Comments on: Random Thoughts: Lunar Excavation Technologies

By: publius

publius — Fri, 10 Jul 2009 04:58:42 +0000

Definitely an interesting concept, essentially a reduction to the differential scale of the shot drills long used in quarrying. I do have a concern, though, as to its effectiveness against the cohesion of the regolith.
My suspicion is that it will pay to separate the function of breaking up, in place, the soil to be excavated from that of moving it to another place. See : http://www.lunarcc.org/papers/0207.html

By: Randy Campbell

Randy Campbell — Wed, 01 Jul 2009 19:43:01 +0000

(Haven’t checked sources yet so this is a “drive-by”

Have panels that “deflect” the regolith upwards and use extra gas to get a vertical velocity of “x”…

Simple math now tells you that the regolith will reach peak altitude an then fall back into place in “x” amount of time…
You now have “x” amount of time to emplace your “habitat” to be buried…

We now return you to your regularly scheduled comments…
(Without Randy’s “smart-axed” comments

Randy

By: Axel

Axel — Wed, 01 Jul 2009 19:07:45 +0000

Interesting article. Thanks for summarizing it.
My favorite way of moving regolith is something like the magnetic conveyor belt ( see http://www.lpi.usra.edu/meetings/lpsc2007/pdf/1662.pdf ).
After I read about lunar dust hovering due to electrostatic forces I imagined something similar with electrostatic instead of magnetic forces. Electron cannon charges dust. The dust is then moved by a peristaltic modulation of electrostatic fields.
This probably moves only very small, loose particles, but for most tasks it is more important to move regolith than to dig deep. Covering a habitat with regolith is sufficient, no need to dig it into the ground.
Such methods need no carrier gas, but they need vacuum, and therefore won’t work at the NASA excavation challenge Which, by the way and IIRC, also does not allow use of gas for excavating.

By: Jonathan Goff

Jonathan Goff — Mon, 29 Jun 2009 14:35:08 +0000

MG,
Pulsed fluid jets do cut better than steady-state ones (that was what my thesis was about), though with 7psi air, I’m not sure how much better. If the central jet was some liquid that only flashed to gas after hitting the lunar regolith, then you could probably do something like the pulsed waterjet work I did for my thesis.

~Jon

By: Jonathan Goff

Jonathan Goff — Mon, 29 Jun 2009 14:33:37 +0000

Eric,
I’ve also been a fan of the street-sweeper approach, but I think the pneumatic excavator has its place, just because it looks like it is very fast, and solves both the excavation and moving steps at the same time. But I do agree, that there’s probably some work in there on making sure that the dust and gas mostly go up the outer tube instead of just blowing all over the place.

~Jon

By: Eric Collins

Eric Collins — Mon, 29 Jun 2009 13:05:12 +0000

I understand the basic concept here, my only concern is that it may be difficult for a robot to keep the nozzle positioned just right so that the path of least resistance for the gas is back up the tube rather than through the regolith and out into space.

I also understand that they are concerned with the mass of the excavator (and this offers a nifty way to get around some of that), but have they considered a design as simple as a street cleaner? Or for that matter, what about using a light-weight frame for the main excavator, and then load it down with regolith (a la dump truck mode), or a manned crew cabin for jobs that require human presence?

By: MG

MG — Sun, 28 Jun 2009 18:54:41 +0000

To move the regolith “back”, one might “only” need a conveyor belt.

Also, I wonder whether there would be advantages to rapidly pulsed gas jets. The scoop benefits from controlled vibrations (tuned to regolith characteristics). The addition of either strong acoustics or mechanical pulsing might complicate things a lot, though.

By: Andrew Swallow

Andrew Swallow — Sun, 28 Jun 2009 14:22:44 +0000

The one gas that can be made on the Moon is oxygen. Inflammability puts limits on the material that the drill can be made from, for instance stainless steel rather than iron.

CO2 is available on Mars.