Hardpoint (missile defense)
Hardpoint was a proposed short-range
In order to fulfill this mission, the Hardpoint concept relied on having extremely rapid and accurate tracking of the incoming warheads. This led to the development of the Hardpoint Demonstration Array Radar, or HAPDAR, a
There was some interest by the Army and
History
Nike Zeus
The Hardpoint ultimately traces its history to the Nike Zeus program of the late 1950s. Nike Zeus was a general-purpose anti-ballistic missile (ABM) designed to provide defenses against any sort of ballistic missile attack. As the program continued, it became clear that the system was subject to a number of serious problems that suggested it would ultimately be useless before it could even be deployed.[1]
Among the problems was the fact that the Zeus system used mechanically steered radars, requiring one radar for each target. A typical Zeus site might have four of these Target Tracking Radars. This was a reasonable number when the Soviet missile fleet contained a few dozen missiles, but it was clear that they were producing more missiles and the Zeus sites would eventually face a large fleet. A report by the Weapons Systems Evaluation Group (WSEG) concluded that an attack by four warheads would lead to one of them getting through 90% of the time, something the Soviets could easily afford by the time Zeus was fully operational in the early 1960s.[1]
Another serious concern was over the use of radar decoys. These consist of lightweight metal foils or metal-coated plastics that produce radar returns that are indistinguishable from the
If this were not enough,
Project Defender
As the problems with Zeus became clear,
One thing that became clear from these tests was that the problems with decoys and blackout both had the same
This provided a solution to the problems of Zeus; an ABM system could successfully attack the reentry vehicles as long as it could develop tracking information and successfully attack the warheads at altitudes below 60 km. To do so would require a very fast-scanning radar, which was possible through the newly emerging active electronically scanned array (AESA) techniques.[6] Combined with a new computer,[7] such a radar would also be able to track dozens of objects at once, eliminating the possibility of simply overwhelming the system through sheer numbers. The system would also need a missile to match this performance, carrying out interceptions in as little as five seconds. By 1963 it was clear that Zeus was not going to be useful, and the Army was directed to use its funding for the development of a new system incorporating these ideas. This became the Nike-X project.[8]
As part of the same ARPA study, a number of other potential ABM system concepts were considered. While the Army went forward with Nike-X, Project Defender continued examining other possibilities. Among these was the concept that eventually emerged as Hardpoint.[9][10]
Hardpoint
One of the concepts considered from the earliest days of the Zeus program was the idea of using the missiles to protect the Air Force's Strategic Air Command (SAC) bases. There were only a few dozen of these, and there was concern that a sneak attack by even a limited force of Soviet missiles could destroy a major portion of the SAC bomber fleet on the ground. As manned bombers gave way to ICBMs in the 1960s, the same concern came to be expressed over the security of the missiles, especially the early examples that had long fueling times and were unprotected while being prepared for launch, which took about 15 minutes.[11]
The survivability of the US ICBM fleet was greatly enhanced by the introduction of missiles stored in a
Additionally, the interception was technically simpler. The accuracy of early Soviet guidance systems was known, through intercepts of tracking information by British and US intelligence services, to be on the order of several miles. This meant the chance that an individual Soviet warhead would destroy a US silo was small enough that they would have to use several warheads for every silo to ensure its destruction.[13] The US could track the incoming warheads and determine which, if any, were actually approaching the silos and then attack only those that would fall within that lethal range. In such an exchange, a small number of interceptor missiles could successfully defend against a very large counterforce attack, wearing it down to such an extent that it could use up a huge amount of the Soviet missile fleet and leave the US fleet largely untouched. This would leave the US with an enormous strategic advantage, one so great that the Soviets would not be willing to launch an attack with this outcome.[9]
In order for this to be successful, the tracks generated for the incoming warheads would have to be extremely accurate and generated very rapidly. A serious problem for the Nike-X system was the high cost of its MAR radar. This was designed to detect the enemy warheads at long range, quickly develop tracks for them, and then use velocity extraction for decoy discrimination. To provide all of these features, MAR used an AESA radar in which each element in the array was a self-contained transmitter/receiver unit. This was both expensive and extremely complex to wire up.[9]
Finally, the system had to be cheap. The basic idea behind Hardpoint was that a defender needed fewer missiles than the attacker to offset any additions to their fleet, but the missiles and radar systems that drove them were complex and expensive. Therefore, the system had to be less expensive than the missiles it would offset, not just less numerous. Otherwise it might be cheaper to build more Minuteman missiles.[9] Today this concept is known as the Nitze criteria.[14]
Although Hardpoint testing was considered to be highly successful, by the time the program was winding down it was clear that the Soviets were holding to the
Hardsite
ARPA's work on Hardpoint generated enough interest to lead to some work by the Army and
Hardsite was interesting enough for the Army and Air Force to carry out a follow-up study, Hardsite-II, to consider a dedicated Sprint base covering the US missile fields.[16] Although initially supportive of the Hardsite concept, by 1966 the Air Force came to oppose it largely for the same reasons it had opposed Zeus in the same role. If money was to be spent on protecting Minuteman, they felt that money would be better spent by the Air Force than the Army. As Morton Halperin noted:
In part this was a reflex reaction, a desire not to have Air Force missiles protected by "Army" ABMs. ... The Air Force clearly preferred that the funds for missile defense be used by the Air Force to develop new hard rock silos or mobile systems.[17]
LoADS
As part of the ongoing debate about how to best protect the
Description
Shortly after the decision was made to move from Nike Zeus to Nike-X, Project Defender decided to begin development of a low-cost radar system, the Hard Point Demonstration Army Radar, or HAPDAR, along with a new short-range, high-acceleration missile, HiBEX.[19] During the initial project definition, the US had begun exploring maneuverable reentry vehicles (MARVs), which were intended to avoid Soviet ABM defences by continually moving and thereby upsetting any pre-computed intercept course. ARPA decided to add another phase of study to consider a highly maneuverable second stage that could be used to counter Soviet MARVs. This became the "Upper Stage Acceleration and Guidance Experiment", or UpSTAGE.[19]
HAPDAR
Hardpoint's mission was entirely different from the one for Nike-X. The area being protected was smaller, the size of the missile field instead of a large suburbanized city, so initial long-range detection could be handled by other radars like the Perimeter Acquisition Radar (PAR). MAR's discrimination capability was not needed because the decoys and radar blackout were well above the altitudes that the system would operate at. What was needed was very high accuracy and a very fast scanning speed, so that accurate trajectories could be rapidly computed and to a degree of accuracy that allowed the dangerous warheads to be picked out. The result was the Hard Point Demonstration Army Radar, or HAPDAR.[20]
For this task, the ARPA team selected the somewhat simpler
In the case of the HAPDAR design, Sperry used a new design known as the TACOL, short for Thinned Aperture Computed Lens. The basic concept was that the back of the phase shifter array was normally formed into a curve so the signal reached all of the shifters at the same time. In TACOL, the phase delay shifters are individually modified to insert this same delay, allowing the back face of the antenna to be flat. The system used a single klystron transmitter and had 2165 shifters, each with a three-bit shift (values 0 through 7). An additional 1585 inactive feeds completed the 3750 element antenna.[21]
The system was controlled by a UNIVAC 1218, a militarized version of the UNIVAC 418 computer. It was able to produce up to five tracks at once.[21]
HiBEX
The goal of Hardpoint was to intercept incoming missiles just far enough away to keep them out of the lethal radius of their warheads. This was nominally set to altitudes of about 20,000 feet (6,100 m). At this altitude, the enemy
To explore whether such a system was possible, ARPA and the U.S. Army Missile Command funded development of HiBEX with
UpSTAGE
With the success of HiBEX, ARPA began initial work on the PRESTAGE project that studied the concept of external burning, a new idea that appeared to provide a simple way to produce huge lateral accelerations. This project was carried out by
In 1968, APRA began the UpSTAGE project. The system used a new "finlet" maneuvering system that injected hot gas between the fuselage and rocket exhaust, which provided enormous lateral thrust up to 300 g and response times in the order of milliseconds.[24] The maneuvering was so rapid that the system had to use the recently developed ring laser gyroscope as mechanical gyroscopes could not react fast enough. Tracking was carried out by the existing Zeus Target Tracking Radars and instructions sent to the UpSTAGE vehicles from the ground. Five UpSTAGE tests were carried out at WSMR between November 1971 and August 1972.[24]
References
Citations
- ^ a b Bell Labs 1975, p. I-33.
- ^ WSEG 1959, p. 20.
- ^ Garvin & Bethe 1968, pp. 28–30.
- ^ Murdock 1974, p. 117.
- ^ Garvin & Bethe 1968, pp. 27–28.
- ^ Garvin & Bethe 1968, p. 28.
- ^ Bell Labs 1975, p. 2-1.
- ^ Reed 1991, pp. 1–14.
- ^ a b c d e Bell Labs 1975, p. 2-13.
- ^ a b c Reed 1991, p. 3.1.
- ^ Threat 2021.
- ^ Reed 1991, pp. 3.1–3.2.
- ^ MacKenzie 1993, p. 429.
- ^ Krepon 2010.
- ^ Reed 1991, p. 3.11.
- ^ Bell Labs 1975, pp. 6-1–6-3.
- ISBN 978-1-4008-5799-9.
- ^ Arkin, Cochran & Hoenig 1984, p. 14s.
- ^ a b Reed 1991, p. 3.3.
- ^ a b Kahrilas & Jahn 1966, p. 286.
- ^ a b Kahrilas & Jahn 1966, p. 287.
- ^ Reed 1991, p. 3.5.
- ^ Reed 1991, p. 3.6.
- ^ a b c Reed 1991, p. 3.9.
Bibliography
- Reed, Sidney (1991). DARPA Technical Accomplishments, Volume 2. Institute for Defense Analyses.
- Kahrilas, P.J. (November 1968). "HAPDAR; An operational phased array radar". Proceedings of the IEEE. 56 (11): 1967–1975. .
- "SM-65 Atlas". Missile Threat. 2 August 2021.
- Bell Labs (October 1975). ABM Research and Development at Bell Laboratories, Project History (PDF) (Technical report). Archived from the original (PDF) on Dec 30, 2014. Retrieved 13 December 2014.
- MacKenzie, Donald (1993). Inventing Accuracy: A Historical Sociology of Nuclear Missile Guidance. MIT Press. ISBN 9780262631471.
- Krepon, Michael (28 July 2010). "Nitze's Strategic Concept".
- US Army Weapons Systems Evaluation Group (23 September 1959). Potential Contribution of Nike-Zeus to Defense of the U.S. Population and its Industrial Base, and the U.S. Retaliatory System (PDF) (Technical report). Retrieved 13 December 2014.
- Garvin, Richard; Bethe, Hans (March 1968). "Anti-Ballistic-Missile Systems" (PDF). . Retrieved 13 December 2014.
- Murdock, Clark (1974). Defense Policy Formation: A Study and Translation. SUNY Press. ISBN 978-1-4384-1394-5.
- Kahrilas, P.J.; Jahn, D.M. (November 1966). "Hardpoint Demonstration Array Radar". IEEE Transactions on Aerospace and Electronic Systems. 2 (6): 286–299. S2CID 51640184.
- Arkin, William; Cochran, Thomas; Hoenig, Milton (August–September 1984). "Resource Paper on the US Nuclear Arsenal". Bulletin of the Atomic Scientists. pp. 3s–15s.