The Pentagon's Ray Gun Can Stall Cars (defenseone.com)

john of sparta quotes Defense One: The Defense Department's Joint Non-Lethal Weapons Program, or JNLWD, is pushing ahead with a new direct energy weapon that uses high-powered microwaves to stop cars in their tracks without damaging the vehicle, its driver, or anyone else. The jammer works by targeting the car's engine control unit causing it to reboot over and over, stalling the engine. Like an invisible hand, the microwaves hold the car in place. "Anything that has electronics on it, these high-powered microwaves will affect," David Law, who leads JNLWD's technology division, said in March. "As long as the [radio] is on, it holds the vehicle stopped."
It weighs 400 pounds -- it's the size of a large copy machine -- and uses 300 kilowatts of power that's generated by a gasoline-powered turbine.

"To deploy it, the driver would pull out in front of the attacker and turn it on."

Comments

Won't damage the driver??

[taylormc]

...with 300 KW of microwave energy? Good luck with starting a family after that.

Re:Won't damage the driver??

[thesupraman]

Ah, but its nice warm fuzzy AMERICAN microwave energy, not evil terrorist radiation.
Its like the American laser 'defense' weapons that instead of burning out eyes, just gently exfoliate the facial skin in a loving caress.
Because, you know, otherwise they would be illegal blinding weapons, against conventions the US signed.

Re:Won't damage the driver??

[Aighearach]

That shielding won't save you, and is actually the point! The shielding absorbs the energy, causing a large transient voltage spike in your car's electrical system. That causes the ECU to crash, because it isn't designed for those conditions.

One of the key things to understand here is that the car only has two electrical connections, battery + and battery -. Battery - is often called "ground," it will tend to be at local ground because it is referenced to the vehicle chassis which will likely be at ground potential when you start the car. But it doesn't have a third wire with an actual Earth connection, and the wheels are usually electrical insulators. What that boils down to is that shielding works by converting the RF interference into a short voltage spike, some of which is converted to heat in the ECU and any other electronics with voltage regulation. All the devices in the car are already expected to survive "double battery condition," which is when the tow truck driver gives you a jump start using 24V, which is really 28V+ because their engine is running and their battery is charging voltage. So there is a huge amount of voltage margin and the shielding works well without even having system-wide voltage regulation. But in the extreme case, as with this device, you eventually overload the ECU's voltage regulation, and since the circuit is designed to be robust, it simply crashes and reboots as soon as the spike dissipates. Repeated use could easily damage a vehicle, though.

For protection against this, I'd want to try something low-tech like a wire brush connected to the chassis that can drag on the ground slightly, so that voltage spikes can find a path to Earth instead of getting stuck in the circuit.

Great use of public funds!

[Gravis Zero]

Another technical achievement that can be defeated by aluminum foil. ;)

One question

[mridoni]

If you have to take along a 300kW gasoline-powered turbine and a copy machine-sized unit, isn't it easier to just throw this stuff in the path of the car you want to stop?

Re:One question

[wierd_w]

Really, I had this idea a very long time ago. You don't need the full 300kw power system if you use a pulsed maser instead of a constant broadcast. That means you can use some kind of storage system with a smaller input, such as an air-coil resonant tank, or a super-capacitor array. You just need to be able to deliver the 300kw on each pulse. It takes time for the ICM to reboot; you dont have to keep roasting its ground lanes with signal. You just have to make it malfunction and restart in a reasonable interval. 1hz pulse width would be sufficient.

Assuming these tools are driving their emitter nonstop, that would let you use 1/60th of the power generation hardware, or ~5kw power system. Even less if you use a 2sec interval instead of 1.

For some variations of the pulse timing, a second alternator on the delivery vehicle would be sufficient; the bulky part would be the super capacitor array, which could be installed in the trunk, or in the rear seats.

The referenced idea I had called for a klystron resonant cavity with a pulsed electron beam, and a low power reference microwave signal produced by a small magnetron. As long as pulse duration time is some whole integer product of the reference signal frequency, it should work fine.

Hilarious that an idea I had as a teenager in the 90s is being seriously considered here though. LOL.

Re:A solution: "very" old tech

[tlhIngan]

passive tech works not very efficient but works, with manual choke

For varying degrees of "works".

It's not just efficiency, it's basically ease of operation. One of the big things about modern cars is they are "twist and go". You twist the key (or push the button nowadays) and the car goes. Doesn't matter if the engine is hot (vapor lock is not an issue), very cold, or any other thing, including poor fuel. You want it to go, it goes, and unless something is very wrong, it will go. (You can even shoot out cylinders and while it stalls the engine, you can have a V8 engine with 6 dead cylinders still barely run. It's not happy, but the computer is able to compensate and get you home, albiet slowly).

Anyhow, did you wonder why it took 300kW to do it? It's because an ECU is very well shielded to begin with - the metal body of the car already is a great faraday cage. But the ECU is also encased in a metal body because it's a very challenging environment with a lot of stray RF caused by all the high voltages around.

In fact, if you're willing to settle for post-millennium vehicles, disrupting the keyfob-car communications will generally be far easier - the windows in the passenger compartment don't generally block RF, and the signal levels are weak since keyfobs are powered by itty coin cell batteries with poor peak power performance, so they don't have much transmit power. (I had to replace the battery in my keyfob - it still measured 3V, while batteries that are generally dead used in PCs measure pretty damn close to 0.5V. Heck, even my watch which died suddenly had a battery that measured around 0.5V. No doubt the battery was low, so it couldn't supply the necessary power for the transmitter)