Title

Directed Energy Deflection Laboratory Measurements

Author Info

Travis Brashears, University of California - Santa Barbara
Philip Lubin, University of California - Santa Barbara
Gary B. Hughes, California Polytechnic State University - San Luis ObispoFollow
Peter Meinhold, University of California - Santa Barbara
Jonathan Suen, University of California - Santa Barbara
Payton Batliner, University of California - Santa Barbara
Caio Motta, University of California - Santa Barbara
Janelle Griswold, University of California - Santa Barbara
Miikka Kangas, University of California - Santa Barbara
Isabella Johansson, University of California - Santa Barbara
Yusuf Alnawakhtha, University of California - Santa Barbara
Kenyon Prater, University of California - Santa Barbara
Alex Lang, University of California - Santa Barbara
Jonathan Madajian, University of California - Santa Barbara

Recommended Citation

Published in Proceedings of SPIE: San Diego, CA, Volume 9616, August 1, 2015.

The definitive version is available at https://doi.org/10.1117/12.2187094.

Abstract

We report on laboratory studies of the effectiveness of directed energy planetary defense as a part of the DE-STAR (Directed Energy System for Targeting of Asteroids and exploRation) program. DE-STAR and DE-STARLITE are directed energy "stand-off" and "stand-on" programs, respectively. These systems consist of a modular array of kilowatt-class lasers powered by photovoltaics, and are capable of heating a spot on the surface of an asteroid to the point of vaporization. Mass ejection, as a plume of evaporated material, creates a reactionary thrust capable of diverting the asteroid’s orbit. In a series of papers, we have developed a theoretical basis and described numerical simulations for determining the thrust produced by material evaporating from the surface of an asteroid. In the DE-STAR concept, the asteroid itself is used as the deflection "propellant". This study presents results of experiments designed to measure the thrust created by evaporation from a laser directed energy spot. We constructed a vacuum chamber to simulate space conditions, and installed a torsion balance that holds an "asteroid" sample. The sample is illuminated with a fiber array laser with flux levels up to 60 MW/m2 which allows us to simulate a mission level flux but on a small scale. We use a separate laser as well as a position sensitive centroid detector to readout the angular motion of the torsion balance and can thus determine the thrust. We compare the measured thrust to the models. Our theoretical models indicate a coupling coefficient well in excess of 100 μN/W optical, though we assume a more conservative value of 80 μN/W optical and then degrade this with an optical "encircled energy" efficiency of 0.75 to 60 μN/W optical in our deflection modeling. Our measurements discussed here yield about 45 μN/W absorbed as a reasonable lower limit to the thrust per optical watt absorbed.

Disciplines

Statistics and Probability

Copyright

2015 Society of Photo-Optical Instrumentation Engineers.

Number of Pages

13

Publisher statement

One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.