How nanotechnology could make airsteading reality
Executive summary: explore the use of nanotechnology in increasing the feasibility of airborne habitats powered primarily by harnessing the energy of high-altitude air currents (jet streams).
Speculations about nanotechnology range from the demise of civilization and the consumption of the entire planet by gray goo, or even the galaxy and beyond via self-replicating Von Neumann probes, to the transfer of the self into non-neural substrate via mind upload. While both these extremes avoid the problem of overpopulation in different ways, this essay will analyze a more practical, albeit still solidly futuristic, method: airsteading - the concept of creating permanent dwellings floating in Earth's atmosphere, called airsteads, outside the airspace claimed by the governments of any standing nation.
Like seasteading, airsteading would enable competition and natural selection among forms of government, novel residential communities, the pursuit of scientific research outside the jurisdiction of nations opposed to controversial issues (e.g. embryonic stem cells), unique tourism and entertainment opportunities (including medical tourism), specific forms of energy production, and other developments yet to be anticipated. Since most legal and social issues concerning an airstead are being discussed by the seasteading community, and given that extensive structural engineering considerations are beyond the scope of this essay, we will focus on the use of nanotechnology in addressing the unique challenges faces by an airstead.
Spaceship Earth at Walt Disney World, a geodesic sphere
The method of keeping airborne a large colony described in this paper is in a sense the complete opposite of how airships stay aloft. Instead of filling a large cavity with a lifting gas then attaching a compartment for payload or passengers, an airstead would house these inside a very large tensegrity sphere. A tensegrity sphere is the name Buckminster Fuller gave to his proosed airborne habitats created from giant geodesic spheres. These spheres are made of triangular components and become stronger as they become bigger, due to how they distribute stress over their surfaces.
The weight of a sphere is a function of its surface, which is a function of its radius squared, A = 4 ÃÂ r2, while the volume of a sphere is a function of its radius cubed, V = 4/3 ÃÂ r3.
This is very significant, because it means that as the radius of the sphere increases, the lift of the sphere increases more. Surface-to-volume calculations show that the structural weight of a half-mile (0.8km) diameter sphere would be 1/1000 of the weight of the air inside.1 If the air inside were heated only one degree, the sphere would begin to float, acting like a thermal airship.
Thus it is not necessary to devise ultralight materials for the tensegrity sphere, but rather to use very strong materials for the sphere walls, such a carbon nanotubes, to withstand adverse atmospheric conditions ranging from storms to hurricanes. Note that the bigger its size, the more stable an airstead would be, similar to how very large tankers are less disturbed by rough seas than smaller sea craft. Since the surface of the sphere would be built of composite materials, an airstead would be a poor lightning target. To reduce changes in mass during rain, the outside of the sphere could be covered with a water-repellent nano-coating, the type already produced by companies like P2i.
The closed ecosystem of the airstead, similar to the Biosphere 2 project in Arizona, could also benefit from nanotechnology:
- nanomaterials with high surface-to-volume ratios can be used to filter gray water before recirculating it in the ecosystem
- nanosensors dispersed throughout the airstead (smart dust) can closely monitor temperature, pressure, humidity, vibration or potential contaminants. Temperature in particular is a critical variable, because it directly influences the buoyancy of the airstead.
To achieve energy independence, an airstead needs to harness its own power from the environment. Solar energy represents an easy target, with half the surface of the outer sphere being illuminated throughout the day in satisfactory atmospheric conditions. Quantum-dot photovoltaic cells achieve near 50% efficiency in converting light into electricity, and transparent thin-film SolarWindow coatings produced by New Energy Technologies generate electricity outperforming today's commercial and thin-film technologies by a factor of 2 to 10. The SolarWindow film coating is 100nm thick, can be sprayed on at room temperature, and placed selectively on see-through glass throughout the sphere, will ensure its natural illumination during the day while simultaneously harnessing electricity.
Clouds along a jet stream over Canada
To achieve massive energy surplus and commercial viability, the airsteads are uniquely positioned near a tremendous and yet untapped energy source: the jet streams.
Jet streams are narrow and extremely strong air currents found at altitudes ranging from 7 to 16 km (23,000 - 52,000 ft) above sea level. They are caused by a combination of Earth's rotation on its axis and atmospheric heating due to the Sun. Jet streams can reach speeds of 310 miles per hour and are very important in aviation: the first time they were used commercially, in 1952, an airplane flight from Tokyo to Honolulu was cut from 18 to 11.5 hours.2
Atmospheric scientist Ken Caldeira at the Carnegie Department of Global Ecology at Stanford University has calculated that tapping into just 1% of the energy in high altitude winds could satisfy the planet's energy demands.3 Even if these calculations are off by an order of magnitude, airsteads represent a highly tempting approach to harnessing this energy source by employing floating wind turbines towards the jet stream.
This is where nanomaterials become crucial:
- carbon nanotubes could prove key to the structural materials that could stand up to the jet stream's buffeting winds
- CNTs could again form the conducting and structural core of the cable that would both transmit electricity generated by the floating turbine, and tether it to the airstead. This technology could further pave the way for the space elevator.
- buckyballs could form the top-grade lubricants required by the turbine propellers
- nanotechnology can be used to provide nano-scale heat and corrosion protection layers for turbine walls and blades
Perhaps the most challenging problem is maintaining control of the floated turbines while following the meandering jet streams. Technology from unmanned aerial vehicles could be leveraged to control altitude and speed, while the airstead could act as counterweight, slowly following the turbine.
Engineering aside, there are concerns with regards to dangers posed to birds and airplanes. In response, it can be pointed out that the turbines fly far above birds, airstead move so slowly that birds are more likely to nest on them, and the tethering cables are thin enough compared to birds. As for airplanes, U.S. authorities have maintained a fleet of tethered balloons along the U.S.-Mexican border, to monitor aircraft as part of drug-traffic-tracking operations. This Tethered Aerostat Radar System typically floats at an altitude of 15,000 feet and planes have never collided with them.
The aerodynamics, electrics, and control of a 240kW prototype flying electric generator, along with a description of the tether mechanics, have been published in the March 2007 issue of IEEE Transactions on Energy Conversion.4
Airsteads could be called "pie in the sky", or "lofty" dreams, but the technology to build them seems to be less of a stumbling block, compared to the legal and social implications: Who gets to live on the airstead? What laws will apply to it as it passes from one country's airspace to another's? How will small communities evolve in a closed ecosystem?
These questions aren't new, and the seasteading movement deals with them as well. Airsteading is one step higher towards conquering the stars and moving some of our species' eggs out of the Earth basket - a move that we need to do sooner rather than later, if we wish to avoid existential risks.
Key to airsteads and to the move off Earth, nanotechnology may prove to be closer to a savior than to a nemesis.
Scientists look high in the sky for power; Jet stream could fill global energy needs, researchers say. San Francisco Chronicle, 2007-May-07. ↩
Roberts, B.W. Shepard, D.H. Caldeira, K. Cannon, M.E. Eccles, D.G. Grenier, A.J. Freidin, J.F. Univ. of Technol., Sydney, NSW - Harnessing High-Altitude Wind Power, IEEE Transactions on Energy Conversion, March 2007, Volume 22, Issue 1, pages 136-144. ↩
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