Hypervelocity Rail Gun (CHECMATE)
Research out of
hypervelocity railgun technology was done to build an information base about rail guns so that SDI planners would know how to apply the technology to the proposed defense system. The SDI rail gun investigation, called the
Compact High Energy Capacitor Module Advanced Technology Experiment (CHECMATE), had been able to fire two projectiles per day during the initiative. This represented a significant improvement over previous efforts, which were only able to achieve about one shot per month. Hypervelocity rail guns are, at least conceptually, an attractive alternative to a space-based defense system because of their envisioned ability to quickly shoot at many targets. Also, since only the projectile leaves the gun, a railgun system can potentially fire many times before needing to be resupplied.
A hypervelocity railgun works very much like a
particle accelerator insofar as it converts
electrical potential energy into
kinetic energy imparted to the projectile. A
conductive pellet (the projectile) is attracted down the rails by
electric current flowing through a rail. Through the
magnetic forces that this system achieves, a force is exerted on the projectile moving it down the rail. Railguns can generate muzzle-velocities in excess of 2.4 kilometers per second.
[64] At this velocity, even a rifle-bullet sized projectile will penetrate the front armor of a main battle tank, let alone a thinly protected
missile guidance system.
Rail guns face a host of technical challenges before they will be ready for battlefield deployment. First, the rails guiding the projectile must carry very high power. Each firing of the railgun produces tremendous current flow (almost half a million
amperes) through the rails, causing rapid erosion of the rail's surfaces (through
ohmic heating, and even vaporization of the rail surface.) Early prototypes were essentially single-use weapons, requiring complete replacement of the rails after each firing. Another challenge with the rail gun system is projectile survivability. The projectiles experience acceleration force in excess of 100,000
g. In order to be effective, the fired projectile must first survive the mechanical stress of firing and the thermal effects of a trip through the atmosphere at many times the speed of sound before its subsequent impact with the target. In-flight guidance, if implemented, would require the onboard navigation system to be built to the same level of sturdiness as the main mass of the projectile.
In addition to being considered for destroying ballistic missile threats, rail guns were also being planned for service in space platform (sensor and battle station) defense. This potential role reflected defense planner expectations that the rail guns of the future would be capable of not only rapid fire, but also of multiple firings (on the order of tens to hundreds of shots).
[65]
