This post is a follow-on to a previous article, The Challenges of Missile Defense. As discussed, the current interceptor-based missile defense solutions have cost, deployability and performance limitations that will be difficult to overcome. Their usage of relatively expensive interceptors mean that these interceptor-based systems will continue to grapple with issues stemming from cost as well as complexity. As such, this article will examine the missile defense potential of the laser, which could supplement missile-based interceptors and provide unique capabilities. A subsequent article will address the railgun.
Lasers (Directed-Energy Weapons)
When most people think of lasers, they likely imagine weapons from Star Wars or other science-fiction media. However, laser weapons systems have already exited the realm of fantasy and entered the realm of reality. Of course, this was an inevitable development. Lasers, referred to as directed energy weapons (DEWs) in military circles, are a natural evolution of weaponry, harnessing energy in a pure form. Basically, a directed energy weapon emits a brief pulse of energy towards a target, with effects varying based on the intensity and type of energy. While simple in theory, these weapons have been notoriously difficult to develop for operational use.
Most military DEWs emit energy in the electromagnetic (EM) spectrum. The type of energy varies based on the application. Some DEWs, such as the non-lethal Area Denial System (ADS), use microwaves to produce their effects. Indeed, ADS functions based on the same principle as a microwave oven: it essentially cooks targets in order to incapacitate or inflict pain upon them. Various military directed energy weapons operate in other bands of the EM spectrum. For example, most defensive lasers, such as the YAL-1 and the LaWS, operate in the infrared spectrum.
DEWs have many advantages over a normal missile-based defense system. The most crucial are operating costs and the ability to fire repeatedly with little resource consumption.
Current missile defense systems are exceedingly costly. One SM-6, a high-performance missile used by the US Navy to engage aerial targets, costs around $4 million dollars (far more than most citizens will earn in their lifetime). If the US Navy was to purchase 20 SM-6s for each Ticonderoga-class cruiser and Arleigh Burke-class destroyer in service, the total bill would be upwards of $6 billion dollars, enough to fund the Malaysian military for more than a year. For every SM-6 fired in combat or in exercises, another $4 million must be spent to procure a replacement, as missiles are always single-use weapons. This critical cost issue hampers procurement and deployment of these interceptor-based systems, especially for cash-strapped militaries. While some anti-missile interceptors are more affordable, this comes at the price of reduced performance, and even the cheapest interceptors cost hundreds of thousands.
High-powered military DEWs could offer a solution to this cost issue. A single DEW burst costs a few dollars in fuel, literally millions of times cheaper than using a missile to engage the same threat. Thus, DEWs could potentially tip the economic scales in favor of missile defense for the first time: the cost of procuring a missile will be, without exception, greater than the cost of eliminating one with a DEW. This could mitigate some of the advantages of saturation and swarm attacks, which rely on quantity of munitions expended to overcome an adversary’s (often more sophisticated) defenses. Even the relatively cheap short-range (and sometimes unguided) missiles used by nations such as Iran to defend their coastlines would be on the wrong side of the cost-imposition curve against a DEW, which could severely restrict the effectiveness of missile attacks. However, this assumes that a large quantity of incoming missiles can be eliminated with a DEW, which may or may not be feasible in combat.
Low operating costs are not the only advantages of a DEW. Conventional missile defense systems employing interceptors require large amounts of space. Each interceptor carried needs to be stored in a large compartment prior to launch. This is especially problematic on ships, where there is a limited amount of space to fit systems. The amount of missile cells available places a concrete limit on the number of interceptors that can be carried, and each interceptor occupies a compartment that could have been used for other armaments such as Tomahawk land-attack missiles or anti-submarine rockets. DEWs, on the contrary, are not bound by the same constraints. A single DEW can repeatedly engage missiles, requiring only a small amount of the ship’s fuel to power its electrical components. This means that a DEW can fire hundreds if not many thousands of times without any sort of replenishment. In addition, fuel is much easier to replenish while underway, whereas vertical launch cells can only be reloaded in port. This means that a DEW-armed vessel could potentially tackle hundreds of interceptions without need for a port call, while current systems would deplete their stock of interceptors long before.
DEWs are thus quite appealing in theory. Combining the requisite components into an operational platform, however, has been challenging. The main problems are energy storage and delivery. For one, DEWs are energy hungry by nature. Unlike conventional weapon systems, which use chemical energy stored in an ultra-dense medium, DEWs need electrical energy, and lots of it, especially when used against high-performance missiles. Even more troublesome is the nature of their energy consumption. Most electrical equipment needs a relatively constant supply of energy; DEWs, in contrast, require a massive surge of power when engaging. Diesels and gas turbines do not operate well under a variable load, nor do they rev up rapidly enough to supply the increased power, so the DEW’s power supply system must bridge this discrepancy between the generator’s limitations and the DEW’s needs. This can be done with a large bank of storage capacitors, although other more novel methods have been proposed as well. In any case, this large volume of electrical support equipment invariably hinders the DEW’s the tactical mobility. As a result, DEWs capable of intercepting high performance threats are always large, vehicle-based, and generally mounted on massive platforms such as heavy lift aircraft or surface ships. As such, a truly anti-missile capable DEW with tactical mobility à la S-300 or even Patriot is not currently feasible.
Another obstacle is that of range. As the DEW’s beam travels farther, its focus is gradually reduced by atmospheric impurities. This effect becomes significant over long distances and is made more acute by clouds or smoke. This dispersion hampers the ability of lasers to operate effectively over long ranges without an even larger amount of power. Lasers also require the target to be within in line-of-sight, a limitation when there are obscuring land features.
Thus, DEW’s main challenges are ensuring adequate power supply and mobility. DEWs, along with many other technologies like electric cars, will continue to become more appealing as power storage technologies improve. When DEWs do become widely fielded, a development which seems inevitable, the very nature of warfare could change. If surface vessels are able to rapidly eliminate incoming missiles without disposable interceptors, some nations will find their maritime defenses compromised. Iran and China, for example, rely largely on cruise missiles to deny adversaries sea access. The Russian Navy also field many cruise missiles on its submarines, ships, and aircraft. These nations would probably find the deterrent value of their cruise missiles reduced, which could embolden DEW possessing navies. On land, where cruise missiles such as the Tomahawk are typically a menace, defenses could be improved drastically as well by the ability to engage multiple threats rapidly.
DEWs may also spur the development of faster and stealthier projectiles, such as hypersonic glide vehicles, which could be able to outrun laser-based defenses. DEWs require a certain amount of engagement time to inflict significant damage on a target, so fast moving projectiles such as ICBMs or hypersonic glide vehicles may be difficult to engage with a DEW, as their speed leaves mere seconds between detection and impact. For this reason, a DEW systems to counter terminal ICBMs is not currently possible, leaving the ICBM threat to be dealt with by other systems such as GMD or the S-500.
Considering the potential of DEWs to alter the landscape of missile defense, it will be interesting to watch these programs develop. With the US Navy sure to field new iterations in the near future, as well as proposals to arm the F-35 with a DEW, the future of lasers in missile defense indeed seems bright.