摘要:

After a pulsed laser beam irradiation, the pressure behind a projectile is increased due to shock wave generated by the ablating gas, resulting in a propulsive impulse generation. This principle can be applied to orbiting space debris. As the first stage, a CO2laser beam was shot on various ablated material in the atmosphere, and projectile launch performance was measured. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1720991

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

The original purpose of this study was to address a partition of propulsive energy between air and metal, when the breakdown is initiated at the metal surface and/or in adjacent air space. Coupling coefficient as a function of air pressure varied in the range 4 mTorr – 1 atm is presented. The experiments were conducted by focusing output pulses of a TEA CO2laser system (0.2‐&mgr;s pulsewidth at 10.6 &mgr;m wavelength and ∼ 10.0 J energy) on aluminum targets. Coupling coefficients were derived from the pendulum displacements. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1720992

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

One of the advantages of laser propulsion is the possibility of controlling exhaust velocity namely specific impulse and optimization of energy and propellant usage. Characteristics of laser plasma interaction with the incident laser intensities of 107∼1010W/cm2have been investigated using multiple plasma diagnostics such as ion collector. Electron temperatures will be discussed. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1720993

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Impulse generation experiments of a liquid propellant laser thruster were conducted using glycerin propellants in the energy range of 60 mJ ∼ 60 J. Momentum coupling coefficients and specific impulses were obtained from momentum impulse and propellant mass measurements. The maximum specific impulse was 18 s at the laser beam energy of 55 J. Experimental data were scaled in terms of the laser beam energy and the diameter of the glycerin droplet to extrapolate laser thruster performance. The results indicate that the diameter of the glycerin droplet must be less than 0.24 mm in these experiments to achieve specific impulse more than 1,000 s that will be required to compete with other space propulsion systems. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1720994

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

A sequential process from pulsed laser irradiation onto a spherical liquid propellant to impulse generation is discussed toward higher specific impulse performance of the thruster. A Q‐switched 10‐ns Nd: YAG laser pulse with 1 &mgr;m wavelength was focused in a 2‐mm diameter glycerin droplet in vacuum condition (∼10 Pa). Visible image of the droplet shot with the laser pulse, laser energy transmitted through the droplet, emission spectrum in visible to near infrared region, and temporal impulse behavior measured with piezoelectric devices were obtained. It is found that the impulse generation mechanism can be divided into energy deposition on the surface and inside of the droplet, and subsequent explosion of the droplet, depending on laser irradiation conditions. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1720995

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

This paper describes hundreds of pendulum tests examining the beamed energy conversion efficiency of different metal targets coated with multiple liquid enhancers. Preliminary testing used a local laser with photographic paper targets, with no liquid, water, canola oil, or methanol additives. Laboratory experimentation was completed at Wright‐Patterson AFB using a high‐powered laser, and ballistic pendulums of aluminum, titanium, or copper. Dry targets, and those coated with water, methanol and oil were repeatedly tested in laboratory conditions. Results were recorded on several high‐speed digital video cameras, and the conversion efficiency was calculated. Paper airplanes successfully launched using BEP were likewise recorded. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1720996

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

The paper deals with the effect of electron emission on a heat transfer in the area of a plasma critical density (near plasma‐solid surface boundary). As is known, experimental data show the limitation of electron thermal conductivity in the mentioned area. In the laser fusion research just the limitation of the heat transfer at target irradiation with long‐wave lasers has made application of CO2‐lasers unreasonable in spite of their high efficiency. On other hand, as to the applied tasks of laser ablation (e.g. in launching small‐scale satellites) the aspect of the CO2‐lasers application is being widely discussed. In the paper the mentioned limitation is explained on the basis of classical representations. It is marked, that the heat transfer limitations arise from the conditions of preserving plasma quasi‐neutrality at the absorption area boundary where the electron density is close to critical one for the given laser wavelength. Possible mechanisms of the electron emission in the mode of the laser ablation are discussed. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1720997

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

This paper presents an updated review of studies on Ablative Laser Propulsion conducted by the Laser Propulsion Group (LPG) at the University of Alabama in Huntsville. In particular, we describe the newest results of our experimental study of specific impulses and coupling coefficients achieved by double‐pulsed ablation of graphite, aluminum, copper and lead targets. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1720998

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

This paper presents an updated review of studies on Ablative Laser Propulsion conducted by the Laser Propulsion Group (LPG) at the University of Alabama in Huntsville. In particular, we describe the experimental technique developed for determination of specific impulses from plasma plume imaging with an intensified CCD camera. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1720999

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Space debris constitutes a significant hazard to low earth orbit satellites and particularly to manned spacecraft. A quite small velocity decrease from vaporization impulses is enough to lower the perigee of the debris sufficiently for atmospheric drag to de‐orbit the debris. A short pulse (picosecond) laser version of the Orion concept can accomplish this task in several years of operation. The “Mercury” short pulse Yb:S‐FAP laser being developed at LLNL for laser fusion is appropriate for this task. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1721000

出版商:AIP    

年代:1904

数据来源: AIP