A fighter jet is soaring through unfriendly skies when its sensors detect a hurtling, incoming missile.
Within seconds, a pod on the fighter activates and shoots out a high-energy laser that destroys the threat.
This isn't the stuff of science fiction. It's the U.S. military trying once again to turn a 50-year-old vision into reality.
Spurred by advances in laser technology, as well as the evolving capabilities of potential adversaries, defense firms are developing laser weapons systems, ranging from aircraft armed with a high-energy laser to attack ground targets to countermeasures to protect future fighter jets from missiles.
In August, Northrop Grumman Corp. won a $39-million contract to build the beam control system for a laser countermeasure project called Self-Protect High Energy Laser Demonstrator, or SHiELD, spearheaded by the Air Force Research Laboratory at Kirtland Air Force Base in New Mexico.
The advanced technology demonstration will determine whether high-energy lasers can disable or destroy missiles shot from the ground or the air more effectively than current countermeasures, which use lower-powered lasers, electronics and decoys to fool the missile, said Richard Bagnell, SHiELD program manager.
In addition to the beam control system, which will be partly developed at Northrop Grumman's Redondo Beach campus, the demonstration system will include a laser and its housing structure.
"We believe that lasers have matured ... to the point where we can package those lasers in a system that can fly on an aircraft and survive the environment and operate as needed for us to defeat the threat," Bagnell said.
But similar hopes have been repeatedly thwarted by the limits of physics, since the first working laser was built at Hughes Research Laboratories in Malibu in 1960.
So far, no one has perfected a system that produces a beam powerful enough to burn through atmospheric disturbance, and then through metal, at great distances, without requiring huge machinery and vast amounts of energy.
That was the case with the last high-profile attempt to put an offensive laser on an aircraft, the so-called YAL-1, which was supposed to shoot down ballistic missiles during their ascent using a large laser mounted in the nose of a modified Boeing 747.
The YAL-1's chemical oxygen iodine laser created energy through reactions caused by mixing chemicals. That technology can create powerful beams, but the chemicals were caustic and the system required huge storage, cooling and power systems.
The YAL-1 destroyed a ballistic missile in a 2010 test off the coast of Southern California, but the program was canceled a year later.
Then-Defense Secretary Robert Gates, who had already cut off plans for a second aircraft, succinctly summarized the program's shortcomings in a congressional hearing:
"I don't know anybody at the Department of Defense … who thinks that this program should, or would, ever be operationally deployed. The reality is that you would need a laser something like 20 to 30 times more powerful than the chemical laser in the plane right now to be able to get any distance from the launch site to fire," he said.
The laser's useful range was so short it would need to orbit "inside the border of Iran" to shoot down a missile, Gates pointed out.
But advances in solid-state lasers have once again raised the Pentagon's hopes. In a solid-state laser, electrons in a solid material, such as a crystal — rather than a gas or liquid — are energized to emit photons, which are amplified to produce the beam.
The Air Force is looking to develop an offensive laser weapon system for its AC-130 gunship aircraft to be test-fired by the end of the decade on ground targets, such as vehicles or buildings. San Diego-based General Atomics is one of the companies interested in working on a laser for the system, and has been developing a prototype.
And the Missile Defense Agency is looking into a long-endurance drone prototype that could be armed with a laser and fly at high altitudes to minimize the atmosphere's effect on the beam.
"If you look across these technology efforts, it looks like within the next four to five years, there will actually be prototypes," said Mark Gunzinger, senior fellow at the Center for Strategic and Budgetary Assessments, a defense research institute.
The Northrop Grumman program would use lasers to defend an aircraft from enemy missiles.
Interest in laser countermeasures dates back at least to the Vietnam War, when U.S. helicopters were being shot down by shoulder-launched missiles, said Dave Rockwell, senior analyst at the Teal Group.
In response, helicopters were equipped with infrared countermeasures, such as wide-angle heat lamps, to distract heat-seeking missiles from the aircraft. Over the years, fighter jets have countered heat-seeking missiles with flares, though those became less effective as missile technology improved to work on two different wavelengths.
Analysts say lasers have a number of advantages as a countermeasure system. They can be more precise than traditional methods and are less expensive to use.
"You don't have to spend money on some sort of defensive weapon," said Loren Thompson, military analyst at the Lexington Institute, a think-tank based in Arlington, Va. "It's just a beam of light."
Today's solid-state lasers use materials like a thin disk or fiber optic cable and mirrors to produce a coherent beam of light. That allows for a more compact weapons system that can fit on smaller surfaces, like fighter aircraft, said Gunzinger.
But there are still a number of challenges.
Lasers lose power the farther their beam has to travel through the atmosphere. Their efficiency decreases when they have to beam through rain, smoke or dust.
A laser countermeasure system also needs to be compact and aerodynamic.
That's an issue Lockheed Martin Corp. tackled recently in creating a prototype laser turret that could fire a laser in all directions. The defense company first started working on the idea in 2008 and developed the project for the Defense Advanced Research Projects Agency, or DARPA, and the Air Force Research Laboratory.
The turret utilizes mirrors to ensure the laser beam can get through the atmosphere and hit its target. When it's not in use, the structure can be stored in one of the plane's weapons bays, making it flush to the aircraft and minimizing air turbulence, said Paul Shattuck, director of Lockheed Martin's directed energy programs in the space systems division.
The turret, installed on a business jet for test purposes, went through more than 60 flight tests in 2014 and 2015.
"We're going to be operating in an environment where there are substantially more threats than there have been in the past," Shattuck said. "The need for self-defense systems … is going to become more and more important."
The beam control system Northrop Grumman is developing for SHiELD will monitor atmospheric disturbances, find and track incoming missiles and then shape and focus the beam on the target — all while the aircraft flies as fast as supersonic, said W. Mark Skinner, vice president of directed energy at Northrop Grumman Aerospace Systems, in a statement.
The SHiELD system will go through ground and flight tests with a lower-powered stand-in laser around 2019, Bagnell said. Once the actual laser is developed, it will be united with the rest of the system for ground and flight tests in 2021.
Whether the system actually makes it into future fighters depends on whether it overcomes the familiar hurdles of cost and effectiveness.
"There are plenty of challenges to go around, all of which we believe we have a pretty good handle on at the moment," said SHiELD's Bagnell.
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