Most extreme high power lasers are chemical in nature, but these are probably somewhat similar to the setup in [1] by the laser power mentioned. I would guess u

Most extreme high power lasers are chemical in nature, but these are probably somewhat similar to the setup in [1] by the laser power mentioned. I would guess using an APU to control conditions but it does not rule out your guess of using the onboard systems. 1. https://en.m.wikipedia.org/wiki/AN/SEQ-3_Laser_Weapon_System https://en.m.wikipedia.org/wiki/AN/SEQ-3_Laser_Weapon_System