# Helmet that shoots lasers?

I have a character who wears a high-tech helmet with a high-powered laser mounted on it. Basically, the wearer “stares” at a stationary victim, and the laser is activated. The laser would take a short time (ideally a couple of seconds) to impart enough energy to cause the victim to explode.

A few obvious issues- the helmet would need to be massive and unwieldy, it would require an absurd amount of power (which would preferably be carried by the wearer), and the user is effectively staring directly at the beam’s reflection. (I’m planning to address the final point somewhat by making the wearer already blind.)

The wearer only needs enough juice to fire once or twice, but I’d suspect even that would require an extreme amount of energy. The wearer is willing to dump huge amounts of resources into building this helmet, but physical limits are physical limits.

Best case scenario, the helmet wouldn’t be much bigger than a motorcycle helmet, and the entire system (power and laser) would weigh less than 100 kg. This seems a bit optimistic, though.

This question may be too technical, but is it possible to make this work with semi-futuristic technology without making the wearer look like MODOK?

• You might want to ask "would a laser make a person explode?' too.
– rek
Apr 4 at 16:17
• @rek yeah, I know I read somewhere on this SE that it’s possible. I couldn’t find the specific answer, or I would link it here. I’m pretty sure imparting enough energy can make practically anything explode, no? I could be wrong. Apr 4 at 16:20
• @MarkPrice an explosion requires more than energy. It requires containment. Light off a fire cracker on your open hand an the worst you’ll get are scorch marks. Hold the same fire cracker in your fist and your fingers will go flying. Apr 4 at 18:58
• Wait, so how is this blind person going to know which direction to stare? They might be able to pick out a general direction by sound, but their accuracy is going to suck at any significant distance... Apr 5 at 13:15
• Strapping this thing to a blind person seems incredibly reckless, you can just have an opaque visor built into the helmet that lowers when the beam is fired. Apr 5 at 13:42

The laser would take a short time (ideally a couple of seconds) to impart enough energy to cause the victim to explode.

I have seen an industrial IR laser, used to vaporize metal, with laser power of several kW. It has a footprint of several tens of square meters of machinery and needs a hell of power and utilities supplied to be generated and amplified, and when fired on a chicken breast it carves a nice, round hole in it within seconds, but it doesn't make it explode.

To have an explosion you would need the laser to be absorbed inside the body and vaporize enough water to build up pressure and cause the subsequent explosion.

The closest thing to achieve this goal would be a microwave laser, basically a microwave on steroids. But I highly doubt it would be anywhere close to something portable and handheld by a single soldier.

• I found this link just now: worldbuilding.stackexchange.com/questions/177479/… Would the concept in the first answer possibly help here? To my understanding, it uses chirps from a laser to “carve” into the target, then vaporize them from the inside. Apr 4 at 19:24
• I've seen DIY microwave lasers used on people (because people are just that stupid). A shotgun sized one could inflict pain but no visible burns with a fraction of second burst. Apr 4 at 20:00
• A computer used to take up a warehouse... now it sits on a chip. I would think that if the basics could be accounted for then the size could be handwaved to "miniaturization". Batteries are also getting more dense and capable. Slowly but... in a world far away and far into the future... Apr 5 at 1:53
• @WernerCD the fundamental limit here that a malfunctioning battery is an impromptu explosive device. And if it's beefy enough to explode an enemy at a distance, if it goes off inside your mech suit, it's going to turn you into pink mist and metal shrapnel, too. Apr 5 at 2:15
• @JohnDvorak that's true of any weapon. A plasma weapon gets bent? boom. in your pocket or on your head. If we can handwave lightsabers to have safe enough power supplies then we should be able to do the same for side arms or head mounted lazers. Plenty of batteries today are safe in different temps and if damaged. Apr 5 at 2:28

I have worked with lasers that are used to cut and bleach jeans pants. They were in a power range much below what you need for a human exploder. They also needed large cooling systems, the kinds that have pipes running cold water.

Your laser helmet would require a connection to a cooling tower bigger than you just to keep you from cooking yourself while shooting.

As an alternative to your design, the helmet could be physically separated from the laser cannon. You stare, and a car sized thingamajib shoots at what you are looking. This way you only kill your victim, besides making it more feasible to power the laser.

#### Been There Done That Got the Laser Safety Goggles

The system you describe has, in form if not in power, existed for decades. Ophthalmology surgeons sometimes use a head mounted laser where the power and lasing machine are in a little box and a waveguide brings the energy up to the helmet and sends it out to the target.

These systems have two lasers, one generates a visible aiming beam and the other a visible or invisible death beam. Your user doesn't have to be blind, he just has to take standard laser precautions, such offering eye safety goggles to all his victims and announcing to them whether his laser is "on" or "off".

At present, the boxes are light, and some even run on batteries. Obviously these are rather low powered. Since you gave us the power of weasel words, semi-futuristic technology, the only real problem is that of power, which you'll solve in another question about miniaturisation of power components!

The helmet itself doesn't have to be heavy: the laser isn't mounted on the helmet, it's in the backpack. Even five to ten years ago you could buy on Ebay a small battery powered laser strong enough to light matches and pop balloons. Time marches on. Probably your kids will be able to buy one these death lazers third hand on Ebay in 15 or 20 years!

• Can you store a laser in a backpack and still “fire” it from your helmet/head? I’d guess you’d need an elaborate set of mirrors to do so. Apr 4 at 19:17
• @MarkPrice -- Fiber optic conduit. Apr 4 at 21:15
• @elemtilas the laser would remain coherent in a fiber optic cable?
– BMF
Apr 5 at 23:07
• @BMF -- I think so Apr 6 at 1:51

To complement the other answers, the power for your HKS (Helmet Kill System) can be provided chemically:

The Hydrogen fluoride-CO$$^2$$ (or deuterium fluoride-CO$$^2$$) laser is used, producing a wide range of wavelengths simultaneously. Tantalisingly the Wikipedia article doesn't exist yet for that specific type - but the reference states that several megawatts can be produced this way with just a couple of little gas-tanks to feed the reaction, like Uncle-Sam's beer-hat:

• Beautiful design. Definitely in the running. I’m also curious why there seems to be so little on Wikipedia about chemical lasers though. Apr 4 at 19:30
• I wonder if it had something to do with people like us who like to tinker, and plot world domination ;-) @MarkPrice Apr 4 at 19:34
• The problem with extracting a lot of energy from a small amount of fluid is how it is usually done. Think of how a car turns the chemical energy from fossil fuel into actual usable energy. You don't want that process happening an inch from your skull. Apr 4 at 21:57
• Yeah I think chemical lasers are the way to go. I believe they just never caught on because the chemicals required are expensive and volatile, so neither industry nor military really ended up going with them. Apr 5 at 15:32

# No

One of the big problems with energy weapons (like lasers) is thermal blooming. As you increase the amount of energy in your laser, the air (and particles in it) will absorb a portion of the energy, and when it does, things in the laser's path will change phase and become better receptors of the energy, so the laser ends up blocking itself to some extent. The problem gets worse if it is foggy or smoky. The only solution is to fire it in a vacuum, or in exceptionally clean air.

Additionally your laser is going to take more power than any 100kg source can currently produce, your future is going to need a lot of advanced mobile power solutions to make this feasible.

It's probably be easier to attach a mind control system, and then have it slice them apart. Just as deadly to anything but a flatworm, too.

Cutting lasers require about 80 Watts of electricity. 10S LiPo batteries get us over 300 in just over 2 kilos (5 pounds). Power, check. The rest of it should be straightforward, attach one of those and a laser device to a bike helmet, and the problem is solved.

The mind control and computer system can be installed semi-easily to the inside of the helmet, and weighs next to nothing.

This system weighs around 10 pounds (4.5 Kilos) plus the bike helmet itself and the attachment setup (Duct Tape?).

(Also, a laser can make someone explode. It heats up the water in their cells, and then the steam makes them blow up with the same concept as a water heater bursting. For that, just add a bunch more LiPos.)

• I could definitely make do with cutting lasers, but would an 80 watt laser be able to handle/output the amount of energy needed to cause a steam explosion in 1-2 seconds? Or could you tack on a bunch more lasers as well? Apr 4 at 17:56
• @Mark Price A Watt is 1 Joule per second, which means 300 watts (output by a 10s Lipo I found online) could boil a gallon of water in around... 275 seconds. Not optimal. In 2 seconds we get 600 Joules, which isn't enough to do much reasonable. We can boil about a cup of water. It is certainly a kill, but whether or not an explosion is hard to find out without testing. Apr 5 at 14:23

## Blinding

The reflection doesn't need to be a problem when using pulsed lasers: tune some kind of shutter (can be LCD, mechanical, or something else) to the pulse speed so it's closed whenever the laser fires a pulse. The drawback is that your vision will flicker somewhat.

## The laser

As for the laser power: as many others already mentioned, it just doesn't exist yet in that form factor. But what could work is having all the actual lasing be done somewhere else and have the helmet work as a beam guiding device. You have a few options then:

• The helmet is a targeting device, using some low power laser to designate a point. The main laser will target that point with its big laser and fry the target.
• The helmet is a focussing device. The big laser points a beam at the helmet which uses some mirrors/lenses to focus it on the target.

To improve coverage put the big laser in a lighthouse-like structure, or for indoor use add exit modules for the laser in all rooms.

I don't think recoil is the main reason we don't attach firearms to helmets.

Your proposal would be harder to aim accurately than a rifle is, unless the gun protrudes forwards enough to be visible to the user. Our idea of "staring" straight ahead doesn't seem precise enough, nor do our tolerances for angle disturbances when fitting a helmet.

• It’s a laser, not a firearm. There’s no recoil. Apr 4 at 19:15
• my point is that we don't put guns in helmets because it would tank accuracy, and that also applies to lasers. Apr 4 at 19:36
• You could put a low power aiming laser through the same emitter as the weapon beam - just place the dot on the target and fire Apr 5 at 8:07
• @ShellGhost good idea, but it also applies to handheld rifles and pistols. Apr 5 at 16:29

## This is more or less doable with modern technology

I read a US military study on this subject a while back that claimed, it takes a 1KW High-Energy Laser (HEL) to kill a person faster than they can get out of the way. It won't make them explode since that is not how lasers work, but it will burn into them causing surface level charring and raises their internal temperature enough to cause internal organs to boil and rupture.

Modern military laser systems like HELLADS weight about 5kg per kilowatt of power meaning that using military technology that more-or-less exists today, it is not unreasonable to assume you can make this a hand held anti-personnel laser.

That said, 5kg is a lot of weight to put into a helmet; so, instead I would mount this weapon on the back or shoulder and just ware the control mechanism on your head... basically giving you a weapon system very similar to Predator's shoulder mounted laser.

There are also newer styles of Solid State HELs that are more scalable the Liquid HELs that are being developed for use on drones right now which may actually be light enough to ware on a helmet, but their exact specs are not public knowledge. Regardless, HEL technology has advanced so fast in the past 15-20 years that if you are planning for an even sort of future tech scenario, then an anti-personnel helmet laser is not at all unrealistic. The only unrealistic part is the person exploding.

As for flash back, there have also been recent military research into "dark" lasers that reflect back self canceling wave patterns (kind of like how noise canceling headphones work) to significantly reduce how bright a laser strike is. Or you could just use protective goggles that filter out the reflected wave lengths since you don't seem too concerned about blinding innocent bystanders.