--- Log opened Fri Nov 19 00:00:37 2021
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06:57 < kanzure> "Concurrent evolution of anti-aging gene duplications and cellular phenotypes in long-lived turtles" https://academic.oup.com/gbe/advance-article/doi/10.1093/gbe/evab244/6430984
06:57 < kanzure> ".. show through comparative genomic analysis that Galapagos giant tortoises have gene duplications related to longevity and tumor suppression" no surprises here
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09:40 < maaku> fenn: it's been a decade since I worked at the lunar science institute and this info would've been fresh on my mind, but iirc Lunar Prospector and Clementine had, at best, very sparse indirect remote observation evidence
09:40 < maaku> which was consistent with volatiles on the surface, but could have been something else
09:41 < maaku> we didn't have high resolution data until LRO, and didn't have ground truth until LCROSS
09:42 < fenn> lcross had spectroscopy of the impact plume but i don't know what data they got from lunar prospector
09:42 < maaku> unfortunately the consensus is that LCROSS seems to have hit a relatively dry spot since although it found volatiles they are much lower in concentration than was expected or could be explained by the alpha and gamma ray observations
09:43 < maaku> fenn: just the gamma ray, alpha, and neutron spectrometers
09:43 < fenn> i mean when lunar prospector impacted the surface
09:43 < maaku> ah
09:43 < fenn> maybe no data
09:44 < fenn> seems like there should be impacts all the time
09:44 < fenn> i wonder if anyone is looking
09:44 < maaku> I don't think anyone is looking at a sufficient detail to capture data
09:45 < fenn> you'd have to be pointing your spectroscope at the point of impact which is much easier to do with a known time and location than a random event
09:45 < maaku> There are people looking for and counting impact flashes, but not doing spectroscopy
09:45 < fenn> or we could just go there...
09:46 < maaku> I forgot that LP was intentionally impacted in a south pole crater
09:46 < maaku> I don't know if I've ever seen that data either, to be honest
09:48 < maaku> Also there's a stupid bias in planetary science for the south pole, whereas it looks like there is vastly more ice on the north pole and easier to traverse too
09:48 < maaku> looks like both LCROSS and LP impacted in the south pole.
09:48 < fenn> i think there are more craters at the south pole
09:48 < fenn> there does seem to be a bias though
09:49 < maaku> the whole region is a crater, and a deep one that excavates many layers of lunar geology, hence the interest in sending geologist astronauts there
09:50 < fenn> i guess i'm just not that interested in geology for geology's sake
09:50 < maaku> from an ISRU standpoint the north pole is much better. we get clear radar reflections of what could be full glaciers in the shadowed craters up there
09:50 < fenn> number one priority should be to establish a beach-head off earth somewhere
09:51 < fenn> interesting
09:51 < maaku> and there aren't kilometer-scale cliffs to descend to get to them like there is at the south pole
09:51 < fenn> something about peaks of eternal light
09:51 < maaku> yeah but we have batteries and fuel cells.
09:51 < fenn> reasonably sized towers (100m or so) can boost your solar duty cycle from 50% to like 90% fairly easily
09:52 < fenn> near the poles
09:52 < maaku> the peak of eternal light is (1) only one spot, (2) 80-90% (not 100%), (3) stupidly far from where we'd actually want the base to be
09:53 < maaku> the make-your-own-peak with a tower idea works better on the north pole iirc, because it is less hilly
09:54 < fenn> https://www.transastracorp.com/lunar-power-generation
09:54 < maaku> but alas NASA is fully focused on the south pole
09:54 < fenn> there's a paper in there somewhere with some simulations and line of sight maps
09:54 < fenn> oh maybe it was a video
09:55 < maaku> a kilopower nuke beats all these ideas though
09:55 < maaku> if only we had civilian access to that tech :(
09:55 < fenn> a few kilowatts are not enough
09:56 < fenn> it's not unreasonable to just fling ice into orbit and do the refining there
09:56 < fenn> but you need power for mining operations too
09:57 < fenn> i guess 50% uptime is not terrible
09:57 < maaku> the kilopower concept scales up to 10 kW in existing designs, and potentially bigger
09:57 < fenn> the crater is half full :)
09:58  * fenn puts on his optimism mask
09:58 < maaku> since you don't need heating elements to keep the base warm,  a handful of those are enough to power a small base
09:58 < maaku> https://en.wikipedia.org/wiki/Kilopower
09:59 < fenn> i've read a fair bit about kilopower
09:59 < fenn> it seems more like a clever political/budget strategy to create a precedent for actually developing new space nuclear systems
10:00 < maaku> yes
10:00 < fenn> the actual performance numbers are underwhelming
10:00 < maaku> ehh, it performs better than no nuclear power
10:00 < fenn> it is ludicrously simple construction, which is a plus
10:01 < fenn> is it better than solar on the lunar poles? i read an analysis for mid-latitude martian surface and solar wins, even taking into account battery mass
10:02 < fenn> i'd expect it to be even worse of a comparison on luna, because it's closer to the sun, and heat rejection is more difficult in vacuum
10:02 < maaku> heat rejection?
10:03 < fenn> from the reactor
10:03 < maaku> that's like the #1 benefit
10:03 < maaku> it keeps you passively warm
10:03 < fenn> so there are humans nearby?
10:03 < maaku> yes
10:03 < fenn> uh, okay
10:04 < maaku> hence the passively safe design
10:04 < fenn> i was imagining something like masten's little mining rovers
10:04 < maaku> with solar power you spend most of the energy you gather keeping your astronauts warm
10:04 < fenn> i don't think insulation is a big deal in vacuum
10:04 < fenn> MLI is crazy good
10:05 < maaku> and if your solar tower gets hit by an impact plume, or if your batteries or fuel cell goes out, you die
10:05 < maaku> a passive nuclear pile under the base is way better from a safety standpoint
10:06 < fenn> even better would be to have it stay warm with body heat
10:24 < L29Ah> fenn: what about heat rejection from the solar panels?
10:24 < fenn> they have a lot of area
10:25 < L29Ah> have to bury the reactor then
10:25 < fenn> with nuclear you have to transport the heat through a radiator, so it ends up being more mass for a given area
10:25 < fenn> for the radiator part anyway
10:26 < fenn> my strategy would be to waste nuclear fuel, have a high delta-T so as to reduce radiator mass, but nobody else seems to think that way for unknown reasons
10:27 < fenn> radiator temperature
10:27 < fenn> space is always about zero so delta-T ~= T
10:29 < fenn> the bar graphs about halfway down show the mass budget for various kilopower designs https://beyondnerva.wordpress.com/2018/05/02/krusty-we-have-fission-kilopower-part-iii/
10:32 < fenn> the numbers get better in the 100kW-1MW range
10:33 < fenn> not sure why the radiator mass is higher for the mars surface systems
10:42 < kanzure> https://yakshaver.org/2021/11/18/covenants.html
10:48 < maaku> Mars is warmer?
10:48 < maaku> That probably has more of an impact than Mars' pitiful atmosphere
11:36 < muurkha> maaku: I think the lunar prospector people were pretty confident that hydrogen meant water
11:37 < muurkha> and the Lunar Prospector impact plume was a big disappointment
11:37 < muurkha> iirc
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12:49 < fenn> .title https://liveness.com/
12:49 < saxo> Liveness.com - Biometric Liveness Detection Explained
12:49 < fenn> we seem to be on the bladerunner timeline
13:11 < maaku> muurkha: yes, but remote observations don't always line up with the ground truth
13:11 < maaku> and both LP and LCROSS impact plumes were disappointments
13:12 < maaku> so I wouldn't bank on abundant volatiles until there is prospecting missions on the ground
13:25 < fenn> just oxygen would be a major boost to in-space propellant availability. and there's solids, Neumann thruster (pulsed cathodic arc thruster with solid metal propellant)
13:26 < fenn> starship for example uses 78% oxygen as propellant by mass
13:30 < darsie> Even while being fuel rich?
13:37 < fenn> you can do the math
13:38 < fenn> i believe in you darsie!
13:39 < darsie> I can.
13:39 < darsie> But I don't see why I should.
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--- Log closed Sat Nov 20 00:00:38 2021