Laser ignition of a cryogenic thruster using a miniaturised Nd:YAG laser

Abstract

An experimental study has been conducted to assess the feasibility of implementing laser ignition in cryogenic reaction and control and orbital manouvering thrusters. A experimental thruster with a single-coaxial injector element combustion chamber for testing with liquid oxygen/gaseous hydrogen and liquid oxygen/gaseous methane was designed for this purpose. Mapping tests conducted using a standard table top laser revealed that the minimum incident energies required for 100% reliable laser plasma and laser ablation ignition of liquid oxygen/gaseous hydrogen are 72 mJ and 14.5 mJ respectively. In addition, the miniaturised HIPoLas® laser was mounted directly on the thruster and used as ignition system. This paper reports locations of energy deposition, levels of delivered energy and associated ignition probabilities obtained. The results indicate the feasibility of using a laser system for the direct ignition of reaction and control and orbital manouvering thrusters and highlight further investigations and developments necessary for the implementation of miniaturised laser systems for vacuum igntion of cryogenic propellants.

Laser Technology in Photonic Applications for Space

“…Another clear advantage over electrical igniters is the fact that electrodes do not have to be inserted inside the combustion chamber, allowing in this case a more controlled combustion propagation. Laser ignition devices have been reported, such as the HiPoLas R by Manfletti et al [123], which is based on a DPSSL Nd:Cr:YAG laser and delivers 30 mJ, 2.5 ns pulses at 1064 nm. Although the miniaturized laser reported seems to emit less than the energy required to efficiently ignite propulsion systems, the technology offers several advantages, such as minimal ignition delay, increased ignition probability for a wider range of mixture ratios, and controlled initial chamber conditions [123]; moreover, laser ignition can be provoked at any point inside the combustion chamber or at various points simultaneously [124].…”

“…Laser ignition devices have been reported, such as the HiPoLas R by Manfletti et al [123], which is based on a DPSSL Nd:Cr:YAG laser and delivers 30 mJ, 2.5 ns pulses at 1064 nm. Although the miniaturized laser reported seems to emit less than the energy required to efficiently ignite propulsion systems, the technology offers several advantages, such as minimal ignition delay, increased ignition probability for a wider range of mixture ratios, and controlled initial chamber conditions [123]; moreover, laser ignition can be provoked at any point inside the combustion chamber or at various points simultaneously [124]. The test results and the demonstration of the feasibility of using this technology for the Ariane 6 launchers have motivated Airbus to claim that it will push forward the development of this technology for its forthcoming Safran launchers [125,126].…”

Compact nanosecond laser system for the ignition of aeronautic combustion engines

“…The minimum ignition energy depends upon the nature of the fuel (gas or liquid droplets). Different laser systems have been developed to ignite the gas mixture of an automobile engine [10][11][12][13][14][15][16][17][18][19]. However, the environment where the laser source has to be placed is often very hostile (vibrations, high temperature variations, oil projections).…”

Multiple-beam output high-peak power Nd:YAG/Cr4+:YAG laser for laser ignition

“…The classical methods of ignition are based on pyrotechnical and electrical effects. Recently, a lot of efforts are made to develop an alternative ignition technology based on solid-state lasers [1]. The energy required for a reliable ignition depends on the working conditions and one alternative to single highenergy laser pulse is a multiple-pulse laser system that allows the focusing of several pulses in a small volume.…”