In "Human orbital spaceflight: the ultralight approach,", Richard Speck looks at a cheap, light, low tech escape system and fleshes out the new rocket adage, "Be the escape system".

In "The challenges of Mars Exploration," Donald Rapp assesses the not-too-bright prospects of various technologies on the necessary timelines for Mars exploration.

There's one I disagree with him on: in-situ lunar oxygen. In-situ oxygen extraction on the Moon need not be a major industrial process. The basic needs are a heat source and vapor recovery. Suppose you have an Earth imported high efficiency pump. Add a lunar glass bell jar and an Earth imported parabolic mirror (later, lunar made). If you make the bell jar big enough, the mirror can sit inside the bell jar. Set the whole thing on a flat piece of lunar glass to make a low efficiency seal.

Operation would be as follows:

1. Dump some ore on a flat piece of lunar glass.
2. Point your parabolic mirror at the ore.
3. Put the bell jar on top.
4. Turn on the pump.
5. Dump it out before the slag sticks to the glass bottom.
6. Repeat.

Some kind of airlock conveyor belt thing where the top layer of the ore is fried might be a more advanced version. It's ore efficiency would be quite low, but there's plenty of ore up there.

Sam, I believe that harvesting lunar LOX via passive solar should be the favored method that needs to be ruled out, because it minimizes the capital investment needed, regradless of technical elegance. That said, the deposition of various outgasses producted on you bell jar will cloud the optics, perhaps quickly. A commenter right here at this site pointed out that issue to me.

One possible solution is to use a solar forge with a large handful of Menards grade mylar mirrors (mounted on parabolic inflatables) pointed at a fresnel lens that is aimed at the sample to be reduced. Just inside the glass seal add gas injectors to slowly inject an inert gas and at the far end install suction to evacuate the outgassed materials.

Create positive air flow away from your solar forge to prevent the deposition of the inevitable crud on the lens. Wouldn't have to be much.

= = =

But it appears you are looking at up-front capital cost - not engineering elegance - being the driving metric for lunar LOX production.

I agree 100%

The deposition problem ought to be something testable on Earth.

I think we should get a big drill rig and drill for gas. If you go down a few thousand feet, there are rocks under hundreds of tons of pressure. "Rock bursts" like those experienced in deep terrestrial mines would be our friend. We might be able to drill for oxygen like the heyday of oil drilling on Earth.

I believe I was the one who pointed out the deposition problem. The solution that occured to me was to interpose an opaque absorber between the optics and the material to be heated. This absorber would transmit heat to the regolith by some combination of conduction and radiation. This absorber needs to be refractory and resistant to both the hot regolith and the evolved gases.

It might end up being easier to use photovoltaics and an electron beam furnace.

There is a paper by Larry Taylor of the University of Tennessee about how efficiently (VERY) microwaves couple to REAL regolith (not stupid JSC-1). It takes only about 100 watts of power and a few minutes to heat regolith to over 1200 c!.

Larry recommended carbon fibers and carbothermal reduction to get oxygen.

Looks very interesting.

It is in the ASCE papers for this year's conference.

Dennis

A slide show from Larry Taylor.