Like hypersonics, laser weapons involve boundary-pushing technology that has been in development for years. After more than two decades and billions of dollars of investment, there are still no deployed laser-weapon systems, which fall under the broad category of “directed energy weapons.” But even as expectations have fallen, some progress has been made. Gone is the 1980s vision of huge energy beams that would fell ballistic missiles in midflight, and fighters equipped with high-energy lasers still exist only in the realm of ambitious PowerPoint presentations. Currently most of the research focus is on more modestly powered beams. The Army, for example, is investing in an effort to develop solid-state lasers and says it will soon reach 100 kilowatts, about the minimum power needed to produce a deployable weapon. The signs look good that they will meet that goal; in February, the Solid State Heat Capacity Laser, built at Lawrence Livermore National Laboratory, hit the 67-kilowatt mark. DARPA is looking at more efficient technologies, like fiber lasers and liquid lasers, which could lead to smaller, more compact devices, while the Navy is researching a Free Electron Laser, an experimental technology that uses high-speed electrons to generate an extremely powerful focused beam of radiation. The Free Electron Laser is still in the lab, though, and probably will not be ready until after 2020.
The Missile Defense Agency for its part is focused more on chemical lasers, which draw prodigious energy from chemical reactions. One such device, the megawatt-class Airborne Laser currently installed on a Boeing 747, is intended to shoot down ballistic missiles. Air Force researchers are also slowly developing a less powerful chemical laser, called the Advanced Tactical Laser, designed to go on C-130H gunship. Mark Lewis of the Air Force acknowledges that even the Advanced Tactical Laser is not ready to deploy: “I’m not sure it’s even the right laser system,” he says. “Ultimately, you probably want to do solid-state [lasers].” Still, he feels that some elements of the system are providing a useful test bed for future weapons.
Despite many years of failed efforts, directed energy weapons are worth the investment, Lewis argues, because they fall into the high-risk, high-payoff category: They may fail, but if they work, they will provide a tremendous capability. “If we’re not failing a little bit, or every so often, then we’re not being bold enough in the research that we’re doing,” he maintains.
But how does the military guard against ideas that are so impossible or improbable that they’re not worth a single dime? A few years ago, DARPA, which prides itself on promoting far-out projects, proposed spending $30 million on a “hafnium bomb,” a type of nuclear weapon intended to release energy from atomic nuclei without either fission or fusion, using an approach similar to how energy is extracted from electrons in a laser. DARPA pursued the project even after outside advisory panels criticized the physics as bad science, and independent researchers were unable to replicate the basic results the research was based on. The agency abandoned the project only after Congress intervened.
DARPA, through its spokeswoman, Jan Walker, declined an interview, but Walker answered written questions. “A DARPA program can be very hard, but it can’t violate the laws of physics (or if so, have as its purpose the discovery of new phenomenology which may in fact cause the current laws to be reconsidered),” she wrote.
What Walker’s parenthetical bureaucratese appears to be saying is that sometimes DARPA will fund projects that violate the known laws of physics. So if current science can’t be used as a filter in such cases, how does DARPA decide which projects are worth funding? “The issue of ‘worth’ goes more to whether or not the proposed program will enable revolutionary change,” Walker replied.
Lewis, who has been at the receiving end of some strange research proposals, agrees that it’s not the subject per se that defines something as crazy, but the approach to it. “I have my own litmus test,” he says. “First, does this violate the laws of physics? That’s the gatekeeper.” Second, he says, is “what is the capability that it brings to bear, and is that an important capability?” By Lewis’s criteria, some ideas that seem wild are worthwhile to fund initially—as long as sponsors are willing to drop concepts that don’t appear to be living up to their promise. “For me, the difference is that the hafnium bomb violated the laws of physics, and we had lots of really smart people who said it violated the laws of physics,” he says. “Making the initial investment, one might argue, isn’t so bad,” he continues. “It’s knowing when to bail.”