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ULA-Lockheed-Bigelow Lunar Depot by brickmack ULA-Lockheed-Bigelow Lunar Depot by brickmack
If you missed it, ULA and Bigelow <a wytiwyg="1" href="www.reddit.com/r/ula/comments/…>recently-ish announced an agreement to place a B330 in low lunar orbit, which Bigelow has termed a "Lunar Depot". Thing is though, a B330 by itself isn't actually very useful for that, since its only got 2 docking ports and no propellant storage. Some had speculated elsewhere (and I cautiously agree) that this could be not only a launch agreement, but a joint project in which Bigelow would provide crew volume and ULA would provide transportation and propellant storage, and in return use it as a staging point for the own cislunar operations. I think this interpretation is somewhat backed up by Tory's statements on having "been working with Bigelow on this for a couple of years" and actively trying to create a cislunar economy with this.

So I got to thinking about what a ULA-built propellant depot might look like. We've seen concepts of this from ULA before, they usually look something like this, a single ACES/Centaur/DCSS with a sunshade and possibly an expansion tank. The problem here though is, this is really small (1, maybe 1.5 at the most optimistic, ACES loads. Not very good for flexibly supporting a very high flightrate), and not very scalable. And these concepts seemed to rely on rotational settling for fluid management, which will be... uncomfortable... with a crew. Plus ACES itself is not a totally zero-boiloff stage, and further, the relatively small solar arrays possible in this configuration are inadequate for powering a complete station (not only its own needs, but life support and experiment payloads in the various pressurized modules, and keep-alive power for docked vehicles).

So where have we seen a zero-boiloff hydrolox propellant depot concept before that can carry several full ACES loads, doesn't rotate, has large solar arrays, and ideally is designed to be manrated? Lockheed Martin has exactly that, in their Mars Base Camp concept, and conveniently they're one of ULAs parents. Hence, the above render.

Including 1 ACES (which I decided to leave attached, to provide additional storage capacity as well as propulsion, since the depot may need to move around a bit and LLO is unstable anyway), the resulting depot would have some 190 tons of propellant capacity. Thats almost 3 full ACES tanks, plenty of operational flexibility right there. Interestingly, this could also be useful for pre-ISRU XEUS missions. Assuming a dry mass for ACES of 6090 kg (calculated from ULAs mass ratio and propellant mass targets), and 4200 kg for tank mass, and 1600 for solar array mass (both given from MBC whitepapers, the latter confirmed from a MegaFlex presentation), and 460 second ISP, ACES can place itself with this depot module in LLO with almost 70 tons of propellant remaining in the tanks. Given that a round-trip XEUS needs about 2.5 km/s delta v to land on the moon and 2.2 to return to LLO, and the bare XEUS with no ascent stage is 7 tons (per a recent ULA presentation), XEUS will need approximately 5.2 tons of propellant to return to LLO empty, and 13.95 tons to land while carrying 10 tons of payload down plus that 5.2 tons return payload (for reference, the entire Apollo LM ascent stage was ~4.7 tons), 20 tons total with a bit of margin. 3 landings each carrying 10 tons, plus maybe 1 lighter one (or heavier, if the infrastructure is finished for ISRU with that mission) is probably enough for a minimal lunar propellant station I'd guess.

Fuck thats longer than I intended... Thoughts?
:iconmavraster:
Mavraster Featured By Owner Dec 23, 2017
Lovely work!

Although I don't think that the tanks would be that... brassy?

Anyway, I truly do love the work; I wish that we'll have something like that before I'm dead.  I'd love to see people on the Moon again.
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:iconbrickmack:
brickmack Featured By Owner Dec 23, 2017  Hobbyist Digital Artist
I guess it is a bit darker than it should be. The best official MBC renders have slightly lighter  colored tanks www.flickr.com/photos/lockheed…, though it varies with angle and lighting. ACES will have a different material on its exterior (some sort of foil MLI strengthened enough to survive wind on ascent without a fairing), but it'll be some sort of gold colored foil so I used the same stuff (ULA still hasn't released any photorealistic renders of Vulcan-ACES yet though)
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