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Relativistic kill vehicle - Wikipedia

A relativistic kinetic kill vehicle (RKKV) 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.

Rationale[edit]

RKKVs 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 RKKV could substantially limit the amount of early warning detection time. Furthermore, since the destructive effects of the RKKV 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 RKKV concept call for the RKKV 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, RKKVs 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 RKKV 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, nuclear pulse propulsion or reactionless drive (see also relativistic rockets). Since an RKKV 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.[1] 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 RKKVs have the advantage of being able to accelerate over a vastly longer distance and period of time.

Calculating energy content[edit]

Newton's formula for kinetic energy, given as E k = 1 2 m v 2 {\displaystyle E_{k}={\tfrac {1}{2}}mv^{2}} , is only an approximation for the kinetic energy of an object, reasonably accurate for speeds well below c  3108 m/s. For higher speeds, Einstein's formula for kinetic energy must be used:

E k = ( γ − 1 ) m c 2 , {\displaystyle E_{k}=(\gamma -1)mc^{2},}

where:

m is the object's mass, c is the speed of light, γ {\displaystyle \gamma } is the Lorentz factor, given by γ = 1 1 − v 2 c 2 , {\displaystyle \gamma ={\frac {1}{\sqrt {1-{\frac {v^{2}}{c^{2}}}}}},}

where v is the velocity of the object in question.

Therefore, expanded the equation is

E k = m c 2 ( 1 1 − v 2 c 2 − 1 ) {\displaystyle E_{k}=mc^{2}\left({\frac {1}{\sqrt {1-{\frac {v^{2}}{c^{2}}}}}}-1\right)}

where the kinetic energy thus tends to infinity as the velocity tends to the speed of light.

Example[edit]

A 1 kg mass traveling at 99% of the speed of light would have a kinetic energy of 5.471017 joules. In explosive terms, it would be equal to 132 megatons of TNT, or approximately 75 megatons more than the yield of Tsar Bomba, the most powerful nuclear weapon ever detonated. 1 kg of mass-energy is 8.991016 joules, or about 21.5 megatons of TNT.

In fiction[edit]

References[edit]

External links[edit]

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