Editing Strategic Defense Initiative (section)

===Hypervelocity Railgun (CHECMATE)===
Research on [[hypervelocity]] [[railgun]] technology was conducted to build an information base about railguns. The SDI railgun investigation, called the Compact High Energy Capacitor Module Advanced Technology Experiment, was 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 railguns 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 like a [[particle accelerator]], converting [[electrical potential energy]] into [[kinetic energy]] for the projectile. A [[conductive]] pellet (the projectile) is attracted down the rails by [[electric current]] flowing through a rail. Through [[magnetic force]]s, a force is exerted on the projectile moving it down the rail. Railguns can generate muzzle-velocities in excess of {{convert|2.4|km/s|mi/s|order=flip}}.<ref>{{Cite news |work=Technology Review |url=http://www.technologyreview.com/Infotech/20164/?nlid=857 |title=Electromagnetic Railgun Blasts Off |date=February 6, 2008 |author=Brendan Borrell}}</ref>

Railguns face a host of technical challenges to be ready for battlefield deployment. First, the rails guiding the projectile must carry sufficient power. Each firing of the railgun sends tremendous current flow (almost half a million [[ampere]]s) 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 rail replacement after each firing. Another challenge is projectile survivability. The projectiles experience acceleration force in excess of 100,000&nbsp;[[g-force|g]]. 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 hitting its target. Any on-board guidance 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 destroying ballistic missile threats, railguns were also planned for service in space platform (sensor and battle station) defense. This potential role reflected defense planner expectations that future railguns would be capable of rapid fire and on the order of tens to hundreds of shots.<ref>{{cite book | author = David Pahl | title = Space Warfare And Strategic Defense | publisher = Exeter Books | year= 1987 | isbn = 0-86124-378-1 }}</ref>