By David A. Fulghum
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Electronic warfare is becoming less a science of developing new technologies and more a process of sensor fusion, target networking and finding new ways to manipulate existing tools of the trade. A case in point--lasers and high-power microwave devices long have been eyed as competing directed-energy attack options. However, researchers are now combining the two to produce smaller, cheaper, more powerful, nonkinetic weapons. Electronic attack has taken a new path as well, shifting from covering enemy emissions with noise to finding, penetrating and exploiting enemy networks from low-power cell-phone networks to sophisticated air defense systems. The following articles explore some of those changes.
High-power microwave weapons may be on the verge of a high-speed turn toward the practical.
An advanced concept, pioneered by BAE Systems' researchers, uses light to multiply the speed and power at which HPM pulses--powerful enough to destroy enemy electronics--can be produced without the need for explosives or huge electrical generators.
Researchers predict leaps of 10-100 times in power output within two years. That advance could push the beam-weapon technology far beyond the 1-10-gigawatt limit of current tactical-size HPM devices. Long-standing industry estimates are that it would require a 100-gigawatt pulse for a few nanoseconds to disable a cruise missile at a useful range.
BAE Systems is not alone in the chase. Northrop Grumman and Raytheon are also building distributed array radars that can produce air-to-air and surface-to-air HPM weapons effects, contend longtime Pentagon radar specialists. In particular, the F-22, F-35, F/A-18E/F and newest F-15 radars are designed to accept modifications that would focus their beams to produce HPM energy spikes powerful enough to disable cruise, anti-aircraft, air-to-air and emitter-seeking missiles. Germany's Diehl is developing suitcase-size HPM devices that could be placed surreptitiously in a target building to damage electronics such as computers.
In addition, the U.S. military is giving classified briefings on the threat of HPM weapon technologies being developed in China and Russia. The Russians are believed to be developing radio-frequency microwave weapons for air defense, and the Chinese are developing HPM and electromagnetic pulse weapons for information warfare.
However, BAE Systems researchers claim they have made a singular leap in HPM weapons technology by combining the use of lasers and radar-like microwaves. Furthermore, the technology is scalable through the use of 4-in.-square arrays, each an integrated structure of dielectrics and electrical conductors. One hundred of them distributed over a square meter, for example, can generate up to 10 gigawatts of power, says Robert D'Amico, BAE Systems' director of advanced programs.
"We have shown everything we claimed with a laboratory testbed," says Oved Zucker, director of photonics programs for BAE Systems' advanced concepts facility here. "We are in the process of demonstrating total power substantially above 10 gigawatts, and we have plans to test [the system] further in an airborne mode.
"The power bandwidth product--how much power and how fast you manipulate it--is potentially the largest of any technology around. Having the bandwidth with larger power is where the money is," he says. There's no dearth of missions for HPM technology, including detecting and detonating improvised explosive devices, finding suicide bombers or hidden explosives, and attacking shoulder-fired anti-aircraft missiles.
There's also the appeal of weapons that can rob a foe of communications, power and mobility--while largely eliminating collateral damage to people and structures--which is a high priority for the U.S. military.
The development of HPM weapons has been hobbled for the last 30 years by seemingly intractable cost, size, beam-control and power-generation requirements. Tests of modified air-launched cruise missiles carrying devices to produce explosively generated spikes of energy were considered big disappointments in the early 1990s because of an inability to direct pulses and predict effects. New active electronically scanned array (AESA) radars can jam emitters or possibly cause damage to electronic components with focused beams. But power levels and ranges are limited by aperture size.
BAE Systems' photonically driven technology could open the way to much smaller and more powerful electronic jammers, nonkinetic beam weapons for cruise and anti-ship missile defenses, and stealth-detecting sensors.
"You could put a [sensor] system on a fighter-size aircraft that could generate enough power, with a 1-ft. resolution, to see stealthy objects at 100 mi." D'Amico says. "You can defeat stealth with enough power. If stealth takes the signature [of an aircraft or missile] down a factor of 10, you have to increase the [sensor's] power by a factor of 10." Most current fighter-size radars have less than a megawatt of peak power. Detecting stealth would require tens of gigawatts, which is now impossible in fighter-size packages.
What effects can HPM produce as an electronic warfare weapon?
"At one end, it can fry anything [electronic] that's out there," Zucker says. "The levels of EW extend from the sledgehammer to just making the [computer's] brain a little bit befuddled so it can't think for a moment. At a lower level, you can kill the detector of the other guy's radar as part of the suppression of enemy air defenses. You don't need much power because you're going after the most sensitive part. You're blinding the system."
The level below that is to momentarily stop electronics from functioning. A radar will try to defend itself by using a chain of circuits to "blink," and thereby shut out intruding signals. One method of exploitation is to do something during the blink. But if an intruding signal is fast enough, the radar can't react in time to keep out the invader.
"You can put energy in there and it won't be able to respond," Zucker says. "Another low-level effect is to make the computer skip bits so that it's not processing efficiently for the moment. All these games have to do with how much power [can be applied] and how fast."
BAE researchers envision HPM pulse weapons that are powerful enough to disable a tank, a missile, perhaps a helicopter or aircraft, but at the same time are small and light enough to function as part of a microwave radar sensor designed into the skin of an aircraft.
Alternatively, the HPM weapons could be scaled up to shipboard size--perhaps 100 sq. meters--to produce terawatt-size energy pulses. That's theoretically a large enough energy spike to stop another ship.
"You kill the brains by aiming at the bridge area because of all the computers and control systems there that run the ship," Zucker says.
This brute-strength scaling up of the technology involves installing a distributed array on the side of a ship. The elements would work together to form a large virtual antenna and then pull enough power from the ship's electric engines to concentrate a beam on vulnerable areas. From a few hundred yards, predictions are that the energy spike--focused in a beam several feet wide--could disable all the electrical equipment, including propulsion, leaving the ship a darkened, drifting hulk.
Researchers have some unusual techniques in mind for the associated antenna arrays.
"We are integrating a large number of transverse electromagnetic [TEM] apertures," to produce the distributed transmitter arrays, he says. "To produce a large number of TEM antennas is sensible only if you can make each one sing to the same tune through this coherence [or synchronization] that comes from using [the speed of] light. That allows us to spread the source [of HPM pulse production] across the whole wing of an airplane. Moreover, TEM doesn't have a cutoff frequency, which gives us flexibility."
Because the high-speed switches modulate the HPM, they match the circuitry to the antenna. Composite skins for fuselages could have the conductors and switches built into them. At the moment, BAE is looking at new, 20-cm.-thick aircraft wings, tapered at the leading and trailing edges, with imbedded antenna structures instead of using a bolt-on system.
"That is my radiator, and it is a phased array," Zucker says. "It can be a radar, communications, receiver or HPM transmitter. The wing is the source with more gain than any aperture that's been available before. I don't have to pump the energy through wave guides. More area means more power and gain. Instead of megawatts, we're talking about gigawatts of peak power."
Researchers say the antennas, photoconductive switches and transformer blocks can be built into conformal skins for unmanned combat aircraft as well. Unmanned designs are favored initially because of the vagaries in distribution of HPM side lobes, the effects of HPM on humans, and the disturbances that energy spikes can create in fly-by-wire flight control systems.
Zucker also is designing fly-by-light flight control systems for UAVs. With fly by light, actuators are triggered by simple blobs of light that can't be disrupted by spikes of electrical energy produced by the aircraft's payload.
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28-10-2007, 15:56
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