LIM-49 Nike Zeus
|Nike Zeus B|
Nike Zeus B test launch at White Sands
|Place of origin||United States|
|Used by||US Army|
|Weight||24,200 lb (11,000 kg) total|
|Length||50 feet 2 inches (15.29 m) total|
|Diameter||36 inches (910 mm)|
|Engine||450,000 lbf (2,000,000 N) booster|
|75 nmi (139 km; 86 mi)|
|Flight ceiling||over 150 nmi (280 km; 170 mi)|
|Speed||greater than Mach 4|
Nike Zeus was an anti-ballistic missile (ABM) system developed by the US Army during the late 1950s and early 1960s, designed to destroy Soviet ICBM warheads before they could hit targets in the United States. It was designed by Bell's Nike team, and was initially based on the earlier Nike Hercules anti-aircraft missile. The original Zeus A, given the tri-service identifier XLIM-49, was designed to intercept warheads in the upper atmosphere, mounting a 25 kiloton W31 nuclear warhead to guarantee a kill. During development it was greatly enlarged and extended into a totally new design, Zeus B, intended to intercept warheads over a much larger area, and mounting a 400 kiloton W50 warhead. In several successful tests, the B model proved itself able to intercept warheads, and even satellites.
The nature of the strategic threat changed dramatically during the period that Zeus was being developed. Originally expected to face only a few dozen ICBMs, a nationwide defense was feasible, although expensive. In 1957, growing fears of a Soviet sneak attack led it to be positioned primarily as a way to protect Strategic Air Command's bomber bases. When the Soviets claimed to be building hundreds of missiles, the US raced to close this mythical missile gap. Building more Zeus missiles to match the Soviet fleet would be expensive, more expensive than building US ICBMs and ignoring the bombers. Adding to the concerns, a number of technical problems emerged that suggested Zeus would have little value against any sort of sophisticated attack.
The system was the topic of intense debate and interservice rivalry throughout its lifetime. When the ABM role was given to the Army in 1958, the US Air Force began a long series of attacks on Zeus, both within defense circles as well as in the press. The Army returned these attacks in kind, taking out full page spreads in popular mass market news magazines to promote Zeus, as well as spreading development contracts across many states in order to garner the maximum political support. As deployment neared in the early 1960s, the debate became a major political issue. The question ultimately became whether or not a system with limited effectiveness would be better than nothing at all.
The decision whether to proceed with Zeus eventually fell to President Kennedy, who was fascinated by the indecision surrounding the ABM system. In 1963, the Secretary of Defense, Robert McNamara, decided to cancel Zeus as it would be ineffective. McNamara directed funding towards studies of new ABM concepts being considered by ARPA, selecting the Nike-X concept, a layered system with more than one type of missile. To Zeus, Nike-X added a short range missile, the Sprint, along with greatly improved radars and computer systems that provided defense over a wide area.
- 1 History
- 2 Testing
- 3 Operational use
- 4 Description
- 5 Specifications
- 6 Notes
- 7 References
- 8 External links
Early ABM studies
The first known concerted effort to attack ballistic missiles was carried out by the Army Air Force in 1946, when two contracts were sent out as Project Wizard and Project Thumper to consider the problem of shooting down missiles of the V-2 type. These projects identified the main problems; the target could approach from anywhere within a vast area, and reached its targets in only five minutes. To start with, existing radar systems would have difficulty seeing the missile launch at ranges in the hundreds of miles. Assuming one had detection of the missile, existing command and control arrangements would have serious problems forwarding that information to any behind-the-lines battery in time for them to find it on their local radars and attack. The task appeared impossible at that time.
However, the early results also noted that the system might be able to work against longer-ranged missiles, where they would have much longer times to prepare. Both projects were allowed to continue as research efforts, and were transferred to the US Air Force when the Air Force separated from the Army. The Air Force faced significant budget constraints and cancelled Thumper in 1949 in order to use its funds to continue their GAPA surface-to-air missile (SAM). The next year they merged the Wizard and GAPA projects to develop a new long-range SAM design, which would emerge a decade later as the CIM-10 Bomarc. ABM research at the Air Force essentially, although not officially, ended.
The Army contacted the Johns Hopkins University Operations Research Office (ORO) to consider the task of shooting down ballistic missiles using a Nike-like system. The ORO report took three years to complete, and the resulting The Defense of the United States Against Aircraft and Missiles was comprehensive. While this study was still progressing, in February 1955 the Army had concluded that missile systems had advanced enough to attack ICBMs, and in March they contracted Bell's Nike team to begin a detailed 18 month study of the problem under the name Nike II.
The first section of the Bell study was returned to the Army Ordnance department at the Redstone Arsenal on 2 December 1955. It considered the full range of threats including existing jet aircraft, future ramjet powered aircraft flying at up to 3,000 knots (5,600 km/h), short-range ballistic missiles of the V-2 type flying at about the same speed, and an ICBM warhead traveling at 14,000 knots (26,000 km/h). They suggested that a single rocket booster could be equipped with either of two upper stages, one with fins for use in the atmosphere against aircraft, and another with vestigial fins and thrust vectoring for use above the atmosphere against missiles.
Considering the ICBM problem, the study went on to suggest that the system would have to be effective between 95 and 100% of the time in order to be worthwhile. They considered attacks against the warhead while the missile was in the midcourse, just as it reached the highest point in its trajectory. They quickly eliminated this, as it would require the ABM to be launched at about the same time as the ICBM in order to meet in the middle, and they could not imagine a way to arrange this. Working at much shorter ranges seemed the only possible solution. Considering the attack itself, the missiles would approach each other at rates on the order of 5 miles (8.0 km) per second; in order to have enough time to maneuver for the final approach, an active seeker in the warhead would have to be very powerful, and thus very heavy. Instead, a command guided solution like the earlier Nikes was selected.
Bell returned a further study, delivered on 4 January 1956, that demonstrated the need to intercept the incoming warheads at 100-mile (160 km) altitude, and suggested that this was within the abilities of an upgraded version of the Nike Hercules missile. The 5 mile per second approach speed of the ICBM warhead, combined the tens of seconds that it took for the Nike missile to climb to the warhead's altitude, required that the warhead be initially detected at about 1,000 miles (1,600 km) range in order to leave enough time to it to be intercepted. Warheads are relatively small and have limited radar cross sections, so this requirement demanded radars of extremely high power.
The interceptor would lose maneuverability as it climbed out of the atmosphere and its aerodynamic surfaces became less effective, so it should be directed onto the target as rapidly as possible, leaving only minor fine tuning later in the engagement. This required that accurate tracks be developed for both the warhead and outgoing missile very quickly, in comparison to a system like Hercules where the guidance could be updated throughout the engagement. This demanded new computers and tracking radars with much higher processing rates than the systems used on earlier Nikes. Bell suggested that their own transistor offered the solution to the data processing problem. After running 50,000 simulated intercepts on analog computers, Bell returned a final report on the concept in October 1956, indicating that the system was within the state of the art.
Army vs. Air Force
The Army and Air Force had been involved in longstanding interservice fighting over missile systems since they split in 1947. The Army considered surface-to-surface missiles (SSM) an extension of artillery and surface-to-air designs as the modern replacement for their anti-aircraft artillery. The Air Force considered the nuclear SSM to be an extension of their strategic bombing role, and any sort of long-range anti-aircraft system to be their domain as it would integrate with their fighter fleet. This led to considerable duplication of effort, which was widely seen as wasteful. Although the Air Force had abandoned their ABM efforts, as soon as the Nike II program was announced in 1955, the Air Force reactivated Wizard. This time the program was not aimed at V-2 class battlefield missiles, but called for a long-range anti-ICBM system of much greater performance than Zeus. This was added to a growing list of tit-for-tat projects, which included the Army's Hercules vs. Air Force Bomarc, and the Jupiter missile vs. Thor IRBMs.
In a 26 November 1956 memorandum, US Secretary of Defense Charles Erwin Wilson attempted to end the fighting by limiting the Army to weapons with 200-mile (320 km) range, and those involved in surface-to-air defense to only 100 miles (160 km). The memo also placed limits on Army air operations, severely limiting the weight of the aircraft they were allowed to operate. To some degree this simply formalized what had largely already been the case in practice, but Jupiter fell outside the range limits and the Army was forced to hand them to the Air Force.
The result was another round of fighting between the two forces. Jupiter had been designed to be a highly accurate weapon able to attack Soviet military bases in Europe, as compared to Thor, which was intended to attack Soviet cities and had considerably less accuracy. The Army was extremely upset about being forced to turn them over to the Air Force, which eliminated any offensive strategic role for the Army. In return, the Air Force complained that Zeus was too long ranged and the ABM effort should center on Wizard. But the Jupiter handover meant that Zeus was now the only strategic program being carried out by the Army, and its cancellation would mean "virtually the surrender of the defense of America to the U.S.A.F at some future date."
Gaither Report, missile gap
In May 1957, Eisenhower tasked the President's Science Advisory Committee (PSAC) to provide a report on the potential effectiveness of fallout shelters and other means of protecting the US population in the event of a nuclear war. Chaired by Horace Rowan Gaither, the PSAC team completed their study in September, publishing it officially on 7 November as Deterrence & Survival in the Nuclear Age, but today known as the Gaither Report. After ascribing an expansionist policy to the USSR, along with suggestions that they were more heavily developing their military than the US, the Report suggested that there would be a significant gap in capability in the late 1950s due to spending levels.
While the report was being prepared, in August 1957 the Soviets successfully launched their R-7 Semyorka (SS-6) ICBM, and followed this up with the successful launch of Sputnik 1 in October. Over the next few months, a series of intelligence reviews resulted in ever increasing estimates of the Soviet missile force. National Intelligence Estimate (NIE) 11-10-57, issued in December 1957, stated that the Soviets would have perhaps 10 prototype missiles in service by mid-1958. But after Nikita Khrushchev claimed to be producing them "like sausages",[a] the numbers began to rapidly inflate. NIE 11-5-58, released in August 1958, suggested there would be 100 ICBMs in service by 1960, and 500 in 1961, or 1962 at the latest.
With the NIE's suggesting the existence of the gap Gaither predicted, near panic broke out in military circles. In response, the US began to rush its own ICBM efforts, centered on the SM-65 Atlas. These missiles would be less susceptible to attack by ICBM than bombers, especially in future versions which would be launched from underground silos. But even as Atlas was rushed, it appeared there would be a missile gap; during the period from about 1959 to 1963 the NIE estimates suggested the Soviets would have significantly more ICBMs than the US. To ensure this did not happen, the Gaither Report called for the installation of active defenses at SAC bases, Hercules in the short term and an ABM for the 1959 period, along with new early warning radars for ballistic missiles to allow alert aircraft to get away before the missiles hit. Even Zeus would come too late to cover this period, and some consideration was given to an adapted Hercules or a land based version of the Navy's RIM-8 Talos as an interim ABM.
Douglas Aircraft had been selected to build the missiles for Zeus, known to them as the DM-15. This was essentially a scaled up Hercules with an improved, more powerful single piece booster replacing Hercules' cluster of four smaller boosters. Intercepts would take place at the limits of the Wilson requirements, at ranges and altitudes of about 100 miles (160 km). Prototype launches were planned for 1959. For more rapid service entry there had been some consideration given to an interim system based on the original Hercules missile, but these efforts were dropped. Likewise, early requirements for a secondary anti-aircraft role were also eventually dropped.
In early 1957 Wilson signaled his intentions to retire, and Eisenhower began looking for a replacement. During his exit interview, only four days after Sputnik, Wilson told Eisenhower that "trouble is rising between the Army and the Air Force over the 'anti-missile-missile'". The new Secretary of Defense, Neil McElroy, took office on 9 October 1957.
Shortly after taking office, McElroy formed a panel to investigate ABM issues. The panel examined the Army and Air Force projects, and found the Zeus program considerably more advanced than Wizard. McElroy told the Air Force to stop work on ABM missiles and use Wizard funding for the development of long range radars for early warning and raid identification. These were already under development as the BMEWS network. The Army was handed the job of actually shooting down the warheads, and McElroy gave them free hand to develop an ABM system as they saw fit, free of any range limitations.
The team designed a much larger missile with a greatly enlarged upper fuselage and three stages, more than doubling the launch weight. This version extended range, with interceptions taking place as far as 200 miles (320 km) downrange and over 100 miles (160 km) in altitude. An even larger booster took the missile to hypersonic speeds while still in the lower atmosphere, so the missile fuselage had to be covered over completely with a phenolic ablative heat shield to protect the airframe from melting.[b] The new DM-15B Nike Zeus B (the earlier model retroactively becoming the A) received a go ahead for development on 16 January 1958, the same date the Air Force was officially told to stop all work on a Wizard missile.
On 22 January 1958, the National Security Council gave Zeus S-Priority, the highest national priority. Additional funds were requested to the Zeus program to ensure an initial service date in the fourth quarter of 1962, but these were denied, delaying service entry until some time in 1963.
Exchange ratio and other problems
With their change of fortunes after McElroy's 1958 decision, Army General James M. Gavin stated that Zeus would soon replace strategic bombers as the nation's main deterrent. In response to this turn of events, the Air Force stepped up their policy by press release efforts against the Army, as well as agitating behind the scenes within the Defense Department.
As part of their Wizard research, the Air Force had developed a formula that compared the cost of an ICBM to the ABM needed to shoot it down. The formula, later known as the cost-exchange ratio, produced a dollar figure; if the cost of the ICBM was less than that figure, the economic advantage was in favor of building more ICBMs, and an adversary could win an offensive/defensive arms race. A variety of scenarios demonstrated that it was almost always the case that the offense had the advantage. This problem had been conveniently ignored during Wizard, but as soon as the Army was handed sole control of the ABM efforts, the Air Force immediately submitted it to McElroy. McElroy identified this as an example of interservice fighting, but was concerned that the formula might be correct.
For an answer, McElroy turned to the Re-entry Body Identification Group (RBIG), a sub-group of the Gaither Committee led by William E. Bradley, Jr. that had been studying the issue of penetrating a Soviet ABM system. The RBIG delivered an extensive report on the topic on 2 April 1958. It suggested that defeating a Soviet ABM system would not be difficult. Their primary suggestion was to arm US missiles with more than one warhead, a concept known as Multiple Re-entry Vehicles (MRV), and ensure they would separate by more than a mile during their flight. Combined with radiation hardening of the warhead, this would ensure that multiple interceptor missiles would be needed to attack them. The US could overwhelm a Soviet ABM system for relatively low cost.
Turning this argument about, they delivered a report to McElroy that agreed with the Air Force's original claims on cost. But they then considered the Zeus system itself, and noted that its use of mechanically steered radars, with one radar per missile, meant that Zeus could only launch a small number of missiles at once. If the Soviets deployed MRV, several warheads would arrive at the same time, and the Zeus would simply not have time to shoot at them all. Only four warheads arriving within one minute would result in one of them hitting the Zeus base 90% of the time. The RBIG noted that an ABM system "demands such a high rate of fire from an active defense system, in order to intercept the numerous reentry bodies which arrive nearly simultaneously, that the expense of the required equipment may be prohibitive". They went on to question the "ultimate impossibility" of an ABM system. The arguments would remain the primary arguments against ABMs for the next two decades.
McElroy responded to the RBIG report in two ways. First, he turned to the newly created ARPA group to examine the RBIG report. APRA, directed by Chief Scientist Herbert York, returned another report broadly agreeing with everything they said. Considering both the need to penetrate a Soviet ABM and a potential US ABM system, York noted that:
The problem here is the usual problem between defense and offenses, measures, countermeasures, counter-counter measures, et cetera, in which it has been my judgement and still is that the battle is so heavily weighted in favor of the offense that it is hopeless against a determined offense and that incidentally applies to our position with regard to an anti-missile that they might build. I am convinced that we can continue to have a missile system that can penetrate any Soviet defense.
When this report was received, McElroy then charged ARPA to begin studying long term solutions to the ICBM defense, looking for systems that would avoid the apparently insurmountable problem presented by the exchange ratio.
ARPA responded by forming Project Defender, initially considering a wide variety of far out concepts like particle beam weapons, lasers and huge fleets of space-borne interceptor missiles, the later known as Project BAMBI. In May 1958, York also began working with Lincoln Labs, MIT's radar research lab, to begin researching ways to distinguish warhead from decoy by radar or other means. This project emerged as the Pacific Range Electromagnetic Signature Studies, or Project PRESS.
In the midst of the growing debate over Zeus' abilities, the US conducted its first high yield, high altitude tests – Hardtack Teak on 1 August 1958, and Hardtack Orange on 12 August. These demonstrated a number of previously unknown or underestimated effects, notably that the fireballs grew to very large size and caused all of the air in or immediately below the fireball to become opaque to radar signals. This was extremely worrying for any system like Zeus, which would not be able to track warheads in such a fireball.
If this were not enough, there was a growing awareness that simple radar reflectors could be launched along with the warhead that would be indistinguishable to Zeus' radars. This problem was first alluded to in 1958 in public talks that mentioned Zeus' inability to discriminate targets. If the decoys spread apart further than the lethal radius of the Zeus' warhead, several interceptors will be required to guarantee that the warhead hiding among the decoys will be destroyed. Decoys are light weight, and would slow down when they began to reenter the upper atmosphere, allowing them to be picked out, or decluttered. But by that time it would be so close to the Zeus base that there might not be time for the Zeus to climb to altitude.
In 1959 the Defense Department ordered one more study on the basic Zeus system, this time by the PSAC. They put together a heavyweight group with some of the most famous and influential scientists forming its core, including Hans Bethe who had worked on the Manhattan Project and later on the hydrogen bomb, Wolfgang Panofsky, the director of the High-Energy Physics Lab at Stanford University, Harold Brown, director of the Lawrence Livermore weapons lab, among similar luminaries. The PSAC report was almost a repeat of the RBIG. They recommended that Zeus should not be built, at least without significant changes to allow it to better deal with the emerging problems.
Throughout, Zeus was the focus of "fierce controversy" in both the press and military circles. Even as testing started, it was unclear if development would continue. President Eisenhower's defense secretaries, McElroy (1957–59) and Thomas S. Gates, Jr. (1959–61), were unconvinced that the system was worth the cost. Eisenhower was highly skeptical, questioning whether an effective ABM system could be developed in the 1960s. Another harsh critic on cost grounds was Edward Teller, who simply stated that the exchange ratio meant the solution was to build more ICBMs.
Kennedy and Zeus
John F. Kennedy campaigned on the platform that Eisenhower was weak on defense and that he was not doing enough to solve the looming missile gap.[c] After his win in the 1960 elections he was flooded with calls and letters urging that Zeus be continued. This was a concentrated effort on the part of the Army, who was fighting back against similar Air Force tactics. They also used the now common tactic of deliberately spreading the Zeus contracts over 37 states in order to gain as much political and industrial support as possible, while taking out advertisements in major mass-market magazines like Life and The Saturday Evening Post promoting the system.
Kennedy appointed Army General Maxwell D. Taylor as his Chairman of the Joint Chiefs of Staff. Taylor, like most Army brass, was a major supporter of the Zeus program. Kennedy and Taylor initially agreed to build a huge Zeus deployment with seventy batteries and 7,000 missiles. McNamara was also initially in favor of the system, but suggested a much smaller deployment of twelve batteries with 1,200 missiles. A contrary note was put forth by Jerome Wiesner, recently appointed as Kennedy's scientific advisor, and chair of the 1959 PSAC report. He began to educate Kennedy on the technical problems inherent to the system. He also had lengthy discussions with David Bell, the budget director, who came to realize the enormous cost of any sort of reasonable Zeus system.
Kennedy was fascinated by the Zeus debate, especially the way that scientists were lined up on diametrically opposed positions for or against the system. He commented to Wiesner, "I don’t understand. Scientists are supposed to be rational people. How can there be such differences on a technical issue?" His fascination grew and he eventually compiled a mass of material on Zeus which took up one corner of a room where he spent hundreds of hours becoming an expert on the topic. In one meeting with Edward Teller, Kennedy demonstrated that he knew more about the Zeus and ABMs than Teller. Teller then expended considerable effort to bring himself up to the same level of knowledge. Wiesner would later note that the pressure to make a decision built up until "Kennedy came to feel that the only thing anybody in the country was concerned about was Nike-Zeus."
To add to the debate, it was becoming clear that the missile gap was fictional. The first Corona spy satellite mission in August 1960 put limits on their program that appeared to be well below the lower bound of any of the estimates, and a follow-up mission in late 1961 clearly demonstrated the US had a massive strategic lead. A new intelligence report published in 1961 reported that the Soviets had no more than 25 ICBMs and would not be able to add more for some time.[d]
Nevertheless, the system continued slowly moving towards deployment. On 22 September 1961, McNamara approved funding for continued development, and approved initial deployment of a Zeus system protecting twelve selected metropolitan areas. These included Washington/Baltimore, New York, Los Angeles, Chicago, Philadelphia, Detroit, Ottawa/Montreal, Boston, San Francisco, Pittsburgh, St. Louis, and Toronto/Buffalo. However, the deployment was later overturned, and in January 1962 only the development funds were released.
In 1961, McNamara agreed to continue development funding through FY62, but declined to provide funds for production. He summed up both the positives and the concerns this way:
Successful development [of Zeus] may force an aggressor to expend additional resources to increase his ICBM force. It would also make accurate estimates of our defensive capabilities more difficult for a potential enemy and complicate the achievement of a successful attack. Furthermore, the protection that it would provide, even if for only a portion of our population, would be better than none at all ...
There is still considerable uncertainty as to its technical feasibility and, even if successfully developed, there are many serious operating problems yet to be solved. The system, itself, is vulnerable to ballistic missile attack, and its effectiveness could be degraded by the use of more sophisticated ICBMs screened by multiple decoys. Saturation of the target is another possibility as ICBMs become easier and cheaper to produce in coming years. Finally, it is a very expensive system in relation to the degree of protection that it can furnish.
Looking for a near term solution, McNamara once again turned to ARPA, asking them to consider the Zeus system in depth. They returned a new report in April 1962 that contained four basic concepts. First was the Zeus system in its current form, outlining what sort of role it might play in various war fighting scenarios. Zeus could, for instance, be used to protect SAC bases, thereby requiring the Soviets to expend more of their ICBMs to attack the base. This would presumably mean less damage to other targets. The next replaced the Zeus missile with a newer model with much higher acceleration, allowing the interceptions to take place much closer to the base and thus declutter the decoys. Another considered the addition of new Passive electronically scanned array radars and computers to the Zeus, which would allow it to attack dozens of targets at once over a wider area. Finally, in their last concept, N-X, they added a new very high speed, short range missile designed to intercept the warhead at altitudes as low as 20,000 feet (6.1 km), by which time any decoys or fireballs would be long gone. N-X became the Nike-X system.
Perfect or nothing
As work on Nike-X began, high-ranking military and civilian officials began to press for Zeus deployment as an interim system in spite of the known problems. The system could then be upgraded in-place as new technologies became available. McNamara eventually became the main opponent of early deployment, while Congressman Daniel J. Flood would be a prime force for immediate deployment.
McNamara's argument against deployment basically rested on two primary issues. One was the apparent ineffectiveness of the system, and especially its benefit-cost ratio compared to other options. For instance, fallout shelters would save more Americans for far less money, and he was adamant that no ABM system should be built without funding shelters as well. The second, ironically, was the concerns about a Soviet ABM system. The US's existing SM-65 Atlas and SM-68 Titan both used re-entry vehicles with blunt noses that greatly slowed the warheads as they entered the lower atmosphere and made them relatively easy to attack. The solution was the LGM-30 Minuteman missile, which used new sharp nosed reentry shapes that traveled at much higher terminal speeds, and included a number of decoy systems that were expected to make interception very difficult for the Soviet ABMs. If there was a budget choice to be made, McNamara supported Minuteman, although he tried not to say this.
In one particularly telling exchange between McNamara and Flood, McNamara initially refuses to choose one option over the other:
Flood: Which comes first, the chicken or the egg? Which comes first, Minuteman because he may develop a good Zeus, or our own Zeus?
McNamara: I would say neither comes first. I would carry on each simultaneously with the maximum rate of activity that each could benefit from.
But later, Flood later managed to get a more accurate statement out of him:
Flood: I thought we had broken through this problem in this country, of wanting things to be perfect before we send them to the troops. I have an enemy who can kill me and I cannot defend myself against him, and I say I should hazard all risks within the rule of reason, to advance this by 2 or 3 years.
McNamara: We are spending hundreds of millions of dollars, not to stop things but to accelerate the development of an anti-ICBM system... I do not believe it would be wise for us to recommend the procurement of a system which might not be an effective anti-ICBM device. That is exactly the state in which we believe the Zeus rests today.Flood: ... You may not be aware of it, but you have just about destroyed the Nike-Zeus. That last paragraph did that.
Cancellation and the ABM gap
By 1963 McNamara had convinced Kennedy that the Zeus was simply not worth deploying. The earlier concerns about cost and effectiveness, as well as new difficulties in terms of attack size and decoy problems, led McNamara to cancel the Zeus project in January 1963. In its place they decided to continue work on Nike-X.
While reporting to the Senate Armed Services Committee in February, McNamara noted that they expected the Soviets to have an initial ABM system deployed in 1966, and then later stated that the Nike-X would not be ready for use until 1970. Noting a "defensive gap", Strom Thurmond began an effort to deploy the existing Zeus as an interim system. Once again the matter spilled over into the press.
On 11 April 1963, Thurmond led the Congress in an effort to fund deployment of Zeus. In the first closed session of the Senate in twenty years, Zeus was debated and the decision was made to continue with the planned development of Nike-X with no Zeus deployment. The Army continued the testing program until December 1964 at White Sands Missile Range, and May 1966 at Kwajalein Missile Range.
As the debate over Zeus raged, the Nike team was making rapid progress developing the actual system. Test firings of the original A models of the missile began in 1959 at White Sands Missile Range. The first attempt on 26 August 1959 was of a live booster stage and dummy sustainer, and broke up shortly before booster/sustainer separation. A similar test on 14 October was a success, followed by the first two stage attempt on 16 December. The first complete test of both stages with active guidance and thrust vectoring was successfully carried out on 3 February 1960. Data collected from these tests led to changes to the design to improve speed during the ascent. The first test of the Zeus B took place in May 1961.
Additional tracking tests were carried out by TTRs at Bell's Whippany, NJ labs and an installation on Ascension Island. The latter was first used in an attempt to track a SM-68 Titan on 29 March 1961, but the data download from Cape Canaveral failed. A second test on 28 May was successful. Later in the year the Ascension site tracked a series of four test launches, two Atlas, two Titan, with tracks developed along 100 seconds. A ZAR at White Sands reached initial operation in June 1961, and was tested against balloons, aircraft, parachutes deployed from sounding rockets and Hercules missiles. A TTR followed and in November, and all-up testing began that month. On 14 December a Zeus passed within 100 feet (30 m) of a Nike Hercules being used as a test target, a success that was repeated in March 1962.
Many test firings were conducted through the early 1960s, but White Sands was too close to its own launch sites to truly test an ICBM flight profile. Consideration was given to using Point Mugu in California, which would launch against missiles flying from Cape Canaveral, but range safety requirements placed limits on the potential tests. The Atlantic Test Range, to the northeast of Canaveral, had a high population density and little land available for building accurate downrange tracking stations, Ascension being the only suitable location. Eventually Kwajalein Island was selected, as it was 4,800 miles from California, perfect for ICBMs, and already had a US Navy base with considerable housing and an airstrip.
A minor Army-Air Force fight then broke out about what targets would be used for the Kwajalein tests. The Army favored using its Jupiter design, fired from Johnston Atoll, while the Air Force recommended using Atlas fired from Vandenberg AFB. The Army had already begun converting the former Thor launchers to Jupiter when an Ad Hoc Panel considered the issue. On 26 May 1960 they decided in favor of Atlas, and this was made official on 29 June when the Secretary of Defense ended pad conversion and Jupiter production was earmarked for Zeus testing.
A key development of the testing program was a miss-distance indicator system, which independently measured the distance between the Zeus and the target at the instant the computers initiated the detonation of the warhead. For testing, a small conventional warhead was used, which provided a flash that could be seen on long exposure photographs of the interceptions. There were concerns that if the Zeus' own radars were used for this ranging measure, any systematic error in ranging would also be present in the test data, and thus would be hidden. The solution was the use of a separate UHF-frequency transmitter in the warhead reentry vehicle, and a receiver in the Zeus. The received signal was retransmitted to the ground, where its Doppler shift was examined to extract the range information. These instruments eventually demonstrated that the Zeus' own tracking information was accurate.[e]
The Zeus site, known as the Kwajalein Test Site, was officially established on 1 October 1960. As it grew in size, it eventually led to the entire island complex being handed over to the Army from the Navy on 1 July 1964. The site took up a considerable amount of the empty land to the north side of the airfield. The launchers were located on the far southwestern corner of the island, with the TTR, MTR and various control sites and generators running along the northern side of the airfield. The ZAR transmitter and receiver were some distance away, also on the northern edge of the airfield but at the eastern end of it. On 24 January 1962, the Zeus Acquisition Radar at Kwajalein achieved its first returns from an ICBM target, and on 18 April was used to track Kosmos 2. On the 19 January it reacquired Kosmos 2 and successfully transferred the track to one of the TTRs.
On 26 June the first all-up test against an Atlas target was attempted. The ZAR began successfully tracking the target at 446 nautical miles (826 km) and handed off immediately to a TTR. The TTR switched tracks from the missile fuselage to the warhead at 131 nautical miles (243 km). When the fuselage began to break up, the computer switched to clutter mode, which watched the TTR data for any derivation from the originally calculated trajectory, which would indicate that it had begun tracking debris. It also continued to predict the location of the warhead, and if the system decided it was tracking debris, it would wait for the debris and warhead to separate enough to begin tracking them again. However, the system failed to properly indicate when the warhead was lost, and tracking was never regained.
A second test on 19 July was a partial success,[f] with the Zeus passing within 2 kilometres (1.2 mi) of the target. The control system ran out of hydraulic fluid during the last 10 seconds of the approach, causing the large miss distance, but the test was otherwise successful. The guidance program was updated to stop the rapid control cycling that led to the fluid running out. A third attempt on 12 December successfully brought the missile to very close distances, but the second missile of the planned two missile salvo failed to launch due to an instrument problem. A similar test on 22 December also suffered a failure in the second missile, but the first passed only 200 metres (660 ft) from its target.
|K1||26 June 1962||Atlas D||Failure, tracking|
|K2||19 July 1962||Atlas D||Partial success, large miss distance|
|K6||12 December 1962||Atlas D||Success, second missile failed|
|K7||22 December 1962||Atlas D||Success, second missile failed|
|K8||13 February 1963||Atlas D||Partial success|
|K10||28 February 1963||Atlas D||Partial success|
|K17||30 March 1963||Titan I||Success|
|K21||13 April 1963||Titan I||Success|
|K15||12 June 1963||Atlas D||Success|
|K23||4 July 1963||Atlas E||Success|
|K26||15 August 1963||Titan I||Success|
|K28||24 August 1963||Atlas E||Success|
|K24||14 November 1963||Titan I||Success|
In April 1962, McNamara asked the Nike team to consider using the Zeus site on Kwajalein as an operational anti-satellite base after the main Zeus testing had completed. The Nike team responded that a system could be readied for testing by May 1963. The concept was given the name Project Mudflap.
Development was a straightforward conversion of the DM-15B into the DM-15S. The changes were mainly concerned with providing more upper stage maneuverability through the use of a new two-stage hydraulic pump, batteries providing 5 minutes of power instead of 2, and an improved fuel in the booster to provide higher peak altitudes. A test of the new booster with a DM-15B upper was carried out at White Sands on 17 December 1962, reaching an altitude of 100 nautical miles (190 km), the highest of any launch from White Sands to that point. A second test with a complete DM-15S on 15 February 1963 reached 151 nautical miles (280 km).
Testing then moved to Kwajalein. The first test on 21 March 1963 failed when the MTR failed to lock onto the missile. A second on 19 April also failed when the beacon failed 30 seconds before intercept. The third test, this time using an actual target consisting of an Agena-D upper stage equipped with a Zeus miss-distance transmitter, was carried out on 24 May 1963, and was a complete success. From that point until 1964, one DM-15S was kept in a state of instant readiness and teams continually trained on the missile.
After 1964 the Kwajalein site was no longer required to be on alert, and returned primarily to Zeus testing. The system was kept active in a non-alert role between 1964 and 1967, known as Program 505. In 1967 it was replaced by a Thor based system, Program 437. A total of 12 launches, including those at White Sands, were carried out as part of the 505 program between 1962 and 1966.
Nike Zeus was originally intended to be a straightforward development of the earlier Hercules system giving it the ability to hit ICBM warheads at about the same range and altitude as the maximum performance of the Hercules. In theory, hitting a warhead is no more difficult than an aircraft; the interceptor does not have to travel any further or faster, the computers that guide it simply have to select an intercept point farther in front of the target to compensate for the target's much higher speed. In practice, the difficulty is detecting the target early enough that the intercept point is still within range of the missile. This demands much larger and more powerful radar systems, and faster computers.
In order to provide the maximum warning time, some consideration was given to the design of a Forward Acquisition Radar (FAR). These would be deployed 300 to 700 miles (480–1,130 km) ahead of the Zeus bases to provide early warning of up to 200 to 300 seconds of tracking data on up to 200 targets. The system broadcast 10 MW pulses at UHF between 405–495 MHz, allowing it to detect a 1 square metre radar reflection at 1,020 nautical miles (1,890 km) or a more typical 0.1 m2 target at 600 nautical miles (1,100 km). Each track was stored as a 200 bit file including location, velocity, time of measure and a measure of the quality of the data. Clouds of objects were tracked as a single object with additional data indicating the width and length of the cloud. Tracks could be updated every five seconds while the target was in view, but the antenna rotated at a relatively slow 4 RPM so targets moved significantly between rotations. Each FAR could feed data to up to three Zeus sites.
Each Zeus Defense Center was based around its Zeus Acquisition Radar, or ZAR, which provided wide area early warning and initial tracking information. This enormously powerful radar was driven by multiple 1.8 MW klystrons and broadcast through three 80-foot (24 m) wide antennas arranged as the outside edges of a rotating equilateral triangle. The ZAR spun at 10 RPM, simulating a single antenna rotating three times as fast. The entire transmitter was surrounded by a 65-foot (20 m) high fence located 350 feet (110 m) away from the antenna. The signal was received on a separate set of three antennas, situated at the centre of an 80 foot (24 m) diameter Luneburg lens, which rotated synchronously with the broadcaster under a 120-foot (37 m) diameter dome. Multiple feed horns were used in the receiver to allow reception from many vertical angles at once. Around the receiver dome was a large field of wire mesh, forming a reflector. The ZAR also operated in the UHF on various frequencies between 495–605 MHz. ZAR had detection range on the order of 460 nautical miles (850 km) on a 0.1 m2 target, but greatly increased data collection to every two seconds, and did not lose sight of targets as the antenna turned.
Data from the ZARs were passed to the appropriate Zeus Firing Battery to attack, with each ZAR being able to send its data to up to ten batteries. Each battery was self-contained after handoff, including all of the radars, computers and missiles needed to perform an intercept. In a typical deployment, a single Zeus Defense Center would be connected to three to six batteries, spread out by as much as 100 miles (160 km).
Targets picked out by the ZAR were then illuminated by the Zeus Discrimination Radar (ZDR, also known as Decoy Discrimination Radar, DDR or DR). ZDR imaged the entire cloud using a chirped signal that allowed the receiver to accurately determine range within the cloud by passing each frequency in the chirp to a separate range gate. The range resolution was 0.25 microseconds, about 75 metres (246 ft). As the signal was spread out over the entire cloud, it had to be very powerful; the ZDR produced 40 MW 2 µs pulses in the L-band between 1270–1400 MHz. To ensure no signal was lost by scanning areas that were empty, the ZDR used a Cassegrain reflector that could be moved to focus the beam as the cloud approached to keep the area under observation constant.
Data from the ZDR was passed to the All-Target Processor (ATP), which ran initial processing on as many as 625 objects in a cloud. As many as 50 of these could be picked out for further processing in the Discrimination and Control Computer (DCC), which ran more tests on those tracks and assigned each one a probability of being the warhead or decoy. The DCC was able to run 100 different tests. For exoatmospheric signals the tests included measure of radar return pulse-to-pulse to look for tumbling objects, as well as variations in signals strength due to changes in frequency. Within the atmosphere, the primary method was examining the velocities of the objects to determine their mass.
Any target with a high probability was then passed to the Battery Control Data Processor (BCDP), which selected missiles and radars for an attack. This started with the assignment of a Target Tracking Radar (TTR) to a target passed to it from the DCC. TTRs operated in the C-band from 5250–5750 MHz at 10 MW, allowing tracking of a 0.1 m2 target at 300 nautical miles (560 km), which they expected to be able to double with a new maser-based receiver design. Once targets were being successfully tracked and a firing order received, the BCDP selected available Zeus missiles for launch and assigned a Missile Tracking Radar (MTR) to follow them. These were much smaller radars operating in the X-band between 8500–9600 MHz and assisted by a transponder on the missile, using only 300 MW to provide missile tracking to 200 nautical miles (370 km). Information from the ZDR, TTR and MRTs was all fed to the Target Intercept Computer (TIC) which handled the interceptions. This used twistor memory for ROM and core memory for RAM. Guidance commands were sent to the missiles in-flight via modulation of the MTR signal.
The nominal battery consisted of three TTR/ZDR pairs, with one normally operating as a hot backup. The site also included ten MTRs, with one of those a backup. This meant that a single Zeus site would normally attack two targets, although a third could be attacked if needed. Each could be attacked by three missiles, although a normal salvo used two.
It was expected that the ZAR would take 20 seconds to develop a track and hand off a target to one of the TTRs, and 25 seconds for the missile to reach the target. With these sorts of salvo rates, a Zeus installation was expected to be able to successfully attack 14 "bare" warheads per minute. Its salvo rate against warheads with decoys is not recorded, but would depend on the ZDR's processing rate more than any physical limit. The actual engagement would normally take place at about 75 nautical miles (139 km) due to accuracy limitations, beyond that missiles could not be guided accurately enough to bring them within their lethal 800 foot (240 m) range against a shielded warhead.
The original D-15 Zeus A was similar to the original Hercules, but featured a revised control layout and gas "puffers" for maneuvering at high altitudes where the atmosphere was too thin for the aerodynamic surfaces to be effective. The Zeus B interceptor was longer at 14.7 metres (48 ft), 2.44 metres (8 ft 0 in) wide, and 0.91 metres (3 ft 0 in) in diameter. This was so much larger than the earlier Hercules that no attempt was made to have them fit into the existing Hercules/Ajax launchers. Instead, the B models were launched from silos, thus the change of numbering from MIM (mobile surface launched) to LIM (silo launched). Since the missile was designed to intercept its targets in space, it did not need large maneuvering fins of the A model. Rather, it featured a third rocket stage with small control jets to maneuver in space. Zeus B had a maximum range of 250 miles (400 km) and altitude of 200 miles (320 km).
Zeus A was designed to attack warheads through shock effects, like the Hercules, and was to be armed with a relatively small nuclear warhead. As the range and altitude requirements grew, along with a better understanding of weapons effects at high altitude, the Zeus B intended to attack its targets through the action of neutron heating. This relied on the interceptor's warhead releasing a huge number of high energy neutrons (similar to the neutron bomb), some of which would hit the enemy warhead. These would cause fission to occur in some of the warhead's own nuclear fuel, rapidly heating the "primary", hopefully enough to cause it to melt. For this to work, the Zeus mounted the W50, a 400 kt enhanced radiation warhead, and had to maneuver within 1 km of the target warhead. Against shielded targets, the warhead would be effective to as little as 800 feet (0.24 km).
When Zeus B was upgraded into the Zeus EX that worked at even higher altitudes and longer ranges, a new type of attack became possible. In the vacuum of space, where the EX operated, x-rays travel long distances and can be used for an attack over a wide area, larger than a practical neutron weapon. To fill this need a much larger gold tampered warhead was developed, the 5 Mt W71. For the short range Sprint that operated closer to the ground, the much smaller W66 was created, operating much the same way as the Zeus' W50 but with a much lower (still classified but ~1 kt) yield. The W66 is widely reported as the first neutron bomb, although any differences compared to the W50, other than yield, are unclear.
- Different sources appear to confuse measures between the Zeus A, B and Spartan. The A and Spartan figures are taken from US Strategic and Defensive Missile Systems 1950–2004, B from the Bell Labs history.
|Missile||Nike Zeus A||Nike Zeus B||Spartan (LIM-49A)|
|Length||44 ft 3 in (13.5 m)||50 ft 2 in (15.3 m)||55 ft 1 in (16.8 m)|
|Diameter||3 ft 0 in (0.91 m)||3 ft 0 in (0.91 m)||3 ft 7 in (1.09 m)|
|Fin span||9 ft 9 in (2.98 m)||8 ft 0 in (2.44 m)||9 ft 9 in (2.98 m)|
|Mass||10,980 lb (4,980 kg)||24,200 lb (10,977 kg)||28,900 lb (13,100 kg)|
|Maximum speed||Mach 4 > (ca. 2800+ mph; 4,900 km/h arbitrary)|
|Range||200 mi (320 km)||250 mi (400 km)||460 mi (740 km)|
|Ceiling||?||170 mi (280 km)||350 mi (560 km)|
400,000 lbf (1,800 kN)
450,000 lbf (2,000 kN)
500,000 lbf (2,200 kN)
|Second stage||?||Thiokol TX-238||Thiokol TX-454|
|Third stage||None||Thiokol TX-239||Thiokol TX-239|
|Warhead||W31 (25 kt)||W50 (400 kt)||W71 (5 Mt)|
- When Khrushchev's son asked why he made this statement, Khrushchev explained that "the number of missiles we had wasn’t so important.… The important thing was that Americans believed in our power". Ironically, Khrushchev's posturing would cause the US to build up an enormous strategic lead, one so great that Kennedy would feel secure standing up to him during the Cuban Missile Crisis which lead to Khrushchev's ousting.
- The outer layer of the missile can be seen turning black in the Bell Labs film.
- Kennedy publicly introduced the term "missile gap" as part of a August 1958 speech.
- It was later demonstrated the actual number of ICBMs in the Soviet fleet at that time was four.
- This result proved useful during later tests of the Sprint missile, where changes in frequency and demands to encrypt all data made the adaption of this simple method much more difficult. Instead, the TTR radars from the original Zeus site were used, as the original tests had demonstrated the TTR data to be accurate.
- Leonard incorrectly states this took place on 19 June. It is one of a number of mistakes in the Chronology section, which indicates references from this list should be checked against other references.
- Canavan mentions there being 14 tests, Bell's history shows only 13 in the table.
- Walker, Bernstein & Lang 2003, p. 20.
- Jayne 1969, p. 29.
- Leonard 2011, p. 180.
- Zeus 1962, p. 165.
- Jayne 1969, p. 30.
- Bell Labs 1975, p. 1.2.
- Bell Labs 1975, p. 1.3.
- Bell Labs 1975, pp. 1.3–1.4.
- Bell Labs 1975, p. 1.4.
- Zeus 1962, p. 166.
- Jayne 1969, p. 32.
- "Nike Ajax (SAM-A-7) (MIM-3, 3A)". Federation of American Scientists. 29 June 1999.
- Leonard 2011, p. 329.
- Kaplan 2006, p. 4.
- Jayne 1969, p. 33.
- Larsen, Douglas (1 August 1957). "New Battle Looms Over Army's Newest Missile". Sarasota Journal. p. 35. Retrieved 18 May 2013.
- Trest, Warren (2010). Air Force Roles and Missions: A History. Government Printing Office. p. 175. ISBN 9780160869303.
- Technical Editor (6 December 1957). "Missiles 1957". Flight International: 896.
- Gaither 1957, p. 5.
- Thielmann, Greg (May 2011). "The Missile Gap Myth and Its Progeny". Arms Control Today.
- Khrushchev, Sergei (200). Nikita Khrushchev and the Creation of a Superpower. Pennsylvania State University Press. p. 314.
- Preble 2003, p. 810.
- Gaither 1957, p. 6.
- Leonard 2011, p. 332.
- Leonard 2011, p. 183.
- Slayton 2013, p. 52.
- "Neil H. McElroy (1957–1959): Secretary of Defense". University of Virginia Miller Center.
- Kaplan 2006, p. 7.
- Zeus 1962, p. 170.
- Berhow 2005, p. 31.
- Walker, Bernstein & Lang 2003, p. 39.
- Leonard 2011, p. 331.
- Leonard 2011, p. 182.
- Kaplan 2008, p. 80.
- Kaplan 2008, p. 81.
- WSEG 1959, p. 20.
- Kaplan 1983, p. 344.
- Yanarella 2010, pp. 72–73.
- Broad, William (28 October 1986). "'Star Wars' Traced To Eisenhower Era". The New York Times.
- Garvin & Bethe 1968, pp. 28–30.
- Leonard 2011, pp. 186–187.
- Baucom 1992, p. 19.
- Kaplan 2006, p. 6–8.
- Papp 1987.
- "US Military and Diplomatic Policies - Preparing for the Gap". JFK Library and Museum. 14 August 1958.
- Kaplan 2008, p. 82.
- Kaplan 1983, p. 345.
- Kaplan 2006, p. 9.
- Brown 2012, p. 91.
- Day, Dwayne (3 January 2006). Of myths and missiles: the truth about John F. Kennedy and the Missile Gap. The Space Review. pp. 195–197.
- Heppenheimer, T. A. (1998). The Space Shuttle Decision. NASA. pp. 195–197.
- Day 2006.
- Leonard 2011, p. 334.
- Yanarella 2010, p. 68.
- Leonard 2011, p. 335.
- Yanarella 2010, pp. 68–69.
- Yanarella 2010, p. 87.
- Yanarella 2010, p. 69.
- Yanarella 2010, p. 70.
- "JFK Accepts McNamara View On Nike Zeus". Sarasota Herald-Tribune. 8 January 1963. p. 20.
- Kaplan 2006, p. 13.
- Allan, Robert; Scott, Paul (26 April 1963). "McNamara Lets Reds Widen Antimissile Gap". Evening Independent. p. 3-A.
- Kaplan 2006, p. 14.
- Gibson 1996, p. 205.
- Walker, Bernstein & Lang 2003, p. 42.
- Walker, Bernstein & Lang 2003, p. 44.
- Bell Labs 1975, p. 1.23.
- Bell Labs 1975, p. 1.24.
- Walker, Bernstein & Lang 2003, p. 41.
- Leonard 2011, p. 333.
- Bell Labs 1975, p. 1.26.
- Bell Labs 1975, p. 1.31.
- Kaplan 2006, p. 10.
- Hubbs, Mark (February 2007). "Where We Began – the Nike Zeus Program". The Eagle. p. 14.
- Bell Labs 1975, p. 1.32.
- "Program 505". Encyclopedia Astronautica. Retrieved 18 May 2013.
- WSEG 1959.
- Zeus 1962, p. 167.
- Bell Labs 1975, p. II, 1.1.
- Bell Labs 1975, p. II, 1.14.
- Bell Labs 1975, p. II, 1.12.
- Bell Labs 1975, p. II, 1.11.
- Program For Deployment Of Nike Zeus (Technical report). 30 September 1961.
- Bell Labs 1975, p. II, 1.25.
- Zeus 1962, pp. 167,170.
- WSEG 1959, p. 10.
- Bell Labs 1975, p. 1.1.
- WSEG 1959, p. 160.
- "Nike Zeus". Encyclopedia Astronautica. Retrieved 18 May 2013.
- Kaplan 2006, p. 12.
- Johnson, Wm. Robert (6 April 2009). "Multimegaton Weapons".
- Berhow 2005, p. 32.
- Berhow 2005, p. 60.
- Bell Labs 1975, p. 1–33.
- Bell Labs (October 1975). ABM Research and Development at Bell Laboratories, Project History (Technical report). Retrieved 13 December 2014.
- Berhow, Mark (2005). US Strategic and Defensive Missile Systems 1950–2004. Oxford: Osprey. ISBN 978-1-84176-838-0. OCLC 62889392.
- Baucom, Donald (1992). The Origins of SDI, 1944–1983. Lawrence, Kansas: University Press of Kansas. ISBN 978-0-7006-0531-6. OCLC 25317621.
- Brown, Harold (2012). Star Spangled Security: Applying Lessons Learned over Six Decades Safeguarding America. Brookings Institution Press. ISBN 9780815723837. Retrieved 13 Dec 2014.
- Garvin, Richard; Bethe, Hans (March 1968). "Anti-Ballistic-Missile Systems". Scientific American 218 (3): pp. 21–31. Bibcode:1968SciAm.218c..21G. doi:10.1038/scientificamerican0368-21. Retrieved 13 December 2014.
- Gibson, James (1996). Nuclear Weapons of the United States: An Illustrated History. Atglen, Pennsylvania: Schiffer Publishing. ISBN 978-0-7643-0063-9. OCLC 35660733.
- Jayne, Edward Randolph (1969). The ABM debate: strategic defense and national security (Technical report). Massachusetts Institute of Technology. OCLC 19300718. Retrieved 13 December 2014.
- Kaplan, Fred (1983). The Wizards of Armageddon. Stanford University Press. ISBN 9780804718844.
- Kaplan, Fred (2008). Daydream Believers: How a Few Grand Ideas Wrecked American Power. John Wiley & Sons. ISBN 9780470121184.
- Kaplan, Lawrence (2006). Nike Zeus: The U.S. Army's First ABM. Falls Church, Virginia: Missile Defense Agency. OCLC 232605150. Retrieved 13 May 2013.
- Leonard, Barry (2011). History of Strategic and Ballistic Missile Defense: Volume II: 1956–1972. DIANE Publishing. Retrieved 13 May 2013.
- Papp, Daniel (Winter 1987–88). "From Project Thumper to SDI". Airpower Journal.
- Preble, Christopher (December 2003). "Who Ever Believed in the 'Missile Gap'" John F. Kennedy and the Politics of National Security". Presidential Studies Quarterly: 801.
- Security Resources Panel of the Science Advisory Committee (7 November 1957). Deterrence & Survival in the Nuclear Age (Technical report). Retrieved 13 December 2014.
- Slayton, Rebecca (2013). Arguments that Count: Physics, Computing, and Missile Defense, 1949–2012. MIT Press. ISBN 9780262019446. Retrieved 15 December 2014.
- Walker, James; Bernstein, Lewis; Lang, Sharon (2010). Seize the High Ground: The U. S. Army in Space and Missile Defense. Washington, D.C.: Center of Military History. ISBN 9780813128092. Retrieved 13 May 2013.
- Yanarella, Ernest (2010). The Missile Defense Controversy: Technology in Search of a Mission. University Press of Kentucky. ISBN 9780813128092. Retrieved 13 May 2013.
- US Army Weapons Systems Evaluation Group (23 September 1959). Potential Contribution of Nike-Zeus to Defense of the U.S. Population and it's Industrial Base, and the U.S. Retaliatory System (Technical report). Retrieved 13 December 2014.
- Technical Editor (2 August 1962). "Nike Zeus". Flight International: pp. 165–170. ISSN 0015-3710. Retrieved 13 May 2013.
- "Nike Zeus". Nuclearabms.info. Retrieved 18 May 2013.
- AT&T Archives: Nike Zeus Missile System, made early in the program
- The Range Goes Green, movie of a Zeus test launch at White Sands