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The experimental results on the laser-supported directed-energy "air spike" (DEAS) in hypersonic flow are presented. A CO2 TEA laser has been used in conjunction with the IEAv 0.3-m Hypersonic Shock Tunnel to demonstratethe laser-supported DEAS concept. A single laser pulse generated during the tunnel useful test time was focused through a NaCI lens ahead of an aluminum hemisphere-cylinder model fitted with a piezoelectric pressure transducer at the stagnation point.
2. Discussion of the Prior Art
In the late nineteen seventies, the Grumman Corporate Research Center, in cooperation with the NASA Langley Research Center, conceptualized an Advanced Flow Laser (AFL) and a Mixing Advanced Flow Laser (MAFL) for fleet defense against air-launched missiles and other missions. In both concepts, a high energy CO 2 laser is incorporated in a hypersonic (i.e., flight speeds greater than five times the local speed of sound), high altitude (i.e., greater than 35,000 ft. altitude) vehicle. During operation, energy from the high enthalpy ram air produces excited states in the N 2 molecules which are transferred by resonance to unstable, excited states of CO 2 constituents in the gas flowing through the lasing cavity. Carbon and water are required to be added to the lasing gas mixture, which flows through an appropriate expansion channel to produce and maintain the population inversion resulting in a 10.6 μm output (CO 2 laser). Because the laser beam intensity on target is inversely proportional to the square of the wavelength, the CO 2 laser is unsuited for missions where extremely long laser beam range is required. Moreover, this technology and approach could not be utilized below the 10.6 μm wavelength, which results in severe limitations on the extent of its practical usefulness.
SUMMARY OF THE INVENTION
Accordingly, it is a primary object of the present invention to provide a gasdynamic laser system for a hypersonic vehicle which operates in the visible or near-to mid-infrared portion of the spectrum at wavelengths shorter than 10.6μ meter down to wavelengths of approximately 1μ meter or less.
A further object of the subject invention is the provision of a gasdynamic laser system for a hypersonic vehicle wherein high enthalpy ram air provides an energy source for thermodynamic excitation of the laser gases, as well, when required, as to drive an electrical generator for electronic excitation of the lasing species.
The present invention provides a hypersonic gasdynamic laser system which overcomes the aforementioned constraints of the prior art by providing a new concept for lasing at wavelengths as much as an order of magnitude shorter than the 10.6 μm wavelength radiation generated by the CO 2 laser approach of the prior art. One advantage of the hypersonic gasdynamic laser described herein over the earlier conceived AFL and MAFL types arises from the removal of the constraint limiting the lasing to CO 2 at the relatively long wavelength of 10.6 μm. For example, a ten-fold reduction in wavelength will result in a hundred-fold intensity increase (over a 10.6 μm laser) on the target, if the product of the laser exit beam power and the square of the exit mirror diameter is maintained constant. A further advantage accrues in situations where the weight of the optical train and not the on-target intensity is the prime design consideration. The dimensions of the optics generally diminish with shorter wavelengths, thus tending to result in an overall system that is smaller and lighter weight.
Electronic excitations of atomic oxygen, nitrogen, or hydrogen can produce laser radiation at approximately 0.85 μm, 0.94-1.46 μm, or 1.88 μm, respectively in a hypersonic airbreathing propulsion system or a special lasing duct. Electronic excitation is also required in some diatomic molecule (e.g. CO) lasers. Since the amounts of electricity required are large, carrying the electrical energy in stored form (batteries, capacitors, inductors, etc.) is not practical just from weight considerations alone. In the hypersonic gasdynamic laser invention described herein, the electrical energy is produced on-board the vehicle, using ram air, or ram air plus fuel combustion, as the power source and an electrical turbogenerator (or another equivalent electrical generator) connected to a supersonic turbine. Preliminary estimates of available shaft power to the electrical generator are 2.5 megawatts per square foot of air duct frontal cross-section at Mach 7 and 30 km altitude.
The idea of creating a plasma field around an aircraft is not a new one either. Such a possibility was thoroughly studied by both Russians and Americans. This was done for very different reasons, however. Aircraft designers want to use a plasma shield generator on hypersonic aircraft. In this application, plasma may be generated by a powerful plasma laser and will act as a heat shield for an aircraft. There are plans to use such a system in conjunction with a magnetohydrodynamic (MHD) propulsion to achieve velocities up to Mach 50.
The system developed by the Russians is also based on electromagnetic wave-plasma interactions, but in a very different way. Russian stealth plasma device creates a plasma field around an aircraft. This field partially consumes electromagnetic energy of a hostile radar or causes it to bend around the aircraft, reducing the aircraft RCS by up to 100 times. Sounds fantastic? Not really: effects of dissipation and bending of electromagnetic signals in presence of plasma field have been observed for decades.
There is more. EHD coupling is also a method of propulsion as it can accelerate the boundary layer and outer flow. Working models have been constructed that utilize this method of propulsion. So in addition to having the ability to control the aircraft's aerodynamic properties you also get some extra thrust. In turn, this means that the energy you expend on creating plasma is not wasted entirely on just smoothing out the airflow. For a military aircraft, in our case, EHD methods could mean fewer control surfaces, higher angles of attack, extra thrust, greater speed and fuel efficiency, high combat survivability.
The air spike is the next design idea to show promise. An airspike has several benefits. The first is it substitutes directed energy for the mass of a nose-cone to drive the air from the plane's path (Kandebo 66:3). It uses an electric arc plasma torch placed in front of the craft. In flight, the arc uses its concentrated energy to drive air radially from the aircraft's path like a blast wave. A low density air pocket forms behind it which reduces the heat transfer effects in the aircraft and that means less stress. It does such a good job that a vehicle traveling at Mach 25 would only experience the conditions of Mach 3
Phase Three : Towards a Flapless ElectroAerodynamics UAV : Developpement of a true EHD Coanda effect and autonomous UAV which will use the knowledge and the experience aquired during the previous phases of this project.
With a such craft design, it is possible to build a dragless and stealth UAV based on the Coanda effect which uses the EHD plasma technology...
Our IHPTET demonstrator engine has successfully demonstrated Mach 3.5 operation.
We are applying our high-speed turbine engine technology to enable Turbine Based Combined Cycle (TBCC) M 6-9 propulsion systems.
The technology for the hypersonic airplane portion of the HASTOL system is being
developed by Boeing and others elsewhere and is not part of the HASTOL effort. However,
vehicle performance, flight trajectory requirements, and operational aspects peculiar to tether
rendezvous and payload transfer in support of development and optimization of the HASTOL
system are, and form a major portion of the hypersonic airplane portion of the HASTOL team
effort. The hypersonic vehicle portion of the HASTOL effort started with an existing design for
the DF-9, a multi-role hypersonic aerospaceplane shown in Figure 2. The DF-9 was developed
by Boeing for NASA Langley Research Center, to perform both long-range hypersonic cruise
missions and space launch missions. The vehicle is designed to operate from existing runways
and incorporates a low-speed propulsion system based on JP fueled, Air (core-enhanced) Turbo
Ramjets (AceTRs) for operations up to Mach 4.5 (46 kft/s or 1.4 km/s). Above Mach 4.5 a
slush-hydrogen-fueled ram/scram system powers the vehicle.
“Boeing Hypersonic Scramjet Applications”
MR. GEORGE ORTON
Program Manager, Hypersonic Design and Application,Boeing Phantom Works
• Prompt Global Strike
To look at, the test vehicle suspended in the hypersonic wind tunnel is little more than a cone. But inside is a small device that could revolutionise the way aircraft fly, saving fuel and heralding a new age of travel.
It's a generator that sends a beam of microwaves upstream into the Mach 6 flow, ripping apart the gas ahead of the model so that it is flying through a plasma--a boiling mix of positive ions and electrons--rather than ordinary gas.
Hypersonic speed will allow the FSV to reach anywhere worldwide within hours. The FSV could also be an exoatmospheric platform. The AFRL says new technologies will be considered to achieve this. "We are looking at plasma fields for high-speed vehicle propulsion," says Dolvin, adding that experimental, analytical and simulation work on plasma technologies has been performed. An X-vehicle technology demonstrator could be funded for 2005-6.
To say that Aurora is a technical impossibility is an incorrect statement – it has been technically feasible for the last 35 or 40 years.
If you were flying over a spot in the GIUK gap at Mach 6, you could do a 150 or 200 mile diameter turn – which is perfect for interdiction, because you wanted the ship or whatever you were tracking to be inside the turn. So as you banked up to do the turn, your sensors would be pointing right straight down at the ground.
In an ideal world, ament scientific and technological
research would build upon the foundation laid by past
generations of researchers. For whatever reason, perhaps
hecause of the temporal disconnect resulting from the near total
hiatus in supersonic and hypersonic research from the
early 1970s to the start of the NASP program in the mid
198Os, today's younger researchers appear to the author to
be generally unfamiliar with much of the prior work in this
arena. In this paper, some of the work performed at GASL
in the 1960-73 time frame is reviewed and appropriate
literature references supplied. It is the author's belief that
many of the problem perplexing current (younger)
investigators, were substantially resolved 20 to 30 years ago.
The hope is that this and a companion paper (ref. 1) will
serve to reconnect today's research to the earlier work done