tag:blogger.com,1999:blog-8587336.post4495075270143933461..comments2024-03-28T04:58:13.341-07:00Comments on CONTRARY BRIN: Peering upward and outward - alien megastructures? Fusion rockets and more.David Brinhttp://www.blogger.com/profile/14465315130418506525noreply@blogger.comBlogger40125tag:blogger.com,1999:blog-8587336.post-69801991113358413082015-11-11T16:47:54.262-08:002015-11-11T16:47:54.262-08:00From the main article:
"All right, the headl...From the main article:<br /><br /><i>"All right, the headline in the Daily Mail is (typically) lurid: "Could bombing Mars make it habitable? Nuclear warheads would heat the red planet to make it more Earth-like, claims Elon Musk." <br />Hmmm. I dig the heck out of my friend Elon, but in this case my physicist instincts call the proposal iffy. I know a better way. Develop techniques to use tiny nudges to send comets plummeting into the polar ice and permafrost."</i><br /><br />Musk proposed neither bombing nor bombardment. He made an off-hand joking comment during an interview on US TV just after the host jokingly asked him if he was a supervillain, then asked about Mars, Musk replied (paraphrasing) "We <i>could</i> set of thousands of nuclear detonations over the Martian poles... (pause for the host to feign shock) ...<i>or, my preference is</i> to engineer powerful greenhouse gases to raise the temperature more gradually, something we clearly already know how to do on Earth...."<br /><br />Aside: Elon's proposal (actually it came from Chris McKay back in the early '90s, IIRC) is the only one that requires a population on Mars. For most Mars terraforming proposals, including David's, any prior settlement on Mars would not only be useless to the effort, but they'd be in the way. So step one to terraforming Mars is to avoid colonising Mars and focus on developing an in-space civilisation rich enough to be able to terraform Mars....<br />Paul451https://www.blogger.com/profile/12119086761190994938noreply@blogger.comtag:blogger.com,1999:blog-8587336.post-6519953534887746882015-11-11T16:46:11.184-08:002015-11-11T16:46:11.184-08:00(Missed the whole thread...)
sociotard,
"Ven...(Missed the whole thread...)<br /><br />sociotard,<br /><i>"Venus has an atmosphere and no magnetosphere."</i><br /><br />Most of Venus' current atmosphere comes from a major resurfacing event about 500-1000 million year ago. We don't know how thick it was before that.<br /><br />Same reason that:<br /><br /><i>"how did the Martian atmosphere form in the first place? Shouldn't the solar wind have blown off all those trace gasses during planetary formation?"</i><br /><br />Mars' atmosphere wasn't collected from space or infalling comets. It came from violent outgasing during Mars' formation. The rate of emission outpaced the rate of erosion. But once Mars cooled and quietened down, the rate of erosion dominated.<br /><br />But about Venus: Larger planets will have a lower rate of erosion than smaller planets, as the higher gravity holds the atmosphere "tighter", lower, creating a smaller cross-section area for solar-erosion to work.<br /><br />However, note that Venus' atmosphere is dominated by the heaviest common gas molecule, CO2. While all the water was split (by solar radiation) into hydrogen and oxygen, and the light hydrogen blown away.Paul451https://www.blogger.com/profile/12119086761190994938noreply@blogger.comtag:blogger.com,1999:blog-8587336.post-76166988773323156772015-11-11T10:51:04.126-08:002015-11-11T10:51:04.126-08:00onward
onwardonward<br /><br /><br />onwardDavid Brinhttps://www.blogger.com/profile/14465315130418506525noreply@blogger.comtag:blogger.com,1999:blog-8587336.post-56032465247165470692015-11-11T10:33:44.857-08:002015-11-11T10:33:44.857-08:00I'll huf n I'll puff... um why is Harry Po...I'll huf n I'll puff... um why is Harry Potter showing up in this joke?David Brinhttps://www.blogger.com/profile/14465315130418506525noreply@blogger.comtag:blogger.com,1999:blog-8587336.post-44560338488828739412015-11-11T10:02:01.752-08:002015-11-11T10:02:01.752-08:00Oh, Mars had a magnetosphere, but the planet coole...Oh, Mars <b>had</b> a magnetosphere, but the planet cooled, the magnetosphere made of sticks was not maintained, and the big bad sun blew that atmosphere down. Got it.sociotardhttps://www.blogger.com/profile/11697154298087412934noreply@blogger.comtag:blogger.com,1999:blog-8587336.post-18719660774289835982015-11-11T09:39:40.392-08:002015-11-11T09:39:40.392-08:00New results from NASA's MAVEN mission indicate...<i>New results from NASA's MAVEN mission indicate that massive solar storms and shocks obliterated the early atmosphere of Mars.</i><br /><br />Question: The article posits that the big bad sun blew the Martian atmosphere off, but the Earth kept its atmosphere because it built its magnetosphere out of bricks.<br /><br />Okay, but,<br /><br />Venus has an atmosphere and no magnetosphere. Mercury has no atmosphere but does have a magnetosphere. (Admittedly, the Mercurial magnetosphere is made of straw). I always thought it was straight up because of gravity. You need a nice gravity well to hold on to an atmosphere.<br /><br />And, if the solar wind blew off the Martian atmosphere, how did the Martian atmosphere form in the first place? Shouldn't the solar wind have blown off all those trace gasses during planetary formation? I know the solar wind can be more or less intense, but I thought it was mostly a cyclical thing. Was it just really quiet all the while Mars formed its first atmo?sociotardhttps://www.blogger.com/profile/11697154298087412934noreply@blogger.comtag:blogger.com,1999:blog-8587336.post-1040187830303196322015-11-11T06:34:11.602-08:002015-11-11T06:34:11.602-08:00So if you're allowing an order of magnitude fo...So if you're allowing an order of magnitude for structure and other components, your solar panels are 50 to 30 times thinner then the lightest solar sails we can do. Nope. Sorry, your structure, power cables, and beaming apparatus are all made of handwavium. <br /><br />And you want to use this ring at 1 A.U. to terraform Mars?! 1 A.U. vs 1.52 A.U., that's about 75 million kilometers to 225 million kilometers. 75 million kilometers makes for a nice beam spread. That pesky inverse square thing again. No, wait. You' didn't say Mars. You said "terraforming operations all over the System". You're thinking of terraforming KBO's with these solar panels parked 1 A.U. from the sun. I guess if your civilization can make massless power cables, a 30 A.U. beam spread is no problem.<br /><br />"There will be more massive stations around to use the power" Well finally you seem to be acknowledging it'd be good to use the power near the solar collectors. Maybe some antimatter factories as you say. Maybe a few habs. Well, to use that much juice you'd need a *lot* of anti matter factories, habs, and/or other users in the neighborhoods. Again, wave good bye to your 13e13 kg infrastructure. <br /><br />And why park all this stuff 1 A.U. from the sun, with zero degree inclination? Putting all this into a tight band around the sun increases possibility of collision and blocking sunlight. Earth's gravitational influence will make maintaining this ring a chore.<br /><br />No, it's better to build infrastructure where the resources sit. In our neighborhood that'd be Luna and a few near earth asteroids. Mercury might be a nice location for an anti-matter factory. But for the most part, it'd be the Main Belt.Hop Davidhttps://www.blogger.com/profile/12923433894475072056noreply@blogger.comtag:blogger.com,1999:blog-8587336.post-68658649114422409462015-11-10T21:10:26.528-08:002015-11-10T21:10:26.528-08:00Present baseline solar sail designs vary from ultr...Present baseline solar sail designs vary from ultra thin Mylar at 5 g/m^2 to 2-micrometer Kapton at 2.8 g/m^2. I have the right order of magnitude for the reflector. It is to be angled such that most light focuses on the (smaller and more massive per square meter) solar panels. Some area, or alternately time, is to be devoted to station keeping, yes. I allowed an order of magnitude, up to ten times the mass of the reflector, for structure and other components. I stand by my numbers to within an order of magnitude. <br /><br />Earth is obviously not the sole user, although any number of terraforming operations all over the System become more feasible with this tool. You are, in reverse, assuming that habitats will be the consumers. Why would that be, either? This structure generates seven orders of magnitude more energy than our entire civilization currently produces, and even considering much higher energy needs for life support, I do not think the resources exist in the Belt to expand the population proportionately. So only a fraction of the stations will be powering habitats.<br /><br />There will be additional, more massive stations around to use the power. The ratio of factory stations to collectors depends on many factors; beaming efficiency, many-body orbital stability, and so forth. I did not address utilization in the design as it was outside scope. But if you asked me, I'd be making antimatter fuel for interplanetary and interstellar ships. This system can make it in kilogram job lots, and make STL interstellar flight almost routine.Catfish N. Codnoreply@blogger.comtag:blogger.com,1999:blog-8587336.post-89778951182553586572015-11-10T18:26:19.939-08:002015-11-10T18:26:19.939-08:00Catfish: One gram per square meter?!
You realize ...Catfish: One gram per square meter?!<br /><br />You realize a dollar bill masses about a gram, right? Your solar panels make Saran Wrap™ look like a sheet of plexi glass, they're about a 100 times less massive per square meter than Saran Wrap™.<br /><br />I suppose you will use light pressure for station keeping. To align these many square kilometers of extremely thin film, you need structure. And how about wires to carry the current? At first glance your solar panels sound a little more plausible than Scrith, but not by much.<br /><br />And where are these panels beaming their energy? Earth? The farthest panels would be 2 A.U. from earth. You mentioned inverse square. Back atcha. 300 million kilometers makes for a nice beam spread.<br /><br />And in the case of earth being the sole user <a href="http://physics.ucsd.edu/do-the-math/2011/07/galactic-scale-energy/" rel="nofollow">Tom Murphy's silly scenario,</a> would apply. Earth's surface is only 2.6e8 square kilomenters. Using that much power over that little area would boil the oceans.<br /><br />No, you need a populace other than earth flatlanders consuming this power. You'd want the populace in the vicinity of the solar panels (remember that inverse square thingy?). So along with your solar panels 100 times thinner than Saran Wrap™, you'd also need human habs. Wave good bye to your your 13e13 kg Dyson swarm.<br /><br />No it's better to build solar collectors where there's radiation shielding, water, carbon, metals and other stuff humans need. In other words, where the asteroids are at, like I said at first.<br /><br />You want to explain KIC's lack of infra red with radiators corresponding to an edge on plane? Sorry that is just silly. Only by strenuous mental gymnastics and furious hand waving can you make this work. If a science fiction writer used that, it would pop my WSOD.Hop Davidhttps://www.blogger.com/profile/12923433894475072056noreply@blogger.comtag:blogger.com,1999:blog-8587336.post-45888537278589029272015-11-10T16:55:39.965-08:002015-11-10T16:55:39.965-08:00It’s been a long time since I’ve read anything by ...It’s been a long time since I’ve read anything by Niven and Pournelle. The Wikipedia synopsis doesn’t sound familiar, so it looks like I skipped past the moties somehow.<br /><br />I was originally looking for a biological model that could be re-used for humanity’s expansion into space. Terran critters didn’t just make the leap from ocean to land. They did all sorts of intermediate things with exchanges between biomes establishing some of the eccentric survival requirements in each. Tidal pools ARE interesting places. Our outward leap (going up the Kardashev scale) could benefit from not having to re-invent everything, but this isn’t a new idea. What bothered me about some space projects and SF stories is that they DIDN’T make use of our past. Mars colonization without ISRU is one. Moon colonization without strong markets in cis-lunar space is another. Giant solar orbiting ’trees’ or fractal retirement homes surrounding stars also bothered me. They made me look at the time needed to evolve such systems and while I don’t think they are impossible, my mind boggles at the time that seems to be needed. Earth may be 4.5 BY old, but the explosive evolution phase only dates to the Cambrian. There hasn’t been a lot of time for evolution to produce what we can imagine in SF. They said as much in Interstellar when discussing life on a planet orbiting a black hole. Not enough time.<br /><br />My epiphany came with the realization that we get more time by upclocking the participants in the game. The post-Cambrian explosion involves a different level of players. After the Permian we get yet another group. Primates change even faster. Tardigrades we are not. That suggests one way to get from K1.0 to K2.0 is to change the players. Terra now has an intelligent player capable of designing others that might be fit in a wider range of niches, so a biological model for humanity’s expansion into space should involve changing everything both by design and by accident. Exchange across biome boundaries is a must, so ‘invasive species’ are going to happen. Purposely and by accident.Alfred Differhttps://www.blogger.com/profile/01170159981105973192noreply@blogger.comtag:blogger.com,1999:blog-8587336.post-81488050533594149062015-11-10T16:52:24.104-08:002015-11-10T16:52:24.104-08:00Molniya orbits should work. They might be useful i...Molniya orbits should work. They might be useful in reducing risks related to solar flares too. Spending most of your time at high solar latitudes changes which storms can deliver a direct hit on you. The nodal and apsidal lines will precess, though. How fast depends on where the Jovians are.Alfred Differhttps://www.blogger.com/profile/01170159981105973192noreply@blogger.comtag:blogger.com,1999:blog-8587336.post-45297477457727573172015-11-10T16:46:23.400-08:002015-11-10T16:46:23.400-08:00Dr. Brin: Good point, hadn't thought of that. ...Dr. Brin: Good point, hadn't thought of that. This might be countered with solar sail thrust, but any use of sunlight for thrust decreases the efficiency of power collection. Hmm. Can a star support something akin to Molniya orbits?<br />Catfish N. Codnoreply@blogger.comtag:blogger.com,1999:blog-8587336.post-50201571954938550502015-11-10T16:05:53.384-08:002015-11-10T16:05:53.384-08:00Alas Catfish, orbits that are tilted WRT the eclip...Alas Catfish, orbits that are tilted WRT the ecliptic experience precession of nodes. They do not remain a ring. In fact, they eventually become dangerous to each other. I am becoming persuaded that the highly elliptical thing may be optimal.David Brinhttps://www.blogger.com/profile/14465315130418506525noreply@blogger.comtag:blogger.com,1999:blog-8587336.post-49503779366125376002015-11-10T15:33:55.618-08:002015-11-10T15:33:55.618-08:00Alas, I would not be a good candidate for NASA'...Alas, I would not be a good candidate for NASA's astronaut program, despite a master's degree. The only non-technical applicants they are considering are those with teaching experience. I suspect NASA is coming to realize they need advocates that can 'fire up' future generations of potential engineers and scientists, and teachers are the best choice for that. NASA has no one obvious like Dr. Neil DeGrasse Tyson who can talk science to the masses.TheMadLibrariannoreply@blogger.comtag:blogger.com,1999:blog-8587336.post-41041025503601195052015-11-10T14:53:13.523-08:002015-11-10T14:53:13.523-08:00Dr. Brin: Thanks! Glad to be appreciated.
Hollist...Dr. Brin: Thanks! Glad to be appreciated.<br /><br />Hollister: As collection efficiency is inverse square, one takes a 6-9 fold hit to leave collectors in the Main Belt. Any swarm collector can also function as a solar sail -- a design built to reflect light into a central collection engine is the most efficient at this. Tacking will enable migration of components to lower orbits. Closer than Earth might or might not be even better; it's not clear where the inner safety limit is.<br /><br />As for moving the Main Belt asteroids, don't be ridiculous. Back of the envelope calculation shows this to be far more work than needed. At a 1 g/m^2 density, 1000km^2 collection/sail surface is 1e6 kg. Positing the total mass of a single Dyson unit of this order, Earth's 1e9km orbit can be covered by a 1e6 unit swarm. Total mass is of order e12-e13 kg, which is less than a millionth of a percent of the mass of the Belt. More significant fractions of specific elements may be needed, however.<br /><br />Alfred, Douglas: If the swarms are each rings, one only loses the collection surface at the ascending and descending nodes relative to each "competing" swarm. There should therefore be "territories" corresponding to mutually beneficial/exclusive groups of orbits. Cooperation would exist within a territory up to the limit of maneuverability. Establishing a swarm directly below an extant one would be a blatant act of war, as there should be little need as long as the sphere is mostly incomplete. Interlopers could be bandit/pirates or traders depending on negative or positive sum interactions: a scenario analogous to the agrarian vs. barbarian interactions of Earth's surface history... but now in a dynamic three-dimensional environment. Very interesting.<br /><br />On the smart dust AI swarm: I do not find this scenario (also presented in Stross' ACCELERANDO) convincing. Distributing the mass so finely is tremendous extra effort. What is gained? What prevents dust cloud collapse? There is no appreciable sail surface, no reaction mass, and solar wind/cosmic rays will defeat electrostatic/magnetic thrust.Catfish N. Codnoreply@blogger.comtag:blogger.com,1999:blog-8587336.post-85055779542383548452015-11-10T13:59:33.669-08:002015-11-10T13:59:33.669-08:00Alfred Differ,
The “The Mote in God's Eye” by...Alfred Differ,<br /><br />The “The Mote in God's Eye” by Larry Niven and Jerry Pournelle (1974) describes something like that.<br />Deuxglasshttps://www.blogger.com/profile/03488986307291616948noreply@blogger.comtag:blogger.com,1999:blog-8587336.post-49075777913016264092015-11-10T13:55:07.739-08:002015-11-10T13:55:07.739-08:00Perhaps we could find allies and supporters among ...Perhaps we could find allies and supporters among the different node groups if the AI is a collection of semi-autonomous AI beings. The AI could be a social organism in some aspects allowing us to be able to negotiate with them. Deuxglasshttps://www.blogger.com/profile/03488986307291616948noreply@blogger.comtag:blogger.com,1999:blog-8587336.post-65142360381847938792015-11-10T13:41:17.407-08:002015-11-10T13:41:17.407-08:00Dr. Brin,
Thank you for the links.
Actually for ...Dr. Brin,<br /><br />Thank you for the links.<br /><br />Actually for me the idea comes from Greg Bear’s “Anvil of Stars” where the galaxy is a very, very dangerous place. As for the networked AI being capturing the energy of a single star I think it is a logical outcome of the development of AI itself. We already imagine using semi-intelligent micro-probes to explore near star systems so why not take this one step further and imagine a network of micro-nodes encompassing an entire star and reaping its energy. The computing power it would have would be mind-boggling and impossible for us to get our minds around it. The light-speed lag would be a problem for this AI but maybe instead of being a monolith it would be a collection of semi-autonomous units in cooperation somewhat like our brains. In that case maybe we could find some common ground although I doubt it. <br />Deuxglasshttps://www.blogger.com/profile/03488986307291616948noreply@blogger.comtag:blogger.com,1999:blog-8587336.post-73551220594423744862015-11-10T13:24:40.350-08:002015-11-10T13:24:40.350-08:00Alfred that's actually a pretty cool model! ...Alfred that's actually a pretty cool model! Dangerous. Path diversions and predators. grist for story.David Brinhttps://www.blogger.com/profile/14465315130418506525noreply@blogger.comtag:blogger.com,1999:blog-8587336.post-60901374062970341202015-11-10T13:03:30.072-08:002015-11-10T13:03:30.072-08:00One thing I could never quite believe was that a K...One thing I could never quite believe was that a K2.0 civilization would be monolithic enough (single entity) to make circular swarm orbits safe. In a biological model, there would be internal competition suggesting the star would be more like a watering hole. Some members of the civilization could establish themselves close by, but weaker members would swoop in on elliptical paths, store what they could, then swoop out and live off reserves for awhile. Being able to change orbit parameters would be useful. <br /><br />As long as there is an ecosystem in place benefiting those who trade independent of their intent, I wouldn't expect a lot of small scale order. What should happen is biome level order.Alfred Differhttps://www.blogger.com/profile/01170159981105973192noreply@blogger.comtag:blogger.com,1999:blog-8587336.post-10305958487498860582015-11-10T12:13:11.425-08:002015-11-10T12:13:11.425-08:00DF all you had to do was Google my name and gerrym...DF all you had to do was Google my name and gerrymandering!<br />http://www.davidbrin.com/gerrymandering1.html<br /><br />and<br />http://davidbrin.blogspot.com/2013/11/the-simple-trick-allowing-citizens-to.html<br /><br /><br />CAtfish -- cool appraisal-summary of K1.5 ecliptic Dyson ring.<br /><br />DF the scenario you describe... in which it is damned dangerous to announce yourself... is the "dark forest" scenario described inLiu Cixin's great Three Body Trilogy. Worth reading!<br /><br />David Brinhttps://www.blogger.com/profile/14465315130418506525noreply@blogger.comtag:blogger.com,1999:blog-8587336.post-44322112952855431152015-11-10T10:14:21.353-08:002015-11-10T10:14:21.353-08:00If we got a runaway greenhouse effect started on M...If we got a runaway greenhouse effect started on Mars, it'd still be near vacuum. From what I can tell, Mars doesn't have enough frozen CO2.<br /><br />We could crash comets to add oxygen and nitrogen to Mars' atmosphere. But to do that, we'd need the ability to build substantial infrastructure on small bodies. In which case it'd be better to use small body volatiles where they sit.<br /><br />I talk about this at <a href="http://hopsblog-hop.blogspot.com/2014/02/terraforming-mars-vs-orbital-habs.html" rel="nofollow">Terraforming Mars vs orbital habs</a>Hop Davidhttps://www.blogger.com/profile/12923433894475072056noreply@blogger.comtag:blogger.com,1999:blog-8587336.post-62900485961123767102015-11-10T08:12:00.234-08:002015-11-10T08:12:00.234-08:00Catfish: In our solar system, the Main Belt would ...Catfish: In our solar system, the Main Belt would be the place to start a Dyson swarm. The Main Belt is only roughly confined to the ecliptic plane. Semi major axi range from 2 to 3.3 astronomical units. Inclinations range from 0 to 30 degrees. These objects occupy a toroidal volume.<br /><br />With this wide variety of semi-major axi and inclinations, collisions are less likely. It is also less likely an asteroid will cast a shadow on his neighbor (as I've already pointed out).<br /><br />Placing all the Main Belt asteroids in Cruithne like orbits would be a very, very, very, VERY large and long-term project. It would also be counter productive as light harvesting surface area would be reduced and likelihood of collision would be increased.<br /> <br />As for light harvesting near the home planet, a mini Dyson swarm within the planet's sphere of influence would not be sufficient to provide substantial occultations like we're seeing with KIC.Hop Davidhttps://www.blogger.com/profile/12923433894475072056noreply@blogger.comtag:blogger.com,1999:blog-8587336.post-69796530429877759402015-11-10T05:56:40.334-08:002015-11-10T05:56:40.334-08:00Hollister: A Dyson swarm is a very, very, very lar...Hollister: A Dyson swarm is a very, very, very large and long-term project. Assuming you are in a single-star system as most models do, you will be consuming a significant fraction of the non-stellar mass of the system building the structures. (Which is why many models assume that the utilization locations are also built into the structures, such as the Crisswell designs seen in HEAVEN'S REACH.)<br /><br />But there are a wide range of possible and expandable designs between our present civilization (K0.725) and a complete swarm (K2.0). It's not unreasonable to start with a swarm in the coplanar orbit of one of your planets, possibly your homeworld. A swarm completely covering Earth's orbit, of collectors 1000 km tall (on the solar north-south axis), would give you a K1.5 civilization (5 orders of magnitude above Earth's theoretical capacity, 5 orders of magnitude below a complete Dyson swarm). Of course you wouldn't have 100% coverage; there are tidal effects, they mustn't collide, etc. A reasonable design would have them in Cruithne-style horseshoe orbits, which could cover up to 90% of the orbital distance while not bothering the anchoring planet or its moons. At this scale, a very small inclination in the orbits of the collectors will prevent the vast majority from occluding each other, and yield a K1.4 energy output. Catfish N. Codnoreply@blogger.comtag:blogger.com,1999:blog-8587336.post-27919769853765640512015-11-10T05:15:51.511-08:002015-11-10T05:15:51.511-08:00Jumper,
Just a speculation, they could be attache...Jumper,<br /><br />Just a speculation, they could be attached to each other by wires. They could be arranged in different bands with different orbits, some close in and others further out and on all planes to the star. That way they could cover the whole sphere collecting the maximum energy. Deuxglasshttps://www.blogger.com/profile/03488986307291616948noreply@blogger.com