Directed energy deflection laboratory measurements

Travis Brashears; Phillip Lubin; Gary B. Hughes; Peter Meinhold; Jonathan Suen; Payton Batliner; Caio Motta; Janelle Griswold; Miikka Kangas; Isbella Johansson; Yusuf Alnawakhtha; Kenyon Prater; Alex Lang; Jonathan Madajian

doi:10.1117/12.2187094

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9 September 2015 Directed energy deflection laboratory measurements

Travis Brashears, Phillip Lubin, Gary B. Hughes, Peter Meinhold, Jonathan Suen, Payton Batliner, Caio Motta, Janelle Griswold, Miikka Kangas, Isbella Johansson, Yusuf Alnawakhtha, Kenyon Prater, Alex Lang, Jonathan Madajian

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Proceedings Volume 9616, Nanophotonics and Macrophotonics for Space Environments IX; 961605 (2015) https://doi.org/10.1117/12.2187094
Event: SPIE Optical Engineering + Applications, 2015, San Diego, California, United States

Abstract

We report on laboratory studies of the effectiveness of directed energy planetary defense as a part of the DESTAR (Directed Energy System for Targeting of Asteroids and exploRation) program. DE-STAR [1][5][6] and DE-STARLITE [2][5][6] 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 [1][2][3][4][5][6]. 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/Woptical, though we assume a more conservative value of 80 μN/Woptical and then degrade this with an optical "encircled energy" efficiency of 0.75 to 60 μN/Woptical in our deflection modeling. Our measurements discussed here yield about 45 μN/Wabsorbed as a reasonable lower limit to the thrust per optical watt absorbed.

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Travis Brashears, Phillip Lubin, Gary B. Hughes, Peter Meinhold, Jonathan Suen, Payton Batliner, Caio Motta, Janelle Griswold, Miikka Kangas, Isbella Johansson, Yusuf Alnawakhtha, Kenyon Prater, Alex Lang, and Jonathan Madajian "Directed energy deflection laboratory measurements", Proc. SPIE 9616, Nanophotonics and Macrophotonics for Space Environments IX, 961605 (9 September 2015); https://doi.org/10.1117/12.2187094

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