The Advanced Tactical Laser (ATL) program was a US military program to mount a high energy laser weapon on an aircraft, initially the AC-130 gunship, for use against ground targets in urban or other areas where minimizing collateral damage is important.
Wikipedia informs us that “The advanced tactical laser was discontinued after successful testing.”
So… what if I need an aircraft-mounted tactical laser? Or is that at the present time useless or of limited utility?
You won’t need one. Nobody needs ones, that’s why they were discontinued. The ATL was smaller than the Airborne Laser, but still probably too big to be useful. Right now, they’re going even smaller, with the MEHEL. It’s 1/10th as powerful, but it’s effective at shooting down sUAS.
Why? Do you know a certain professor that hates popcorn?
Two words: “unlimited magazine”. Electricity is your “ammunition” and jet engines can continuously generate it.
Given the prospect of maneuvering small munitions (search on Golden Horde weapons for the US version), the prospect of running out of physical bullets before you can take out all the targets is very real.
Unfortunately, this isn’t true of the COIL lasers used in US ATL programmes. They are are chemical laser, and the lasing process requires a significant chemical reaction from which the energy is largely derived. One of the big criticisms of the entire ATL project was the limited number of shots a laser could fire before depleting its chemical reserves, requiring removal of the reaction products and re-supply with lasing reagents. The toxicity and general difficult handling requirements of the reagents and products was another criticism. A large part of the aircraft was taken up with tanking, and even then the number of shots available was not good. The demonstration 747 based COIL laser was only capable of 20 full power shots before running out of reagents.
General wear on the optical system is pretty significant too. Directing a beam capable of destroying a target without vaporising the optics is not trivial.
When it comes to delivering energy to a target, the efficiency of kinetic delivery is hard to beat.
And even if you do have an electrically-powered laser weapon, it’s only “unlimited”, in any meaningful sense, on a nuclear-powered vehicle. That electricity, after all, is still ultimately coming from some sort of chemical reaction, and so for every shot, you need to store enough chemicals to react to produce the energy for that shot. It makes little difference if the chemicals used are gunpowder in bullets or jet fuel.
Except, of course, that bullets are a much more efficient way of delivering energy to a target than lasers are, and so you’d actually need much more jet fuel than gunpowder.
“Even if you do have an electrically-powered laser weapon…”
You do realize that is exactly what we have today and the Air Force is developing for deployment on aircraft by 2025. All laser weapons currently under development or being actively integrated as weapons are so called “electrical lasers” (as opposed to chemical lasers of the 80’s).
Lasers for guiding other munitions? Absolutely. Lasers for blinding enemy pilots or sensors? Sure. Lasers as a primary munition? Got a cite for that?
That’s going to be tough, especially these mythical fiber laser systems. Hmm…
Of course, these are still in development for deployment on aircraft. It’s not like anyone has made a magical laser that can shoot down a drone…
“Electrical” lasers have been the dominant weapons lasers since the 90’s. First slabs, then much more efficient fiber lasers. They’ve been demonstrated against small boats, drones, mortars, and missiles.
IIRC, isn’t one of the problems with lasers also that they require a significant amount of time to cool-off between shots, or overheat much more easily than an old-fashioned gun?
No- heat is a major engineering issue in building a hundred’s of kW class laser weapon, but it isn’t like a gun barrel. The heat has to be dissipated, but it isn’t concentrated in one spot. Think of it more like a CPU in your PC. You don’t shut the CPU down after each program runs to cool it down, right. That’s because you dissipate the heat continuously.
ETA: Though you may have been thinking about the NIF? (which isn’t intended for a weapon application)
To be clear, I never said that laser weapons are absolutely impossible. Clearly, they are possible. They’re just really impractical. A ship is big enough that you can fit an impractical weapon on it anyway, to show off for the politicians and public. An aircraft, though, has much less room for impracticality.
“Very interesting Whittle, my boy, but it will never work .”
Cambridge Aeronautics Professor, when shown Frank Whittle’s plan for the jet engine .
Lasers on aircraft are definitely coming. First defensively as a way to disable/destroy incoming missiles. There are formidable efficiency (and cooling) issues to be dealt with before fighters are pew pewing at each other from a distance a la Star Wars. But whenever that capability is finally fielded it will be such a game changer that everything that came before will suddenly be, if not obsolete, at least obsolecent.
The aerospace industry is nothing if not good at converting taxpayer dollars into advanced weappns. Eventually.
This
And I’m not sure the problems will ever be overcome to the degree that would allow Star Warsian/ Doc Smithian weapons possible.
Lasers are inherently inefficient. They have to be, in order to generate the population inversion needed for lasing*. That means that an awful lot of energy has to go somewhere, almost invariable into heat, which heats your plane. A lot.
Color center lasers had light-to -light efficiencies of up to 80%. Nowadays there are systems with efficiencies in the high nineties. But even if you have 99% efficiency, that means that a megawatt laser generate 100 kilowatts of heat that has to be dissipated somehow. Even worse, a lot of these high efficiency lasers have to be driven by another, lower efficiency laser, so that’s more heat generated.
I have worked with (laboratory-based) very high output lasers. They had to have prodigious water cooling.
Most bullets miss their target, probably by a factor of hundreds. Smokeless powder has less energy density than kerosene, even taking conversion efficiency into account (6 MJ/kg vs. 46 MJ/kg; the latter is better even at 20% efficiency). And lasers don’t need bullets.
That would be 10 kW. But even 100 kW isn’t much at these scales.
Aircraft can dump the heat into their prodigious fuel tanks. The F-35 has a tank capacity of ~8000 kg, and kerosene has a heat capacity of 2 kJ/kg-K. So it takes 160 s at 100 kW just to raise the temp by 1 K. That’s a huge firing time. The fuel tanks won’t be full all the time, but even at 1/4 capacity that’s still a lot.
And if a big heat exchanger is too much trouble, just carry some water and let it boil away. You get 22 seconds of firing time at 100 kW per kg of water.
Is that because of the bullets? Or, is it because of the targets? If you’re going to use this in your efficiency calculations, then you’re going to need to do the same for the lasers. When the targets are moving around and hiding behind objects, the lasers are going to miss as well–by the hundreds.
The advantage of a laser is that the time from targeting to impact is, for all intents and purposes, instantaneous. No time of flight to reach a spot the target isn’t in anymore.
Speed of light muzzle velocity for bullets, that would be a breakthrough.
Ever play “Duck Hunt”?
The time to identify the target, line up the sight, and pull the trigger are not instantaneous. Human reaction time is still a factor. Anyone who has every played a video game where shooting is involved knows that pulling the trigger at the right time is not as easy as it sounds. When the target is moving and hiding, it’s going to be just as hard.
When the target pops up from behind cover, the human brain will need to process that. Then, the shooter needs to put the sight onto the target. Then the shooter needs to press the trigger to fire the laser. By then, the target is likely to have moved, or popped back down.