Tag Archives: computing

The DNA Multi-sigma Damage Prediction Rule MSIG – 1 Cold War slide rule

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.

DNA MSIG-1 Multi-Sigma Damage Prediction Rule 2

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.

DNA MSIG-1 Multi-Sigma Damage Prediction Rule 3

DNA MSIG-1 Multi-Sigma Damage Prediction Rule 4

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.

DNA MSIG-1 Multi-Sigma Damage Prediction Rule 1


Leave a comment

Filed under Cold War, Cold War Calculators

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

Leave a comment

Filed under Calculators, Cold War, Cold War Calculators, Uncategorized

RAND Damage Probability Computer for Point Targets with P and Q Vulnerability Numbers


The Damage Probability Computer for Point Targets with P & Q vulnerability numbers was created to provide military planners with a quick way of estimating the outcome of nuclear bomb attacks on overpressure-sensitive targets (PVNs) and  dynamic pressure-sensitive targets  (QVNs).  PVN targets are destroyed by crushing [vertical blast pressure], QVN targets are destroyed by being knocked over [horizontal blast pressure].  A tank might be resistant to overpressure but capable of being tipped over by dynamic pressure effects. A hardened missile silo might be immune to dynamic pressure and have to be destroyed by overpressure.

The computer  was first issued in 1974. A modified version,  with an additional scale for calculating optimum air burst heights, was issued in 1977. The computer shown is the 1977 version.  It is approximately 7 inches in diameter [18 cm] and is made of plastic. It was manufactured by Perrygraf.

At the time the US and the UK had a Single Integrated Operational Plan [SIOP] which listed all potential targets in the Warsaw Pact countries [and some other countries].  Each target was given a vulnerability number [see this post for an explanation of vulnerability numbers] and a desired probability of destruction. The desired probabilty was usually 0.75 but some targets were seen as more important and had higher probability numbers. What constituted ‘destruction’ was also defined for each target. For example, steel surface storage tanks had to be ruptured to be considered destroyed.

A point target is a small target which needs an accurate strike to destroy it. A city would not be a point target, a missile silo would.

Also, at this time the US and UK were introducing multiple independently targetable re-entry vehicles [MIRVs] to replace unitary warheads [a single, usually large, warhead].  The increase in the number of warheads allowed military planners to add a large number of targets to the SIOP.   MIRVs carried more warheads but smaller ones.


The Poseidon Submarine Launched Ballistic Missile [SLBM], introduced in 1972, carried 10 or 14 W68 40 kiloton warheads [the Hiroshima bomb yielded 16 kilotons and the Nagasaki bomb 21 kilotons]. The Minuteman III had three 170 kiloton warheads.  Such warheads could be used for point targets as well as city busting.

The computer only calculates blast effects. Thermal, cratering, ground shock and fallout [or other radiation] effects are not taken into account.

Performing Calculations

Damage Probability Computer noexif  3

The red side of the computer is used for P targets (PVN) and the blue side for Q targets (QVN).

Inputs to the computer are – Continue reading

Leave a comment

Filed under Calculators, Cold War Calculators

Underwood Samas Punched Card Sales Brochure

This is a sales brochure from the Samas punched card division of Underwood. Before electronic computers a lot of companies did their data processing on punched card machines.

Underwood Samas Punched Card Brochure 03

In 1915 the American company Powers Tabulating Machine Company established European operations through the Accounting and Tabulating Machine Company of Great Britain Limited, in 1929 renamed Powers-Samas Accounting Machine Limited (Samas, full name Societe Anonyme des Machines a Statistiques, had been the Power’s sales agency in France, formed in 1922).

In 1952, Underwood, the typewriter manufacturer,  acquired the American punched card tabulating equipment assets of the British Powers-Samas company.

Unlike IBM equipment Powers-Samas equipment was entirely mechanical. Rectangular holes in punched cards were converted into electrical signals as they passed under a row of wire brushes. Pins that could drop through round holes in cards were connected to linkages and their displacement when a hole was present actuated other parts of the mechanism to produce desired results.”


Underwood Samas Punched Card Brochure 04

Samples of cards

Continue reading

1 Comment

Filed under History, IT

IBM Port-A-Punch

Punched cards were  first used in the 18th century to store the programs used to control silk looms.  In the late nineteenth century they were  used by Hollerith to process census data, then widely in government and business  in the era of punched card data processing. Until about the mid 1970s they  were also used as an input medium in the early electronic computers.

The pocket sized Port-A-Punch was introduced by IBM in 1958 to allow  the ad hoc production of small numbers of punched cards. For example, if an operator or engineer needed to introduce one or two extra control or data cards  in a run they could be quickly produced on a Port-A-Punch. Another use was in program testing. A programmer might submit a thousand card programme and on its first run have it fail at, say, card 54 because of a mistake on that card. The Port-A-Punch  allowed the programmer to quickly produce a new card and submit the batch of cards for their second run.

IBM claims that ‘The product was also intended for “on-the-spot” recording operations — such as physical inventories, job tickets and statistical surveys — because it eliminated the need for preliminary writing or typing of source documents. Among the Port-A-Punch’s customers and applications were: Ford Motor Company, to locate new car prospects and other marketing data; New York State Department of Public Works, to conduct traffic surveys in the field; Reynolds Metals Company, for sales personnel call reports; U.S. Army Ordnance Tank Automotive Command, to report on vehicle R&D tests; Chesapeake & Potomac Telephone Company, for time reporting by field installers and repairmen; Jackson Brewing Company, to invoice customers at time of delivery; Thompson-Ramo Woolridge Corporation, for faster production line reporting; Varina Wholesale Builders Supply Company, for point-of-sale recording of chain store sales and inventory data; and Peckham Road Corporation, to prepare job tickets on customer shipments leaving various plants.’

I doubt if Port-A-Punchs were used to produce more than a few cards at a time.  They were too slow. For larger volumes of data it was faster and easier to enter the data on  coding sheets and then have cards produced on a machine such as a IBM 029 Card Punch by a skilled operator.


The images below show the plastic mask used on the Port-A-Punch to ensure accurate punching, the card holder and the punching tool.

IBM Port-A-Punch 2 Continue reading

Leave a comment

Filed under IT

Hewlett Packard Circuit Board Yield Calculator

HP Board Yield Calculator 1 HP Board Yield Calculator 2

Leave a comment

Filed under Calculators, IT

The Computing Gallery at the London Science Museum

This slideshow requires JavaScript.

Leave a comment

Filed under History, IT