A couple months ago, I had a friend run an interesting idea past me for a way of soft-landing serious sized payloads on the moon using existing launchers, even before full-fledged depots are operational. After looking at the idea, I realized it also had the potential for even allowing manned lunar missions. While I think that full-fledged depots offer you much greater possibilities, I figured these ideas were worth a quick airing on the blog.
For sake of splitting things up, I’ll discuss the unmanned concept my friend came up with int this post, and my next post will take the idea from there to manned applications.
Pre-Depot Dual Launch Unmanned Concept
My friend’s pre-depot lunar architecture concept would use two of the larger EELVs–either Atlas V 55x’s or a Delta-IV Heavies or a mix of both. The first launch would put a single-use LOX-tank and the second launch would lift a partially-fueled Lunar Lander Centaur and the payload.
The single-use LOX tank would be based on the Centaur stage’s LOX tank, and would include a sunshield, and a docking port. It would likely use the upper stage to spin up the LOX tank (similar to Frank Zegler’s LOX-only depot concept he discussed on the propellant depot panel we had at Space Access ’08). By prechilling the LOX before launch, and using a sunshield, the LOX tank could actually afford to wait for over a month without self-pressurizing to the point where it would need to vent.
The Lunar Lander Centaur would be similar to the LM/ULA horizontal landers we’ve discussed on the blog, but with slightly stretched tanks, and only a partial LOX load. The Lunar Lander and payload would dock with the prepositioned LOX tank, transfer propellants, and then head out. The Centaur would perform TLI, LOI, and the descent, with the lander kit providing the actual soft-landing. The end result was that with two stock Atlas V 552’s, you could place the Lunar Lander Centaur and about 8000lb of payload onto the lunar surface.
Alternately, if you left off the the lunar mission kit and just used the stretched Centaur as a interplanetary departure stage, you could loft pretty impressively big missions. For instance, you could launch payloads to Venus or Mars that would be 4-4.5x bigger at injection than Mars Science Laboratory of the Magellan Probe. And for high velocity missions like New Horizons, you could still inject 2.7x the payload. Here’s a chart my friend provided of payload mass versus C3 for two different concepts (one using two stock Atlas V 552’s, one using two Delta-IV Heavies with the new RS68A upgrade that should be in service by 2011):
Now, admittedly this is overlooking the docking part of the propellant transfer problem, so you’d end up spending at least some extra mass handling that, but that would still leave some fairly impressive capabilities. Tomorrow I hope to show how you might be able to extend this idea to performing realistic, near-term manned lunar missions.
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