Experimental investigation of laser-pushed light sails in a vacuum

Leik N. Myrabo; Timothy R. Knowles; John O. Bagford; Daniel B. Seibert II

doi:10.1117/12.407375

16 August 2000 Experimental investigation of laser-pushed light sails in a vacuum

Leik N. Myrabo, Timothy R. Knowles, John O. Bagford, Daniel B. Seibert II

Proceedings Volume 4065, High-Power Laser Ablation III; (2000) https://doi.org/10.1117/12.407375
Event: High-Power Laser Ablation, 2000, Santa Fe, NM, United States

Abstract

Laser-boosted light sail experiments were carried out on 13 - 20 Dec. 1999 with the 150 kW LHMEL II carbon dioxide CW laser at Wright Patterson Air Force Base, using a 2.74-m long, 2.13-m diameter vacuum chamber evacuated to 36 - 44 microTorr. The 5-cm diameter laser sail discs (i.e., the test articles) were fabricated from an ultralight carbon microtruss fabric that was sputter-coated with molybdenum on one side only, to improve its reflectivity to 10.6 micrometer laser radiation. Four laser sails discs with three different areal densities (one at 6.6 g/sq.m., two at 27 g/sq.m., and one at 28 g/sq.m.) were tested as magnetically-supported pendulums with an overall length of 18 cm. Pendulum deflections for the three heavier sails, ranged from 2.4 to 11.4 degrees, measured as a function of incident laser powers from 7.9 to 13.9-kW. These pendulum sails had masses of 83.7, 87.3, and 88 milligrams each; their center-of-mass was located at 11.5, 11.7, and 11.9 cm (respectively) below the magnetic bearing. Laser photon thrust ranged from 3.0 to 13.8 dynes, as calculated from pendulum deflections. Seven of the 10 data points fell in the feasible range of 3.3 to 6.67 N/GW for photon propulsion physics; the other three (higher laser power) data points exceeded the 6.67 N/GW limit by as much as 50%. From this data set, the onset for significant ablation was clearly identified to be 12.9-kW. Laser sail temperature was monitored with an optical pyrometer, and fell in the range of 2270- K to above 2823-K for laser powers from 8-kW to 20.8-kW, respectively. The experiments are the first known measurements of laser photonic thrust performance with real candidate light sail materials.

Citation Download Citation

Leik N. Myrabo, Timothy R. Knowles, John O. Bagford, and Daniel B. Seibert II "Experimental investigation of laser-pushed light sails in a vacuum", Proc. SPIE 4065, High-Power Laser Ablation III, (16 August 2000); https://doi.org/10.1117/12.407375

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