--- Log opened Sat Dec 04 00:00:51 2021
00:06 < fenn> i always figured the purpose of OTS timestamps was for third parties to detect that someone had manipulated the logs
00:09 < muurkha> as kanzure points out, that doesn't help if you timestamp the manipulated version at the time
00:09 < muurkha> (you can wait to publish the manipulated version until later)
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00:13 < fenn> that requires far more cleverness
00:13 < fenn> it stops the attacker from retroactively modifying history
00:14 < muurkha> yes, it prevents retroactive modification, if third parties are sufficiently hard-assed about demanding timestamps
00:15 < fenn> maybe some day computers will be useful and do things we want
00:15 < fenn> it doesn't exactly take AGI to verify that a log has been timestamped
00:16 < fenn> what does CFS stand for?
00:17 < muurkha> cyclic fabrication system
00:17 < muurkha> sorry
00:17 < muurkha> the issue is not verifying that a log *has* been timestamped
00:17 < muurkha> it's ignoring logs that *haven't*
00:18 < fenn> well recently gnusha has been going senile and having trouble staying in the channel, and we have to go root around and manually fix things, so it's not a costless operation to ignore any log that hasn't been timestamped
00:18 < muurkha> exactly
00:18 < fenn> there's a non-zero number of logs that have been retroactively modified, for legitimate reasons
00:19 < muurkha> that too
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03:32  * nebuchadnezzer_1 uploaded an audio file: (13796KiB) < https://libera.ems.host/_matrix/media/r0/download/matrix.org/AHlaTRaidaFRLnEWtrFCbgWf/Grandyzer%20-%20Adrift.mp3 >
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08:17 < Jay_Dugger> Hello, everyone.
08:33 < darsie> .
09:01 < docl> adlai: I was using the "baseball diamond" -- the idea being that the dependency tree for any product isn't continually growing as you go down it but eventually collapsing as redundancies come up. not intended to be a clean analogy as the points it collapses at are not uniformly distributed... directed acyclic graph is the appropriate highbrow term I believe
09:02 < docl> .wik Directed_acyclic_graph
09:02 < saxo> "In mathematics, particularly graph theory, and computer science, a directed acyclic graph (DAG or dag /ˈdæɡ/ (listen)) is a directed graph with no directed cycles." - https://en.wikipedia.org/wiki/Directed_acyclic_graph
09:08 < abetusk> https://www.inverse.com/innovation/robot-chemist-advances-science
09:08 < abetusk> .title https://www.inverse.com/innovation/robot-chemist-advances-science
09:08 < saxo> Robot scientists have solved the biggest challenge in chemistry
09:10 < docl> .tw 1467157080431857665
09:10 < saxo> Engineers are naturally contrarian and like to poke holes in things so we need lots of lazy arrogant dismissals of orbital ring plans with lots of details please // (FWIW Nelson's version goes in a different direction from my ideas) // https://www.reddit.com/r/SpaceXLounge/comments/9cda8k/this_claims_we_can_build_an_orbital_ring_with_one/e5a8i67/ (@lsparrish)
09:11 < docl> some thoughts about Nelson's orbital ring... I think the idea of using 30km/s bolts strains credulity (maybe)
09:14 < docl> and the idea of using electrostatics seems a bit contentious
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10:38 < muurkha> 30 km/s bolts?
10:55 < docl> yeah, for an orbital ring's mass stream he's thinking 470 cylindrival bolts, 40kg each
10:55 < docl> *cylindrical
10:56 < docl> I think they are hollow, so as to use electrostatic repulsion
10:57 < docl> problem to me is these would be about ten seconds from each other, so the platform is falling at 100m/s when it hits them and needs 10,000 gees to return to neutral
11:00 < docl> It's this paper https://jenda.hrach.eu/f2/Low%20cost%20design%20of%20an%20orbital%20ring%20-%202017-1.pdf
11:01 < Jenda> Hello! :)
11:02 < Jenda> I think the problem was with keeping up charge in this orbit - full of ions, which will be attracted to the rods and will neutralize the charge.
11:02 < docl> how fast does that happen?
11:03 < Jenda> no idea
11:04 < docl> apparently he calculates the interval between bolts at 2.7 seconds, but that doesn't sound right to me... for 470 bolts and 71 minutes it would be around 9 seconds
11:04 < docl> I'm looking at calculation 4
11:05 < docl> maybe he changed the number in his notes and forgot to update page 2
11:08 < docl> oh, I'm using orbital velocity and he's using 30km/s
11:11 < docl> the skeptic guy on spacex was saying the bolts charged to 200C would have a nuclear bomb's worth of energy. I wonder if that's a comment on their cylindrical shape... Nelson refs Tesla having done this on a sphere
11:12 < docl> maybe it's better to use 2 tethered spheres instead of cylinders to do the electrostatic thing
11:18 < docl> I think magnetic deflection is probably better... although I'm not confident this is the case. one concern I have is the high charge might introduce inertial anomalies from ionospheric weather events
11:19 < docl> plus he's talking about some heavy duty magnets anyway
11:25 < docl> .title https://www.youtube.com/watch?v=N7tIi71-AjA
11:25 < saxo> Lenz's Law with Copper Pipe - YouTube
11:26 < docl> if you move a magnet past a conductor, it generates repulsion. based on resistance and speed it also generates some drag
11:26 < docl> at orbital velocity the drag should be fairly minimal
11:27 < docl> the conductor in this case would be the aluminum bolts, with the platform having the magnets
11:28 < docl> you could also use an appropriately timed mechanical oscillator to cause the bolts to exit faster by having the magnet be closer to the bolt as it exits and more distant as it enters
11:46 < docl> https://www.reddit.com/r/IsaacArthur/comments/6nd4ui/leovator_space_elevator_for_70m_lifts_5_tons_per/
11:47 < docl> .title
11:47 < saxo> Leovator: space elevator for $70M lifts 5 tons per day to 350km altitude (draft) : IsaacArthur
11:47 < docl> seems to be an early draft of the same doc
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15:22 < muurkha> https://old.reddit.com/r/IsaacArthur/comments/6nd4ui/leovator_space_elevator_for_70m_lifts_5_tons_per/
15:23 < muurkha> docl: I'd think that at multi-kilogram scale it usually makes more sense to use magnetics than electrostatics
15:24 < muurkha> oh, I see you said tat
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19:20 < lsneff> Been trying to try out xls
19:20 < lsneff> Doesn’t build on my computer
19:20 < lsneff> I hate giant C++ projects
19:34 < kanzure> this one? https://google.github.io/xls/
19:35 < kanzure> one of the people listed on that page has been a user of this channel. i could rally him up if you have specific questions.
19:36 < lsneff> Yes, that one
19:36 < lsneff> Very interesting that one of the contributors is part of this group of people
19:37 < lsneff> I’ll wait to see if they respond to the issue I made
19:40 < lsneff> been thinking about whether it’d even be possible to build an open source high performance processor legally these days
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21:05 < lsneff> and whether that would really be as much work as people think
21:34 < fenn> docl: aluminum alloy seems like a poor choice for something undergoing a large number of mechanical deflections, due to its lack of a fatigue limit. eventually the aluminum "bolts" will crack and break
21:35 < fenn> docl: there are a lot of problems with this Nelson paper and i'm not sure it's worth the time to dig into it
21:40 < fenn> eddy currents, the whole charge transfer thing is wonky, no description of or calculations for how the bolts are accelerated
21:41 < fenn> "the bolt will then be accelerated in an adjacent orbit until it's velocity matches the ring's velocity then it is added to the ring" doesn't work for several reasons, not least of which is that the bolts would be moving at above earth's escape velocity
21:43 < fenn> starship is estimated to launch payloads to LEO at $5/kg and we have much a better rationale for believing those numbers
21:47 < fenn> i wonder why nobody is proposing rotating tethers to redirect the masses
22:01 < fenn> fatigue on a cyclically loaded tether will also be a problem
22:02 < fenn> with a rotating skyhook style tether launch assist, you only use the tether once per payload, not constantly like in an orbital ring
22:09 < fenn> anyone seriously proposing alternative non-rocket launch systems needs to read at least some of http://web.archive.org/web/20180201231845/http://www.tethers.com/Bibliography.html
22:09 < fenn> i'm not seeing _any_ benefits to an orbital ring
22:10 < fenn> energy storage as orbital velocity is just too good to give up
--- Log closed Sun Dec 05 00:00:52 2021