A rare British Cold War calculator. Presumably intended for use by civil defence after a nuclear attack.
Category Archives: Cold War Calculators
The MSIG – 1 Multi-sigma slide rule was produced by the US Defense Nuclear Agency to assist military planners in calculating the probability of damage resulting from a nuclear detonation.
The rule is 8″ [205 mm] in diameter and produced by Perrygraf. It was designed by the DNA and is dated April 1987. This rule is very collectable but the hardest to find of all the DNA slide rules. The one shown was never issued and is in mint condition.
The MSIG -1 was the last slide rule to be produced by the DNA. After that they only supplied software for use on desktop and hand held machines. A list of the slide rule and software can be found in this post.
The complete package as issued consisted of a binder, hard cover, documentation, slide rule and two floppy disks.
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.
This 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.
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 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 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.
Cold War Weapon Effects Rule designed by Horizons Technology for the US Defense Nuclear Agency and manufactured by Perrygraf.
This Cold War Damage Prediction calculator [version 2] was commissioned by the Defense Nuclear Agency and designed by Horizons Technology Inc. of San Diego in 1986. The 8″ diameter rule is made of plastic and was produced by Perrygraf. It consists of seven desks, a base disk and three tabbed disks [for HOB, VN adjustment and yield] on either side.
See an earlier post for the 1982 version of this rule. The 1982 version of the rule colour coded the sides for P and Q type targets. This rule prints the target type on the rule. The rule has the same purpose as the Damage Probability Computer produced by RAND [see this post] but is far more sophisticated.
For more posts about Cold War calculators click on the Cold War Calculators category on the right.
The rule uses the vulnerability number system to calculate the probability of destroying a target given variables such as warhead yield, CEP [circular error of probability, accuracy of delivery vehicle], HOB [height of burst], WR [weapons radius] and the target’s vulnerability number [e.g. 18P5]. Continue reading
This Cold War Damage Prediction calculator [VN 1] was commissioned by the Defense Nuclear Agency and designed by Horizons Technology Inc. of San Diego in 1982. The 8″ diameter rule is made of plastic and was produced by Perrygraf.
The purpose of the rule was to allow planners to calculate the probability of destroying an enemy point or area target by attacking it with a nuclear weapon.
The rule has the same purpose as the Damage Probability Computer produced by RAND [see this post]. The DNA rule is more sophisticated and has the following additional features.
1. It can be used for attacks on area targets [towns and cities] and not just point targets.
2. It allows aim point offset.
3. It allows conversion from feet to meters [useful when used in a NATO context because at the time some NATO members were using the metric system and some imperial units].
The rule’s documentation makes clear that calculations are made using the Vulnerability Number system [see this post]. The blue side of the rule was used for targets assigned a P vulnerability number and the green side for those with a QVN.
When used in planning attacks on a area target the RT is the target radius which includes 95% of the target elements. HOB is height of burst. Continue reading