Lasers and the future of warfare
Riffing on two great ToughSF posts
ToughSF has two new posts on how progress in laser technology will change warfare. They’re packed with interesting stuff and I recommend reading them now. For a short overview, I wrote two threads on the big ideas.
Matterbeam believes that around 2050, lasers will get cheap enough and efficient enough to support 1 to 10 MW beams for tens of millions of dollars. If that threshold is reached, the battlefield will change significantly.
Suddenly, things that fly like planes, drones, missiles, and artillery are at a huge risk; a powerful laser can cut through them in a tenth of a second. Things that swim like submarines, UUV’s, and torpedoes are safe because lasers can’t penetrate far in water. Tanks and infantry rise in status because they can effectively counter a laser weapon system.
Naval ships see a mixed blessing. On one hand, lasers effectively protect them missiles, their biggest threat. On the other, the airplanes and rockets that navies use for offense can be countered by enemy lasers.
These posts got me thinking about how a laser weapon might be countered on the battlefield and how laser weapons might change geopolitics.
Countering lasers on the battlefield
Assuming lasers prove effective, how will warfare change? As Matterbeam points out, tanks and infantry can be an effective counter to ground-based laser weapons systems. There are a few things infantry can do to threaten ground based laser weapons1:
Destroying the optics or energy system by snipers armed with anti-materiel rifles.
Laying mines or attacking the weapon with traditional anti-tank measures while it’s moving and can’t aim.
Smoke, electronic warfare, or radar jamming can make it hard for the laser to hit a target.
Attacking the energy infrastructure (e.g. battery swapping stations) that supports the weapon.
Infantry could be equipped with directed energy weapons2 and ambush the weapon. These countermeasures can also be used to manipulate pockets of air around an enemy laser, confusing the adaptive optics.
Unmanned ground vehicles could play the role of tanks. Low flying drones may be able to sneak close enough to the laser to take a pot shot at it.
For airplanes, the best hope is stealth; lasers can’t hit what they can’t see. However, powerful lasers could also be used as a LIDAR system to scan the sky for enemies. To increase survivability, planes will fly low, stay out of range, and utilize long distance weapons.
For ships, mounting their own laser system is a huge boost to defense since it can protect from missiles, small boats, drones, and enemy aircraft. The net effect is to raise the importance of submarines and torpedoes34. There’s a small risk of naval ships taking direct fire from lasers. Fortunately, they can afford to add a little more armor, cool it with seawater, and spray seawater around the ship to absorb the laser for long enough to provide counter fire.
The biggest losers are the traditional munitions used in battle: artillery, missiles, and more recently, drones. Is there a way to protect these from laser weapons? Simply rotating the projectile helps distribute the beam over a wider area. Varying speed and position can also help. Specialized armor could incorporate active cooling or smoking to diffuse the laser energy56.
In the next section, I consider what munitions could counter laser weapons.
Throwing metal
A laser weapon only has a finite amount of power available to it. Each projectile requires a certain amount of energy to incapacitate. So if you fire projectiles at the laser weapon fast enough, it will overwhelm the weapon’s ability to counter them.
Naturally, laser systems deployed at the front line will move around frequently to avoid a concentration of enemy fire. But say your recon team has found where a laser weapon is stationed, what munitions do you send to destroy the weapon in a short time frame?
One option is flechettes: numerous small metal projectiles. They would be hard to counter and even a few hitting the laser system could incapacitate it. Flechettes can’t fly for very long ranges, so they would have to be delivered with something like a stealth bomber or cruise missile, which would be vulnerable to the laser.
Perhaps a better option is a metal spear similar to a Rod from God. A slug of metal can take a long time to melt. For example, consider a rod of tungsten that is 0.1 meters wide and 1 meter long. Assuming the laser can provide a megawatt of heating to the rod, it would take over a minute to melt the rod fully. That might be enough time to hit the laser.
The ideal material has high specific heat, high heat of fusion, and a high melting point. These factors combine to require a lot of energy to melt the projectile. Since melted material absorbs laser light more efficiently and can shear off, you want to distribute the heat quickly through the bulk of the projectile. So high thermal conductivity is an asset. As the projectile flies through the air, it is also subjected to heating due to drag. So you’ll want a denser material for a given projectile mass.
Tungsten offers a nice balance across these properties and isn’t too expensive, so I imagine a tungsten rod with some copper mesh for heat distribution and ablative heat shielding would be a good counter-laser projectile.
There’s an interesting trade off for fast moving projectiles. The faster they go, the more heating they experience from drag which makes them more susceptible to the laser. The ideal speed may be quite slow, which may make railguns ineffective for this purpose. Delivery via low flying and stealthy cruise missiles may be a better option.
The math behind all of this will be the topic of a future post. But for now, I assume precisely targeted metal rods can counter laser weapons systems to some degree.
Countering nukes
Probably the most interesting effect is how lasers change nuclear war. Lasers can easily defeat nuclear missiles and nuclear bombers. Matterbeam says:
Theoretically, spending $1 billion on laser defences (with radar already available) would shield any site from nuclear attacks of 700-1300 warheads. That’s nearly all the active nuclear warheads Russia has ready for launch, even after they’re forced to arrive at one location within the same one-minute window. We also find that small increases in the cost of each turret (perhaps by doubling their mirror diameter to 2m and increasing their cost to $12m each) massively increases the number of warheads taken out, by 50% or more.
Practically, raising the threshold for a nuclear attack to roughly 100 warheads, at the cost of $100 million, is enough to greatly trouble the largest nuclear powers as they can no longer divide their strike across dozens of targets; they’d have to concentrate their nukes on a few heavily defended locations and thereby become unable to guarantee ‘complete destruction’ of their opponent.
The nuclear capability of smaller nations, like France, the UK, India, Pakistan, Israel and North Korea, who only have a few hundred to a few dozen active warheads, could be countered by laser defences worth $100m or less.
The post goes on to discuss some countermeasures and caveats, the most important being that each location needs a separate laser system. But the take home point is that defense against nuclear weapons may become much cheaper. With further progress, laser defenses may all but eliminate the threat of nuclear armaggedon.
Today the vast majority of nations don’t build nuclear weapons due to the cost and diplomatic issues they entail. If laser weapons render them ineffective, there’s even less reason to start a nuclear program. Nations with only a few hundred warheads may balk at the thousands they would need to pose a real threat, and consider dismantling their program.
The U.S. and Russia have enough warheads to pose a threat to at least a few major cities. They may opt to build far more warheads, but this is a costly and ineffective strategy. My hope is that they content themselves with the ability to destroy one major city and adapt their nuclear strategy accordingly.
Lasers don’t completely eliminate the threat of weapons of mass destruction. Nuclear powered EMP’s, nuclear torpedoes, and rods from god would still be viable.
Geopolitical implications
The first post has an interesting discussion of the geopolitical implications of countering nukes. Instead of reviewing that, let’s consider how each nuclear armed geopolitical conflict changes in the presence of laser defense.
For U.S. and NATO vs Russia, not much changes. Both sides possess sufficient warheads to destroy a handful of opposing cities. That cost is high enough to deter nuclear war. Though lasers will change nuclear doctrine a bit.
For North Korea and South Korea, South Korea can easily build enough laser defenses to render North Korean nukes useless. Matterbeam suggests that this would force NK to use their weapons before they become obsolete. But I don’t think that is the case. North Korea can still threaten Seoul with conventional artillery and there is no prospect of one country invading the other. Even without nukes, both countries have the ability to impose severe costs on each other. I think an uneasy peace will remain.
Iran and Israel’s conflict is mostly unchanged by laser defenses. Now neither can use missiles or airpower against the other. The stalemate is strengthened.
India and Pakistan’s conflict may be worsened by laser defense systems because India has a more capable military and exerts control over Pakistan’s water supplies. A laser defense that renders Pakistan’s nukes obsolete might force their use. Alternatively, Pakistan can focus on threatening one major city to maintain deterrence. Ideally, both sides could establish enough laser defense systems that they could all but abandon their nuclear programs.
China and Taiwan conflict becomes a stalemate. With sufficient laser defenses, China essentially can’t attack Taiwan. Missiles, planes, and boats are easy targets for Taiwanese laser defenses making an already challenging invasion nearly impossible for China. Taiwan is outside of the horizon of the mainland, so the use of lasers in offensive roles is limited. Perhaps China could launch enough counter-laser munitions from the mainland to take out Taiwan’s defenses, but that seems unlikely. It also becomes safer for other nations to send their navies to defend Taiwan.
However, taking Taiwan is a major goal for the CCP and even the threat of invasion is a valuable bargaining chip. Promising Taiwan is supposedly a means for the CCP to appease the populace and maintain legitimacy. Threatening to take away that option may force China to invade.
Stepping back, would building laser defenses be politically infeasible given their potentially destabilizing effects? I don’t think so. With the exception of North Korea and Pakistan, all of the members of these conflicts already have ballistic missile defense systems in place. Laser systems might be part of a natural progression of existing missile defenses. Though perhaps providing North Korea and Pakistan with missile defenses would increase stability.
Regardless, building missile defenses, done thoughtfully, is a good idea. Ideally laser defense systems are adopted by all countries at a similar rate so that nobody enjoys a temporary advantage7.
What happens to all the investment the U.S. has put into carrier strike groups as a mobile platform for waging war? Enemy laser defenses make the carrier’s missiles and planes far more vulnerable. Instead, the navy might need to rely on Marines to suppress enemy laser defenses before proceeding. That dramatically raises the personal and financial cost of using carrier groups.
Conclusion
Directed energy weapons are the inevitable next step for warfare. We are very good at throwing matter at targets via bullets and bombs and bots. But light beams have stayed out of reach for decades.
Will another innovation change the rules of war again? I don’t think so. Lasers feel like the last big innovation in terrestrial warfare. Soon any country can augment their military with lasers and have defenses that would make even the great powers think twice.
Could cyberwarfare upset the equilibrium? I doubt it. In the software domain more capability means defenders just win. AI will only accelerate that.
What about drones? At least for aerial drones, we’ve watched them change the war in Ukraine. Both sides have adapted to a new equilibrium. Drones have been a significant, but not revolutionary change8.
I expect unmanned ground vehicles and unmanned underwater vehicles to go the same way. Initially, they provide a temporary edge, only to see opponents adopt the same approach and develop mitigations leaving the offense defense balance relatively unchanged.
The red queens race between modern weapons and their countermeasures will continue, but nothing on the horizon feels like a revolution. If anything, it looks like future technological developments will favor peace.
Further reading
For further reading on lasers, Naval Gazing has a three part series on lasers at sea and Perun covered directed energy weapons here.
More ToughSF on future of war:
Some of these are mentioned in the original posts, some I’ve added myself.
This could take the form of lasers, but microwave beams or focused sound could also be used. A smaller version of this system could be mounted on a drone if it can get close to the laser without being detected.
What mitigations exist for torpedos? Counter torpedoes exist, torpedo nets have been used in the past. I wonder if focused underwater sound could work too.
I expect lasers will increase reliance on long range torpedoes and UUV’s too. Aircraft carriers could switch to a role supporting submersibles instead of planes.
I wonder if the plasma around hypersonic missiles might absorb laser light. Though this article suggests that lasers can get through the plasma.
Something akin to an ablative heat shielding might perform well.
Nuclear no first use policies become more important as the world transitions to laser defense systems.
Regardless, lasers will only diminish the importance of aerial drones on the battlefield.
Fantastic post. Quick speculative thoughts on warfare could continue to evolve post-laser revolution.
The primacy of rods from god means access to space is critical. The side that can have more ‘rods from god’ aloft in space has a huge advantage. If you can take out your opponent's laser defences, you’re likely to be able to dominate. Space launch systems will be highly vulnerable to space-based lasers. (Rockets must have thin skins and lots of fuel due to the rocket equation. An easy laser target.) Who initially controls the ‘high ground’ of space has a huge advantage that’s hard to contest - except with laser subs as you mention.
With lasers stalemating the air and land battlefields, the new frontline of warfare could be tunneling. Plasma boring could 100x tunneling speeds to 1km per day. Still slow, but faster than Russia’s assaults are advancing in Ukraine. In a stalemated laser-dominated battlefield, 1km a day could be divisive. The front line moves underground, in a war of tunnels and counter-tunnels.
If controlling the ‘high ground’ of space with lasers is decisive, (it gives you rods from god dominance) and submarine-mounted lasers are the counter to this, then being able to defend your assets in space from laser attack becomes crucial. Protecting yourself against lasers means lots of mass. You want huge objects to hide behind. That could mean being able to mine or move asteroids becomes crucial. Or maybe installing a mass driver on the moon to orbit millions of tonnes of regolith. Essentially, what’s the easiest way to put a big o’ lump of rock/ice/metal between you and the laser sub?
Wait, lasers can counter missiles. How about plain old naval gunfire? 2000 pounds, how much energy to melt all that, or at least enough to make it non-effective?
Dare I hope for a return of the battleships?