Dallas Bienhoff:
Architecture has propellant depots, “depot tugs” between LEO and EML1, and landers from EML1 and the moon. Breaking up propulsion steps makes system more efficient. Can be launched and supported in 25-ton chunks (no HLV needed). Can also get tonnage back to LEO via aerocapture, to allow delivery of lunar water there.
Consists of personnel modules (zero-gee and g-oriented), propellant carrier, two modular depots, reusable transfer vehicles, aerobraked reusable vehicle, lander, all Lox/hydrogen.
Top ten techs:
10. Variable mixture ratio lox/hydrogen engine.
9. Low-g and zero-g oxygen/hydrogen liquefaction
8. Low-g water electrolysis
7. Deep-space autonomous rendezvous and docking (AR&D)
6. Aerocapture (need to fly aerocapture experiment from eighties that never flew)
5. Long-life reusable lox/hydrogen engine
4. Aero-assisted entry, descent and landing
3. Long-term zero-g cryo storage
2. Zero-g cryo transfer
1. Zero-g cryo fluid management (storage). Can be done with cryo coolers.
NASA flight technology demos (FTDs) support some but not all, but schedule far too long. Really important stuff out in 2025 time frame.
10, 9, 8, 7 and 5 (half of them) not covered by FTDs.
Needed now, cryo management, storage, transfer.
Next, AEDL, then aerocapture.
First three technologies enable depots, AEDL enhances ETO propellant tankers, long-life engines help cost, deep-space enables depot assembly and lander/stage mating.
Overall, enable reusability, enhance efficiency, promote reduced propellant delivery cost to LEO.
[Update a while later]
Dallas went too fast for me to capture everything, but in answer to a comment here, the reason for variable mixture ratio is that due to other uses (e.g. oxygen for life support), differential boil-off rates in storage, etc., you can’t count on any particular mixture ratio. Electrolysis gives you stoichiometric output, but while that’s the most efficient ratio in terms of energy production, it doesn’t maximize specific impulse (6:1 is the best for that). But the point is that you don’t want to waste any propellant when it cost so much, so you don’t care about Isp per se, as long as the engine can turn whatever ratio into useful thrust. The trades for this problem are very different than the ones for launch systems, when propellant, in whatever ratio desired, is a trivial part of the launch cost.
Why would you want a variable ratio lox/H2 engine? Anything but the stochiometric ratio is a waste…… or is it?
Better density. NASA did a lot of research on it in the eighties and nineties. I stumbled across this the other day on NTRS.
Actually, stoichiometric doesn’t give you the highest Isp. The low molecular weight of hydrogen favours a fuel rich mixture.
A serious contender for this list, I think, is LOX/metal hybrid motors. What makes them special is that they’re possible with ISRU techniques anywhere on the Moon and asteroids (where oxides are present). It takes considerable energy as well to break down oxides.
The list underemphasises ISRU technologies IMO. All long term and probably merely nice to have, but so are the other technologies that do make the list. And the biggest missing piece is of course cheap lift, though the other technologies will favour its emergence. Strictly speaking it’s a capability, not a technology, so maybe it doesn’t belong on the list.
MPM. I agree that ISRU is underemphasized, but I have to look dubiously at some of the stuff that did make it. 8 appears to already be done (I suspect we already have electrolysis setups that will work in low gravity). 10 don’t seem that useful. And cryo propellant handling and storage has been divided up into 3 items on the list.
In comparison, LOX/metal hybrids just need modest industrial capability on the Moon for support. It’s likely that LOX from regolith (or even just pressurized oxygen gas) will be an early ISRU product for any settlement that’s not at the poles. And under those circumstances, refined metals are fairly easy to produce as well.
Finally, I think the obstacle to cheap access to space is more economic than technological. For example, I think all launch systems currently in use could drop considerably in price per launch from higher launch frequency. Hence, I agree that the idea shouldn’t be on the list.
10 don’t seem that useful. And cryo propellant handling and storage has been divided up into 3 items on the list.
The list displays the customary emphasis on LOX/LH2 technologies, which is not surprising for Boeing (or LM or ULA). We might quibble about the priorities, but the technologies do seem very useful in the long run.
In comparison, LOX/metal hybrids just need modest industrial capability on the Moon for support.
They also need a lot of power, but Dennis Wingo has persuasively argued that that is a good idea anyway, which could benefit from surface nuclear power, but would work with solar power too. And LOX/metal hybrids need more R&D too. Using lunar ice might be a lot easier.
There needs to be a trade study between hydrocarbons and hydrogen. Sure H2 gives more isp, but its deep cyrogen and low density makes it problematic. If the cost to LEO fell enough, would we move away from LH2?
There is a large amount of “free” oxygen available from regolith with roasting. 20:1 LOX/LH2 seems likely, especially for just getting off the moon, which favors a lower ISP.
I might also put cheap stations/hangers (inflatables perhaps) on the list. Railways need stations where stuff can be done.
If the cost to LEO fell enough, would we move away from LH2?
Of course. If we wanted we could even start without LH2. All (literally all) the technologies on that list are optional. None of them is needed to establish a reusable cislunar transport infrastructure. With cheap lift none of them is even necessary for affordable exploration. Cheap lift is all we need, the rest is gravy.
How far along are we on any type of beamed power launch?
http://www.cartanova.ca/green-community-blog/item/65-laser-motive-space-power-mosquitos-and-more
The architecture described sounds very much like the architecture (the now defunct) t/Space proposed back in September 2004; with multiple cryogenic propellant depots and LEO aerocapture.
http://www.nasa.gov/pdf/65852main_tSpace.pdf
That t/Space architecture may be making a reappearance if CCDev is adequately funded.
If that architecture makes a reappearance, EML-1 becomes a very valuable location. A private sector entity that built a transfer station there could become quite profitable.
I object to the assumption that fuel has to be launched from Earth to the refueling points. Whilst this may be the only solution in the short term, long term wise the fuel should be lunar (and eventually from sources even further afield). The requirement to start mining operations on the moon would mean a huge investment, but once in place the advantages of transportation from the moon vastly outweigh the alternatives (the only other alternative that might be able to compete would be a space elevator, but that is still quite a long way off).