At that speed one kilogram has 5*10 E11 Joules of energy, about the same as three ATBIP bombs, basically scaled up MOABs. But each 'pellet' weighs in at several tonnes of deuterium/hydrogen ice, and is ignited by a kinetic slug accelerated to a blistering 1,000 km/s, or 0.33% of the speed of light. In the designs for the ~250 km long Bond/Martin worldship design the drive is a scaled up Deadelus style pulse system. Electron beams and particle beams can also be used in the same way, although with greater difficulty re-routing the beams. This also introduces and interesting tactical element when a spacecraft's commander must decide between firing his laser cannon, or accelerating.

Surely a spacecraft could be designed with the lasers deep within the hull, routing beams either to the weapons or drive as needed.

The other kind of nuclear pulse propulsion, that of Inertial Confinement Fusion has a battery of powerful lasers as part of the drive system. Of all the different spacecraft drive systems so far invented or imagined, which lend themselves most readily to a particular weapons system? An externally powered craft like the Michael has to generate power if lasers and EM guns are used, so unpowered weapons like Bomb Pumped Lasers become ideal, as well as dovetailing nicely with the existing logistical needs. These are nuclear pumped lasers, primed by the same detonations that accelerate the spacecraft. It carries a secondary armament of battleship gun turrets, but the primary weapons are the so called 'spurt bombs'. In Footfall, one of the greatest SF invasion stories ever written, the battleship Michael uses an Orion pulse drive. The connection between weapons and drives is much more closely intertwined however. Most photon drives, mass drives, and a few others have collimated exhausts, and are in essence gigantic DEW weapons. The direct effects of the particles, along with secondary radiation, could damage or destroy sensors, weapons, and any other equipment mounted on the exterior of the craft and making a boarding action feasible. With a plasma exhaust, however, it might make an effective 'soft-kill' weapon.

Of course, the drive plume of most spacecraft is not well collimated, and so it would be a short ranged weapon at best. Given the energies involved with fast interplanetary flight, or even slow interstellar, the most powerful weapon a future space warcraft may have at its command is the main drive unit. Would you want to be standing behind an Orion drive spacecraft when it started a burn? How about a mass drive system, or a Beam Core Antimatter Drive with a exhaust of pure gamma rays? And photon drives have 300MW of power per newton of thrust. Postulated by the SF author Larry Niven the Kzinti Lesson states simply that 'A reaction drive's efficiency as a weapon is in direct proportion to its efficiency as a drive.' Or as TV Tropes calls it, the weaponised exhaust.

Fsx acceleration weapons