For the purposes of the test, the truck had its engine and drive train running, although the vehicle itself was up on props. Rather than causing the engine to explode, as per Hollywood, the truck was simply rendered unable to move. Reading between the lines, perhaps Lockheed believes that the gear will be a useful, potentially non-lethal precaution against explosive vehicles being driven, at speed, towards infrastructure points, guard towers or military bases.
ATHENA is based on Lockheed's earlier ADAM system, which was designed to shoot down enemy rockets while in mid-air. This time out, the hardware used a technique called "spectral beam combining," which involves taking multiple laser modules and pointing them in the same place to create a single, powerful, high-quality laser beam. Now, feel free to disagree with us, but doesn't that sound an awful lot like how the Death Star's main weapon worked?