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April 27, 2010

Dyson Bubbles, Statites, Molecular Nanotechnology and Submerged Dyson Spheres


Another type of Dyson Sphere is the "Dyson bubble". It would be similar to a Dyson swarm, composed of many independent constructs.
Previously, nextbigfuture had written about Dyson Swarms and dyson Spheres

Unlike the Dyson swarm, the constructs making it up are not in orbit around the star, but would be statites—satellites suspended by use of enormous light sails using radiation pressure to counteract the star's pull of gravity. Such constructs would not be in danger of collision or of eclipsing one another; they would be totally stationary with regard to the star, and independent of one another. As the ratio of radiation pressure and the force of gravity from a star are constant regardless of the distance (provided the statite has an unobstructed line-of-sight to the surface of its star), such statites could also vary their distance from their central star.


A statite deployed around our own sun would have to have an overall density of 0.78 grams per square meter of sail. The total mass of a bubble of such material 1 AU in radius would be about 2.17 × 10^20 kg, which is about the same mass as the asteroid Pallas. If you placed the statites closer to the sun at say 2.5 million miles from the surface of the sun, then the surface area would be about 28 trillion square miles or about 1000 times less than the 1 AU surface area. 2.17 × 10^17 kg (217 trillion tons) of material would be needed. The surface area would be about 12 times the surface area of the sun and about 150,000 times the 197 million square mile surface area of the Earth. About 100,000 tons of material (deployed as 2.5 million mile from the sun statite energy collectors) would be needed to capture the energy for a Kardashev level One civilization (equal to the solar energy hitting the earth). If you could get another one million miles closer then the amount of material would be halved. (2 million mile diameter sphere instead of 3 million mile). The systems would need to be able to handle the heat, variable magnetic fields and flares.

Let me repeat some key takeaway from this:
1. when we have nanotechnology that is able to produce carbon solar sails/solar power collectors/statites that are about four times lighter than we can make now and produce and launch 100,000 tons of it and get it in close to the sun and transmit and use the power then we are at Kardashev level one. It would be early molecular manufacturing capability or good high volume carbon nanotube and graphene capabilities. The amount of material would be about 20,000 times less than the surface area of the earth or about 10,000 square miles.

2. It would be even simpler and easier to make a weaponized version of this. You would not need to collect the energy but just focus it and guide it where you wanted. 100,000 tons of near molecular nanotech in space and nuclear bombs would be like firecrackers. Molecular nanotech also provides the technology for insanely powerful access to space.



Statite Space Colonies
If such a sail could be constructed at this areal density, a space habitat the size of the L5 Society's proposed O'Neill cylinder – 500 km², with room for over 1 million inhabitants, massing 3 × 10^6 tons – could be supported by a circular light sail 3,000 km in diameter, with a combined sail/habitat mass of 5.4 × 10^9 kg. For comparison, this is just slightly smaller than the diameter of Jupiter's moon Europa (although the sail is a flat disc, not a sphere), or the distance between San Francisco and Kansas City. Such a structure would, however, have a mass quite a lot less than many asteroids. While the construction of such a massive inhabitable statite would be a gigantic undertaking, and the required material science behind it is as yet uncertain, its technical challenges are slight compared to other engineering feats and required materials proposed in other Dyson sphere variants.

In theory, if enough statites were created and deployed around their star, they would compose a non-rigid version of the Dyson shell. Such a shell would not suffer from the drawbacks of massive compressive pressure, nor are the mass requirements of such a shell as high as the rigid form


Here is the patent on statite spacecraft by Robert Forward (science fiction author)

Submerged Dyson Spheres

Nick Szabo proposed that since communications delays are rather long in a normal-size dyson sphere and energy densities grow as it becomes smaller, it would be advantageous to build spheres closer and closer to the star for advanced "solid state civilizations". The logical conclusion would be a shell around the core of the star, through which all energy would be filtered.

The problem with this is that the amount of energy that can be extracted from the radiation depends on the difference in temperature on the two sides of the shell, and inside the star this will be rather low, while outside the star the difference will essentially be between the shell temperature and the cosmic background radiation. But it should be noted that if neutrinous can be captured, they would provide a kind of temperature differential that could be used (since the sun is almost transparent to them).


Building things inside the sun would probably need very powerful magnetic shielding to prevent the high temperature plasma from destroying the physical structures. If the Dyson energy collectors were inside the Sun then the visual signature would not be the same as the infrared signature of regular 1 AU Dyson Spheres.

Solar Energy Closer to the Sun

NASA sent the Messenger probe to Mercury and it had special solar panels that reduced the glare.

Solar Probe Plus is a Nasa designed mission 167 pages that is designed to go to 8.5 solar radii above the surface of the sun.

Solar Probe+ will be an extraordinary and historic mission, exploring what is arguably the last region of the solar system to be visited by a spacecraft, the Sun’s outer atmosphere or corona as it extends out into space. Approaching as close as 9.5 RS * (8.5 RS above the Sun’s surface), Solar Probe+ will repeatedly sample the near-Sun environment, revolutionizing our knowledge and understanding of coronal heating and of the origin and evolution of the solar wind and answering critical questions in heliophysics that have been ranked as top priorities for decades.

Power is provided by two separate solar array systems. MESSENGER-heritage solar panels are baselined for the primary solar arrays, which will be used outside 0.25 AU. Array temperature is controlled by including optical surface reflectors (OSRs) with cells and tilting the arrays with respect to the Sun to keep the cell temperature within qualification limits. Inside 0.25 AU, the primary arrays will be folded inside the TPS umbra, and the spacecraft will be powered by the secondary solar arrays, two panels of high-intensity solar cells mounted on moveable, liquid-cooled base plates. At the start of a solar encounter, at 0.25 AU, the secondary panels are fully extended outside the TPS; as the spacecraft approaches the Sun, they will be partially retracted behind the TPS to maintain constant temperature and power output.

The solar cells baselined for the secondary solar array are triplejunction GaAs-based concentrator cells optimized for high-intensity illumination and high current density. Each cell has an active “aperture” area of 0.989 cm2. The cover glass, which is used for radiation protection and optical filtering, is cerium-doped microsheet with dual antireflective coating.

The illumination to which the secondary arrays will be exposed will vary in intensity between 16 and ~250 equivalent Suns, which is well within the range for which concentrator photovoltaic cells have been designed. Characterization tests for concentrator photovoltaic cells have been performed at up to 1000 equivalent Suns. Under the predicted range of operating conditions, the effective conversion efficiency of the secondary array cells will vary between 13% and 20%, with a junction temperature of 120° C, resulting in an additional 2259 to 1897 W of thermal energy absorbed by the cells.


FURTHER READING
Another path to Kardashev level one is J Storr Halls aerostat weather machines. These would need about 200 times more material (20 million tons). The weather machines could be placed into the atmosphere of Venus along with energy collectors and get about twice the solar energy of the earth.
Sunlight intensity in the solar system at the different planets.

Kardashev scale at wikipedia

Robert Freitas proposed diamond trees to control the earth's weather

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