The US Navy is developing the Free Electron Laser (FEL) weapon system designed to defend its ships against missiles. (US Navy)
What are the potential future warfare applications of directed-energy microwaves and laser beams? BILL READ FRAeS looks at the technical background behind such weapons and what progress has been reached in their development.
In common with most technology, the power of the electromagnetic (EM) spectrum of light and radio waves can be used for good applications and also for bad. EM varies depending on its wavelength or frequency - the shorter the wavelength, the higher the frequency. At one end of the spectrum are low-frequency radio waves, which are thousands of miles long while, at the other, are light waves, which can be smaller than an atom. Groups of consecutive frequencies within the spectrum are divided into ranges which may overlap.
Lasers and microwaves operate at opposite ends of the EM frequency - laser wavelengths are about 10,000 times smaller than microwaves and vibrate at a higher frequency. At lower power settings, microwaves can be used for such application as microwaves ovens and lasers for laser pens. However, turn up the power and both lasers and microwaves start to become much more dangerous. This has led to the development of directed-energy weapons (DEWs) which produce a beam of concentrated electromagnetic energy which can be focused onto an enemy target.
ADS and E-bombs
High power microwave (HPM) weapons can be used to disrupt and destroy electrical systems. One variant is the millimeter wave device which can be focused on a target at long range and creates a burning sensation. The technology has been used in the US to create the Active Denial System (ADS) - also known as the ‘heat ray’ - which is reported to have been used in prisons to break up fights. Russia and China are also reported to be developing their own ADS systems.
Microwave technology can also be used to create the electromagnetic bomb (E-bomb) which emits a non-nuclear electromagnetic pulse capable of destroying electronic circuitry and communications networks.
MBDA laser effector. (MBDA)
High-energy lasers (HELs) consist of powerful energy beams that travel in straight lines at the speed of light. Because laser wavelengths are smaller than those of microwaves, they diffract less over distance and are more accurate over long distances. The weapons use mirrors to focus the beams onto a small spot on the target.
Lasers can be configured at different power and frequency settings to produce different effects depending on how much power is used. Low-energy lasers can disrupt vision while high-powered lasers can burn through the surface of the target - in the case of an aircraft or missile - disrupting flight, disabling warheads, or igniting fuels or explosives.
To operate, HEL systems require power levels of at least 50kw. To destroy an anti-ship cruise missile would require around 500kw. The most powerful megawatt-level outputs come from chemical fuel which requires special handling, so most lasers rely on electric power. However, these are not as effective as much of the energy required to operate them is dissipated as heat which causes cooling problems on the platforms they operate from.
Most HEL systems include an acquisition, tracking, pointing, and fire control (ATP/FC) system fitted with controlled or self-directing low-powered infrared lasers to detect and locate targets. The sensors include both wide-area broad sensors and refined sensors which provide a more accurate view of the target. In the case of a missile interception, an infrared sensor would be used detect the missile’s heat signature of the missile, another would determine its flight path and another would locate a point on the missile and fire an energy beam at that target. Based on the result, the FTP/FC unit then assesses the next course of action and selects the next target. Optical lasers are also used in other military targeting and guidance systems.
The laser advantage
The US Missile Defense Agency conducted tests of the Airborne Laser (ABL) designed to down ballistic missiles aboard a modified Boeing 747-400F (YAL-1). (USMDA)
Directed-energy weapons are appealing to the military because they offer a number of advantages over other weapon systems, particularly missiles. Although expensive to build lasers cost much less to use than a missile (one estimate claims a $1 a shot). Provided that they have access to a power supply, lasers also have virtually unlimited magazines which could be vital when defending a ship or other target if an enemy should attempt to overwhelm them with multiple attacks from missiles or drones.
Other advantages include long range, attacks at the speed of light, a high degree of accuracy (which also reduces the risk of collateral damage), ability to hit multiple and moving targets, scalability from lethal to non-lethal, ability to pass through walls, all weather capability, quick deployment and silent operation.
However, there are also problems associated with using lasers - the first of which is generating enough power to make them work effectively. A high-powered laser not only requires space for itself but also for the additional power generating and cooling equipment needed to operate it. Not all warships have sufficient space and power generation capability to use DEWs which does not make them currently practical for aircraft - although the US Missile Defense Agency has conducted airborne tests of the Airborne Laser (ABL) fitted aboard a modified Boeing 747-400F (YAL-1). Designed to destroy incoming tactical ballistic missiles in mid-flight., the YAL-1 successfully destroyed two test missiles in 2010 but failed to down a third. The aircraft proved very expensive to develop and operate and was broken up in 2014 after its finding was withdrawn.
Lasers also have the drawback that they need clear air to work properly and can be hampered by smoke or dust. Poor atmospheric conditions can also degrade the weapon’s ability to track and destroy targets while flying through air and turbulence can disperse the energy of the beam.
In 2014, the USN conducted trials of a prototype of the Navy’s 33kw laser weapons system (LaWS) on the USS Ponce. (US Navy)
To address these issues, a number of projects are currently underway designed to look at how lasers could be improved and added to airborne arsenals. While a number of countries are believed to be working on military laser weapons, the most readily available information comes from the US and Europe.
All the divisions of the US armed forces are reported to be working on developing military laser weapons which could be used by the 2020s. The US Army demonstrated weak lasers from a land vehicle in 2013 while the US Marine Corps has expressed interest in testing an anti-drone laser on a truck. In 2010 the US Navy began research work on the Free Electron Laser (FEL) weapon system designed to defend its ships against missiles which could also be used for tracking, sensing and target designation. In 2014, the USN conducted trials of a prototype of the Navy’s 33kw laser weapons system (LaWS) on the USS Ponce which was used to successfully shoot down a ScanEagle UAV and target high-speed small boats. In 2015, US Air Force Special Forces announced plans to install both airborne lasers and active denial systems onto AC-130J Ghostrider gunships within the next five years.
As to the issue of airborne lasers, the US government military research agency DARPA (Defense Advanced Research Projects Agency) is to conduct ground-based field tests this year on the High Energy Liquid Laser Area Defense System (HELLADS) developed by General Atomics designed to be small enough to fit on board of an aircraft. The lasers from the 150kw system would be powerful enough to target missiles and artillery shells.
US-based defence company Raytheon has specialised in military laser targeting devices for many years but also produces high energy laser weapon systems designed to counter missiles, mortars and swarming boat attacks. In 2014 the company announced that it had won an $11m contract from the US Office of Naval Research to develop a vehicle-based laser device capable of destroying low-flying threats such as drones. Raytheon's scalable HELs are designed to be fitted to a variety of manned and unmanned airborne, marine and ground platforms.
Lockheed Martin has tested a low-powered laser fitted in a turret aboard a business jet. (Air Force Research Laboratory)
Addressing the problem of turbulence, Lockheed Martin conducted 60 successful tests in 2014 and 2015 of a low-powered laser fitted in a turret aboard a business jet. Uses aerodynamic and flow-control technology the system was able to counteract the effect of turbulence on a laser beam. Entitled Aero-adaptive Aero-optic Beam Control, the research project was funded by DARPA and the Air Force Research Laboratory. Lockheed is also working on the development of a fibre-based laser which could operate using the electrical power that could be generated on an aircraft but using beam-combining technology to achieve higher power levels. The technology has also been used to conduct a 30kw demonstration and Lockheed is now aiming for power up to 100kw.
Boeing has also been busy working with the US Army on the High Energy Laser Mobile Demonstrator (HEL MD) which can track and target rocket, artillery, mortar and drone targets in adverse weather conditions such as wind and fog. HEL MD uses a 10kw, high energy laser installed on a tactical military vehicle and can be fired repeatedly using power generated from a diesel engine. Boeing plans to follow on from this research with a 50 or 60kw laser. In 2015 Boeing won a $29.5m contract to design and develop a beam control system for US Navy ships which could improve targeting of high energy lasers.
MBDA Deutschland’s lasergun demonstrator. (MBDA)
In Europe MBDA Deutschland has developed a high energy laser weapon demonstrator which was tested in 2012 against a wide range of threats at distances of up to 2km, including mini-UAVs. The technology demonstrator features a multi-stage, highly precise tracker and laser effector that uses the principle of geometric coupling to bundle numerous laser sources into a single laser beam.
MBDA is considering the system for ground, sea and air applications with capacities in excess of 100kW for close and intermediate-range protection against micro UAVs, missiles and mortars.
An image from Chinese television of the Low Altitude Guard laser.
A number of other countries, including Russia and China, are also reported to have made progress in developing military lasers but details of their progress and capabilities are less easy to come by. At the 2014 Singapore Air Show, Israeli defence company Rafael announced the launch of the Iron Beam laser defence system which it claims can destroy missiles at ranges of up to 2km. In addition to developing laser-based air defence, Russia is also reported in 2012 to be working on an aircraft-based laser system mounted on an Ilyshin-76 platform.
An image from Chinese television of a drone shot down by a laser.
In 2014 a consortium led by China’s Academy of Physics Engineering built a 10kw laser designed to shoot down small drones and was developing larger systems. Last year the Chinese government broadcast a demonstration of its new LAG (Low Altitude Guard) laser weapons system being tested at a military site. Mounted on a towed trailer, LAG was shown to be able to detect and destroy aerial targets and drones. Chinese researchers from Peking University and the Chinese Academy of Sciences recently published a paper in Science announcing the development of a supercapacitor which could produce up to 26kw/kg while weighing only 40kg - ideal to power an airborne laser.
All these laser warfare systems projects currently under development are likely to require a great deal more time and money to bring into military service. But, as soon as one country’s military forces has lasers, then all their rivals will want and need to have them too.