[1] Reagan called for a system that would render nuclear weapons obsolete, and to end the doctrine of mutual assured destruction (MAD), which he described as a "suicide pact".

These programs have continued to be key sources of funding for research scientists in particle physics, supercomputing/computation, advanced materials, and other critical science and engineering disciplines.

"[19] Through declassified intelligence material, the wider implications and effects of the program revealed that due to the potential neutralization of its arsenal and resulting loss of a balancing power factor, SDI was a cause of grave concern for the Soviet Union and its successor state Russia.

[22][23] CIA Director Mike Pompeo called for additional funding to achieve a full-fledged "Strategic Defense Initiative for our time, the SDI II" though it is unclear what this had to do with SDA.

[25] This led to a series of projects including Nike Zeus, Nike-X, Sentinel and ultimately the Safeguard Program, all aimed at developing a system to defend against attacks by Soviet ICBMs.

[34] Though classified at the time, a detailed study on a Soviet space-based laser system began no later than 1976 with the Polyus, a 1 MW Carbon dioxide laser-based orbital weapons platform prototype.

Instead, Teller was promoting his latest weapon, the X-ray laser that was finding only limited funding, his speech in Italy was a new attempt to synthsize a missile gap.

However, in early 1983, the Joint Chiefs of Staff met with the president and outlined the reasons why they might consider shifting some of the funding from the offensive side to new defensive systems.

According to a 1983 US Interagency Intelligence Assessment, good evidence indicated that in the late 1960s the Soviets were devoting serious thought to both explosive and non-explosive nuclear power sources for lasers.

Strategic Defense System (SDS) was the low-earth orbit (LEO) Smart Rocks concept with an added layer of ground-based missiles sited in the US.

Subsequent studies suggested that this approach would be cheaper, easier to launch and more resistant to counterattack, and in 1990 Brilliant Pebbles was selected as the baseline model for SDS Phase 1.

Against novel threats the Brilliant Pebbles would have limited utility, largely because the missiles fired for only a short period and the warheads did not rise high enough for them to be easily tracked by a satellite above them.

The Homing Overlay Experiment (HOE) was the first such system tested by the Army, and the first successful hit-to-kill intercept of a mock ballistic missile warhead outside the Earth's atmosphere.

Once in space, the KKV could extend a folded structure similar to an umbrella skeleton of 13 ft (4 m) diameter to enhance its effective cross section.

[53] For each test a Minuteman missile was launched from Vandenberg Air Force Base in California carrying a single mock re-entry vehicle targeted for Kwajalein lagoon more than 4,000 miles (6,400 km) away.

[56] At the urging of Senator David Pryor, the General Accounting Office investigated the claims and concluded that though steps were taken to make it easier for the interceptor to find its target (including some of those alleged by the New York Times), the available data indicated that the interceptor had been successfully guided by its onboard infrared sensors in the collision, and not by an onboard radar guidance system as alleged.

Nuclear explosions give off a burst of X-rays, which the Excalibur concept intended to focus using a lasing medium consisting of metal rods.

However, on March 26, 1983,[61] the first test (known as the Cabra event), was performed in an underground shaft and resulted in marginally positive readings possibly caused by a faulty detector.

According to BMDO, the research on neutral particle beam accelerators, originally funded by SDIO, could eventually be used to reduce the half-life of nuclear waste products using accelerator-driven transmutation technology.

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 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.

[88] A major objective of that strategy was the political separation of Western Europe from the United States, which the Soviets sought to facilitate by aggravating allied concern over the SDI's potential implications for European security and economic interests.

They commonly expressed the notion that SDI was equivalent to starting an economic war through a defensive arms race to further cripple the Soviet economy with extra military spending.

[95][clarification needed] In 2014, a declassified CIA paper stated that "In response to SDI, Moscow threatened a variety of military countermeasures in lieu of developing a parallel missile defense system".

[100] In comments to the media on March 7, 1986, SDIO Acting Deputy Director Dr. Gerold Yonas described "Star Wars" as an important tool for Soviet disinformation and asserted that the nickname gave an entirely wrong impression of SDI.

Ashton Carter, then a board member at MIT, assessed SDI for Congress in 1984, noting difficulties in creating an adequate missile defense shield, with or without lasers.

They said that a defensive system was costly and difficult to build yet simple to destroy and claimed that the Soviets could easily use thousands of decoys to overwhelm it during a nuclear attack.

In March 1984, Bethe coauthored a 106-page report for the Union of Concerned Scientists that concluded "the X-ray laser offers no prospect of being a useful component in a system for ballistic missile defense.

"[103] On June 28, 1985, David Lorge Parnas resigned from SDIO's Panel on Computing in Support of Battle Management, arguing in eight short papers that the SDI software could never be made trustworthy and that such a system would inevitably be unreliable and menace humanity in its own right.

When Reagan proposed technology sharing again, Gorbachev stated "we cannot assume an obligation relative to such a transition", referring to the cost of implementing such a program.