摘要:

I have taken the title of this talk from the title of a wonderful book of prophesy written in 1929 by the great x‐ray crystallographer J. D. Bernal. His scientific work laid the basis for the discovery of the double helix structure of DNA. His prophesy in this tiny 81 page book has had a great impact on my thinking. My remarks are an update divided into the same three parts, which constitute the main chapters of his book. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1582091

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The early years of laser propulsion were driven by the vision of Arthur Kantrowitz and his team of researchers at the Avco Everett Research Laboratory. The pioneering research continued during the 1970s both at Avco and Physical Sciences Inc. (PSI), a company founded by Avco scientists. This paper presents the results of the experimental and theoretical research that was the precursor for much of the work that was done in the 1980s and 1990s. The successes are presented as well as the failures, and the enthusiasm of the early days is discussed, as well as the matching realization that the limiting factors for progress in the 1970s were the progress in laser development and the identification of missions for such systems. All this set the stage for research activities of the 1980s that were carried out by subsequent believers of the Kantrowitz vision. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1582092

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

In the spring of 1986, a Workshop on Laser Propulsion was held to discuss the feasibility of using large free electron lasers to launch payloads into Earth orbit. This workshop kicked off a four‐year program, supported by the U.S. Strategic Defense Initiative Organization (SDIO), to develop laser propulsion technology. This talk reviews the concepts addressed by the SDIO Laser Propulsion Program, and the results of both modeling and experiments on double‐pulse planar ablative thrusters, which remain a promising approach to laser launch. Other program topics to be discussed include trajectory and system modeling, and air‐breathing thruster and vehicle concepts. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1582093

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Systems studies initiated by NASA HQ in 1991 confirmed that important new missions can be implemented by ground‐to‐space laser power beaming. Large near‐term space development opportunities can be enabled by fast, efficient and relatively inexpensive transportation of massive payloads from low earth orbit to any location in cislunar space. Early development of a permanent lunar base would be made feasible by this capability. Near‐earth objects up to 20 meters in diameter could be captured and maneuvered into useful orbits. All key technology requirements were quantified by our studies, and several research and development efforts were funded. The present paper will review the overall rationale, discuss tradeoff issues and quantify system requirements. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1582094

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

This paper presents a brief history of the laser lightcraft research and development project that lead to the first outdoor free‐flight demonstrations for the U.S. government on November 1997 ‐ using the 10 kW PLVTS CO2 laser at the High Energy Laser Systems Test Facility (HELSTF), White Sands Missile Range (WSMR), NM. Summarized herein are some of the technological milestones that brought the Lightcraft Technology Demonstrator (LTD) concept vehicle to its present state of development: 1) from the initial LTD conceptual design, systems integration, and performance analysis for the Strategic Defense Initiative Organization (SDIO); 2) through laboratory engine bench testing, indoor wire‐guided and vertical free‐flight testing phases under contract to NASA and the USAF; and 3) finally resulting in outdoor flights to the current record altitude of 71 meters (233 ft) on 2 October 2000, sponsored by the Foundation for International Non‐governmental Development of Space (FINDS). © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1582095

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

A laser propulsion technology program was conducted between 1977 and about 1987 at the NASA Marshall Space Flight Center. The project ended in about 1987, when the high power laser failed. In addition to the experimental activity, several contracted efforts, mostly aimed at modeling the physics of laser‐plasma interactions, are briefly described. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1582096

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

This paper describes the status of laser propulsion research and related studies in Japan. Japan covers wide range of laser propulsion research including from ground launching to orbital transfer applications. The current status of Japanese laser propulsion is introduced and the elemental studies of Tohoku University, National Aerospace Laboratory, University of Tokyo, Tokai University and Institute for Laser Technology are presented. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1582097

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Activities related to laser supported propulsion concentrate on investigations of the fundamental phenomena arising from the interaction of high‐power CO2laser pulses with a simple bell engine. Breakdown dynamics, plasma, and lightcraft accelerations are carefully measured using optical and laser diagnostics. In a first‐order approach the expanding plasma can be described by the point explosion model with counterpressure. Wire guided vertical flight experiments in the laboratory have been undertaken and analyzed. Comparative impulse measurements in ambient air and ablated material are presented for a series of experiments performed either at atmospheric pressure or at reduced pressures down to vacuum. Impulse coupling coefficients, average exhaust velocities,specific impulse, and jet efficiencies are derived from the experimental data. The repetitively‐pulsed CO2laser device used in all experiments shows a potential of achieving 50 kW average power. Finally, long‐term perspectives of laser propulsion will be addressed. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1582098

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Energy conversion efficiency in the Repetitive Pulse Laser Thrusters has been studied. Whole conversion processes are divided into two processes; Energy conversion from the laser energy to the blast wave energy and conversion from the blast wave to impulse. The fraction of laser energy that is converted into the blast wave energy was deduced to be 50&percent; by visualizing the blast wave motion. A simple model has been proposed to estimate the impulse from the blast wave energy, and it has been validated by the experimental results. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1582099

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

We studied the vertical launch performance of the Laser‐driven In‐Tube Accelerator (LITA). This device is primarily characterized by accelerating a projectile in a tube. Owing to the confinement effect, the thrust performance is enhanced. The driver gas can be specified and its pressure be turned so that the impulse performance is optimized. In the experiments, a 3.0‐gram projectile was vertically launched. The effects of the projectile exit condition, the laser beam incident direction and the driver gas species were experimentally studied. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1582100

出版商:AIP    

年代:1903

数据来源: AIP