Monday, November 09, 2015

Peering upward and outward - alien megastructures? Fusion rockets and more. reports on the recent attempt by the SETI Institute’s Allen Array to examine KIC 8462852, the star with an anomalous set of transit brightness dips that may be due to swarms of comets… or else conceivably a convoy of orbiting alien mega structures. 

I wouldn’t put any money on the latter, unless given great odds. Moreover, preliminary negative results obtained by a couple of Allen Array SETI scans set (rather high) upper limits to the radio activity of such a civilization cluster. Later scans are planned. Still, the ensuing public interest and conversations have been vivid and interesting.

It’s worth noting that we’re talking about a very large, co-orbiting swarm of purported alien structures that presumably collect and utilize sunlight (hence blocking our view of the star, part of the time). This would be be a substantial step — by perhaps a few percentages — toward a Kardashev Type II civilization, utilizing large fractions of the star’s emitted energy.  At one extreme this would become a “Dyson Swarm or Sphere.” 

The way you look for such an advanced system is by finding one with a huge excess in the infra-red, radiating waste heat into space. No such profound infrared excess is observed at KIC 8462852 — another crack in the alien civilization hypothesis. 

Only hold on a second. One fellow I know -- long time space power systems promotor Keith Henson -- has pointed out that such co-orbiting mega structures would orient their cooling systems the way we do, on the International Space Station, so that the radiator panels line their edges toward the sun, and their big, flat faces either north or southward, orthogonal, or at ninety degrees away from the hot star. 

Envision the situation.  We are observing these objects (whether comets, planets or cities) transiting — passing between us and the star — precisely because we are lined up with their orbital planes.  So any heat dissipation radiators would likewise be edge-on to us, as well!  And hence we would be unlikely to see much infra-red excess, even if these are prodigious, Kardashev-type structures. 

Hence, the lack of an infra-red excess may not be meaningful after all.  The jury is still out.  So stay tuned. Keep watching and listening to the skies! And meanwhile, let’s stay quiet ourselves.

Oh... and no these are not Kardashian structures.  Remember the topic is intelligent life.

== Interesting! ==

Among the cool projects seed funded by NASA’s Innovative and Advanced Concepts group is Helion Energy - they received a $3.8M DoE grant for fusion energy production and are an outgrowth directly from a NIAC grant! The Fusion Driven rocket (FDR) represents a revolutionary approach to fusion propulsion where the power source releases its energy directly into the propellant, not requiring conversion to electricity. 

I am proud to serve on NIAC's board of external councilors. We just gathered at NIAC's symposium -- under the Seattle Space Needle -- and I'll have more to say about that in-future.  Meanwhile...

Do you have the right stuff? NASA is accepting applications for future space missions. 

See the latest roundup on the Billionaires' Bet on new approaches to manned spaceflight, from SpaceX to Blue Origins to Virgin Galactic and so on.

One of the best TED talks ever. My colleague Michelle Thaller takes you on a tour of galactic gravitational lensing and Dark Matter and just about everything else. Hugely enlightening!  

== Exploring the Solar System ==

New results from NASA's MAVEN mission indicate that massive solar storms and shocks obliterated the early atmosphere of Mars.

NASA is eyeing potential landing sites on Mars for a future manned mission.

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.” 

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.  That pasting would be orders of magnitude cheaper to produce and orders of magnitude more powerful in outcome, and without radioactive fallout.   Heck we almost had an example, had comet Siding Springs passed just a wee bit closer to Mars, last year.  See this comparison detailed here

To be clear, I’d not want this done till we had a major civilization working in space, in order to detect and easily stop anyone from using the same method… to settle grudges on Earth.

Micro-satellite capture: A new, NASA-funded device will draw as well as repel satellites at the same time, meaning it will hold a satellite at a distance and won’t allow it to move away or toward the capture device. This will enable the capability to capture and possibly manipulate micro-satellites or other objects without making physical contact with them.  Based on Magnetic Field Architecture (MFA) technology, a more efficient way to transmit electromagnetic energy. Strategic applications of MFA technology and the use of its hover engines include structural isolation, recreation and entertainment, industrial automation, and transportation.  

The Comet Hitchhiker concept: NASA is developing plans to hitch rides on passing comets, using tethers and harpoons. This started as a project we funded at NIAC!

A wonderfully innovative lander explorer for small bodies in the solar system… the “hedgehog” uses flywheel momentum to spin and flip itself over any obstacle. We got to play with this and it is so cool. Go NIAC.  Go us! 

Oh my. Pluto is so gorgeously strange. Cryovolcanism: NASA's New Horizons finds evidence for ice volcanoes on the dwarf planet. See the latest images from New Horizons. WE DID THIS. YOU HELPED PAY FOR IT. A couple of bucks. Worth it. 

Rosetta probe reveals Comet 67's complex water cycle: "The data suggest that water ice on and a few centimeters below the surface ‘sublimates’ when illuminated by sunlight, turning it into gas that then flows away from the comet. Then, as the comet rotates and the same region falls into darkness, the surface rapidly cools again. However, the underlying layers remain warm owing to the sunlight they received in the previous hours, and, as a result, subsurface water ice keeps sublimating and finding its way to the surface through the comet’s porous interior. But as soon as this ‘underground’ water vapor reaches the cold surface, it freezes again, blanketing that patch of comet surface with a thin layer of fresh ice. Eventually, as the Sun rises again over this part of the surface on the next comet day, the molecules in the newly formed ice layer are the first to sublimate and flow away from the comet, restarting the cycle."

To Scale: The Solar System   On a dry lakebed in Nevada, a group of friends build the first scale model of the solar system with complete planetary orbits: a true illustration of our place in the universe. 

== And the cosmos ==

Giant ring-like structure spans the cosmos: A survey of gamma Ray Bursts (GRB) – among the most energetic events known – has revealed an unexpected pattern in the sky which suggests some kind of bubble structure up to 5 billion light years across.  Not mentioned in the article – rings of such scale could indicate causal contact with “other universes.” 

Mapping the universe: The Department of Energy has approved the start of construction for a 3.2-gigapixel digital camera – the world’s largest – at the heart of the Large Synoptic Survey Telescope (LSST). 

What happens when black holes smash together? A pair of co-rotating quasar black holes 3.6 billion light years away may be only a few light weeks apart, spiraling toward imminent collision that will send gravitational waves pounding across space.  "The pair of black holes was initially discovered last winter, by a team at the California Institute of Technology in Pasadena, through the flickering lights called quasars that black holes produce as they burn through the gas and and dust around them. Typically, quasars illuminate sporadically. When two black holes are about to collide, however, the quasars brighten at regular intervals. These particular quasars, PG 1302-102, were found to brighten by 14 percent every five years."

Alien oceans could be detected by looking for surface glint.

== Life in the cosmos? ==

At a conference of the UK Seti Research Network (UKSRN) in Leeds, a straw poll of the group's 20 members were split down the middle over the issue of beaming yoohoo messages into the cosmos. "We did a show of hands and we were perfectly evenly split," said Dr Anders Sandberg, speaking to journalists at the British Science Festival in Bradford. I'm very explicitly in favour," Dr. Jill Stuart, who studies space law and policy at the London School of Economics.

Yes, but I have a standing offer of a wager.  That such conclaves will always shift toward less willingness to transmit, after they are exposed to detailed facts in a debate between "message" zealots and those calling for caution.  It happens every single time.  Which is why the zealots so strenuously avoid such debates.

Remember (above) talking about Kardashev type 2 (or lower) civilizations. Well we've been looking also for something a wee bit bigger.

No Signs of Galactic Super-Civilizations: Have astronomers eliminated the possibility of Kardashev Type 3 civilizations in the universe? A group at Penn State, Jason Wright and colleagues Matthew Povich and my longtime compatriot Steinn Sigurðsson have been conducting the Glimpsing Heat from Alien Technologies (G-HAT) project, which scans data in the infrared from the Wide-field Infrared Survey Explorer (WISE) mission and the Spitzer Space Telescope. In their sampling: “…out of the 100,000 galaxies that WISE could see in sufficient detail, none of them is widely populated by an alien civilization using most of the starlight in its galaxy for its own purposes,” reports Paul Gilster.

Another group -- M. Garrett of Leiden University and his team -- have searched through the G-Hat data for galaxies emitting the kind of infrared excess that might come from billions of stellar systems surrounded by Dyson spheres or swarms, sucking in nearly all of the high energy photons and re-emitting waste heat. No blatant “type 3 signatures” were found.

Fascinating news.  Though my gut-check guesstimate is that they've only eliminated type 3 down to maybe 2.7… (on a Richter-like logarithmic scale)… where a majority of stars are left alone and less than a third are surrounded and dyson-sorbed...which is pretty much the situation I described in Heaven's Reach

In fact, a full Type 3 seems silly, because it leaves no room for creation of new generations of sapient life at nursery worlds.  Such monomania would be seen as threatening by other type 2.5 civilizations. who might step in, deeming the type 3s to be insatiable perverts.

Finally, the Ig Nobel prizes for this year: studies that make you go "Huh?"


Deuxglass said...

Having the cooling panels oriented edge-wise to us can explain only partially the lack of infra-red radiation since their structures themselves should also radiate in the infra-red unless they have super-conduction skins on their habitats that shunt the excess heat to the radiating panels without loss of heat.

Tony Fisk said...

The radiators of those mythical Dyson structures may be edge on to us as they eclipse their star, but they would be full on to us when the phase angle increases to 90 degrees.

Kudos to the guys willing to spend a weekend setting up a full scale 2D model of the Solar System in the Black Rock Desert. Melbourne sports a model to the same (billionth) scale along the St.Kilda - Port Melbourne foreshore. A decent walk or bike ride. It may be 1D and static but it does include Pluto* and, for those willing to circumnavigate the globe, there's Proxima Centauri as well.

*trivia: the orbit of Charon fits comfortably within the diameter of Neptune.

Tony Fisk said...

... radiators, I seem to recall 'Sundiver' proposed a means of dumping excess energy in a much more concentrated form.

David Brin said...

NOTES: - I replied to Mr. Fenton re gerrymandering in the last post.

Tony in Sundiver the ship had to use a very hot laser to dump heat by heating the already very hot sun. That is very costly. An efficient Dyson Swarm would be radiating at only a few dozen degrees above the microwave background.

Sorry your orbital mechanics are wrong. We see tis star's system edge on all the time cause its ecliptic is edge on to us, That is why we are getting eclipse darkenings.

duncan cairncross said...

It's not obvious (at least it wasn't to me)
But if you are going to have lots of "things" in orbit around your star having them in one plane would reduce the delta v requirements for moving between things

Given that you are using that plane then you would aim your heat rejection system out of that plane so you didn't bother nay of your neighbors

So as we are in the same plane - or we wouldn't see the darkening then we would not see the heat rejection

Greg said...

On the radiator orientation issue, it appears that David is (reasonably!) presuming that the beginnings of a Dyson swarm would be in the plane of the ecliptic, and (possibly less reasonably) that the radiator fins would be oriented in that plane. Tony is either assuming a "north-south" orientation or a random orientation, in which case we would see significant thermal radiation from parts of the swarm that have moved 90 degrees around their orbits.

The question I have is why Dyson swarm objects would have a significantly different thermal signature from a comet swarm - which also would absorb and re-radiate. I'm guessing the answer is that typical comets have high albedo, while (by their purpose) Dyson swarm objects are thought to have very low albedo.

Greg said...

And while I was typing, Duncan came up with a reasonable justification for orienting the radiator fins in the plane of the ecliptic, thus dumping the heat mostly "north-south". Not bad.

Tony Fisk said...

Got it.

Tony Fisk said...

...No really, thanks for putting me right, folks.

From the first close-up images of Pluto's clearly geologically active surface, I have been wondering what could be powering this?

Activity on Enceladus and Triton could be down to tidal heating, but there seems to be no possibility of this where the only significant gravity source is little Charon, to which Pluto is tidally locked anyway.

There has been mention of heating from radioactive decay. That's possible. I tend to think heavier elements would have fallen further into the Solar System, but that doesn't mean there's no uranium left out there.

What really strikes me is that, with Utopia Planitia, you have this one large area of flowing ice. I wonder if it could be the result of an impactor causing localised heating? (These ices have fairly low melting points, so the temperature increase wouldn't need to be huge)

David Brin said...

Tony, some believe that the change of crystalline structure in the very common mineral Serpentine, relaxing to a lower state across BILLIONS of years, could release heat just like radioactivity.

locumranch said...

Assuming that a Dyson swarm (and/or sphere) capable civilisation exists, why do you all assume that their thermocouple technology is only capable of marginal human levels of efficiency?

After all, our Carnot Limit may not be their Carnot Limit, especially if we assume the existence of either a perfect thermal insulator or perfect superconductor, meaning that such a sufficiently advanced structure may be capable of radiating less heat than we currently think possible.

And, why do we assume that such massive interstellar structures need be solid? Wouldn't it be easier to surround a star with some type of mechanised interstellar dust instead of massive metal plates *riveted* together like some bad NexGen mock-up?

Maybe we should be looking for interstellar cold spots instead.


Hop David said...

Having all the objects in the ecliptic plane defeats the purpose of a Dyson swarm. To maximize light harvesting surface area, you'd want the swarm in a variety of orbits inclined to one another. That way an inner object wouldn't come between the star and an outer object unless it was crossing an ascending or descending node.

Deuxglass said...

Dr. Brin,

On gerrymandering can you direct me to the post where you gave the way to eliminate it in more detail please? I would like to have fun with it especially the part of how to get it implemented.

If KIC 8462852’s signature comes from recent planetary collisions wouldn’t some large objects be projected into orbits roughly 90% to the orbital plane? Kepler couldn’t pick that up but the Radial velocity method might be able to detect the star wobbling caused by a large planetary chunk in a highly inclined orbit and out of our line of sight. I think that would eliminate any speculation of structures built by intelligence.

For fun let’s say that it actually is a Type II civilization. What can that tell us about their mentality and the state of relations between highly-advanced space-faring civilizations? I think it can tell us a lot. First it means they are not hiding. In fact you can say they are advertising to the whole galaxy if with our primitive means we can detect it from 1500 light years away you can be sure that an advanced civilization could see it from much further away. This implies that the galaxy is a safe place for intelligent species with no invasions or fleets of conquering space ships to worry about. There will be no Klingons or Cardassians breathing down our necks when we master space travel. So can we look forward to a peaceful universe? Not so fast. Let’s take the paranoid route. Are they advertising because they have no fear or could it be just a gigantic, juicy flytrap designed to lure in and identify potential competitors and once there destroy them? It’s a decoy and a ruse drawing attention away from their true location. Here we are, a fat, happy, trusting and naïve civilization just waiting to be conquered. Come and get us!

Deuxglass said...


You said something very interesting when you wrote:

"And, why do we assume that such massive interstellar structures need be solid? Wouldn't it be easier to surround a star with some type of mechanised interstellar dust instead of massive metal plates *riveted* together like some bad NexGen mock-up?"

If a type II civilization is made up not of biological units but rather a networked AI then it could consist of very small particle-like structures orbiting the star rather than the large-scale constructions that we assume. It might even be the best way to fully capture the energy from the star. I wonder what type of signature such a civilization would produce?

Jumper said...

Such smart dust would need the ability to not coalesce into larger masses. Given small abilities to steer; what sort of automata rules are needed to achieve this in the gravity well?

Deuxglass said...


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.

Catfish N. Cod said...

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.)

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.

Hop David said...

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.

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).

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.

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 David said...

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.

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.

I talk about this at Terraforming Mars vs orbital habs

David Brin said...

DF all you had to do was Google my name and gerrymandering!


CAtfish -- cool appraisal-summary of K1.5 ecliptic Dyson ring.

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!

Alfred Differ said...

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.

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.

David Brin said...

Alfred that's actually a pretty cool model! Dangerous. Path diversions and predators. grist for story.

Deuxglass said...

Dr. Brin,

Thank you for the links.

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.

Deuxglass said...

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.

Deuxglass said...

Alfred Differ,

The “The Mote in God's Eye” by Larry Niven and Jerry Pournelle (1974) describes something like that.

Catfish N. Cod said...

Dr. Brin: Thanks! Glad to be appreciated.

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.

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.

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.

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.

TheMadLibrarian said...

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.

David Brin said...

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.

Catfish N. Cod said...

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?

Alfred Differ said...

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 Differ said...

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.

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.

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.

Hop David said...

Catfish: One gram per square meter?!

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™.

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.

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.

And in the case of earth being the sole user Tom Murphy's silly scenario, would apply. Earth's surface is only 2.6e8 square kilomenters. Using that much power over that little area would boil the oceans.

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.

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.

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.

Catfish N. Cod said...

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.

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.

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.

Hop David said...

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.

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.

"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.

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.

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.

sociotard said...

New results from NASA's MAVEN mission indicate that massive solar storms and shocks obliterated the early atmosphere of Mars.

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.

Okay, but,

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.

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?

sociotard said...

Oh, Mars had 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.

David Brin said...

I'll huf n I'll puff... um why is Harry Potter showing up in this joke?

David Brin said...



Paul451 said...

(Missed the whole thread...)

"Venus has an atmosphere and no magnetosphere."

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.

Same reason that:

"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?"

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.

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.

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.

Paul451 said...

From the main article:

"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."
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."

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 could set of thousands of nuclear detonations over the Martian poles... (pause for the host to feign shock) ...or, my preference is to engineer powerful greenhouse gases to raise the temperature more gradually, something we clearly already know how to do on Earth...."

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....