Their current plan is for a quick stunt to the moon, Apollo 8 style, once J-120 is operational, around 2013. Assuming they get their way of course. They’d use a Delta IV Heavy Upper Stage as an EDS. It’s a bit like the architecture you discussed a while back, just with a DIVHUS instead of a Centaur, the advantage being that it’s bigger.

The DIVHUS gets tantalisingly close to placing an Orion into a circular LLO, so close that I wondered if you could close the gap by using direct ascent. Another trick the DIRECT team is studying is putting the Orion into a highly elliptical orbit to same some fuel. Either way it would be very cool.

I was really excited about this, because it promised good results soon without spending outrageous amounts of money and while using some off the shelf hardware.

A little calculation showed something I found even more exciting: a J-120 + DIVHUS plus Orion comfortably gets an Orion to L1. It also gets the standalone space station ESA is planning on building to L1. This means that within 4 to 5 years we could have a functioning L1 gateway up there!

Of course the next thing the DIRECT guys want to do is to build a big upper stage to they could get an Altair up there too. Since, probably like most of you, I’m more interested in economic development of LEO (and then beyond) first, and only then in going to the moon, I wasn’t so enthusiastic about that.

But the Altair is quite heavy, so a single DIVHUS wasn’t going to be enough. At first this seemed like a serious spanner in the works. But then it hit me: what if you made the Altair use hypergolic fuels, just like the Apollo LEM did? Then you could send cargo, propellant and lander to L1 on separate DIVHUS’s. No need to develop an expensive upper stage! No excuse for postponing depots and tugs!

Of course a hypergolic lander would be less efficient, but it would allow commercial participation early on. It should be relatively cheap to convert the Orion SM into a tug that can pick up small or large dumb payloads launched on commercial launchers. Building a hypergolic depot should be much easier than a cryo depot. You could get the bugs out of the proximity operations very early on. You could reuse that knowledge (and the commercial launch infrastructure!) once you got cryo depots up and running.

Then Chuck Longton came up with a brilliant suggestion: with refueling, you can afford to make your lander bigger. And that means you can land your future moon base in bigger chunks without having to build a monster rocket like Ares V. And I understand that even with Ares V there having mass problems. All of this goes away with L1 refueling. And hypergolic fuel transfer on orbit is a proven technology!

Hypergolics have further advantages as well. Since they are storable, you could use Belbruno trajectories to offset some of the inefficiencies due to lower Isp. Once you develop SEP, either from LEO to L1 or from L1 to LLO, you can reduce inefficiency a bit further. Also, hypergolics are denser than H2 so you save may some tanking mass. They also allow you to build a more squat lander that doesn’t tip over so easily, another problem Constellation is having to deal with.

So all in all, a lot of advantages. Key point: J-120 + Orion + ESA L1 gateway + hypergolics may be the quickest way to the sort of commercial infrastructure operations we’d all like to see. This stuff could happen really, really soon.

A light scout outpost masses eight mt and can support two men for 14 days (the early lunar access habitat was estimated at 8.5 plus 1 mt of solar arrays and consumables delivered on an earlier flight. If use of an inflatable structure cut structure mass in half, eight mt would be plausible.

A four man fixed base as per First Lunar Outpost would be 36 mt not including pressurized rovers, and capable of supporting eight month rotations. A mobile base of the same capacity, as per Lunox of Morphlab, would be 55 mt, and include two general purpose pressurized rovers, 5 mt each, and two power carts, 1.5 mt each. In three months the mobile base can move itself up to 1000 km through a combination of autonomous navigation and teleoperation.

An 8 mt logistics module can support 16 man/months of operations, i.e two men for eight months or four for four.

Now suppose that you have decided to devote half of the landings to building up and supporting a four man base, but you also must make a total of 12 manned visits within four years to widely separated locations on the lunar surface. The main base counts as one, so this can be accomplished by setting down 11 light scout outposts and visiting them. This takes 22 landings, leaving you two to land additional logistics and outpost equipment to expand one outpost to an 18 mt two man base and keep the crew there for six months. Total surface man months for this campaign, 17.

Or you could put down two two-man mobile bases (55 mt) plus two extra pressurized rovers and power carts so each mobile base has redundancy (13 mt) This takes nine landings. You land 11 crews to different locations, moving the bases between visits, and enough logistics to give each a 3 month stay. Total surface stay time, 66 man months, with greatly enhanced mobility at each location.

Alternatively, you could reflect that the moon isn’t going away any time soon, and that you can afford to be methodical. You set down a four man mobile base and make four four man visits to four locations, staying eight months each time. Total surface stay time, 128 man months.

The longest possible stays are vastly more cost effective. And if you expect to be preparing for Mars, you should really be working towards two year rotations if possible.

Note too that if your metric is risk per amount of the moon explored, the long stays get a lot more stay time out of each risky manned rocket voyage.

A discussion on the progression of exploration: robotic, sortie, base, would be interesting.

Anyhow, I think I need to write a few more blog posts, fleshing out this idea a bit further. I don’t think that the lunar depot concept I’m talking about here is mutually exclusive with the concept of building a fixed base first if that turns out to make the most sense. But I do think it gives you more flexibility so you’re not forced into a base-first solution if you’re not sure yet where your base should be.

~Jon

Do you have any evidence for this belief? Because I really don’t see much difference. If anything, burying a “mobile base” module that has to be able to move again later seems even harder than burying a light habitat module that you’re planning on leaving at the outpost site.

I guess I’m just not so much a fan of tying yourself to one location so early on. With the light-outpost approach, you have more flexibility to mix base and sortie expeditions, while with the existing architecture, you can only really do base missions. If your goal is to really explore the moon and really find out about where the valuable resources are, etc. tying yourself to one base so soon seems to be very suboptimal. And such a base-centric architecture does absolutely nothing for reducing most of the key risks of a lunar mission–the descent, ascent, and departure phases of the transportation.

~Jon

~Jon

~Jon

Providing shielding for a mobile base is more difficult than at a fixed one, but easier than doing it for a “light scout oupost”

At some point the lunar base may be “finished” and there are more trips to the base than one needs hardware, spares, etc. At this point it may make sense to start reusing hardware. The dual axis lander concept seems to be particularly suited to reuse. The RL10 is kept well off of the surface, out of danger of being damaged by debris kicked up during landing. At this point it may make the most sense to store the LO2 and LH2 in surface dewars. These dewars could be spent lander tanks with lots of added insulation to support very efficient lunar surface storage. Upon landing, exess propellant from the lander would be transfered into these surface dewars. When ready for ascent the ascent vehicle would be loaded with enough LO2 & LH2 for the ascent trip. Descent propellant would be supplied from the orbital depot.

As you point out alternative propellants are an option. I still favor LO2 and LH2 because the are very useful for the base as well. You can make potable water as well as store energy for the fuel cells. If one wants to store power during the lunar night you are going to need a lot of LO2 and LH2. Having a common comodity (LO2 & LH2) for all of these uses would simplify the infrastructure of the lunar base.