The Sentinel/Safeguard Program was the ultimate development of the Nike series of missiles. It was originally proposed in 1967 as the
Sentinel Program, and would have covered most of the continental United States, but in 1969 it was trimmed down to the
Safeguard Program for defending strategic sites. Eventually it came down to a single site in North Dakota defending the air base and missile fields around
Grand Forks Air Force Base, but that system closed shortly after becoming operational. As is typical for many of these early programs, the ABM systems themselves (the short range
Sprint and long range
Spartan) proved to work well, but the electronics weren't quite up to the job.
However, it's possible that Sentinel/Safeguard was held back by using 1960s vintage electronics. The United States Navy suffered similar missile success and electronic failure during development of its
Typhon Combat System in the 1960s before succeeding with AEGIS in the 1970s. It's possible that a revived program could have achieved more success through using newer computer technology, especially with the development of the microprocessor (the Navy F-14 Tomcat program being an early user).
Given the Reagan Administration's interest in strategic warfare and its revival of many other cancelled programs, it seems that Sentinel/Safeguard is something that might have been looked into. It also has the advantage of being legal to test (underground tests for the nuclear warheads, and live tests for the missiles/conventional warheads) and even field on a limited basis (at least in North Dakota) under the
Anti-Ballistic Missile Treaty. Also, unlike many other systems developed by the United States in the 1980s, it wouldn't be creating a new weapons category or arms race, as the Soviet Union already had the
A-35 anti-ballistic missile defense system fielded around of Moscow.
Is reviving this something that Reagan might have done? What might the repercussions have been? Also, why wasn't it revived historically?