The US Army had considered the issue of ballistic missile defense (BMD) as early as late in World War II. Studies on the topic suggested attacking a V-2 rocket would be difficult because the flight time was so short that it would leave little time to forward information through command and control networks to the missile batteries that would attack them. Bell Labs pointed out that although longer-range missiles flew much faster, their longer flight times would address the timing issue and their very high altitudes would make long-range detection by radar easier.
This led to a series of projects including Nike Zeus, Nike-X, Sentinel and ultimately the Safeguard Program, all aimed at deploying a nationwide defensive system against attacks by Soviet ICBMs. The reason for so many programs was the rapidly changing strategic threat; the Soviets claimed to be producing missiles "like sausages", and ever-more missiles would be needed to defend against this growing fleet. Low-cost countermeasures like radar decoys required additional interceptors to counter. An early estimate suggested one would have to spend $20 on defense for every $1 the Soviets spent on offense. The addition of MIRV in the late 1960s further upset the balance in the favour of the offense. This cost-exchange ratio was so favorable to the offense that it appeared the only thing building a defense would do would be to cause an arms race.
The Extended Range Nike Zeus
of the late-1960s was designed to provide full-country defense as part of the Sentinel-Safeguard
programs. Projected to cost $40 billion ($309 billion in 2019) it would have offered minimal protection and damage prevention in an all-out attack.
When initially faced with this problem, President Eisenhower asked ARPA to consider alternative concepts. Their
Project Defender studied all sorts of systems, before abandoning most of them to concentrate on
Project BAMBI. BAMBI used a series of satellites carrying interceptor missiles that would attack the Soviet ICBMs shortly after launch. This boost phase intercept rendered MIRV impotent; a successful attack would destroy all of the warheads. Unfortunately, the operational cost of such a system would be enormous, and the US Air Force continually rejected such concepts. Development was cancelled in 1963.
Through this period, the entire topic of BMD became increasingly controversial. Early deployment plans were met with little interest, but by the late 1960s, public meetings on the Sentinel system were met by thousands of angry protesters. After thirty years of effort, only one such system would be built; a single base of the original Safeguard system became operational in April 1975, only to shut down in February 1976.
A Soviet military A-35 anti-ballistic missile system was deployed around Moscow to intercept enemy ballistic missiles targeting the city or its surrounding areas. The A-35 was the only Soviet ABM system allowed under the 1972 Anti-Ballistic Missile Treaty. In development since the 1960s and in operation from 1971 until the 1990s, it featured the nuclear-tipped A350 exoatmospheric interceptor missile.
Lead up to SDI
The bright spikes extending below the initial fireball of one of 1952's Operation Tumbler–Snapper
test shots, are known as the "rope trick effect
". They are caused by the intense flash of thermal
released by the explosion heating the steel tower guy-wires white hot. The development of the W71
and the Project Excalibur
x-ray laser were based on enhancing the destructive effects of these x-rays.
George Shultz, Secretary of State under Reagan, suggests that a 1967 lecture by physicist Edward Teller (the so-called "father of the hydrogen bomb") was an important precursor to SDI. In the lecture, Teller talked about the idea of defending against nuclear missiles using nuclear weapons, principally the W65 and W71, with the latter being a contemporary enhanced thermal/X-ray device used actively on the Spartan missile in 1975. Held at Lawrence Livermore National Laboratory (LLNL), the 1967 lecture was attended by Reagan shortly after he became the governor of California.
Development of laser weapons in the Soviet Union began in 1964-1965. Though classified at the time, a detailed study on a Soviet space-based laser system began no later than 1976 as the
Skif, a 1 MW Carbon dioxide laser along with the anti-satellite
Kaskad, an in-orbit missile platform.
A revolver cannon (Rikhter R-23) was mounted on the 1974 Soviet Salyut 3 space station, a satellite that successfully test fired its cannon in orbit.
In 1979 Edward Teller contributed to a Hoover Institution publication where he claimed that the US would be facing an emboldened USSR due to their work on civil defense. Two years later at a conference in Italy, he made the same claims about their ambitions, but with a subtle change; now he claimed that the reason for their boldness was their development of new space-based weapons. According to the popular opinion at the time, and one shared by author Frances FitzGerald; there was absolutely no evidence that such research was being carried out. What had really changed was that Teller was now selling his latest nuclear weapon, the X-ray laser. Finding limited success in his efforts to get funding for the project, his speech in Italy was a new attempt to create a missile gap.
In 1979, Ronald Reagan visited the NORAD command base, Cheyenne Mountain Complex, where he was first introduced to the extensive tracking and detection systems extending throughout the world and into space. However, he was struck by their comments that while they could track the attack down to the individual targets, there was nothing one could do to stop it. Reagan felt that in the event of an attack this would place the president in a terrible position, having to choose between immediate counterattack or attempting to absorb the attack and then maintain an upper hand in the post-attack era. Shultz suggests that this feeling of helplessness, coupled with the defensive ideas proposed by Teller a decade earlier, combined to form the impetus of the SDI.
In the fall of 1979, at Reagan's request, Lieutenant General Daniel O. Graham, the former head of the DIA, briefed Reagan on an updated BAMBI he called High Frontier, a missile shield composed of multi-layered ground- and space-based weapons that could track, intercept, and destroy ballistic missiles, which would theoretically be possible because of emerging technologies. It was designed to replace the MAD doctrine that Reagan and his aides described as a suicide pact. In September 1981, Graham formed a small, Virginia-based think tank called High Frontier to continue research on the missile shield. The Heritage Foundation provided High Frontier with space to conduct research, and Graham published a 1982 report entitled, "High Frontier: A New National Strategy" that examined in greater detail how the system would function.
Graham was not alone in considering the anti-missile problem. Since the late 1970s, a group had been pushing for the development of a high-powered chemical laser that would be placed in orbit and attack ICBMs, the Space Based Laser (SBL). More recently, new developments under Project Excalibur by Teller's "O-Group" at LLNL suggested that a single X-ray laser could shoot down dozens of missiles with a single shot. Graham organized a meeting space at the Heritage Foundation in Washington and the groups began to meet in order to present their plans to the incoming president.
The group met with Reagan several times during 1981 and 1982, apparently with little effect, while the buildup of new offensive weaponry like the B-1 Lancer and MX missile continued. 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, there was good evidence that in the late 1960s the Soviets were devoting serious thought to both explosive and non-explosive nuclear power sources for lasers.