摘要:

The progress of power laser is now opening new applications in science and industry. The laser for the inertial fusion requires the most advanced and heavy specifications, typically a few MJ in 10 ns pulse with 10Hz repetitive operation with the efficiency higher than 10&percent;. The challenge to develop such a laser include basic and generic laser and photonics technologies as power diode laser, solid state laser material, nonlinear optical material, high efficiency energy conversion between the light and electricity, high power optical beam propagation and control, heat treatment of optical components. The power laser application to space is supported by these common technologies and gives us new dreams such as laser propulsion, laser energy network in space, energy supply to the ground energy system such as electricity and/or hydrogen fuel. The technical perspectives are reviewed. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1720981

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

The recent progress in our experimental investigation on the air‐breathing mode of laser propulsion has been reported. With a high power TEA‐CO2pulsed Laser, both horizontal and vertical propulsion experiments were conducted. The energy of each pulse is 15–18J. The frequency can be adjusted from 20–180Hz. Several parabolic reflectors of aluminum alloy with different focus f were used in the experiments. A high speed CCD camera was applied to record movement variables of the reflectors. For single pulse experiments, the measured momentum coupling coefficient Cmis 27.7dyne.s/J for f=10mm, and 22.82dyne.s/J for f=15mm. For multi‐pulse experiments (frequency 50Hz, work time 0.5s), the horizontal propulsion distance was greater than 1.5m, and the vertical propulsion height exceeded 1m, but the average Cmis lower than that of single pulse experiments. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1720982

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Laser propulsion is a new concept technique of propulsion and will have important application in future space technology. In this paper, the analytic formulas for the impulse and momentum coupling coefficient based on point explosion theory have been derived by considering the restraint of the reflector. In the numerical study, a new method that combining the self‐similarity solution for point‐explosion at the first stage and the high resolution PPM mesh at the second stage, has been applied to calculate the high‐temperature plasma flow field generated by the focused laser beam. The simulated results show that the efficiency of laser propulsion, such as thrust, total impulse, momentum coupling coefficient etc are strongly related to the geometry of the reflector and the power of the input laser beam. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1720983

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Thrust generation of a laser pulsejet with a conical nozzle has been studied. An impulse imparted by a laser‐induced blast wave to the conical nozzle was measured experimentally, and the computational analyses were performed to clarify the relationship between the nozzle configuration and the fluid motion. As a result, it was found that the optimum nozzle length was predictable for given blast wave energy conversion efficiency. The impulse was quite sensitive to the divergence angle of the nozzle. This sharp decrease is mainly due to the fluid motion during the refilling stage of the engine cycle. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1720984

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

In the paper a specially designed airspace laser propulsion engine is examined at the non‐conventional laser beam input into the engine nozzle. The experiments are carried out by using of the laboratory stand and pulsed CO2laser. In the experiments, geometrical parameters of the engine and laser pulse characteristics are varied. The technique of the experiments allowed measuring of momentum coupling coefficient Cmwith accuracy of ±10&percent;. The coupling coefficient Cmwas experimentally measured and compared with Cmdetermined theoretically. The dependences of the coupling coefficient on the laser pulse characteristics and geometrical parameters of the engine are also obtained. In the paper the analysis of the flight model of the airspace laser propulsion engine is considered too. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1720985

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

This paper summaries the characteristics of in‐tube propulsion powered by laser energy. The thrust is enhanced due to confinement effect in a tube. This method has a large payload capability because the propellant does not need to be on board. Also, this has various advantages on application aspects. The performance and impulse production mechanisms are discussed based on results of laboratory experiments using 500‐W lasers. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1720986

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

For developing laser propulsion, it is very important to analyze the mechanism of Laser‐Supported Detonation (LSD), because it can generate high pressure and high temperature to be used by laser propulsion can be categorized as one type of hypersonic reacting flows, where exothermicity is supplied not by chemical reaction but by radiation absorption. I have numerically simulated the 1‐D and Quasi‐1‐D LSD waves propagating through an inert gas, which absorbs CO2gasdynamic laser, using a 2‐temperature model. Calculated results show the fundamental properties of the non‐equilibrium LSD Waves. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1720987

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Similar to the concept of pulse detonation engine (PDE), a detonation generated in the “combustion chamber” due to incoming laser absorption can produce the thrust basically much higher than the one that a laser‐supported deflagration wave can provide. Such a laser‐supported detonation wave concept has been theoretically studied by the first author for about 20 years in view of its application to space propulsion. The entire work is reviewed in the present paper. The initial condition for laser absorption can be provided by increasing the electron density using electric discharge. Thereafter, once a standing/running detonation wave is formed, the laser absorption can continuously be performed by the classical absorption mechanism called Inverse Bremsstrahlung behind a strong shock wave. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1720988

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Recently, several laser propulsion vehicles have been launched successfully. But these vehicles remained in a very low subsonic flight. Laser‐driven In‐Tube Accelerator (LITA) is developed as unique laser propulsion system at Tohoku University. In this paper, flow characteristics and momentum coupling coefficients are studied numerically in the supersonic condition with the same configuration of LITA. Because of the aerodynamic drag, the coupling coefficient could not get correctly especially at the low energy input. In this study, the coupling coefficient was calculated using the concept of the effective impulse. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1720989

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

At Tohoku University, experiments of Laser‐driven In‐Tube Accelerator (LITA) have been carried out. In order to observe the initial state of plasma and blast wave, the visualization experiment was carried out using the shadowgraph method. In this paper, dependency of initial plasma size on LITA performance is investigated numerically. The plasma size is estimated using shadowgraph images and the numerical results are compared with the experimental data of pressure measurement and results of previous modeling. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1720990

出版商:AIP    

年代:1904

数据来源: AIP