LISP: Laser impulse space propulsion

Abstract

It is not often that a new form of transportation suddenly appears and replaces what was hitherto regarded as mankind's only realistic option. In space and upper atmosphere transportation, chemical rockets have held center stage for over half a century. Tsiokolvsky's ideas led to Wernher von Braun's V2, which in turn led to the Soyuz, Apollo, and Ariane programs and the Space Shuttle. But recently theoretical and computational studies as well as a few initial experiments have pointed to a new option: laser impulse space propulsion (LISP). This may offer a more efficient and less ecologically damaging means of putting payloads into orbit. The world high-power laser community is well suited to following and aiding developments in LISP, though most practical research is still at an embryonic level. Obviously an effort of the size required to develop a laser-driven low-earth-orbit (LEO) launcher would require a multinational commitment. LISP could then be regarded as a parallel challenge to those of achieving ICF rriicrofusion yield and of improving X-ray lasers, especially in the “water window.” Any physicist or engineer involved with the latter projects would find many points in common with the former. It therefore seems appropriate to briefly review the progress made in LISP and also to communicate some recent results from high-power laser-matter experiments that have lead to conceptual designs.

Diode Laser-Driven Microthrusters: A New Departure for Micropropulsion

“…4,5 The maximum momentum per joule of incident laser light is produced at a fluence opt , which is at or just beyond the threshold for plasma formation, because plasma inhibits coupling. Even with laser spot size d s as small as 5 µm, impulse coupling efficiency C m and the fluence opt at which it occurs are well-predicted.…”

“…2 (Refs. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. Figure 2 predicts that diodes with pulse durations at least 0.2-1 ms will be able to produce plasma jets.…”

“…Ablation efficiency can approach 100%, as direct measurements with other types of lasers on cellulose nitrate in vacuum verify, 5 but a value of 50% or even less is likely. The impact of η AB < 1 is that the C m value deduced from a given v E might be less than the maximum permitted by conservation of energy.…”

“…Passively Q-switched, repetitively pulsed, diode-pumped solid-state lasers that weigh only 15 g are now available in the 1-W average power range (Dunton, E., private communication, Litton-Airtron Corp., Los Angeles, June 2001). Nanosecond-duration pulses give 50-kW peak power, allowing us to access all materials and create temperatures high enough for very large I sp (8000 s have been measured with nanosecond-duration laser pulses 5 ). Diode-pumped, glass fiber lasers offer an interesting alternative for achieving higher CW power with adequate brightness and small mass penalty.…”

Tracking Control and System Development for Laser-Driven Micro-Vehicles

“…However, new propulsion and control technology must be developed to both miniaturize and lighten with required stability. Laser propulsion [3][4][5][6] is significant in achieving a miniature and light micro-airplane. A laser-driven microairplane has been studied by Yabe and Kajiwara et al [7][8][9][10] A laser-driven micro-airplane requires precise laser tracking control to achieve continuous flight.…”