He also taught controls classes at the University of New Mexico for seven years. Mark Spencer, with five years of experience past his doctorate, is primarily an optical scientist and engineer. He works at the Air Force Research Laboratory in adaptive optics where he has specialized in atmospheric transmission and compensation. The authors found that their diverse backgrounds made working together on this book very enjoyable. They would like to thank several people for their assistance in revising and improving this second edition: Matthias Banet, Terry Brennan, Richard Brunson, Stanislav Gordeyev, Eric Jumper, and Larry Sher for comments and direction; Directed Energy Professional Society editor-in-chief and publisher, Sam Blankenship, for many suggestions and much needed guidance in assembling the book; and technical editor Barbara Kohl and production editor Caroly Leyba who were excellent to work with and significantly improved the book.
Preface to First Edition Dr. Paul Merritt has worked on laser systems for 35 years, and has taught control theory at the University of New Mexico for approximately 12 years. Therefore, this book will be biased towards control theory problems and solutions as applied to laser beam control. Merritt joined the U. Air Force Civil Service in and had the opportunity to start work on laser systems for the Air Force in Merritt interrupted his civil service career in to work for Hughes Aircraft until and then rejoined the civil service until retirement in It also is limited to accessible, man-negotiable forest areas.
To improve on this manual backfire approach, helicopter approaches were developed Refs. In these, the helicopter holds a torch or a dispenser of a flaming chemical on a cable which is maintained slightly above the ground.
While this removes the man-on-the-ground safety issue, now the crew is at risk since the helicopter must fly relatively close to the ground in order to minimize the sway of the cable to allow some precision in the setting of the backfire line. This issue is exasperated because of the upwelling winds that are produced by a large fire and its smoke that may obscure vision.
In addition, the helicopter is restricted to certain airspace, away from power lines, hills, and other aircraft, and therefore its backfire cannot always be placed in the desired location. And finally, the rate of setting this backfire by the torch or dribbled incandescent chemical means is very slow, thus allowing time for the fire to spread before efficacious backfire suppression.
Herein we will show that a craft equipped with a properly configured laser system can obviate many of these shortcomings. We begin by showing three military airborne laser systems Refs. But those military systems are not suitable for the needed firefighting service since they use large, heavy, low efficiency chemical lasers which are very difficult to service in the field and also which provide much higher laser beam power than needed.
In the applications discussed herein the range and power requirements are much lower than these prior demonstrated laser systems. This allows the use of much smaller and lower weight, laser systems rather than heavy chemical lasers. Although the lower power lasers provide shorter range backfire starting capability, even with an easily achievable range capability of up to a kilometer the craft will be out of harm's way.
It also will have an excellent field of view to see the conflagration and chose the optimal backfire path to quickly set. We estimate that the times to set the foliage afire will be at least ten times faster than by the state of art burning drip means.
The will allow both backfire of treetops as well as ground fire to be easily set. David Leigh and Zrika Arni Ref. Herein we provide the laser system design approaches that would allow fulfillment of their speculation. Such capability is only assumed in their referenced work without consideration of the many requirements and design issues required for operational firefighting capable laser airborne systems as we consider herein.
In particular, the state-of-art laser system designs we will consider will be based upon the use of the electrically-driven, lightweight RELI Robust Electric Laser Initiative -class lasers Ref. Other electric-driven laser types, and perhaps others, would also suffice if they provide the desirable characteristics of the RELI class lasers. The lighter RELI weight, higher efficiency, better beam quality, and robustness for reliable operation in a severe environment, like that encountered by a fire-fighting helicopter, offer a more tolerant capability for the variety of helicopter lift capabilities that might be used for the multipurpose applications we desire.
In accordance with one embodiment, an air vehicle manned or unmanned aircraft, helicopter, or lighter-than-air ship equipped with a moderately high power laser system module, said module configured to allow quick insertion or replacement into the craft, that has a means of controlled beam pointing and tracking, is equipped with an infrared or other imaging system to allow observation in darkness or even through smoke of the nearby fire or of the laser beam target interaction, will provide a safe range and rapidly implementable means to set backfires to more quickly contain conflagrations.
In addition, there are other uses of such laser beams beyond firefighting. These include setting controlled burns and cleaning of dust from high tension equipment.
Replacement of the laser module with a state-of-art water or chemical holding tank would allow the aircraft to perform that conventional mode of firefighting. Of course it would also enable agriculture fertilizing or chemical pest control spraying. Their modular exchange capability would allow these aircraft to carry out these and many other tasks throughout the year even outside the usually short month fire season.
This would enhance the modules' financial benefit. Advantage The details of one or more embodiments of the invention are set forth in certain of the accompanying drawings and their description below.
Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. In these, closely related figures have the same number but different alphabetic suffixes. Its tank refill hose is Payloads are supported by the cable It directed its beam to targets using its beam director 20 mounted atop its fuselage. An adjacent aerodynamic foil 22 minimized its wind buffeting.
It was equipped with innovative beam control technology, including 24 , a nose-mounted telescope and 26 , a laser ranger mounted atop its fuselage. In late the ABL fulfilled its demonstration goal to be the first laser equipped aircraft to destroy a distant, fast-moving, theater ballistic missile in its boost phase.
It was decommissioned in As seen it used a third method of mounting its beam director 28 , on its belly. Before its decommissioning ATL demonstrated the ability to hit and combust ground based targets. Note that this drawing is not to scale. Note that the relative subassembly dimensions are not to scale although the overall laser system envelope is to scale relative to the aircraft's scale.
Note the counter-rotating helicopter blades for stability and lift. A typical tank effluent plume is shown. S Marine program. The stability of this dual rotor helicopter bodes well for supporting a spin-stabilized laser system module in this fashion. One embodiment of the invention is illustrated in FIG. This helicopter is now manufactured by Erikson Air-Crane, Inc. Simplex Aerospace, Portland, Oreg. To allow for interchange of this tank for other modules, allowing dual use capability of the aircraft, the tank 34 is quick-clamped by hydraulic fittings 36 in FIGS.
Our embodiment uses this same holding method developed by Simplex Aerospace, thus allowing the dual use scheme they perfected for their chemical tank to be used for our laser system module chamber. The operational aspects of the backfire setting aircraft mode, shown here with an intense focused laser beam 38 impacting targets 40 such as treetops or ground foliage 40 L and resulting fire 40 R , will be discussed later when we complete identification of the major laser system equipment elements.
The latter is very large since it can even transport things like houses held from the helicopter's cables. In the embodiment figures shown we have assumed the laser module box 34 to be about 5 m As reference, the aircraft is Note that other helicopters with less or more capability may also serve to carry other laser system modules for the firefighting service we claim in this embodiment.
Alternatively, some of that higher weight capability could be used to increase aircraft fuel capability and hence the range and time in the air before needing to refuel. Such trades between margins for the carrier and the laser system load are common for those familiar in the laser weapon systems trade Ref. Below, as the laser subsystem assemblies are discussed, similar trades are encountered. In the embodiment discussed here, 34 is the typical laser system LS module which will be more fully discussed below in FIG.
Note the rear protrusion 42 from the module, in FIGS. This is the laser beam director assembly which contains the optics that directs the laser beam to the target area where the laser-induced backfire is to be set.
This particular commercial unit 42 contains many components and subassemblies as seen in FIGS. In FIG. After passing through the input window 74 , the beam enters the set of optical elements in the Beam Control Assembly As its BCA name implies, these optics precondition the optical beam for its path ahead so that is arrives with desired good focus and with little jitter and beam wander away from its desired point of impact on the treetop or foliage.
We will do this for other boxes seen in FIG. There are many manufacturers like MZA Associates that sell such subassemblies designed to customer specifications. This series of five mirrors accomplishes an important task, namely to keep the forward moving laser beam aligned with the turret axis, from whence it began, to now as it leaves mirror 66 , even as the turret assembly 42 is rotated about its axis using the rotational bearing assembly There is a second rotation angle EL, the elevation angle also seen in the figures.
This corresponds to the rotation of 68 the spherical shell that holds the telescope's secondary mirror 62 and primary mirror In the figure the EL angle is 0 degrees and the beam leaves the shell though its output window 44 moving along the turret axis. If the operator commands it to move 90 degrees, the beam would move orthogonally out of the plane of the figure.
Clearly the operator has a wide range of beam direction angles that are at his control by rotating the turret about its axis combined with a rotation of the telescope's shell.
However it is written into the controller's real time control software, instructions for the laser beam to cease whenever an angular choice would have the beam strike the aircraft, its landing gear, or any other than the desired treetop or foliage.
Another aspect of the telescope is its ability to expand the beam's diameter and to focus that expanded beam onto the distant target. The SLBD was later modified to utilize shared aperture tracking.
Note the red autoalignment beam was injected into the center of the high-power beam instead of surrounding the beam as had been used in the APT and the NPT. The SLBD successfully demonstrated the benefits of using an IRU labeled Gyro Reference Package in the figure for beam stabilization; the problems of structural resonances in the beam expander were minimized.
It also successfully demonstrated shared aperture tracking and tracking of highly dynamic flying targets. In , the SLBD demonstrated the acquisition and active track of a boosting missile. This was one of the demonstrations required by the DoD prior to approving the plans for the airborne laser system. The techniques of active tracking, e. Figure 15 shows three different images acquired during active tracking of a boosting missile.
The IRU concept of the SLBD was included in the beam-control system, but the small stable platform was placed behind the primary mirror where the structure was. In February , the ABL successfully engaged two boosting missiles.
However, the program was scaled back in and the aircraft was sent to the long-term storage facility at David-Monthon Air Force Base outside of Tucson, Arizona, in These systems used beam-control approaches already discussed in this paper.
The six beams are incoherently combined at the target. Instead of routing the HEL beam through a beam path in the beam directors gimbals, the output fibers from the six lasers were brought directly to the output telescope. Future laser systems built with fiber lasers may include coherently combined beams from fiber lasers.
A squarelaw increase in far field irradiance, instead of incoherent combinations linear increase, can be obtained. References Fig. There were two adaptive optics systems, one to clean up the outgoing beam and one to compensate for the atmosphere. There were two illuminators used in the ABL, one for a beacon return for the correction of the atmosphere, and one for flood illumination to track the target.
A schematic of the ABL beam train is included as Fig. Perram et al. Paul H. His work primarily involved analysis and testing of the control systems. He then taught control theory classes at the University of New Mexico for seven years. He has written many papers on laser beam control and contributed chapters to three other books on laser systems. He now works part time for Schafer Corporation. John R. Albertine has a BS in physics from Rose Polytechnic Institute and a masters in applied physics from Johns Hopkins University with research in satellite navigation.
He began working with precision tracking, optical propagation, and high power lasers in the early s while at the space division of Johns Hopkins Applied Physics Laboratory.
In , he joined the Navys High Energy Laser Program Office where he led the development, integration and test of the first. He retired from government service in and began independent technical consulting for the defense department. He has been a technical advisor to the high energy laser joint technology office for over 10 years and chaired the independent review team for the AirBorne Laser Program.
He is a fellow of DEPS. Pular no carrossel. Anterior no carrossel. Merritt Enviado por Suman Basak. Denunciar este documento. Fazer o download agora mesmo. Salvar Salvar Merritt para ler mais tarde. Pesquisar no documento. Merritt John R. Using the subscript 0 for the unjittered beam, and the subscript b for the jittered beam, 2b 20 2j : 6 Strehl ratio terms are obtained for many of the components of the pointing and tracking beam, like the local loop jitter, the device jitter, and the tracking jitter, and then multiplied by the ideal on axis irradiance to estimate the time averaged on-axis irradiance.
The higher-order Strehl is calculated by measuring Fig. Their purpose is to generate an electronic image of the target and send it to the Fig. Optical Engineering They both had four gimbals: coarse azimuth and elevation gimbals for large angular coverage plus fine azimuth and elevation gimbals that were inertially stabilized using gyros.
Optical Engineering There were also test flights that removed the output window from the APT to see if the airflow around the turret would permit propagating a beam without using the window. The IRU concept of the SLBD was included in the beam-control system, but the small stable platform was placed behind the primary mirror where the structure was Fig. Optical Engineering 1. Documentos semelhantes a Merritt Eric Sun. Siti Nadiah.
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