The Defense Nuclear Agency’s Cold War calculators

The Defense Nuclear Agency was an offspring of the Manhattan Project and is now part of the Defense Threat Reduction Agency. In its various guises it had many responsibilities connected with America’s nuclear weapons programmes.

In the 1980s and 1990s it produced a series of calculators to help the military plan its nuclear attacks on targets in the USSR and other countries. The US had a list of target Vulnerability Numbers [see this post].  Planners could use these numbers and the DNA calculators to decide whether  a bomber, a submarine launched missile or a ground launched missile be used against a target [they had different levels of accuracy] to achieve a specified level of damage and probability of success.

Vulnerability Numbers 1The first calculators were circular slide rules, designed by the DNA and produced by Perrygraf. These rules are now both very collectable and very rare. A list of these rules is below.

Defense Nuclear Agency Cold War slide rules and software 4This blog has posts on all these. The list is incomplete because the DNA produced a Damage Prediction Rule VN – 1 in 1982 [see this post].

As soon as a introduction of the IBM PC created a technical standard for personal computers the DNA began producing nuclear targeting software programs.  Some of the DNA’ss programs duplicated the functionality of the above slides rules. The Multi-sigma Damage Prediction Rule was produced as both a physical slide rule and as  software programs for hand held and desktop machines.  Programs for a long list of other targeting functions were added to the DNA catalogue.

Defense Nuclear Agency Cold War slide rules and software 2

Defense Nuclear Agency Cold War slide rules and software 3

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Defending Chicago [Part 1] – A New Threat

Nike missile batteries 02

During the 1950s the USA military started to worry that Russian bombers might fly over the Arctic and Canada and drop nuclear bombs on American cities.

The decision to drop atomic bombs on Japanese cities did little to shorten the war but it did create an existential threat to the USA.  Several things  followed from the American’s demonstration that  nuclear bombs worked, that they had some and were prepared to drop them on civilian targets.

1   Other countries would have to have such bombs or be prepared to obey America. Sure enough, in 1949 The Soviet Union detonated Joe -1, its first atomic bomb. Five years before the CIA expected the Soviet Union to have a A bomb.  The bomb was about Hiroshima size.

2   Bombs would get more powerful. In 1952 the USA tested a 10.4 megaton hydrogen bomb, but it was too heavy to be deliverable. In 1953 the Soviet Union tested a hydrogen bomb which had a much lower yield but was deliverable.  Soon both sides had multimegaton hydrogen bombs which were deliverable.

Until the US introduced the world to the nuclear age America had been effectively immune to aerial bombing. Now it wasn’t and the bombs were a lot more powerful. A successful attack could turn the USA into a third world country.


The US military realised that America was almost defenceless.  In a simulated Soviet attack [Operation Tailwind], 94 SAC bombers tested the air defence system of the continental USA by flying over Canada at night, and using electronic countermeasures to simulate a Soviet raid. Only 7 of the planes were spotted by radar and “shot down.

America had no reliable way of detecting approaching Soviet bombers. If incoming bombers were detected there was no good way of destroying them.

It might not even know  it had been attacked. If Los Angeles was destroyed or the SAC base at Homestead in Florida, how long would it take for Washington and SAC at Omaha to realised what had happened?  Probably too long. Even more worrying; what if the USA wrongly believed it was being attacked and started WW3?

In 1961, when tensions were very high during the Berlin Crisis, SAC headquarters in Omaha lost contact with the  Thule radar base in Greenland. A SAC officer called NORAD headquarters in Colorado Springs to find out what was wrong. The line was dead. Both Thule and NORAD were considered key bases that were likely to be hit very early in any Soviet attack. That they were both offline strongly suggested that an attack was in progress. A technical fault seemed unlikely since one base was east of Omaha and the other to the west.

It later emerged that a single AT & T switch in Black Forest, Colorado had failed and cut most of SAC and NORAD’s communications circuits. AT & T had not provided redundant switches, despite have told the US government that it had done so.

General LeMay of SAC thought that spending money on defence was a waste of time since some Russian bombers would always get through. He believed that all the money should be spent on offensive weapons. ‘ If the Soviets launched an attack with 200 bombers and American forces somehow managed to shoot down 90 percent of those planes, the United States would still be hit by at least 20 H-bombs, if not more.’  [Quoted in the excellent  Command and Control. by Eric Schlosser 2013]. Being a psychopath he did not realise that saving even a single American city was worthwhile.

LeMay’s arguments did not prevail and the USA began building its defences.

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The Nuclear Bomb Effects Computer Versions 1, 2 & 3

There were three versions of the Nuclear Bomb Effects Computer.  The first was designed by EG&G.

“EG&G, formally known as Edgerton, Münchhausen, and Grier, Inc., was a United States national defense contractor and provider of management and technical services. The company was involved in contracting services to the United States government during World War II and conducted weapons research and development after the war.” Wikipedia.

The calculator was based on test data published in the first edition of the ‘The Effects of Nuclear Weapons’.  The calculator is made of plastic and is 4″ in diameter. A complete set consists of the calculator, a red and white sleeve and an instruction pamphlet.  This cold war calculator is very rare.

Nuclear Bomb Effects Computer V1

Nuclear Bomb Effects Computer V1

Nuclear Bomb Effects Computer V1 02

Nuclear Bomb Effects Computer V1 03

Nuclear Bomb Effects Computer V2

A revised version of the calculator was designed by the Lovelace Foundation. See this post for more information. Like V1 this calculator is very rare.

Nuclear Bomb Effects Computer V2

Nuclear Bomb Effects Computer V3

The third version of the calculator was also designed by the Lovelace Foundation. Its design is much improved over the earlier versions and is based on a revised test data set which was published in the second edition of the ‘The Effects of Nuclear Weapons’. The calculator is 5″ in diameter and is made of plastic. This version is not rare. Copies of the calculator were on public sale for $1 along with the revised edition of the ‘The Effects of Nuclear Weapons’ for $3.  The calculator was used as a prop in the Dr Strangelove film and copies were given away to promote the film. See this post for more information.

Nuclear Bomb Effects Computer V3

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The Nuclear Club

worlds nuclear club

Note that the US had 31,255 warheads in 1967. See this post.

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January 17, 2016 · 7:50 pm

U.S. Cold War Nuclear Target Lists Declassified for First Time


Screen Shot 2015-12-23 at 20.52.15

“ON JANUARY 25, 1991, General George Lee Butler became the head of the Strategic Air Command. During his first week on the job, Butler asked the Joint Strategic Target Planning Staff to give him a copy of the SIOP. Butler decided to look at every single target in the SIOP, and for weeks he carefully scrutinized the thousands of desired ground zeros. He found bridges and railways and roads in the middle of nowhere targeted with multiple warheads, to assure their destruction. Hundreds of nuclear warheads would hit Moscow—dozens of them aimed at a single radar installation outside the city.

During his previous job working for the Joint Chiefs, Butler had dealt with targeting issues and the damage criteria for nuclear weapons. He was hardly naive. But the days and weeks spent going through the SIOP, page by page, deeply affected him.

For more than forty years, efforts to tame the SIOP, to limit it, reduce it, make it appear logical and reasonable, had failed. “With the possible exception of the Soviet nuclear war plan, this was the single most absurd and irresponsible document I had ever reviewed in my life,” General Butler later recalled. “I came to fully appreciate the truth … we escaped the Cold War without a nuclear holocaust by some combination of skill, luck, and divine intervention, and I suspect the latter in greatest proportion.

Butler eliminated about 75 percent of the targets in the SIOP, introduced a targeting philosophy that was truly flexible, and decided to get rid of the name SIOP. The United States no longer had a single, integrated war plan. Butler preferred a new title for the diverse range of nuclear options: National Strategic Response Plans”

Excerpt From: Schlosser, Eric. “Command and Control.” 2009.      Link

It appears that during the Cold War the defence industries kept churning out nuclear bomb and the military kept trying to find targets for them. If a war had started by accident or design it would have destroyed most life in the northern hemisphere and perhaps triggered a nuclear winter. One lesson is the need to keep the military under very close supervision.

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Child's Polaris submarine

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December 7, 2015 · 12:30 pm

London’s Cold War Targets

London Targets Map  1

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December 7, 2015 · 12:28 pm