get in and out, relative to Kerbin and the Mun, approximates the proportions between real-life and the Kerbin system.

Gateway makes sense if you are strapped to low-dV Orion+SLS, which makes sense if you are determined to continue the SLS pork project. Otherwise not. If your lunar aspirations are not constrained to the lunacy (see what I did there?) of Orion, then a frozen orbit at 86° will do just fine, as long as you don't mind periodic occultation. That's what relays are for. Lunar reuse is just messy. It takes an engine to deliver fuel...so unless you have a "fuel ferry" that carried props from LEO to your cislunar station, then returns, aerobrakes down to LEO, and is refueled...what's the point? You might as well just expend. But if we have the gateway... Prop transfer for pressure-fed hypergols with nitrogen press is a solved problem (ISS). I could envision a reusable hypergol-fueled manned lander carrying about 3 km/s when full, docked to the Gateway. Orion would arrive at the Gateway with crew and consumables, then a cryo space tug (based around ACES or a BE-3 architecture) would arrive from LEO carrying hypergols as payload. It would transfer hypergols to the lander and mate to it, then drop it off suborbitally on the moon as a crasher stage. The lander performs touchdown, ascent, and return to the Gateway under its own power. The same space tug design could be used to drop stuff off at the Gateway and deliver payloads to the lunar surface, perhaps with multiple planned uses (if boiloff management could be solved) per mission. The other immediate architecture would be a beefier lander with about 2 km/s in its internal tanks and another 2 km/s in drop tanks. The same sort of space tug would carry hypergols and replacement (full) drop tanks, attach them to the lander, and then tug the lander to an 86° frozen orbit. The lander would descend, drop its tanks, and land, then perform the ascent on internal tanks to rendezvous with the tug for the tow back to the Gateway. Of course then you end up with a derelict tug.

The challenge I see in cislunar reuse is the delivery mode. Sure, fine, you design a reusable architecture...but how do you deliver propellant? Presumably you're going to have to launch it from Earth with a docking-capable delivery vehicle with its own engines. What do you do with that vehicle? Expending one rocket to deliver fuel for another seems like a colossal waste of time. Unless your fuel delivery vehicle (and its engine) is planned for return to Earth for refurbishment and relaunch, then it just makes more sense to make your delivery vehicle an expendable tug and have it deliver fuel for a smaller reusable stage.

Nice to see you over here on the East Coast, buddy. It's still hard for me to wrap my head around the idea of using hot gas to pump itself. I can think through it, of course, but still.

With LOP-G in a NRHO rather than a frozen orbit, the dV cost between the station and the surface is 2.6 km/s. That's pretty high, too high for a single-stage reusable lander (which must bring 5.2 km/s by comparison) running on anything but cryos. I would love to see NASA put up money for some actual missionable architectures, like "Give us a space truck that will deliver X tonnes from LOP-G to the surface" and then let the market compete over reuse. If you want a manned lander then you can have the manned lander delivered as a payload to the surface by the space truck. I like the idea of an autonomous space truck that will deliver a significant payload to a low suborbital trajectory...like, to the point that you only need 300 m/s or so to safely land. Then the payload can perform its own landing rather than being tied into some specific touchdown configuration determined by the space truck. The space truck would drop the payload, move away, and then boost itself back to LOP-G to refuel. Could also work with a manned lander; the space truck would drop it off just short of landing, and then it would land on its own and return to LOP-G later as a single stage.

Reusable moon lander is a pretty simple problem, honestly -- simple enough that you can boil it down to 3 or 4 basic configurations. Anyone listen in?