《航空周刊》观点：激光武器的发展已接近临界点

Opinion: Nearing A Laser Tipping Point
Laser weapons could be closer than you think
Apr 15, 2015 Bill Sweetman Aviation Week & Space Technology



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May 1977 saw the premiere of an epic tale in which an evil empire deployed powerful directed-energy weapons in its quest for total domination. Star Wars was first shown in the same month, but AW&ST’s serial scoops on the Soviet Union’s supposed development of laser-based missile defenses were a hit in their own right.

Inspired by ultra-hawkish Maj. Gen. George Keegan, just retired as chief of U.S. Air Force intelligence, the scoops suggested the Soviets were preparing to end the Cold War on their own terms. Within a few years, the Star Wars title had been co-opted for the Pentagon’s own Strategic Defense Initiative (SDI).

Talking about megawatt-class space-based lasers (SBLs) just 17 years after the first laboratory-bench laser was like expecting the Wright brothers to build a 747. SDI quickly found that only Darth Vader could make them work. Russia’s SBL program crashed along with the 80-ton Polyus spacecraft in May 1987. SDI’s impractical Airborne Laser lumbered on until 2011. The only thing of consequence that any of them destroyed was confidence in laser weapons.


Credit: Bill Sweetman/AW&ST
Today, expectations and technology have converged, and practical high-energy laser (HEL) weapons may be close to combat-ready.

New HEL weapons are smaller than the 1980s monsters, with a goal of 100-150 kw, and powered by electricity rather than rocket-like chemical systems. Modest power permits more precise optics and—in some cases—the use of commercial off-the-shelf fiber-laser sources, improving beam quality (that is, focus) and reducing cost.

Star Wars lasers were intended to hit things that missiles could not touch. The new generation exploits different characteristics: a magazine as deep and easily replenished as the fuel tank, and a low cost per shot (about $1, says Rheinmetall). The idea is to deal with targets that missiles cannot engage affordably.

A mini-UAV is a threat because it can target ground forces for artillery. It is cheaper than any surface-to-air missile, but a laser can blind it, destroy its payload or shoot it down. Rocket and mortar defense is another application. Rafael’s Iron Beam laser is a logical follow-on to Iron Dome, which is practical and affordable only because it ignores rockets that will fall on open ground; that will no longer work when weapons are guided.

Close behind the systems already shown by Rheinmetall, Rafael and MBDA—certainly not a technological leap away—is the new Gen 3 HEL being developed by General Atomics Aeronautical Systems to fit on an Avenger unmanned air vehicle (AW&ST Feb. 16-March 1, p. 30). If what we hear is correct, it combines an output as high as 300 kw with high beam quality; it can fire 10 times between 3-min. recharges; and a version might fit in the 3,400-lb. pod that Boeing designed for the Advanced Super Hornet (see photo). A bomber or a special-operations C-130 could carry it easily.

This is a tipping point, because what you can do with 300 kw also depends on what you are trying to protect. If the goal is to knock down a supersonic antiship cruise missile (ASCM), there are two problems: water in the atmosphere (which attenuates laser energy) and the fact that a damaged ASCM can still hit the target. But if the target is an evasively maneuvering aircraft, it will often be in clear, dry air; and it is enough to destroy the missile’s seeker, put a hole in the radome, even at well-sub-kilometer range or weaken the motor tube to cause a miss, even at well-sub-kilometer range.

Shooting a small, fast target is a laser’s forte, because what makes it new as a weapon is its instantaneous impact. The century-old basic air warfare problem—figuring out where the target is going to be when the bullet or missile gets there—is over.

Two laser-armed fighters in a formation could act as escorts, with 20 quick shots to defeat a pop-up threat. A bomber could penetrate the outer zone of a hostile fleet’s defenses. Countermeasures are expensive: Mostly they are meant to harden a missile, invariably adding weight.

Conversely, improving laser power and beam quality are engineering challenges, not alter-the-laws-of-physics problems. Something like a 500-kw, 2,000-lb. weapon—just over twice the weight of an internal M61 gun—would mean another tipping point for air warfare. Provided that adaptive optics can be developed to fire the laser through friction-heated air, a moderately agile laser-armed supercruiser would be a tough target, stealthy or not. A laser fighter would not need extreme agility, either to put weapons on target or to evade enemy fire.

But the near- to mid-term developments will have an impact: consider the reaction if, between now and 2020, a Chinese H-6 bomber variant emerges with a functioning, fractional-megawatt SAM zapper. It’s a lot more likely than antimissile SBLs were in 1977—and could well cause panic on a similar level.

This column was originally published in the April 9 digital edition of Aviation Week & Space Technology.

据中国国防科技信息网报道，2015年4月8日，美国通用原子航空系统公司(GA-ASI)宣布，一支独立测量小组已利用美国防部高能激光联合技术办公室(HEL JTO)提供的政府持有的诊断系统(GDS)，完成了对该公司第3代高能激光器(Gen 3 HEL)系统的光束质量和功率测量。

　　在美国防部国防高级研究计划局(DARPA)“高能液体激光区域防御系统”( HELLADS)项目资助下，GA-ASI最初发展了第1代高能激光器技术；最近接受光束质量鉴定的第3代高能激光器技术引入了大量的升级，具有更好的光束质量、更高的光电转换效率、更小的尺寸和更轻的重量，旨在演示验证可用于战术平台的可部署式激光武器系统结构。接受测试的高能激光器组装件极为紧凑，尺寸只有1.3.米×0.4米×0.5米，采用1套紧凑的锂离子电池供能，其运行时间只受电池容量限制；该组装件也是正在发展的“战术激光武器模块”(TLWM)的一个单元体，TLWM将采用灵活、可部署的系统结构，设计用来在陆基、海基和空基平台上使用，将具有4种基本型别，其输出功率分别为50、75、150和300千瓦。

　　独立测量小组是根据美国政府授予的合同要求，来对GA-ASI的第3代高能激光器技术进行光束质量和功率测量。该小组利用GDS鉴定了GA-ASI的第3代高能激光器在一系列运行功率和时间下的光束质量，其中最大连续运行功率超过50千瓦，持续运行时间超过30秒，在这些情况下该激光器均保持了卓越的光束质量。美国防部高能激光联合技术办公室官员杰克·斯莱特(Jack Slater)表示，在他们利用GDS测量过的所有高能激光器中，该激光器实现了最好的光束质量；他们对该激光器能够在输出功率和运行时间增加的情况下保持光束质量印象深刻。GA-ASI任务系统业务执行副总裁克劳迪奥·佩雷达(Claudio Pereida)表示，这些测量确认了该公司的第3代高能激光器具有卓越的光束质量。