Laser Weapons - Science Fiction Becomes Reality
by Rahul Rao, Varun Rao and Yasir Aheer
Summary:
Laser weapons are common tropes in science-fiction but their uses in the real world have hitherto been more mundane
Recently the US Navy released footage of the destruction of a drone by a ship-mounted laser weapon.
The advantages of such a weapon are several - accuracy, cost, size, and weight.
Some technological challenges remain, but they will be whittled down with time and effort.
Lasers have been a common trope in science-fiction. From light sabers in Star Wars to phasers in Star Trek, ray or beam devices have often been seen as the weapons of choice for technologically advanced civilisations. The film version of Goldfinger had the villain inches away from victory over 007 with a high powered laser. Doctor Evil from the Austin Powers movie series believed that sharks with laser beams attached to their heads were the pinnacle of modern weaponry. In the real world, things have been somewhat more mundane.
After the discovery of lasers in 1960, it didn’t take long for engineers to figure out that they could be used for cutting a variety of materials, including metals. By the 1980s, approximately 20,000 laser cutting machines were in use in different industries across the world. Today they are versatile tools of several trades, including eye surgery, computer hardware, and entertainment.
Whilst lasers have clearly been useful in a variety of everyday tasks, they are yet to live up to the hype of science fiction works. Things, however, may be changing.
A new type of weapon
The surprisingly quick development of drone technology has necessitated a cheaper and more precise alternative to anti-aircraft missiles. DARPA has recognised the impracticalities of using multimillion-dollar Patriot missiles to destroy drones worth a few hundred dollars. Missile technology is not the appropriate response to threats posed by drones and small UAVs.
On May 16th, the US Navy successfully tested an anti-aircraft laser weapon. The USS Portland downed a drone with what is believed to be a 150kW laser. The video shows a brilliant beam of light emanating from the deck of a ship. The ray is tightly focused; very little spread is observed in the beam as it travels away from the ship. The video then cuts to footage of burning debris falling to the earth, presumably that of the drone that was the target of the laser.
The video looks like a scene from a science-fiction movie. Imagery from HG Wells’ classic The War of the Worlds comes to mind. Heat-Ray weaponry mounted to the alien Tripods shoot out beams of concentrated energy that vaporise anything in their way – metal, wood, or flesh.
Smaller, faster, lighter, cheaper
Compared to the current state-of-the-art – guided missile systems – laser weapon systems have some compelling advantages.
In 2017, the US Navy demonstrated a much smaller 30kW laser weapon in the Persian Gulf. Lt. Cale Hughes, a laser weapons system officer at the time, described some of the operational advantages – lasers are not affected by wind or range and they travel at the speed of light. This makes aiming the weapon a trivial exercise. Traditional projectiles such as missiles and bullets travel orders of magnitude slower than light does; therefore the projectile must be aimed some distance ahead of where the target is observed, to account for the movement of the target during the time the projectile is in flight. Gunners have had to learn this traditional art of “leading” the target since the days of World War I and the use of airplanes as weapons.
In contrast, lasers can be aimed at a moving target, with miniscule leading as lasers travel faster than physical projectiles.
Modern guided missiles avoid the “leading” problem somewhat but can be confused by defensive flares fired from the target which confuse the missile with their heat signatures. Not so with lasers. The image below shows the simplicity of hitting a moving target with a laser. In the left image, the hot plume of exhaust gases behind a target is clearly visible. The target is then hit by a laser beam (middle) and begins to burn, showing a small spot of luminescence separate to the plume. Finally, in the image on the right, the exhaust plume is nearly extinguished while burning fragments of the target continue on the flight trajectory. No guidance is needed and there is no opportunity for the target to distract the laser with decoy flares.
Lasers are also advantaged by having no payload per se. Without needing to transport explosive warheads, casings, and the associated electronic gadgetry of missiles, lasers can save on weight, size and cost.
A comparable weapon – the SeaRAM ship defence system – uses RIM-116 missiles that are 2.79m long and have a diameter of 127mm. Each missile weighs 73.5kg and costs more than a quarter of a million USD. In contrast the “projectiles” of any laser weapons weigh nearly nothing, have no size until they are deployed, and cost only the energy required to generate them. This currently stands at under 1 USD per shot.
For the more ethically minded, there are two properties of laser weapons that stand out – precision of targeting and selection of lethality. Laser beams can be targeted to a very small area; without the need for explosive power, damage is confined to this area and surrounding regions are left unaffected. Traditional explosive warheads struggle to limit the collateral damage of a strike.
There is also the ability to finetune the power of the beam emitted. Low power beams can be generated to disable rather than destroy enemy facilities. This property could be used to neutralise rather than eliminate enemy units.
But wait...
Significant caveats apply to the use of laser technology at this time; some of these are merely engineering problems to surmount, while others are limitations of the physics of laser beams.
Current laser emitters are fine-tuned pieces of equipment designed more for the laboratory than for the battlefield. They contain sensitive optics that must be suitably isolated from the environment. The vibrations of missile launches and incoming projectiles could shorten the life of a laser so as to render them impractical. Solid state lasers are more resistant to shock but isolation measures must still be taken.
Atmospheric conditions also affect laser more than they do traditional missiles. Humidity, fog, and smoke attenuate and scatter laser beams. The advantage of precision is then lost and, additionally, their power when they reach the target is lower. Above a given attenuation level, traditional missiles will outperform laser. Smoke is also a big concern – battlegrounds are smoky places with the burning rubble of buildings, ships, or equipment staining the air. Smoke is also exceptionally easy for an enemy to create, with smoke grenades having been in use since the 19th century.
Another key limitation is the requirement for line-of-sight. Whilst this is not of concern when laser weapons are required to replace surface-to-air missiles, it does pose an issue when the target is a low-flying cruise missile, or is obscured by the curvature of the earth.
Finally, the key change needed before lasers can achieve tactical supremacy over missiles is an increase in power. Whilst the US Navy achieved a six-fold increase in power between 2014 and 2020, there is no guarantee that that rate can be maintained, or that these power levels can be achieved in fully operational, productionised systems.
So while there is likely some time to go before we see weapons such as these used regularly, sci-fi fans will be pleased to hear that we’re getting there. Like with many technological advances, there is the “be careful what you wish for” aspect to lasers. A remake of Jaws with laser beam-equipped sharks would look very different and much more terrifying.
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Disclaimer: This article is based on our personal opinion and does not reflect or represent any organisation that we might be associated with.