Editing Project Nike (section)

=== Nike-X ===
{{main|Nike-X}}
[[File:Sprint missile maneuvering after launch.jpg|thumb|The Sprint missile was the main weapon in the Nike-X system, intercepting enemy ICBM warheads only seconds before they exploded.]]

'''Nike-X''' was a proposed [[US Army]] [[anti-ballistic missile]] (ABM) system designed to protect major cities in the United States from attacks by the [[Soviet Union]]'s [[ICBM]] fleet. The name referred to its experimental basis, it was intended to be replaced by a more appropriate name when the system was put into production. This never came to pass; the original Nike-X concept was replaced by a much more limited defense system known as the [[Sentinel program]] that used some of the same equipment.

Nike-X was a response to the failure of the earlier [[LIM-49 Nike Zeus|Nike Zeus]] system. Zeus had been designed to face a few dozen Soviet ICBMs in the 1950s, and its design would mean it was largely useless by mid-1960s when it would be facing hundreds. It was calculated that a salvo of only four ICBMs would have a 90% chance of hitting the Zeus base, as their radars could only track a few warheads at the same time. Worse, the attacker could use [[radar reflector]]s or [[high-altitude nuclear explosion]]s to obscure the warheads until they were too close to attack, making a single warhead attack highly likely to succeed.

Nike-X addressed these concerns by basing its defense on a very fast, short-range missile known as [[Sprint (missile)|Sprint]]. Large numbers would be clustered near potential targets, allowing successful interception right up to the last few seconds of the warhead's re-entry. They would operate below the altitude where decoys or explosions had any effect. Nike-X also used a new radar system that could track hundreds of objects at once, allowing salvoes of many Sprints. It would require dozens of missiles to overwhelm the system. Nike-X considered retaining the longer range Zeus missile, and later developed an extended range version known as [[LIM-49 Spartan|Zeus EX]]. It played a secondary role in the Nike-X system, intended primarily for use in areas outside the Sprint protected regions.

Nike-X required at least one interceptor missile to attack each incoming warhead. As the USSR's missile fleet grew, the cost of implementing Nike-X began to grow as well. Looking for lower-cost options, a number of studies carried out between 1965 and 1967 examined a variety of scenarios where a limited number of interceptors might still be militarily useful. Among these, the I-67 concept suggested building a lightweight defense against very limited attacks. When the Chinese exploded their first [[Thermonuclear weapon|H-bomb]] in 1967, I-67 was promoted as a defense against a Chinese attack, and this system became Sentinel in October. Nike-X development, in its original form, ended.