Sentinel program

Residents of the cities to be protected protested that it simply made them targets for more Soviet bombs, and there were a number of well organized public demonstrations against the system.

The US Army began ABM research in 1955, after a Bell Labs report concluded that modern computers, radars, and missile systems had improved to the point where attacks on ICBM reentry vehicles (RVs) were a possibility.

The task is not trivial; RVs are travelling at about 5 miles (8 km) per second and have a small radar cross section, perhaps only 0.1 square metres (1 sq ft).

The first was to replace Zeus' mechanical radar systems with an active electronically scanned array, which would allow it to track hundreds of targets at once, both the incoming ICBMs as well as the outgoing interceptors.

[13][a] In 1962 the US carried out a series of high-altitude nuclear tests, notably Starfish Prime, which demonstrated that the burst of x-rays released by a warhead can travel long distances.

This led to the development of the low-cost Perimeter Acquisition Radar (PAR), whose function was to measure the threat tubes while they were still minutes away, determine their targets, and warn the appropriate SCDs.

A follow-up meeting the next month initially appeared to be leading to a deployment being forced upon them, but McNamara managed to convince the president, Joint Chiefs of Staff, and others that the system simply didn't work.

[27] He then continued that he was worried about the same happening with defensive weapons, but on this point Kosygin disagreed, quoting a speech McNamara had made about the cost-exchange ratio, and suggesting that basing your military policy on such a concept was morally bankrupt.

The blood rose to his face, his veins swelled, he pounded the table and he said - he could barely talk he was so emotional - he said "Defense is moral, offense is immoral!

"[27]Others who also saw the exchange, including Walt Rostrow, suggested that McNamara's telling of the story is "a lot of nonsense" and recalls it only coming up when Kosygin proposed a toast to the effect that "only defense is good".

Within political circles, support was split, even across party lines, with Senators Stennis, Anderson, Tower, and Hickenlooper being notably in favor, while Church, Clark, and Fulbright were opposed.

[38] This misguided decision would ultimately prove fatal; they simply didn't consider "good old American feelings about real estate" when presented with the fact that nuclear missiles would be placed in their neighbourhoods.

[39][d] Lieutenant General Alfred Dodd Starbird further confused matters by explaining that the $5.5 billion earmarked for Sentinel would only protect against China through the 1970s, and he expected further expansions to be required in the future.

[44] When the Corps of Engineers began test drilling at five potential sites around Chicago in November, the issue blew up in the press, and by December local polls were showing the public was firmly opposed to the system.

[43] This coincided with a series of public releases by a number of well respected scientists who outlined the problems with the ABM concept as a whole, and pointed out the destabilizing effects such a system might have on the balance of power.

[41] Commenting on the Reading meeting, a DOD official wrote a memo to the Assistant Secretary of Defense for Research and Engineering, John S. Foster, Jr., stating that he found the crowd to be "extremely well informed" and expressed his opinion that if this reaction was typical, "there is a very good chance that the Congress would have to act to cancel the system".

[48] Echoing the almost continuous refrain of the Johnson administration for the past six years, Nixon noted that: When you are looking toward city defense, it needs to be a perfect or near perfect system because, as I examined the possibility of even a thick defense of cities, I have found that even the most optimistic projections, considering the highest development of the art, would mean that we would still lose 30 million to 40 million lives...[49]Instead, the new system was intended to be: ...a safeguard against any attack by the Chinese Communists that we can foresee over the next 10 years.

The new arrangement would still provide nationwide coverage against light attacks, but the bases were positioned well outside of major cities, and its primary purpose, at least initially, was to protect the US missile fields.

The MSR was built in a boxy extension on the north-western corner of the roof, with two sides angled back to form a half-pyramid shape where the antennas were mounted.

To test this concept, a second launch site was built on Illeginni Island, 17.5 miles (28.2 km) northwest of Meck, with two Sprint and two Spartan launchers.

MAR could detect incoming tracks at very long distances and used sophisticated beam shaping and data processing intended to allow it to rapidly discriminate targets.

Because the MAR would be defending a large metropolitan area, and the Sprint had a range of only tens of miles, the missiles would be hosted at a number of locations spread about the city.

Instead, Bell proposed using a second radar dedicated to the early detection role, PAR, which would forward information to the TACMSRs so they would know where to look when the warheads became visible.

This meant that PAR was no longer disposable in the Sentinel system; if it was destroyed, warheads approaching in its area would appear on the MSRs too late to be intercepted by the Spartan missiles.

The limited northward extent was primarily due to the detection range of the PARs not leaving enough time to intercept warheads attacking northern targets.

[64] For Nike-X, Bell ran a number of studies to identify the sweet spot for the MSR that would allow it to have enough functionality to be useful at different stages of the attack, as well as being inexpensive enough to justify its existence in a system dominated by MAR.

The basic concept, sometimes known as a staring array, allows the otherwise relatively multi-directional transmitters and receivers be focused into a narrow beam by applying different delays at each of the exit points from the face of the radar.

PAR was initially designed as a low-cost long-range system that would be used in the Small City Defense in order to allow the TACMSR sites to have enough warning time to lock its radar onto the targets.

However, the follow-on Phase II design effort was then paused while the team re-evaluated the entire concept in light of studies carried out by the Institute for Defense Analyses (IDA) the previous summer.

Using lessons learned on Nike-X's MAR, a UHF PAR was considered to consist largely of off-the-shelf parts, and the team was confident that the first example would work without building a previous prototype.