Impulse Generation Using 300-J Class Laser with Confinement Geometries in Air

Abstract

t: time elapsed after U attains U 0 U: flyer disk speed U 0 : peak value in U U TOF : flyer disk speed determined by time-of-flight method Ám: mass reduction of flyer disk (or separate ablator) after laser pulse irradiation x: distance from initial location : constant, Eq. (4) 0 : density of ambient air Subscripts 1: sensor 1 for time-of-flight method 2: sensor 2 for time-of-flight method Impulse generation using laser energy from a remote device has several advantages in aerospace propulsion, such as remote manipulation ability and vastly reduced onboard mass (along with accompanying cost). Moreover, the specific input energy is not limited by the inherent energy of the working fluid. After Kantrowitz proposed the concept of laser propulsion in 1972, 1) impulse generation using laser pulse irradiation has been examined experimentally using various configurations, such as ballistic pendulum tests, [2][3][4][5] flyer (including micro-airplane) launches, 6,7) and vertical launches with repetitive laser pulses. [8][9][10][11] This technology even holds promise for removal of space debris. [12][13][14][15] Since laser impulse generation has nonlinear characteristics, laser pulse energy is an important parameter to specify. For example, in order to obtain an impulse on the order of 0.1 Ns, which corresponds to a speed increment of 100 m/s for a 1-g mass, a laser pulse with an energy on the order of 100 J or more is required. To our knowledge, laser impulse generation under such conditions is not reported extensively in the open literature. The objective of this study is to obtain a large impulse using a 300-J class single-laser pulse and to examine the fluid dynamic confinement effects. All experimental data are obtained in air at atmospheric pressure. Experimental ApparatusThis study used a transversely-excited atmospheric (TEA) CO 2 laser with a wavelength of 10.6 mm. The power history of the laser pulse has two peaks; one with a full width at half maximum (FWHM) of 50 ns containing 12% of the total energy, and a second with a relatively-low peak power and long-duration tail; 90% of the total energy is output in 2.5 ms. The beam has a square cross-sectional area of 150 Â 150 mm with the central 80 Â 80 mm in the shadow of the mirror of the unstable resonator. The output laser beam was reflected onto plane and concave (focal length: 5 m) mirrors and then directed onto a flyer disk in the atmosphere. The effective laser pulse energy incident on the flyer disk was equal to 310 AE 20 J. The effective beam cross-section on the flyer disk was reduced to a 30 Â 30-mm square. The average fluence over the flyer disk, excluding the shadow of the resonator mirror, was equal to 480 AE 30 kJ/m 2 . The flyer disk was 42 mm in diameter and 0.5-mm thick, with a 0.5-mm thick, 4.5-mm long rim. Four flyer disk materials were examined: polyamide (PA), polyethylene (PE), polycarbonate (PC), and polyacetal (POM). Unless otherwise stated, the laser beam was directly incident on the flyer disk (the flyer disk itself was also used as an ab...

Light erosive optical discharges investigation. I. Investigation of radially confined light erosive pulsed optical discharges

“…Как известно, исследование импульсных течений га-зоразрядных процессов представляет значительный интерес для фун-даментальных и прикладных исследований [1]. Радиально ограни-ченные лазерно-индуцированные потоки используются в таких при-ложениях, как лазерное сверление глубоких отверстий [2], лазерная генерация тяги [3][4][5], увеличение выхода ВУФ-, ЭУФ-и МР-излу-чения [6][7][8], генерация ударных волн и инжекция плазмы, лазерное инициирование капиллярного разряда [9], ускорение тел лазерной волной детонации в канале с испаряющейся стенкой [10] и др.…”

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On verification of micro-nanonewton range recoil momentum evaluation techniques at solid targets laser ablation

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