Artificial Suns and how to make them

Tom Kalbfus · 2016-10-11 22:32:09

This idea came out of an idea on how to terraform Titan, the problem here is Titan is ten times as far from the Sun as Earth, the second problem is that Titan orbits Saturn instead of the Sun directly, so that means building giant mirrors to focus sunlight on Titan from the Titan-Sun L1 point is impossible, because there is no Titan-Sun L1 point, there is a Saturn-Sun L1 point but that point is very far away, because the Sun's gravity at this distance is very weak, and you have to travel very far from Saturn to find the balance point between Saturnean and Solar gravity, so any mirror placed there would have to be huge, and would have to track Titan, but there is an easier way, that is to create an artificial sun. I described how to do that in Terraforming Titan, basically it is a ball of molten Tungstein who's temperature is raised to that of the surface of the Sun, so that it glows the same as the Sun. The interesting property here is that Tungstein stays a liquid at the temperature a the surface of the Sun, so surface tension plus its weak gravity could hold it together, if it were a ball of gas, it would just expand into space and dissipate, but as a liquid it keeps its volume, that is a useful property.

This ball of tungstein orbits Titan at a radius of 11,455 km, its mass is 1.1e19 kg, and its radius is 50 km with such a radius and a temperature of 5,772 K this ball will be white hot, and look just like our Sun as seen from Earth. The real trick is how to keep this fromm cooling/

Antius · 2016-10-12 05:19:58

A fission powered sun would tend to leak fission products into space, which are lighter than tungsten and more volatile. If even a fraction of these reached the surface of Titan it would have a compromising effect on the habitability of the place.

A more efficient use of resources would be to build compact gas cooled fast breeder reactors on the surface, close to Titan's lakes. These would then benefit from the excellent heat sink provided by liquid methane, which can be pumped into compact heat exchangers and boiled off. The reactors will then provide lots of cheap electricity that you can use for powering sealed human habitats on the surface, containing locally terraformed environments. With the excellent heat capacity provided by the methane lakes, these could be allowed to grow to enormous sizes and can be cooled by methane evaporation. One can imagine habitats with ecosystems spanning multiple levels and therefore achieving power density that would be impractical in space due to the waste heat problem.

Tom Kalbfus · 2016-10-12 09:02:36

Antius wrote:

A fission powered sun would tend to leak fission products into space, which are lighter than tungsten and more volatile. If even a fraction of these reached the surface of Titan it would have a compromising effect on the habitability of the place.
A more efficient use of resources would be to build compact gas cooled fast breeder reactors on the surface, close to Titan's lakes. These would then benefit from the excellent heat sink provided by liquid methane, which can be pumped into compact heat exchangers and boiled off. The reactors will then provide lots of cheap electricity that you can use for powering sealed human habitats on the surface, containing locally terraformed environments. With the excellent heat capacity provided by the methane lakes, these could be allowed to grow to enormous sizes and can be cooled by methane evaporation. One can imagine habitats with ecosystems spanning multiple levels and therefore achieving power density that would be impractical in space due to the waste heat problem.

Yes but an artificial Sun would make the entire surface of Titan or whatever world available. I think fission might not be the best way to power the artificial sun, but I can think of something else. a micro-black hole. the kind you would use for a black hole starship would be the kind you'd use to make an artificial Sun.

According to the authors, a black hole to be used in space travel needs to meet five criteria:
1.has a long enough lifespan to be useful,
2.is powerful enough to accelerate itself up to a reasonable fraction of the speed of light in a reasonable amount of time,
3.is small enough that we can access the energy to make it,
4.is large enough that we can focus the energy to make it,
5.has mass comparable to a starship.
Black holes seem to have a sweet spot in terms of size, power and lifespan which is almost ideal. A black hole weighing 606,000 metric tons (6.06 × 108 kg), or roughly the mass of the Seawise Giant (the longest sea-going ship ever built) would have a Schwarzschild radius of 0.9 attometers (0.9 × 10–18 m, or 9 × 10–19 m), a power output of 160 petawatts (160 × 1015 W, or 1.6 × 1017 W), and a 3.5-year lifespan. With such a power output, the black hole could accelerate to 10% the speed of light in 20 days, assuming 100% conversion of energy into kinetic energy. Assuming only 10% conversion into kinetic energy would only take 10 times longer to accelerate to 0.1c (10% of the speed of light).[1]
Getting the black hole to act as a power source and engine also requires a way to convert the Hawking radiation into energy and thrust. One potential method involves placing the hole at the focal point of a parabolic reflector attached to the ship, creating forward thrust. A slightly easier, but less efficient method would involve simply absorbing all the gamma radiation heading towards the fore of the ship to push it onwards, and let the rest shoot out the back.[3] This would, however, generate an enormous amount of heat as radiation is absorbed by the dish.

https://en.wikipedia.org/wiki/Black_hole_starship
It would be easier to make this artificial sun than a starship out of it. The black hole would settle at the center of the Tungsten ball, and start absorbing tungsten surrounding it, on its way down into the black hole, some of the tungstein would get converted into x-rays, that x-rays would be absorbed by the surrounding tungsten and converted into heat. the Hawking radiation emmittend by the black hole would also get absorbed by 50 km of surrounding tungsten an get converted into heat. If the artificial sun it the right size and mass in relation to the power output of the black hole at its center, it will radiate visible light if its surface temperature is the same as the Sun, the bul of it acts as a radiation shield to black the x-rays and gamma rays coming from the black hole, just as the outer layers of the sun does for gamma rays emitted by nuclear fusion at the sun's core. If you get the right mass for the ball of tungstein, it will feed the black hole at its center at the same rate that the black hole converts matter into Hawking radiation, and at that point, you jus keep on adding more tungstein to the artificial Sun at the same rate that the black hole depletes it.

Tom Kalbfus · 2016-10-12 09:16:56

Titan's surface area is 32.05 million sq miles (83 million km²), the black hole emits 160 petawatts or 160 × 10^15 W, or 1.6 × 10^17 W. 83 million km² is 8.3 * 10^16 m² this is 2 watts per meter squared of radiation, the Solar Flux on Earth is 1350 watts per meter squared. We will need 690 black holes in this artificial sun to produce the correct power output to terraform Titan, or perhaps a larger black hole with 690 times the mass.

Last edited by Tom Kalbfus (2016-10-12 09:18:58)

Tom Kalbfus · 2016-10-12 22:15:31

There are other ways to heat the artificial sun, one way would be impact fusion on the far side of the molten ball of Tungstein, all you need are fusion powered mass drivers in Saturn's rings, accelerate pellets of fusion fuel so they hit the far side of the artificial sun hard enough so as to undergo nuclear fusion, and shower a broad swath of the far side so as to keep the artificial sun at Solar surface temperatures, the 100 km wide sun shields Titan from gamma rays emitted by the nuclear explosions, about half the radiation is wasted, being radiated into space instead of heating the tungsten ball. For autumn and winter, the artificial sun is allowed to cool a bit, for spring and summer the bombardment begins again causing the artificial sun to heat up once more.

Spaniard · 2016-10-13 05:48:40

Why not a simple approach. Make as nuclear fusion plants as you need, in different places of the moon, and use artificial light with the fusion energy.
Simple.
5 Petawatts could be enough. Around half million 10 GW fusion plants.

Bruteforce. But even more efficient that create a big ball of fusion that waste a lot of energy in wrong direction.
And generate a lot of energy to use as you want. Because only a small fraction is needed to be converted into visible light, the rest only is used to heat the moon, you can use this usefull energy to whatever you want.

It is some kind of open paraterraformation, where energy is artificially supplied from fusion directly created on reactors.

Tom Kalbfus · 2016-10-13 07:29:41

Half a million Fusion plants? Doesn't sound simple to me, and all those street lights, if one fails, you call the repairman to fix it. How about a million mass drivers instead, orbiting within Saturn's rings, processing the ring material to make pellets and then accelerating them towards the Artificial Sun, the pellets hit, and make a nuclear explosion. If a mass driver fails, it is repaired, the artificial sun continues to radiate its stored heat, and receive hits from other mass drivers to keep it hot, it is a target 100 km in diameter, it shouldn't be that hard to hit.

Spaniard · 2016-10-13 09:25:55

It's simple because it doesn't need a plan. It's just make dommed cities, more, and more, until the people generate so much heat that the low atmosphere reach Earth's temperature level.
Then you can focus into turn breathable.

Not need to wait for a megaproject to terraform. It's only that paraterraforming moves naturally from closed to open form when the waste hear is so high that you can warm the whole atmosphere.

I hope that far way planets could have deep atmospheres where warm atmosphere are only on low altitude and on high altitude the temperature is so low that even small moons won't lost fast by thermal escape.

A lot of reactors means redundancy too. ¿One reactor fails? ¿Ten? No problem. You have time to repair them.

The number doesn't need to be so high if we build bigger models. But I doesn't see why a high number is a problem.

Tom Kalbfus · 2016-10-13 11:34:53

So your vision is of Titan as a City Planet like Coruscant in Star Wars.

Not exactly my idea of what terraforming would be.

My vision looks more like this. While we could use mirrors, we'd be stuck with a 16 day rotation period if we did. I think we could use solar power to heat up an artificial Sun. Imagine if we were to reverse the paths of light rays so that the go to a surface rather than being emitted from the Sun's surface. If we can achieve the same light intensity at the surface of the Sun, we can heat another object to Solar Temperatures. Once it is hot enough, it ill give off its own illuminations and illuminate Titan.

Terraformer · 2016-10-13 12:20:48

Or you could just do, um, "conventional" paraterraforming.

Tom Kalbfus · 2016-10-14 00:58:58

We could do an artificial Sun for Venus, use the shade to collect solar energy, fire lasers at the artificial Sun, have it orbit inside the shade, and maybe have an artificial Moon orbit inside the orbit of the artificial Sun, then we could turn Venus into a Ptolemaic model of the Earth.

Tom Kalbfus · 2016-10-14 08:26:12

One can do the same for Proxima b, its problem is similar to Venus as far as lack or rotation is concerned, and it might be easier to terraform than Venus. On the positive side, it rotates once every 11 days, which is much fastr than Venus, it probably has a magnetic field because of this rotation, it is cooler than Venus, may have more water. We can erect a shade around the planet and build an artificial sun like I described. In addition the Alpha Centauri system may have a higher metal content because more metals were detected in their star's spectrums, than means we can perhaps find more tungsten to build these artificial suns out of. The energy that Proxima gives off should suffice for making an artificial Sun hot. For a planet like Proxima b with a mass of around 1.3 Earths, the 24-hour orbit is around 46,000 km according to the calc tool for orbit periods.
http://www.calctool.org/CALC/phys/astro … anet_orbit
Since the one I proposed to orbit Titan would orbit at 11,455 km, 46000/11455 = 4 times the diameter of the Titan artificial sun, which would make it about 400 km in diameter, its mass would thereforebe 704,000,000,000,000,000,000 kg or 7.04e20 kg, to get an idea of how much mass this is, our Moon has a mass of 7.15e22 kg, so this artificial sun would have one hundredth as much mass as our Moon.

Tom Kalbfus · 2016-10-16 07:00:25

Another use for an artificial sun.

Last edited by Tom Kalbfus (2016-10-16 07:06:56)

karov · 2016-10-17 13:15:49

Here it is.

A quote from Karl Schroeder's "Permanence"

A pinprick of light appeared on the limb of Treya and quickly grew into a brilliant white star. This seemed to move out and away from Treya, which was an illusion caused by Rue's own motion. Treya's artificial sun did not move, but stayed at the Lagrange point, bathing an area of the planet eighty kilometers in diameter with daylight. The sun was a sphere of tungsten a kilometer across. It glowed with incandescence from concentrated infrared light, harvested from Erythrion by hundreds of orbiting mirrors. If it were turned into laser power, this energy could reshape Treya's continents— or launch interstellar cargoes.
A flat line of light appeared on Treya's horizon. It quickly grew into a disk almost too bright to look at. When Rue squinted at it she could make out white clouds, blue lakes, and the mottled ochre and green of grassland and forests. The light was bright enough to wash away the aurora and even make the stars vanish. Down there, she knew, the skies would be blue.
She could have stared at that beautiful circle of earth and sea all day.

Sorry, I remembered it wrongly. Indeed the O'Neill rotating habitats in this brown dwarf system are illuminated by electromagnetic orbital thethers.:

Erythrion itself was visible now, a gigantic red eye in the night. The halo world was a brown dwarf, sixty Jupiters in mass, too small to be a sun and too big to be a planet. Like countless billions of others it moved through the galaxy alone in the spaces between the lit stars. So small and invisible were the halo worlds that they hadn't even been known to exist until the end of the twentieth century. But to Rue, Erythrion was huge and magnificent and all the civilization she hoped to ever see.
There were three major nations at Erythrion, one of them in the oceans under the ice surface of the Europan planet Divinus, one visible as scattered sparkles of light— orbital habitats scattered throughout the system— and one on Treya. As Rue's ship made its final approach through Erythrion's radiation fields, she swung the prospecting scope around to look for Divinus and Treya. Erythrion's dull red glow wasn't enough to make them shine; she spotted Divinus after long searching when it eclipsed a star. That absence was a planet. Treya, though— she could actually see it, a diffuse oval of light, like a fuzzy star. She stared at it until her eyes were sore.
Closer to hand, brilliant filaments of light illuminated dozens of O'Neill cylinders. Each cylinder was twenty or more kilometers long, home to nearly a million people. They utterly dwarfed the tiny station where she was born and raised and she gaped at them as they slid silently by.
Even the colonies were dwarfed by their surroundings. They swarmed like insects around incandescent filaments hundreds of kilometers in length. Each filament was a fullerene cable that harvested electricity from Erythrion's magnetic field. They were kept in orbit by vast infrared sails, visible only as a shimmer of reflected stars. The power running through the cables made them glow in exactly the same way that tungsten had glowed in light bulbs for billions of people on twentieth-century Earth. These cables were vastly bigger, of course; the colonies concentrated the light to provide «daylight» for whole populations with the waste product of electricity production.
The glowing cables had been built to provide power for launching starship cargoes. To see them serving merely as lamps was somehow saddening.

At big moons like Titan, the tungsten sphere could hang beyond the L1 planet-moon point so to balance the moon-directed weight of the electrodynamic thether, producing simultaneously electricity and light for the whole moon, on expense of slowly-slowly deorbiting it...

Tom Kalbfus · 2016-10-17 19:56:12

I think the hill sphere of Titan would be greater than the 24-hour orbit radius, so you can just have the orb orbit the moon. Anyway if placed at L1 with a moon that is tidally locked would create the same situation that supposedly exists on Proxima b.

karov · 2016-10-18 05:38:09

Tom Kalbfus wrote:

I think the hill sphere of Titan would be greater than the 24-hour orbit radius, so you can just have the orb orbit the moon. Anyway if placed at L1 with a moon that is tidally locked would create the same situation that supposedly exists on Proxima b.

If the 'incandescent sun' rather uses 'lightbulb filament' configuration it could be wraped around the illuminated body.

or

if point-like - then - statite mirrors / annular 'photonic parachute mirror' for the 'dark side'.

Tom Kalbfus · 2016-10-18 09:47:59

In order to use a light bulb filament, it would have to be cooler than the surface of the Sun. Tungsten has a melting point of 3695 K (3422 °C, 6192 °F)
Proxima Centauri has a surface temperature of 3,042 K This is interesting, apparently Tungsten can come into contact with the surface of that star, even though fusion is going on in that star's center, and the tungsten will remain a solid. That also means you can have an artificial star that is as hot as Proxima, shed light like Proxima yet remain solid, if it is solid, it can be made into a hollow shell, and we can put something radioactive and fissionable in its center. The Tungsten shell would keep the radioactive stuff on the inside, and it the stuff is above critical mass, it will undergo a runway chain reaction. We want it to maintain temperatures of around 3,042 K. Probably would take a lot of uranium or plutonium to keep this thing glowing and illuminate Titan. I suppose at some point, we would need to refuel this artificial Sun. It would be hard to get close enough to do this, perhaps we could build another sun to pick up the slack while we wait for the older sun to cool enough so we can touch it, empty out its contents and then refuel it with fresh nuclear materials.

karov · 2016-10-18 11:38:32

3550 o
Data Zone
Classification: Carbon is a nonmetal
Color: black (graphite), transparent (diamond)
Atomic weight: 12.011
State: solid
Melting point: 3550 oC, 3823 K

karov · 2016-10-18 13:24:32

https://en.wikipedia.org/wiki/Color_temperature

Carbon is better then tungsten.
Higher melting point.
Helluva cheaper.

Temperature Source
1700 K Match flame, low pressure sodium lamps (LPS/SOX)
1850 K Candle flame, sunset/sunrise
2400 K Standard incandescent lamps
2550 K Soft white incandescent lamps
2700 K "Soft white" compact fluorescent and LED lamps
3000 K Warm white compact fluorescent and LED lamps
3200 K Studio lamps, photofloods, etc.
3350 K Studio "CP" light
4100 – 4150 K Moonlight [2]
5000 K Horizon daylight
5000 K Tubular fluorescent lamps or cool white / daylight
compact fluorescent lamps (CFL)

5500 – 6000 K Vertical daylight, electronic flash
6200 K Xenon short-arc lamp [3]
6500 K Daylight, overcast
6500 – 9500 K LCD or CRT screen
15,000 – 27,000 K Clear blue poleward sky
These temperatures are merely characteristic;
considerable variation may be present.

---

At 3000K it will be good global high-class white light illumination.

[image]https://upload.wikimedia.org/wikipedia/ … arison.png [/image]

Tom Kalbfus · 2016-10-18 15:10:40

So what would you put here?

this is a complete artificial world, basically a giant O'Neill cylinder the size of but not the mass of the Earth. I think it might need some counter-rotated buttress bands to augment the tensile strength of the hull. Lots of carbon in diamond or nanotube form to hold it together. It rotates once every 90 minutes, the atmosphere piles up against the hull due to rotation, The walls at the edges are 500 km high to retain atmosphere, the rest is open to space. that ball in the center I estimate would be about 200 km in diameter to appear the same size as the Sun at the substellar point, the further you move towards the ends, the lower the angle of the Sun, and also the smaller the Sun appears because it actually is farther away. My feeling is you might want to draw a smaller cylindrical shade around this Sun for night, and also the night shade contains lasers or some other heating device to heat up the Sun for the next day. Maybe there is a long rod connecting the shade to a power planet or a very large solar power station. the Cylinders are maneuvered to keep the Sun in the center, as it isn't attached to anything. My choice would be to have the artificial sun at the same temperature as the surface of the real Sun. Tungsten is a liquid at this temperature, so if it won't hold a shape, it will at least hold a volume in the shape of a ball of liquid metal. I don't believe carbon liquefies in vacuum but Tungsten does. At a lower temperature, you can have a glowing solid. 15,000 - 27,000 K seems extremely hot, maybe a Type B star perhaps I wonder how an LCD screen have the same temperature as the Sun's surface.

karov · 2016-10-19 12:14:10

Tom,

From.:
<<<
DISTANT STAR
The Electronic Magazine of the Living Universe Foundation
January 15, 2001
The Use of Nanofibers in Space Construction
The Highest Home: Super Colonies and the Ultimate Human Habitat
By Eric Hunting
>>>

A colony structure like this would be easier to build if one could eliminate the mirrors and windows. This could be done by replacing the windows with a big optical diffuser running down the core of the cylinder. This would be made from ultra-light holographic membrane. A relatively small window in one end cap could provide entry for light collected by a much larger Sun-facing, non-rotating solar collector mirror in the manner of a Cassegranian teoptics telescope

orrrr, focused light from any source.

BUT, I think your tube is too wide, to structurally tolerate 1G inner-surface centrifugal force.

from.: http://www.orionsarm.com/fm_store/CEMS% … t%20...pdf

pages 6 & 7

6.1 Rotating Space Habitats
Suitable locations for space colonies include orbits around the Earth-Moon Lagrange points. Consider a large
fat cylinder rotating on its axis (Fig 6.2); a landscape of seas, plains and mountains girdles it within, while
sunlight, reflected from external mirrors, enters through the end caps.
Paper read to BIS/CEMS Syposium "Bringing Worlds to Life" at Birkbe... http://www.paulbirch.net/CustomPlanets.html
8 of 16 10/27/2006 11:09 PM
The total mass of the habitat works out at around 40 tonnes per square metre of habitable land, more or less
equally divided amongst atmosphere, crust, geosphere base and toposphere (Fig 6.3).
The geosphere base uses a low-density fractal architecture to keep the structural mass low, slotted together
out of strong but readily available fractal blocks of fused rock (Fig 6.4). This is a constructional technique
equally suitable for supramundane planets and rotating space habitats; it provides strength in tension as well
as compression whereas normal masonry construction only has strength in compression.
The maximum size of conventional rotating space colonies is determined largely by the strength of available
structural materials. The limit is about 250 km radius for quartz, 1000 km for sapphire, and 2500 km for
diamond. That last case is actually pretty big, a colony equalling the land area of the Earth. Even so, most
conventional space colonies will be considerably smaller than natural planets.
To some extent we can get around the size limit by making colonies longer, because the constraint is on the
radius not the length. An extreme example is the macaroni habitat (Fig 6.5), an ultra-long habitat with a
sunshine tube down the middle, if we loop it all the way round a star the total habitable area may be around
2000 times that of the Earth. And if we stretch a macaroni tube along tramlines between one star and another,
the habitat area becomes something like 100 million Earths. There is sufficient material in the solar system to
construct macaroni habitats thousands of light years long.
Even the largest diamond colony or the longest macaroni habitat is not a planet, though, because planets have
horizons and you live on the outside, whereas space colonies have the outside on the inside!

max. 500 km wide for quartz

max. 1000 km wide for sapphire

max. 5000 km wide for carbon

karov · 2016-10-19 15:03:21

Tom,

I can't really calculate it but I guestimate that made from carbon, at 1/4 Gees (??) the tensile strength of the material will withstand the centrifugal force of your 12800km wide one and about one rotation per ~2.8 hours ?>

Spaniard · 2016-10-19 15:20:10

Tom Kalbfus wrote:

So your vision is of Titan as a City Planet like Coruscant in Star Wars.
http://www.swtorstrategies.com/wp-conte … dkabab.jpg
Not exactly my idea of what terraforming would be.
http://images4.wikia.nocookie.net/__cb2 … udedit.png
My vision looks more like this. While we could use mirrors, we'd be stuck with a 16 day rotation period if we did. I think we could use solar power to heat up an artificial Sun. Imagine if we were to reverse the paths of light rays so that the go to a surface rather than being emitted from the Sun's surface. If we can achieve the same light intensity at the surface of the Sun, we can heat another object to Solar Temperatures. Once it is hot enough, it ill give off its own illuminations and illuminate Titan.

Well. While you use energy, it generates a lot of waste heat, and throught water exchange, a lot of vapor, so while from a infrarred the Moon could be more similar to the first image, at the visible light it should be more similar to the second.

In any case, outside aspect is not too much relevant. From ground perspective, I will do a lot of plants. A city could be integrated with plants to create a wonderful environment.

http://6iee.com/data/uploads/20/609351.jpg

Tom Kalbfus · 2016-10-19 22:29:55

karov wrote:

Tom,
From.:
<<<
DISTANT STAR
The Electronic Magazine of the Living Universe Foundation
January 15, 2001
The Use of Nanofibers in Space Construction
The Highest Home: Super Colonies and the Ultimate Human Habitat
By Eric Hunting
>>>
A colony structure like this would be easier to build if one could eliminate the mirrors and windows. This could be done by replacing the windows with a big optical diffuser running down the core of the cylinder. This would be made from ultra-light holographic membrane. A relatively small window in one end cap could provide entry for light collected by a much larger Sun-facing, non-rotating solar collector mirror in the manner of a Cassegranian teoptics telescope
orrrr, focused light from any source.

BUT, I think your tube is too wide, to structurally tolerate 1G inner-surface centrifugal force.
from.: http://www.orionsarm.com/fm_store/CEMS% … t%20...pdf
pages 6 & 7
6.1 Rotating Space Habitats
Suitable locations for space colonies include orbits around the Earth-Moon Lagrange points. Consider a large
fat cylinder rotating on its axis (Fig 6.2); a landscape of seas, plains and mountains girdles it within, while
sunlight, reflected from external mirrors, enters through the end caps.
Paper read to BIS/CEMS Syposium "Bringing Worlds to Life" at Birkbe... http://www.paulbirch.net/CustomPlanets.html
8 of 16 10/27/2006 11:09 PM
The total mass of the habitat works out at around 40 tonnes per square metre of habitable land, more or less
equally divided amongst atmosphere, crust, geosphere base and toposphere (Fig 6.3).
The geosphere base uses a low-density fractal architecture to keep the structural mass low, slotted together
out of strong but readily available fractal blocks of fused rock (Fig 6.4). This is a constructional technique
equally suitable for supramundane planets and rotating space habitats; it provides strength in tension as well
as compression whereas normal masonry construction only has strength in compression.
The maximum size of conventional rotating space colonies is determined largely by the strength of available
structural materials. The limit is about 250 km radius for quartz, 1000 km for sapphire, and 2500 km for
diamond. That last case is actually pretty big, a colony equalling the land area of the Earth. Even so, most
conventional space colonies will be considerably smaller than natural planets.
To some extent we can get around the size limit by making colonies longer, because the constraint is on the
radius not the length. An extreme example is the macaroni habitat (Fig 6.5), an ultra-long habitat with a
sunshine tube down the middle, if we loop it all the way round a star the total habitable area may be around
2000 times that of the Earth. And if we stretch a macaroni tube along tramlines between one star and another,
the habitat area becomes something like 100 million Earths. There is sufficient material in the solar system to
construct macaroni habitats thousands of light years long.
Even the largest diamond colony or the longest macaroni habitat is not a planet, though, because planets have
horizons and you live on the outside, whereas space colonies have the outside on the inside!
max. 500 km wide for quartz
max. 1000 km wide for sapphire
max. 5000 km wide for carbon

You are forgetting that the whole structure doesn't have to rotate, those parts that have no rotation have no weight, but they still have tensile strength.

Now imagine either the train or the track is rotating, but not both. Whatever is not rotating has no weight because it is not subject to centrifugal force, lets suppose it is the track that is not rotating, and lets bend both the track and the train into a circle. the train goes round and round in a circle on the inside of the track, the track stays put. The track supports the train and bends its path into a circle. Since the track does not have to support its own weight, it can easily support the weight of the train, if the train weighs too much for the track to support, you simply make the track thicker, with the increased thickness of the track you get greater tensile strength at no cost in extra weight.

So lets say the track is made out of carbon, if it is rotating to produce 1-g it can support its own weight up to 5000 km. Lay out a track of sufficient thickness that forms a circle 12,800 km in radius, then on the inside you have a cylinder that is slightly less than that it radius, the track supports the weight of the cylinder spinning once every 90 minutes. You can create a ribcage of 12,800 km wide circular tracks, you could even embed them within the hull structure of the cylinder so the tracks are neither visible from the outside or the inside. If you look at it from the outside, it appears to be a single object that is rotating as a piece in space. The tracks are buried within the thickness of the hull within evacuated tunnels.

karov · 2016-10-20 01:47:51

Yeah.

Like massive maglev bearing.

But I have no idea how to calculate the structure: how thick/massive the non-moving 'topobase' to be etc.

What are the limits?

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#1 2016-10-11 22:32:09

Artificial Suns and how to make them

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Re: Artificial Suns and how to make them

#14 2016-10-17 13:15:49

Re: Artificial Suns and how to make them

#15 2016-10-17 19:56:12

Re: Artificial Suns and how to make them

#16 2016-10-18 05:38:09

Re: Artificial Suns and how to make them

#17 2016-10-18 09:47:59

Re: Artificial Suns and how to make them

#18 2016-10-18 11:38:32

Re: Artificial Suns and how to make them

#19 2016-10-18 13:24:32

Re: Artificial Suns and how to make them

#20 2016-10-18 15:10:40

Re: Artificial Suns and how to make them

#21 2016-10-19 12:14:10

Re: Artificial Suns and how to make them

#22 2016-10-19 15:03:21

Re: Artificial Suns and how to make them

#23 2016-10-19 15:20:10

Re: Artificial Suns and how to make them

#24 2016-10-19 22:29:55

Re: Artificial Suns and how to make them

#25 2016-10-20 01:47:51

Re: Artificial Suns and how to make them

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