摘要:

Modern progress of laser propulsion is highlighted with considerable developments in both design of state‐of‐the‐art laser propulsion engines (LPE) and understanding of their possible applications for launching satellites and in‐space missions. LPE are characterized by efficiency of 20–40 &percent; and specific impulses from 103s for systems utilizing shock waves with fluid propellants and up to 4×103s for ablative laser propulsion. These systems can be used for both long‐term vehicle space missions and short‐term missions on near‐Earth orbits. In a view of these developments, the paper opens a discussion for a possible in‐space laser propulsion demonstrator (ISLPD) mission, which can be accomplished in the nearest future. Technical requirements for ISLPD implementation will be presented. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1721001

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

We show that perfect propulsion requires a constant momentum mission, as a consequence of Newton’s second law. Perfect propulsion occurs when the velocity of the propelled mass in the inertial frame of reference matches the velocity of the propellant jet in the rocket frame of reference. We compare constant momentum to constant specific impulse propulsion, which, for a given specification of the mission delta V, has an optimum specific impulse that maximizes the propelled mass per unit jet kinetic energy investment. We also describe findings of more than 50 &percent; efficiency for conversion of laser energy into jet kinetic energy by ablation of solids. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1721002

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Advanced Space Propulsion‐Investigation Committee (ASPIC) of the Japan Society for Aeronautics and Space Sciences (JSASS) selected the Laser Orbital Transfer Vehicle (LOTV) project for development of non‐chemical space propulsion systems that have a capability to sustain expanded human space activities in the 21st century. This talk is presenting an analysis of the laser propulsion researches made within the frames of the ISTC Project &mesh; 1801 as applied to the LOTV Project. The study includes the development of techniques for low‐thrust maneuvers of the spacecraft to achieve geostationary orbits. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1721003

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Laser‐powered lightcraft systems that deliver microsatellites to low earth orbit have been studied for the Air Force Research Laboratory. One result of this Study has been discovery of the significant influence of laser wavelength on the power lost during laser beam propagation through Earth’s atmosphere and in space. Here, energy and power losses in the laser beam are extremely sensitive to wavelength for earth‐to‐orbit missions. And this significantly affects the amount of mass that can be placed into orbit for a given maximum amount of radiated power from a ground‐based laser. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1721004

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

A proposed development program for the heat exchanger thruster and a parallel program for other key elements of a laser launch system are described. The HX thruster will be tested with different working fluids (hydrogen, helium, nitrogen, water) and power sources, and at scales from a few kW up to megawatts. Subscale launch vehicles can be tested with a variety of existing lasers, including LHMEL II and MIRACL. Laser and system development is simplified by designing around a “beam module” containing a modest‐power laser and beam director, which can be replicated to produce any desired total power. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1721005

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Laser propulsion offers the potential to become a competitive alternative for the rapid, efficient transport of small satellites from ground into low earth orbit. Based on recent laser propulsion experiments in our laboratory at DLR we studied the mission characteristics for a 50 kg satellite launch. This comprises reflections on the available or required laser power, the transition of the lightcraft through the atmosphere, the laser range, the transmissivity of the atmosphere for the laser radiation, the turning of the vehicle for final orbit insertion and some general restrictions to the launch site. Finally we present a roadmap for the development of a commercial laser propulsion based launch system for nanosatellites in Europe. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1721006

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

The work deals with the laser application for extending the life‐time of small‐scale satellites launched with lasers into a low‐altitude earth orbit. The required laser powers and the substance for laser ablation are discussed. It is demonstrated that for lack of needed laser ablation substance on the satellite higher requirements are imposed on the velocity of laser ablation products exhaust . As a result, the laser power consumption prove to be higher than in optimal (on laser energy expenses) conditions of acceleration of a moving body. At the same time the high laser energy consumption can be quite justified by extension of the operation time of high‐cost equipment on the satellite. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1721007

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

The peculiarities of laser radiation delivery to a space vehicle in the concept LOTV which are concerned to the introduction of a lead angle is considered. It is shown that the use of direct phase conjugation of radiation of a laser beacon beam placed on a space vehicle does not provide a required degree compensation of the radiation phase distortions caused by the turbulent atmosphere. Two‐circuit adaptive laser system for high — power radiation delivery is offered in this case. In the system the processes of registration of the information about atmospheric distortions and formation of radiation are functionally partitioned. A key element of the system is a hologram — corrector being phase analogue of distortion occurring in the laser beam path between the system and lead point. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1721008

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

In the context of LOTV Mission (Laser Orbital Transfer Vehicle) the analysis of laser beam delivery efficiency has been carried out for power beaming with a 200‐kW‐solid‐state laser from an aircraft to a space “tugboat” having a beam receiving collector of 10‐meter‐size. Application of nonlinear‐optics and adaptive optics techniques of laser beam control for correction of optical distortions in the propagation path caused by vibration and thermal deformation of optical elements as well as by atmospheric turbulence is discussed. Possible architecture of laser beam transport systems including a laser beacon on the receiver, a repetitively pulsed solid‐state laser in MOPA‐PCM configuration and a beam director telescope of 1‐meter size is considered. The results of computer simulation of a MOPA‐PCM system as well as the system as a whole are presented. The requirements to optical elements of the system are discussed. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1721009

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

In the scope of the LOTV concept optical problems have been considered of a laser power transport from an airborne laser, flying at a 10‐kilometer altitude, to a space “tugboat” with a laser propulsion engine (LPE), intended for payload orbital transfer from LEO to GEO. For a transmitter telescope size of 1–1.5 m the range of optimal sizes of a receiver collector as well as the range of optimal specific impulses of LPE have been determined for the radiation wavelength of 0.5 &mgr; and 1 &mgr;, and payloads of 3–5 t. The optimization was carried out by searching a trade‐off between propellant mass saving and the orbit transfer time reduction. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1721010

出版商:AIP    

年代:1904

数据来源: AIP