Laser beam projection for starshot launch

Justin Hyatt, Ryker Eads, Nicholas Didato, Roger Angel

Research output: Contribution to conferencePaper

Abstract

The Breakthrough Starshot Initiative aims to send a nanocraft to the Proxima Centauri system. Light sails 4 m in diameter will be accelerated by a 100 GW laser beam projected from a segmented aperture of several kilometer diameter. Adaptive optics to maintain a coherent beam require wavefront and phase sensing across the entire aperture. One projection system considered here comprises millions of 1 m2, 20 kW block of lasers each passing through beam expanding and beam directing units with a steering flat to project a 2 m x 2 m square diffraction limited beam. These units are packed close together for ~70% filled aperture. The beam expanders allow for mechanical and servicing access between the laser blocks. The off-axis Mersenne beam expanders both project the outgoing laser beam and receive incoming light from a beacon or the spacecraft for wavefront detection. A dichroic mirror separates the outgoing and incoming light. A wavefront sensor measures the atmospheric aberration across each 2 m aperture, and an adaptive deformable mirror is used to correct the projected beam to the diffraction limit over each 2 m aperture. Our approach is compatible with fixed frequency or tunable lasers. For fixed frequency lasers, a dichroic coating that transmits 99.99% at 1060 nm and reflects 90% of the redshifted return beam from the spacecraft accelerated beyond 70 km/s for P polarization. The 2m square beams will be steered over 2.5° to aim the beam during the 10 minute launch interval. Atmospheric wavefront tilts will be measured and the beam wavefront will be adaptively corrected by modulating laser phases. A preliminary trade study will compare performance and material and mass production costs for these two options.

Original languageEnglish (US)
StatePublished - Jan 1 2019
Event6th International Conference on Adaptive Optics for Extremely Large Telescopes, AO4ELT 2019 - Quebec City, Canada
Duration: Jun 9 2019Jun 14 2019

Conference

Conference6th International Conference on Adaptive Optics for Extremely Large Telescopes, AO4ELT 2019
CountryCanada
CityQuebec City
Period6/9/196/14/19

Keywords

  • Laser beam steering
  • Phase sensing
  • Wavefront sensing

ASJC Scopus subject areas

  • Space and Planetary Science
  • Control and Systems Engineering
  • Mechanical Engineering
  • Electronic, Optical and Magnetic Materials
  • Astronomy and Astrophysics
  • Instrumentation

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  • Cite this

    Hyatt, J., Eads, R., Didato, N., & Angel, R. (2019). Laser beam projection for starshot launch. Paper presented at 6th International Conference on Adaptive Optics for Extremely Large Telescopes, AO4ELT 2019, Quebec City, Canada.