A Review of Laser Ablation Propulsion

Abstract

Laser Ablation Propulsion is a broad field with a wide range of applications. We review the 30-year history of laser ablation propulsion from the transition from earlier pure photon propulsion concepts of Oberth and Sänger through Kantrowitz's original laser ablation propulsion idea to the development of air-breathing "Lightcraft" and advanced spacecraft propulsion engines. The polymers POM and GAP have played an important rôle in experiments and liquid ablation fuels show great promise. Some applications use a laser system which is distant from the propelled object, for example, on another spacecraft, the Earth or a planet. Others use a laser that is part of the spacecraft propulsion system on the spacecraft. Propulsion is produced when an intense laser beam strikes a condensed matter surface and produces a vapor or plasma jet. The advantages of this idea are that exhaust velocity of the propulsion engine covers a broader range than is available from chemistry, that it can be varied to meet the instantaneous demands of the particular mission, and that practical realizations give lower mass and greater simplicity for a payload delivery system. We review the underlying theory, buttressed by extensive experimental data. The primary problem in laser space propulsion theory has been the absence of a way to predict thrust and specific impulse over the transition from the vapor to the plasma regimes. We briefly discuss a method for combining two new vapor regime treatments with plasma regime theory, giving a smooth transition from one regime to the other. We conclude with a section on future directions.

Imaging spectroscopy of polymer ablation plasmas for laser propulsion applications

“…The current study thus highlights the role of oxygen in enhancing the energy release on material ablation and isolates one aspect of the good performance afforded by POM in laser ablative propulsion. In contrast, much prior work has taken poly(vinyl chloride) (PVC), rather than PE, for comparison to other polymers; 4 however, the decomposition of PVC is not necessarily purely endothermic since the HCl product has a larger bond enthalpy than the C-Cl moiety in the polymer. The results shown in Fig.…”

“…4 Relative to PLA in vacuum, additional physical processes occur in the presence of background gas, including shock wave creation and propagation, 5 plasma confinement, 6 and charge exchange during plasma formation and expansion. Many techniques have been employed to characterize the shock wave, including fast photography, 6 shadowgraphy, 7 interferometry, 8,9 time-gated emission imaging, 10,11 or spectroscopy.…”

Potential of laser-induced ablation for future space applications

“…Acting on the surface of the given body, the ejecta plume provides a resultant force that would be used to propel the spacecraft into space. Alternatively thrust can also be achieved by using a laser-induced blast wave [2,4]. Here, by illuminating sufficiently dense portions of the atmosphere, a highly focused laser beam can create a series of detonations.…”

“…Instead of burning propellant, previous proposals have suggested the use of a highly focused or collimated laser beam as a remote energy source [1,2,32]. Supplied by either a ground or space-based facility, a laser would be used to transform the exposed material e either a solid or a liquid e directly into a gas.…”

Influence of Microscopic Crater Formation on Impulse Generated with Repetitive Pulsed Laser Ablation

“…1) Based on such distinctive characteristics, the method has a promising application for the de-orbiting of space debris that results in the growing danger of a collision with active satellites in orbit. [1][2][3] For practical use, repetitive irradiation of the laser pulse is useful for obtaining a sufficient impulse. The impulse, I, generated on the object surface by laser ablation can be expressed as,…”