Ignition Characteristics of GH2/GOx Mixture Using a Laser Ablation Ignition.

Abstract

: Irradiating a nano-second laser pulse on a solid surface, a GH2/GO2 combustion chamber was operated to measure the minimum ignition energy for three parameters: the spot diameter, the thruster pressure, and the target material. It was confirmed that this method is useful since the minimum ignition energy can be much less than that of the laser spark ignition. It turned out that the minimum ignition energy increases as the spot diameter increases, and decreases monotonously as the thruster pressure increases. In addition, it was suggested that the ignition is possible even after the irradiation of a million laser pulses by applying the metallic targets (tungsten and stainless). On the other hand, the carbon target provided poor ignition probability.

Effects of Target Position on Direct Initiation of Detonation using Laser Ablation

“…For usual laser ignition by laser ablation, it has been reported that the critical laser energy density per unit area is independent of the spot diameter. 18) However, the present Trans. Japan Soc.…”

“…This result is consistent with the usual ignition characteristics using laser ablation. 18) For ¹2 mm L 4 mm, the critical laser energy increased slightly as L increased, and much larger laser energy was needed for direct initiation in the range of L > 4 mm.…”

“…4. Erosion caused by laser ablation [17][18][19][20] can be found in all cases. The position of the beam spot was changed after each shot so that a fresh target surface was irradiated with the laser beam, and several erosion marks appeared.…”

“…It should be noted that the ignition characteristics using laser ablation are affected by the relative position between the target surface and the focal point of the laser beam. 17,18) In the present work, laser ablation was applied for direct © 2015 The Japan Society for Aeronautical and Space Sciences + initiation of detonation, and the effects of the target position relative to the focal point of the laser beam were examined. The effects of the target position on the characteristics of direct initiation were discussed using emission images of plasma formed by laser ablation recorded on an Intensified Charge Coupled Device (ICCD) camera.…”

Laser Ignition Condition for a New RCS Thruster Using Green Propellant

“…The other is the use of breakdown of the ambient gas by focusing the pulsed-laser beam in the gas. It was clarified that the ablation method needed lower energy than that of the breakdown method 1) . In the other previous works using the ablation method 2,3) , minimum ignition threshold energy of the 10-ns laser pulse of 1064 nm in wavelength from a conventional Q-switched Nd:YAG laser system was 30 μJ with optimal mixture ratio and pressure of gaseous oxygen (GOX) and gaseous hydrogen (GH2).…”