Science Fixer: Laser guns!

Outline

A quickstart, to take you right in the action:

First glance

I bet you’ve seen many space soldiers, guardsmen or loose cannons zapping the enemies with flashy laser beams from hand-held guns. An elegant and attractive concept. Seems legit at first glance. Many of you probably wonder why there are no laser pistols or rifles existing so far. It’s 21st century after all, and the first lasers were constructed in early sixties of 20th century, right? Some of you may even heard about undergoing research on laser guns for zapping drones or sattelites such as LaWS onboard USS Ponce or Rheinmetall HEL or Boeing HEL MD.

But before we poke this whole laser gun stuff, let’s think why anyone would actually deem worthy developing and implementing a laser weapon:

  • budget friendly: with no ammunition that needs to be produced, stored and transported, cost of firing LaWS is estimated at 1 dollar per shot
  • fast & precise: zero-mass effector traveling with the speed of light means no need for any ballistic corrections and almost instant hit (assuming planetary scale)
  • reduced collateral damage: no explosions, no unexploded remains, missed shots do not fall on the ground
  • silent & clean: no muzzle flash, no noise, no smoke

So, if we agree it’s worth checking out laser weapon concept, let’s have a quick look at some curious facts, that you might already be aware of:

  • Shooting a laser gun would not be as spectacular as shown in movies. Usually you don’t see the laser beam, unless it crosses some aerosol (such as smoke, myst or dust cloud) and scatters on it’s molecules (Rayleigh scattering). It’s due to that dispersion, the beam loses coherence and emits non-axial rays that reach your eye.
  • The above point is true only for the lasers that emit in visible spectrum of 390 to 700 nanometer wavelength. There are however a number of lasers that emit outside that spectrum (such as CO2 lasers or fiber lasers), and in these cases even in smoke you will not see the beam.
  • The beam itself also does not make any sound. The only possible noise may be generated by power source, and maybe energy discharge but it would be highly dependent from electric components used (coils, tranformers ect.) but I’d guess it would be more like buzzing, whining or cracking. Oh, and there is no kickback when firing a laser gun, as there is no projectile that would cause a recoil with respect to 3rd law of dynamics…
  • …but that with the ‚kickback’ may not entirely be true when going quantum scale. Photons, despite having zero mass, carry energy that may exert some pressure on encountered surface. And where’s pressure, there’s force and where’s force, there’s reaction force and thus the kickback! These, are relatively tiny and negligible values, but when it comes to really powerful laser gun – who knows?
  • In vacuum, the laser beam can travel for infinite distance, but when it encounter some molecules it’s Rayleigh scattering that makes the beam loose energy on it’s way through the non-vacuum. So, if you’re ever targeted by laser gun, seek cover in dust or smoke – at least you’ll get less burnt.
  • The laser beam refract (go off the course) depending from air temperature and its resulting density.
  • Instead of delivering a short high-energy impulse, it is more feasible to ‚stretch’ the laser shot in time and fry a target for a few moments. It allows you to use a smaller power source, but the tradeoff is that you need to keep a beam on target for some time, so precision aiming of essence here. The Iron Beam anti-missile system, for example, needs 4-5 seconds of firing to disable a target. ATHENA system, which is ‚only’ 30kW is able to damage an airborne drone in about 3 seconds. This approach requires advanced automatic targeting and tracking systems which make the stuff very finesse.
  • In 1984 soviets designed and prototyped Makarov TP82-based fiber-laser gun, as a part of cosmonaut’s survival kit. This weapon was meant to damage the optical systems of enemy aircraft, but I have no idea what was the use-case scenario for this device (cowboys in space?). Possibly, the designers also were not sure about it, because the project was canceled and the gun was put into glass box at the Museum of the Strategic Missile Forces of the Military Academy in Moscow.
  • There has been some buzz recently about Chineese laser rifle ZKZM-500, that was supposedly able to carbonize a human skin from a distance of 1 km. What’s curious – it uses a lithium-ion battery, so it’s the same power supply technology as in laptops and cell phones. That seems a way too little to put a hole in a man, but the designers from Xian Institute of Optics and Precision Mechanics at the Chinese Academy of Sciences in Shaanxi describe the gun as non-lethal weapon for crowd control – so possibly it does not require insane amount of power.  To do the justice to Li-Ion batteries – there are 100Wh batteries on the market, which means they can deliver 100W within one hour – which may indeed prove sufficient to fuel non-lethal laser. The information about ZKZM-500 was met with scepticism and blames of propaganda. In response to criticism, chineese propa media released the video showing the ZKZM-500 setting distant T-shirts and tires  on fire. How long it took to actually burn a hole in a target is not clear, because the shooter needs to be still for a certain amount of time to deliver an energy required start a fire, and the video starts with a shooter already aiming the gun.
  • Laser beam, being essentially a stream of light is prone to optical phenomena such us refraction, dispersion and reflection, and these could be used to counter the damaging effect of high-energy beam. For example, a smoke screen could make the beam lose coherency and reflective coating on armor could cause a beam to ‚ricochet’ from it. For now these are merely theoretical guesses, but still they’re fun – check out this cool forum for some inspiring discussions.

A fistful of numbers

So, if the military guys already know how to build a high-power ship-mounted laser cannon, building an anti-personnel handgun shouldn’t be a problem, right? Well, not quite. If you want a significant energy emission in a reasonably short time it means you need a lot of power, because it is how the power is defined: power = energy/time. For the big picture, let’s look at the examples of various lasers and their output power:

  • a harmless laser pointer has output power around few mW (1000 mili Watts make 1 Watt) – don’t worry it will not fry your cat or vaporize eyeballs, still it’s better not to stare at it, just to be sure
  • you need around 40 W to cut few millimeters deep into human tissue for surgery  – wielding it may not make you a Jedi, but a respected plastic surgeon is more like it
  • you need around 50kW output if you want to whack a drone – and that’s more than 1000 times more than surgery laser
  • a beam of one megawatt and more is what you want to deal some serious damage to military vehicle – in other words it’s million Watts

Check out that simple visual representation of laser powers given in ‚laser pens’ below.

If you’re more into numbers – look, I even drew some fancy graph for you to feel the difference. Pay attention, however, because the vertical scale is not linear – it’s logarithmic. If it were linear, you’d end up scrolling for hours.


Heavy fuel

Look at the graph once more and make sure you see the spread. But that’s not all – I was talking about an output power. And to produce that output power, you will need even more input power! ‚Why the hell’s that?’, you may ask. Well, that’s because the input power supplied to any device is partially wasted (mainly in the form of heat) due to physics. The input/output power ratio of the device is called an efficiency and is displayed in percents. And, for example, in case of CO2 laser you’ll get a bit over 30% efficiency at best, which means, that you need to supply at best over three times more power than you produce at output. And these lasers are considered as pretty efficient! Below you’ll see a simple graph illustrating how much from an input power actually goes out as effective beam, while the rest is dispersed and lost.

Now, imagine an AK-47 class laser rifle that could bring down a drone. Let’s assume it would product a beam of 50kW, so, at best, it would require 150kW to shoot.  Of course, it would have cool sci-fi look and ergonomic design, but most probably it would also be plugged to enormous battery spoiling all the fun. Such a battery would encumber a shooter greatly – be it a backpack, barrow or a fellow soldier carrying it around him. That does not sound very practical.

To use a hypothethical laser handgun or rifle you would need a powerful energy source condensed to the size of the clip! So unless we invent some ground-breaking power source technology with high energy density, good old bullets will still rule the battlefields. The closest shot would be some miniature hydrogen bomb – a pocket-size sun, but I doubt if anyone would like to keep it close. Anyway, it’s a lot of research and insane experiments before we get even close containing high potential energy in a small box. Just for a big picture, to see how big would be 100 MW battery based on lithium-ion technology check out the super-battery from Tesla, deployed in Australia. It was not designed to power the laser guns, of course, but to sustain the electrical power grid, but anyway it’s a hell of an installation. For a laser handgun, thousand times smaller power would still be fine, but consider that you’d need to fire many shots before recharging the battery for few hours, so still you’ll need a lot of power capacity and thus – the size . Keep the faith, however, because research on more efficient battery technology is underway. By the way, this whole power supply stuff is a decent matter for some more Science Fixers to come.

But let’s assume, we came across some ground-breaking invention, allowing us to store all that power in a small box. Once we have the main power supply power problem solved, new problems emerge, but these are of the minor nature: how to handle the excessive heat and not get burnt?, how to shelter optical systems from mechanical shocks?, how to inform a shooter that the gun was shot? etc. There is also a problem of a rapid energy discharge when shooting hi-power laser. Hardly any battery would allow that, so a middle energy bank should be put between battery and laser emitter. A sort of capacitor, like in flash lamps, that would be charged from battery and rapidly discharged on shot. And the sound of charging capacitor would add that cool whizzing sound! But, like I said, these are not critical issues. Just give me that pocket-size power plant, and I’ll get all the rest done.

But for now, forget about a portable laser gun.



Reality check

OK, let’s face it – it’s a long way ahead to invent that ‚magical’ pocket-size power source. But what can be done with the technologies already at hand? Well, as it is written in the opening part of this post – the arms industry has already placed their bets on heavy duty armaments. That’s because the big guns are usually put on big platforms, with really high payload capacity – tanks, battleships, aircraft carriers or stationary posts. In these cases, it’s easier to put some extra load, that is relatively small portion of the total weight. It’s all heavy as hell, after all. This is why Lockheed Martin’s ATHENA laser system is turret-mounted that can be deployed as stationary ground post or warship payload, and HEL MD is mounted on a monstrous truck. Chineese army is testing anti-drone and even anti-satellite laser system. Israeli company Rafael designed the Iron Beam – a supplementary system to Iron Dome anti-missile defence system. Iron Beam uses fiber laser technology to bring down rockets and mortar missiles.

In other words: in aspiring hard sci-fi setting laser handguns should be likely less to occur than heavy duty vehicle mounted weaponry.

And in real world of today, the most promising and already implemented direction is to use laser weapons as a part of stationary anti-missile defences.


Game concepts

Since all this research is for our science fiction game, we would like to share some not-so-obvious concepts that might make an SF setting less commonplace and predictable:

  • Abandon the hand-held laser guns, but stick to vehicle mounted ones, with some moderate progress in terms of miniaturisation and energy efficiency, at least to make it deployable on aircrafts.
  • Managing the energy between high-power impulse or conservative beam would add to tactical aspect of dogfighting.
  • Reflective coating sounds like an interesting concept for anti-laser protection. This would make a fine aircraft upgrade, and add some tactical spice as it would be completely useless against projectile weapons. It may be really challenging from technological point of view to build a reflector able to withstand a high-energy laser beam.
  • Targeting assistance system is another idea for aircraft upgrade. It would make manual targeting easier, or even obsolete, allowing you to focus on tactical positioning of your aircraft.
  • Laser beam visibility issues would make manual aiming more challenging and add tactical depth. For example, you could use clouds or dust as natural aiming assistance, but also it would reduce the damage dealt by you and to you.
  • The idea of rapid-discharge capacitor may introduce some diversity to shooting mechanics by having the player to wait for the capacitor to charge before firing. Or he can choose to quickfire but with low-power beams. Oh, and don’t forget that whizzing sound when charging!

Time for a final disclaimer. We’re doing this research on the fly during the development of our Vital Deal science-fiction game. This means that the concepts that are appealing to us are not yet implemented so they will probably be morphed, tested and developed over time. But the general idea remains as is – to play with the reality check of SF concepts and make the game content a bit more ‚hard’. We’d also like to stress out, that despite this material being weapon-centric, the Vital Deal game will not be about fighting. There will be direct and indirect violence in the game but it will not be the core of the setting – rather a complementary component. Vital Deal will be the game about making and negotiating potentially world-shaking deals, but it’s smart to have a trusty laser cannon installed in your drone-car, just in case the things go bad.

Thanks for Kuba Główka for tech-heresy scrutiny and some potent remarks!

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