Progress to a 20% of Light Speed Sail

The Limitless Space Institute is reviewing the work of Interstellar grant recipients.

It is feasible but very difficult to make a laser pushed sail reach 20% of the speed of light.

The general parameters are for an array of lasers with 100 Gigawatts of power to push a 1 gram solar sail that has 4 meter width by 4 meters length.

This means about 200 gigawatts of power that is converted into laser power with 50% efficiency. This would be about double the installed US nuclear power. It would also be about 11 times the power of China’s Three Gorges Dam.

The 1 gram sail would be 40% of the weight of a penny.

A few years ago photonic laser crystals were made that had dimensions of 350 microns by 350 microns. This means the width and the length would need to be increased by 10,000 times in each dimension.

Recently, the University of Delft has made photonic crystals that are 4.5 centimeters by 4.5 centimeters. We need increase the size by 900 times on each side.

How are the photonic crystals made. They use Silicon Nitride and they use electron beams to etch away unneeded material. They leave very thin supports holding each corner. The strand supporting each corner were made as thin as 50 nanometers. They etch many holes into the material to reduce weight and so optical interactions enable the material to become a mirror. They have made it 99.6% reflective.

The current size of the photonic crystal is limited by the size of a chip wafer.

Special purpose fabrication facilities will need to be made to expose a 4 meter by 4 meter ultrathin membrane with electron beams.

Written By Brian Wang,

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