In order to achieve an effective defense against an all-out ICBM attack from the Soviet Union, the Fletcher Study, that in 1983 created the plan for the SDI, reported that Boost Phase Intercept would be needed. I explore this in great detail in my new book “Death Rays and Delusions” available now at Amazon.com. We believed the midcourse and terminal phases could overwhelm the defense with countermeasures if a large fraction of the boosters were not destroyed. Burning boosters provided a bright target that was easy to find and the thin missile skin made them relatively easy to kill. Missile vulnerability was demonstrated with a high power laser directed at a mock-up of a booster subjected to its acceleration and pressure stresses. The test was described by one of the technical skeptics as a “strapped down chicken test.”

Although the booster was very vulnerable to attack, intercepting the booster required deployment of either space based missiles or lasers. The lasers were far off in the future, and the numbers of missiles appeared to require a prohibitively large launch capability, unless the missiles were miniaturized, eventually resulting in the “Brilliant Pebbles” concept. This concept was seriously pursued for five years and then canceled when the Soviet threat disappeared in the ‘90s. Small interceptor missiles, however, did appear to provide a realistic path to BPI based on advancing missile technology.

The preferred approach in 1985, however, was the ground based laser (GBL) with only relay mirrors in space, and substantial efforts were begun to develop enormous free electron lasers to produce beams of the required power and wave length. A significant development was the invention of optics that could correct for sources of beam distortion. A remaining problem was the need for multiple high altitude locations to deal with clouds. In addition, the laser technology and physics did not cooperate, and for want of a laser, the GBL was dropped, but development of aircraft based lasers continued.

Chemical lasers on 747s enjoyed $5 billion of support for dealing with the evolving North Korean ICBM threat, but the concept was dropped by the Secretary of Defense as impractical, expensive and easily defeated. So the quest for a laser remained until recently with the development of short wave length, efficient, rugged, light weight, fiber lasers. Such lasers could be based on aircraft and be used to directly intercept boosters or relayed from space or possibly drone based mirrors to their targets. Nevertheless, this development is still many years away. So what about the near future? With the recent North Korea tests of a very high yield nuclear device and an  ICBM, the threat demands that we get very serious about deployment of an effective missile defense.

For short range defeat of boosters launched from North Korea, it is possible to utilize aircraft based very fast small missiles, and drone platforms have been proposed, as outlined in this column: http://www.sandiegouniontribune.com/military/guest-voices/sd-me-herman-northkorea-defense-20170816-story.html. So BPI, which was from the beginning of the SDI thought to be desirable or even necessary, seems to be emerging based on drone based fast missiles,  and could evolve eventually to laser weapons. To learn more, check out “Death Rays and Delusions” now available on Amazon.com.