Friday, July 22, 2016

Moving day

(Note: the following is one of various posts that were copied here from the forum for the sake of preserving the early days of the project. It was originally posted there on Feb 10th, 2016.)

After much contemplation, Cernan's Promise will be moved today to a spot half a kilometer north of its current location. Several changes in approach go with this move. Turns out planning an entire Moon colony, even just for education and inspiration, has a steep learning curve full of false starts, half-baked ideas, and a wide variety of mistakes. As hikers learn over time where best to pitch a tent, my feel for how best to make use of what the Moon offers is slowly growing.

I have now modeled this section of the rim of Lalande Crater much better, and made much better use of LRO photos to do so. I have done my best to make the boulders and outcrops shown in the photo accurate, and properly assess their scale. This is made more difficult by the fact that there exist only 2 photos of this area from LRO. In fact, to roughly estimate the downward slope heading away from the crater, i made some use of the photo taken by Apollo 16. As near as i can tell, the boulders in the foreground above are about 20 m high at their tallest, and the mound behind about 15 m at its tallest. Those 2 areas, and the large number of other boulders nearby, are the justification for the move.

There are several reasons.

  • How to store heat and energy through the night has been my main focus recently. Many recent posts discuss the matter. In my view, you want the right balance of two things.
    • Enough powder and fine-grain regolith to prevent heat from diffusing quickly, because even packed tightly such material is about half voids and it conducts heat so slowly it is decent insulation.
    • Enough dense rock to store heat in vast quantities so that power use for heating at night and cooling during the day is minimal. If you have enough such rock, you need no heating or cooling at all. Just let in the right amount of sunlight during the day.
    • There were boulders to be had near Teacup Crater, but this area has a true bounty. Teacup's boulder resources didn't seem adequate once i thought about it a lot. A big factor here is that the more i think about it, the more i suspect that the fine regolith layer at the rim of Lalande is very deep. Though it is mixed with a lot of boulders, it would be a mistake to assume there are enough in a particular area without evidence. Digging down to the mega-regolith layer to access superior thermal mass resources will be difficult, unless it is done through the inside wall of Lalande Crater. Though it is only a guess, i think there is sufficient evidence to postulate that the fine-grain regolith layer could be 100 m deep.
  • The inside wall of Lalande Crater is paydirt. We want to get down in there and start digging as fast as we can. I'd already identified that collection of large boulders i have started calling Gibraltar as the place to anchor ourselves so that is easier and safer. Now i think it is important to capitalize on them that way even more than i thought before, and even sooner. The slope inside the rim here is about 40 degrees on average, and steeper in spots. Lunar regolith compacts extremely well and flows extremely poorly, but you really, really don't want your rovers to get stuck, or heaven forbid, be struck by a boulder that has started rolling downhill. Gibraltar will live up to its name by having a winch with a long strong cable bolted to it, and anchor points for further cables. Advancing deep into Lalande will require the loose rocks be cleared, a winch will come in very handy.
    • Some of those loose rocks are paydirt on their own, because chances are they are composed of purer minerals than powder regolith.
    • About 300 m below the rim and 500 m east there is a ridge that looks very much like an outcropping of a strata of solid rock. Most likely, that is highland material extending from the hills 2 km or so to the west of the rim.
  • The adequacy of regolith as radiations shielding is much worse than i thought. The 1.2 m of packed regolith i'd envisioned in the early dome idea would only have made human residents sick. Cosmic radiation is so powerful that atomic nuclei are smashed when hit with such a particle, creating a cascade effect that takes over 5 m of loose regolith to block. That's not blocking all the radiation, just the extra radiation due to the particle cascade. To then protect against the dose that you'd get on the open surface, you need another 2.5 m of regolith. This issue was what made me decide to dig out the habitat, however difficult that is, because the lenses really help with that and it is by far the safest thing. The deeper you can dig the better, because the smaller the portion of sky you see, the less radiation you get. The closer to the rim of Lalande you can dig, the better, because then you can tunnel to it - an excellent place to expand the colony.

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