Description: This is an idea for using microwave beam propulsion against a solar sail. It was first proposed by the physicist Robert Forward in the 1980s as part of his quest to create propellantless propulsion systems. The source of the microwave beams would be a large 10,000s km circular diameter Fresnel zone lens perhaps located in Earth orbit with a mass of 10,000s tons. It would be accelerated using a 10s GW microwave beam to over 100 g attaining a cruise velocity of 10,000s km/s and possibly up to 20% of light speed. Although Forward had speculated it may be possible to accelerate it to near light speed. The sail would be constructed of a material that was ultra-low mass such as carbon and have a wire thickness of order microns. The wire sail constitutes its own payload to minimize mass and would need to have a uniform density throughout to ensure a polarized beam push. Considerable work was done to advance the concept by Geoffrey Landis.

Members: Robert Forward.


Key References:

  • Forward, R.L, Starwisp: An Ultra-Light Interstellar Probe, 22, 3, pp.345-350, May /June 1985.
  • Forward, R.L, Roundtrip Interstellar Travel Using Laser-Pushed Lightsails, J.Spacecraft, 21, 2, pp.187-195, March-April 1984.

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