Relativistic Kill Vehicle

A relativistic kill vehicle (RKV) or relativistic bomb is a hypothetical weapon system sometimes found in science fiction. The details of such systems vary widely, but the key common feature is the use of a massive impactor traveling at a significant fraction of light speed to strike the target. Therefore the weapon would be an extreme example of the real-life concept of a kinetic bombardment.

RKVs have been proposed as a method of interstellar warfare, especially in settings where faster than light travel or sensors are impossible. By traveling near the speed of light, an RKV could substantially limit the amount of early warning detection time. Furthermore, since the destructive effects of the RKV are carried by its kinetic energy, destroying the vehicle near its target would do little to reduce the damage; the cloud of particles or vapor would still be traveling at nearly the same speed and would have little time to disperse. Indeed, some versions of the RKV concept call for the RKV to explode shortly before impact to shower a wide region of space.

As providing terminal guidance for such a high-speed object would likely be difficult, RKVs are usually proposed as a strategic weapon targeted against large and predictable targets such as planets. However, they can still be used against smaller targets like spaceships, by aiming the weapons in the area they are in, and detonating a fuse in advance to shatter the mass into swarms of smaller particles, all traveling at nearly the same speed. This would cover a much larger area, and destroy smaller targets in space. Accelerating a mass to such velocities in the first place will likely require vast amounts of energy and large, unwieldy accelerators.

An RKV could theoretically be launched using any of the spacecraft propulsion techniques that are capable of accelerating starships to relativistic velocities, such as antimatter rockets, Bussard ramjet systems, or nuclear pulse propulsion (see also relativistic rockets). Since an RKV would be unmanned, higher accelerations could be used (though with most propulsion methods high acceleration may not be the most efficient approach).

In some science fiction smaller relativistic projectiles can sometimes be found depending on the technologies imagined in any particular scenario. In the movie Eraser, for example, characters used man-portable "gauss rifles" that were able to fire bullets at relativistic velocities. Man-portable weapons of this type would have extreme issues with reaching such high speeds over such a short distance; to reach 1% of light speed over the length of a one-meter accelerator would require 4.5 · 1012 m/s2 (or over 450 billion g) of acceleration. Space-based RKVs have the advantage of being able to accelerate over a vastly longer distance and period of time.