The nature of directed energy weapons — lasers — favors surface troops, Jonathan Jeckell explains:
The U.S. and Israel have had increasing success lately testing lasers to intercept missiles and artillery. We could be entering a new laser age — with huge implications for American military power.
But it could be a mostly defensive, ground-based laser age, to begin with. Aerial energy weapons need a lot more work and could lag far behind.
In December, the Army shot down 90 mortar rounds and several drones using a truck-mounted laser. The Navy is adding an experimental laser gun to its Persian Gulf base ship Ponce. The Army and Navy weapons work today. The Air Force, by contrast, is planning to install an energy weapon on jet fighters around the year 2030.
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Unlike missile defenses using projectiles — which must fight against gravity and require storage space and sophisticated manufacturing — lasers require only the requisite energy and the ability to shed excess heat.
Lasers also move at the speed of light, meaning the target would have no warning or opportunity to maneuver before it strikes. Suddenly the energetics that have favored air power are reversed.
Historically the high ground lent decisive advantages in combat because gravity works in your favor. Anti-aircraft shells and missiles flying up to intercept aircraft must struggle against gravity to approach their target. They lose energy, and the ability to maneuver, as they ascend.
Meanwhile, air-launched ordnance uses gravity to its advantage, increasing its range so it can often strike first and from a standoff distance. This has been a major factor in helping aircraft fend off increasingly sophisticated air-defense systems.
Lasers will level that field, as surface forces will have effective lasers first. Placing energy weapons on planes runs up against serious constraints on the weight and space needed for shedding waste heat and providing energy to the laser. The Air Force Airborne Laser project, for example, used up nearly all the interior space in a 747 for a laser capable of shooting down just a handful of ballistic missiles.
Better lasers might eventually solve these aerial problems with more compact cooling and improved energy generation — but these advancements will also enhance ground-based systems that don’t suffer gravity’s constraints. With energy weapons, the conditions are set for air defense to leap ahead of air attack.
Lasers can not strike anything beyond the horizon.
One might expand that horizon to nearly half of the planet with space-platform lasers. They might make sense at some point, but it seems they would remain vulnerable to any ground based laser that could see them.
That is indeed a limitation, Andreas, but your enemy has to send something closer than the horizon to hurt you. Thus, while lasers aren’t necessarily ideal for long-range offensive applications, the current rate of development is likely to see them become very important for defensive purposes over the next 20 years or so.
Their chief limitation is how they interact with a simple Holtzman shield.
The world of David Drake’s Hammer’s Slammers made real. All that’s missing are the fusion-powered hovertanks, and the Helion Energy Fusion Engine is closing the gap on even that.
Aircraft die. First time, every time.
Lasers favour ground troops — unless they’re so expensive the best way to take out an anti-missile laser is two missiles. 747-sized means a lot of metal, which means a lot of dollars. It also means a large, stationary target, meaning the missile can accelerate without limit, as it doesn’t need to manoeuvre.
Tomahawks cost 1.6 million and probably aren’t even the most efficient option. Tanks are 6-9 million. The laser is probably more like the 747 it fits inside, a couple hundred million.
As for the truck-mounted one, the cheaper 120mm mortar rounds are $100-$200 each. Fire five of them at once? Hope your laser truck had insurance.
As always, there is no defense that cannot be saturated. The question comes down to relative effectiveness, which shifts with technological developments and the dance of countermeasure, countercountermeasure, etc. Also keep in mind the importance of virtual attrition – rounds aimed at defenses are yet more rounds deducted from those aimed at what’s being defended.
The ABL was designed to knock down boosting ICBMs hundreds of km away, and used complicated, high-power, and somewhat outdated technology for the actual beam generation. The lasers being discussed for deployment as point-defense in the next decade are solid-state laser diode units designed to knock down artillery and mortar shells from <1 km away in rapid succession.
If I cover a mortar round in retroreflectors, will it substantially damage the laser or just end up blinding everyone near the truck?
Probably neither, you need high-quality precision optics for that. I don’t think it’s easy to make precision optics robust enough to shoot it from a mortar. The laws of physics don’t prohibit it, but the round will probably be very expensive. Also, it’s difficult to damage a laser by reflecting its light back into it, since a laser is already reflecting most of its light within itself.
Also, the laser is not a parallel beam but a cone focused at the target. A weapons-grade laser, at the target, isn’t much reflected by mirrors; the intensity of energy deposition is such that it burns through them. The shorter the laser pulse and the smaller the spot size at the target (for a given energy), the more pronounced this effect is. ABM lasers do have to deal with reflective surfaces as a defense because their targets are so far away that it’s hard to focus the beam down to a point.
Even if it did work, coating a mortar round in lab-grade mirrors that can survive being fired from a mortar tube (probably some sort of sabot approach would do the trick) already represents a tremendous amount of virtual attrition.