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.
The 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.
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.
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
This slide chart was produced by IBM and is approximately 7.5 inches by 3 inches. It was used to calculate how long it would take to process a certain number of punched cards through different punched card machines [punches, verifiers, sorters, collators and accounting machines].
Filed under Calculators, IT
The Rocket Performance Computer was produced by E H Sharkey of the RAND Corporation in December 1958. The package consists of an eighteen page booklet and a 100mm [4″] diameter plastic calculator. The calculator is described as being intended for rapidly calculating approximate solutions for single stage rockets [though it can also be used for multi stage rockets by adding solutions to single stage calculations].
Though Moon Escape, Mercury and Pluto are printed on the calculator the references in the booklet are to calculating payloads and ranges for IRBMs [Intermediate Range Ballistic Missiles] and ICBMs [Intercontinental Ballistic Missile].
The Cold War was in progress when the computer was produced. In 1957 the Strategic Air Command had started a 24/7 nuclear alert in anticipation of a Soviet ICBM surprise attack capability and the Soviets had launched the Sputnik satellite. The Soviets had produced the first ICBM and put the first satellite in orbit.
The computer appears to have been intended for use by engineers working on both military and space programs.
Most slide rules are 10-12 inches long and accuracy is difficult. The Gilson Atlas circular slide rule has three scales on its front. One is 23 inches long, the other is a 50 foot spiral [other sources give the length as 75 feet but a page from the instruction manual is reproduced below and gives the length as 50 feet].
Results on the outer 23 inch scale can be read to three figures and on the central spiral to five figures. The innermost scale may be intended for counting rotations around the spiral.
The disk is 8 and 5/16ths inches in diameter and 5/16th inches thick. It is made of aluminium covered in white celluloid enamel. There are two cursors on front and one on the back.
The Atlas slide rule was produced by the Gilson company, founded by Clair Amasa Gilson