A report describes experiments performed as part of a continuing investigation of the feasibility of laser ablation of materials as a means of propulsion for small spacecraft. In each experiment, a specimen of ablative material was mounted on a torsion pendulum and irradiated with a laser pulse having an energy of 5 J. The amplitude of the resulting rotation of the torsion pendulum was taken to be an indication of the momentum transferred from the laser beam. Of the ablative materials tested, aluminum foils yielded the smallest rotation amplitudes— of the order of 10°. Black coating materials yielded rotation amplitudes of the order of 90°. Samples of silver coated with a fluorinated ethylene propylene (FEP) copolymer yielded the largest rotation amplitudes — 6 to 8 full revolutions. The report presents a theory involving heating of a confined plasma followed by escape of the plasma to explain the superior momentum- transfer performance of the FEP specimens. It briefly discusses some concepts for optimizing designs of spacecraft engines to maximize the thrust obtainable by exploiting the physical mechanisms of the theory. Also discussed is the use of laser-ablation engines with other types of spacecraft engines.
This work was done by David L. Edwards, Ralph Carruth, and Jonathan Campbell of Marshall Space Flight Center and Perry Gray of Native American Services. In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to
Native American Services
Inc. 3411 Triana Blvd. SW Huntsville
AL 35805 Telephone No.: (256) 539-7928
Refer to MFS-31532.