July 01, 2011

Instead of a 100 year plan for interstellar space there should be a 50 year plan

NASA and DARPA have a project called the 100 year Starship study.

The 100 Year Starship™ Study is an effort seeded by DARPA to develop a viable and sustainable model for persistent, long-term, private-sector investment into the myriad of disciplines needed to make long-distance space travel practicable and feasible.

The Icarus project has projected dates when 1% of GDP could afford to pay for interstellar projects of various costs. Compounding the Global GDP at 4% returns a date of 2099 for when construction of the ‘Budget Daedalus’ represents only 1% of the planets GDP.

The keys to how soon we can send a major interstellar effort is how rapidly we can develop the economy of earth and the solar system. We need to grow energy, resources, technology and wealth.

More aggressive economic growth would look like this.

Increasing growth every 20 years
Year    flat 6% 6-11%   6-18%
2015    100     100     100    (trillions of dollars, World GDP PPP)
2020    134     134     134  
2030    241     241     241    2.5 times energy
                               30K per cap  
2040    431     474     571    3-4 times energy
                               50-70K per cap 
2050    770     940    1390    5-10 times
                               80K-140K per cap 
2060    1380   2000    4300    10-20 times energy
                               140K-430K per cap
2070    2500   4500   13700    15-40 times energy
                               250k-1.37 Million per cap

I think that it is clear that societies will spend first on developing the local solar system. So interstellar would be about 0.01 to 0.1% of GDP as most of the space effort would be in the solar system.

A thrifty Dyson probe works out in the 2050 to 2060 time frame with faster economic growth even with 0.1% of a budget for the world economy. Assuming that China and India continue to grow quickly and there is some bump in growth rate from exponential technologies.

Growing energy capabilities is the key to long term high wealth growth rates.

A kardashev level one weather machine and energy generation system would only need about 5 million tons of relatively basic molecular nanotechnology.

Nanotechnology and other technology advances and better designs can also lower the cost of the interstellar probes.

Imaging worlds with Hypertelescopes for Recon and Motivation

A 100-pixel image of a planet twice the width of Earth some 16.3 light years away would require the elements making up a space telescope array to be more than 43 miles apart. Such pictures of exoplanets could make out details such as rings, clouds, oceans, continents, and perhaps even hints of forests or savannahs. Long-term monitoring could reveal seasonal shifts, volcanic events, and changes in cloud cover.

* To resolve 30 foot objects looking 4.37 light years away the elements making up a telescope array would have to cover a distance roughly 400,000 miles wide, or almost the Sun's radius. The area required to collect even one photon a year in light reflected off such a planet is some 60 miles wide


Hypertelescope website

46 page presentation - The hypertelescope concept and its applications at different scales (1 km, 100 km, 100000 Km)

Flotilllas of satellites are obviously needed for optical arrays in the size range from kilometers to hundreds and thousands of kilometers. Among the possible hypertelescope schemes, those with a concave primary array and focal combiner appeared well suited for space versions with multiple free -flyers . Either spherical ( CARLINA scheme) or paraboloïdal shapes can be considered for the primary array. Early orbital tests are desirable for developing the techniques of formation flying. Our group investigates the design of nano-satellites driven by solar sails, and plans to test them in geostationary orbit . “Gossamer” free -flyers having a mass as low as 100 grams are considered. With a rigid sail of area 0.1 square meter, driving a membrane stellar mirror of comparable size, accelerations can reach 10 microns per square second, providing motions of 5 m in 1000 seconds.

Once control techniques for a flotilla of space mirrors will be mastered, it will perhaps not take many years to expand their size from hundreds of meters to hundreds of kilometers. This is the size needed to obtain well resolved visible images of an exo-Earth within a few parsecs . Simulation 37 have shown that visible “portraits” of such planets can be obtained in 30 mn of exposure, using a 150 km hypertelescope with 150 mirrors of 3 meters.

For ever larger optical arrays, sizes will ultimately be limited by the number of photons received per resel. The, number decreases when exploding an array since it shrinks the celestial resels The Crab pulsar , believed to contain a compact neutron star of visual magnitude 18, requires huge baselines beyond 100,000 km to resolve the 20 km neutron star , but its extreme luminance can provide enough photons per resel through such a highly diluted aperture, with sub -apertures of a few meters . A “Neutron Star Imager” hypertelescope, spanning several hundred thousand kilometers is therefore conceivable. It can be similar to the EED or EEI., but requires primary mirror elements as large as 8 meters to concentrate their focal Airy peaks within a comparable size, so that they be collectible with beam-combiner optics of manageable size.

Laser Driven Hypertelescope
Feasibility of a laser-driven hypertelescope flotilla at L2 (28 page presentation)

• Many small mirrors better than few large ones • But how small ? Minimum size about 30mm for tolerable beam spread • 40,000 mirrors of 30mm for same area as JWST ? …. Laser-trapped flotilla ?

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