--- Log opened Sat Sep 17 00:00:21 2022
04:01 < TMA> somewhat related to the futurism/punditism/predicteerism is the book Loonshots by Safi Bahcall; it "explains" why innovation is not by itself sufficient -- which is why many of the futurist visions fail to materialize or they are at least postponed by many years 
05:43 < kanzure> 77924767133230d5b078647f993cd8d6b632db4dd8703ec00f33b48f6c7f9c17
05:43 < kanzure> 232e50c6436175912ad2a1b01d259310cddc8edefa9dcabf85ae4209550bd2ce
05:43 < kanzure> a225446c168abdbfbdd84a5881f1e7cc3a6cf9e44ca067ab53f7a37dc293df13
05:57 < kanzure> .wik shell-less chick embryo culture
05:57 < saxo> "Shell-less chick embryo culture is the process of growing chick embryos in vitro, without their protective egg shells, for scientific observation. /  Chick embryos and other avian embryos have been biological models to visualize the developmental stages of embryos for [...]" - https://en.wikipedia.org/wiki/Shell-less_chick_embryo_culture
05:59 < kanzure> "A novel shell-less culture system for chick embryos using a plastic film as culture vessels" https://www.jstage.jst.go.jp/article/jpsa/51/3/51_0130043/_pdf
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08:53 < muurkha> TMA: thanks!
10:21 < kanzure> .title https://news.ycombinator.com/item?id=32875995
10:21 < saxo> A subpolar-focused stratospheric aerosol injection deployment scenario | Hacker News
10:21 < kanzure> https://iopscience.iop.org/article/10.1088/2515-7620/ac8cd3
10:34 < superkuh> I think massive industrial scale production of reflective super-pressure balloons would be a more controlled way to do it. Once you release the aerosol there's no going back.
10:34 < superkuh> Also interesting to think about the increase in noctilucent clouds that might be attributable to rocket launches.
10:37 < muurkha> superkuh: what mass of stratospheric solids would be needed to achieve, say, a 1% reduction in albedo, with each of the two approaches?
10:38 < muurkha> I'm curious whether they're of the same order of magnitude
10:38 < muurkha> because I would naively assume that stratospheric aerosols can be about 1 micron thick, while balloon walls would need to be at least an order of magnitude thicker
10:39 < superkuh> The balloon method is definitely magnitudes harder. But not as out of control.
10:46 < fenn> "I consulted an expert on the matter. My son who is indeed a toddler. He said the colors are red, pink, dark gray, white, medium gray, and light gray." https://old.reddit.com/r/CrappyDesign/comments/xglnn6/this_toy_for_toddlers_with_3_barely/
10:50 < fenn> " there are age-related changes in threshold values and logMAR [minimum angle of resolution] visual acuity after the age of 6 years and that these visual functions do not become adult-like until the age of 8 to 9 years"
10:50 < fenn> they don't say which way it goes though, better or worse
12:33 < kanzure> is there a writeup of the atmospheric balloons?
12:41 < kanzure> http://web.archive.org/web/20000614170338/http://www.clonejesus.com/
13:05 < docl> has anyone written up a venturi effect space launcher? with a long tapered tube, maybe wind could be converted into a stream of air moving fast enough to reach orbit
13:07 < docl> I suspect there are substantial issues with it hammering the walls of the tube with too much turbulence or something like that
13:30 < docl> Ah, I see the principle is at work in light gas gun designs
13:30 < docl> https://en.wikipedia.org/wiki/Light-gas_gun
13:31 < muurkha> the biggest issue is that you reach choked flow at Mach 1, and with regular air at STP orbital velocity is Mach 23.8
13:32 < muurkha> but yeah light-gas guns can reach near orbital velocity
13:39 < muurkha> the Munroe effect routinely accelerates solids to orbital velocity and even escape velocity (11.2 km/s) from launchers small enough to be handheld, but as you can imagine, such a rapid acceleration tends to damage the payload
13:54 < docl> hmm. munroe effect relates to shaped charges... oh I see, part of the explosion is bounced inward and pushes the rest of it inward/forward, similar to the walls of a tube in the venturi effect 
13:54 < muurkha> the other issue of course is that the launch vehicle needs enough sectional density to penetrate whatever atmosphere is between it and orbit without slowing down too much; do you know about Newton's penetration depth approximation?
13:55 < docl> the term is new to me
13:55 < muurkha> yeah, I don't understand the Munroe effect at all, and I suspect that nobody understands it very well in a from-first-principles fashion
13:55 < muurkha> fluid dynamics go dramatically nonlinear once you approach the speed of sound
13:55 < docl> I'm looking at this illustration https://upload.wikimedia.org/wikipedia/commons/thumb/a/a5/Explosively_formed_penetrator.gif/310px-Explosively_formed_penetrator.gif
13:56 < muurkha> hello to my friends in domestic surveillance
14:00 < muurkha> I don't know if there is a way to tame this effect enough to launch a working satellite
14:02 < superkuh> If you want to go one step further look up "Voitenko accelerator"
14:02 < superkuh> Sometimes also called "voitenko compressor"
14:03 < muurkha> neat
14:05 < docl> https://en.wikipedia.org/wiki/Voitenko_compressor "The velocity of the resulting shock wave was a phenomenal 67 km/s"
14:06 < muurkha> yeah, note though that that's just the shock wave
14:06 < muurkha> they only managed to launch actual atoms at 40 km/s
14:06 < superkuh> https://arxiv.org/abs/2206.15003
14:07 < muurkha> .t
14:07 < saxo> [2206.15003] An Explosively Driven Launcher Capable of 10 km/s Projectile Velocities
14:07 < muurkha> neat
14:09 < superkuh> With any impulsive launch there's always the problem of circularizing the orbit though. And if you can fit a rocket engine on the projectile that can do that you might as well just use those engines to go up in the first place.
14:10 < L29Ah> but you don't want to pull a fuel/oxy tank with you
14:10 < muurkha> I don't think you can circularize completely aerodynamically but I suspect you can get most of the way there
14:11 < docl> basically the air interacts differently with the tube walls when the tube has a relative velocity of the speed of sound. I wonder if there's a way to fake it by suspending a plasma near the surface of the tube (electrodynamically avoiding contact) and accelerating it to higher speeds as you go
14:11 < muurkha> and the Δv for circularizing can be pretty small depending on how elliptical of an orbit you're willing to accept
14:12 < superkuh> It's raising perigee that matters. Ground level.
14:12 < muurkha> right
14:12 < superkuh> I don't think that's pretty small.
14:12 < muurkha> it can be arbitrarily small as your initial launch velocity approaches escape velocity
14:12 < muurkha> docl: it's an interesting question, but I know even less about plasma dynamics than I do about aerodynamics
14:13 < L29Ah> yes, to get an arbitrarily far circular orbit ;)
14:14 < muurkha> well, that's true too,  but I was thinking of an elliptical orbit with an arbitrarily low perigee, but some arbitrarily annoying apogee
14:14 < L29Ah> who needs orbits anyway, we're going interplanetary gunshots!
14:15 < muurkha> if you're below escape velocity by just enough to start falling back toward the earth after two months, for example, you just need enough sideways velocity to have traveled one earth radius by the time you pass the center of the earth
14:15 < muurkha> after two months
14:15 < muurkha> .units earthradius/two months
14:15 < saxo>  Definition: 1.2113366 m / s 
14:16 < muurkha> I think?
14:16 < muurkha> I haven't played enough KSP clearly
14:17 < L29Ah> anyway, gunpowder energy efficiency sucks, and the light gas and shaped charge hacks don't exactly contribute to it
14:18 < L29Ah> so the musky way of carrying and returning tanks has more merit
14:19 < muurkha> the benefit of Jules-Verne-style launching from cannons is that, even if you need a lot of fuel, you don't need additional fuel to lift the fuel
14:19 < muurkha> so you can escape from the exponential tyranny of Tsiolkovsky's rocket equation
14:20 < L29Ah> yes, that's why there should be electrically accelerated space launchers
14:20 < docl> yeah, also if it's ground based you don't need to build light so you can build reusable
14:21 < muurkha> yeah, electrical launch helps somewhat with reusability, though we're still talking about very high power densities
14:22 < docl> and if you build a rocket that you fire out of a cannon it doesn't have to push the limits as much for self acceleration so it can be reusable more easily
14:22 < muurkha> maybe, yeah
14:23 < docl> another thing is you can just build a massive catcher in orbit. mostly circular / self correcting as needed. then your launcher just needs to supply altitude to reach it
14:24 < muurkha> you only need to launch once
14:26 < docl> the catcher can use electromagnetic induction braking (eddy current is a simple way to go if you don't mind wasting energy) or it can have a long pressurized tube for aerobraking in (since that doesn't have the sonic limitation)
14:27 < L29Ah> except that you impart your impulse to the catcher, so its orbit is no longer circular
14:27 < L29Ah> you can try to compensate it with multiple launches tho
14:27 < L29Ah> .t https://www.youtube.com/watch?v=EBKUU0Mneb8
14:27 < Muaddib> [EBKUU0Mneb8] Ayreon - My House On Mars (Universal Migrator Part 1&2) 2000 (7:49)
14:27 < saxo> Ayreon - My House On Mars (Universal Migrator Part 1&2) 2000 - YouTube
14:30 < docl> yeah and the catcher can have its own rockets to recircularize. it also needs to be more massive than the payloads it catches to keep the orbit near circular
14:30 < kanzure> ayreon is good ('space metal' album)
14:31 < docl> another way to do it is having 2 catchers in opposite orbits that interact electromagnetically
14:32 < muurkha> one orbit is enough, but if you choose your payload correctly, and you have enough Δv to reach escape velocity, you only need to launch once
14:35 < docl> true enough. but 2km/s is a lot easier to reach than 11km/s, especially if you have to add enough to penetrate the atmosphere
14:38 < muurkha> oh, you're thinking not even launch to orbital velocity, but to acquire it from the catcher?
14:39 < docl> yep
14:39 < docl> so it's a momentum banking system
14:40 < muurkha> it's an interesting idea, maybe you could even use a tether to snatch your launch vehicle from a stratospheric balloon
14:41 < muurkha> an orbital tether into the stratosphere has to deal with three orders of magnitude less air resistance than an orbital tether to sea level
14:42 < docl> true
14:45 < docl> I like something that's more of a linear track rather than rotating because it seems not to take up as much space, and it's never under very much tension. you could have a 250km long track for braking to orbit at a rate slow enough for humans to handle
14:47 < muurkha> a stratospheric to LEO tether system brings down the necessary free breaking length down into the range where existing materials like carbon fiber or basalt fiber might be adequate for the tether; it wouldn't require exotic nanotube ropes or anything
14:49 < docl> horizontal strictures tend to want to rotate to vertical, so I'm not sure I would want it to be one structure. but it could be a series of T shaped components with each vertical part being an electrodynamic tether that reaccelerates/passively circularizes in the ionosphere
14:54 < docl> yeah I'm aware, tethers are a great option compared to the geosynchronous tower idea everyone wants to talk about. I do think it's a more complex proposition than the track though. for one thing if it busts you can get scraps outside the drag of earth's atmosphere relatively easily so there's a kessler risk to mitigate (not that it can't be done)
14:58 < docl> speaking of cheap stratospheric access, this talk about dynamic pressure is making me think about vacuum towers
15:00 < docl> when a high speed stream of gas hits something from the side, the pressure is diminished. but a centrifuge causes gas pressure to increase towards the edge. I wonder if there's a way to balance the two effects to make thin walled partially evacuated towers
15:01 < docl> basically with controlled low pressure vortexes inside
15:10 < muurkha> stratospheric access is super cheap already, an unpressurized polyethylene bag full of methane will get you there
15:11 < docl> it has to stretch as it rises, right?
15:12 < muurkha> generally it's more a matter of inflating than of stretching, though rubber weather balloons do both
16:35 < docl> .t https://www.project-atlantis.com/
16:35 < saxo> The Atlantis Project
16:36 < docl> Intriguing, and also fresh. I like the focus on stratospheric real estate and shipping/transit for the pacific basin. Not sure it's a worthwhile tradeoff to need the ring speed to be so much higher, but maybe solving it for 17km/s isn't that much harder than for 8km/s
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17:33 < kanzure> "The synthetic biology firm Ginkgo Bioworks is acquiring its competitor Zymergen in a deal worth about $300 million"
18:00 < docl> maaku: something puzzles me about dynamic pressure reduction based on relative velocity. If you use a big torus instead of a straight tube and move the gas really fast, does it suck air in from the outer edge? the units of velocity per unit centripetal acceleration are higher the bigger the torus
18:01 < docl> I'm tempted to think this is what big storm systems actually do
18:09 < docl> I'm tempted to think this is what big storm systems actually do
18:09 < docl> 5~
18:09 < docl> C
18:09 < docl> 5~
18:11 < docl> sorry, the baby got at the keyboard
19:06 < kanzure> who you have a mini me?
19:11 < docl> yeah I got married and had a kid, she's about a year and a half or so, toddler stage
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21:52 < lsneff> oh congrats man!
21:58 < lsneff> docl: just realized I haven’t met you in person yet
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23:54 < nmz787> docl: I've got a 4.5 yr old, I was still taking college math classes (one at a time) for fun until he turned 1.5... he quickly exceeded the previous 10ft/30-mins norm for moving around, and keeping track of him started being a much more constant-attention sort of task
--- Log closed Sun Sep 18 00:00:22 2022