A rare British Cold War calculator. Presumably intended for use by civil defence after a nuclear attack.
Tag Archives: calculators
After WW2 the USA needed to develop and test its nuclear technology. It set up two proving grounds.
Nevada Proving Ground
The Nevada Proving Ground was only 65 miles from Las Vegas and gamblers could watch the mushroom clouds from the casinos and hotels. Most of the 928 tests were under ground but 100, including the notorious ‘Dirty Harry;’ test, were atmospheric. and winds carried the fallout of these to the west. The town of St. George was particularly badly affected and there were increases in leukaemia, lymphoma, thyroid cancer, breast cancer, melanoma, bone cancer, brain tumours, and gastrointestinal tract cancers. Over 200,00 cases of thyroid cancer were believed to have been caused [see this post]. Nuclear Test Participation certificates were issued to the people who took part in testing [see post]
Pacific Proving Ground
Only low yield weapons were tested in Nevada. Most of the big bangs took place in the Pacific Proving Ground [1946-62], on the Enewetok and Bikini Atolls in the Marshall Islands. A few of the later tests were conducted on Christmas Island and Johnston Atoll.
A total of 105 atmospheric and underwater tests were conducted in the Marshall Islands. This was only 14% of the total number of tests but accounted for 80% of the megatonage, The estimated total yield of the Marshall Islands tests was about 210 megatons, including the 15 Mt Castle Bravo shot on Bikini in 1954. The Castle Bravo bomb got out of control and produced over twice the expected yield, spreading radioactive contamination over several of the Marshall Islands atolls and a large area of the Pacific.
An atomic stick chart
The Marshall Islands are known for the stick charts charts their navigators created to help them sail between their 29 atolls and 5 islands. These are spread over a huge area of sea and navigation was a non trivial problem. I have made a stick chart to clarify the geography and identify the atolls that the USA used for military purposes. There is more about stick charts in a separate post.
The Enewetok and Bikini [the swimsuit was named after the atoll] atolls were the ones used for testing. Kwajalien is still used by the USA as the the Ronald Reagan Ballistic Missile Defense Test Site. Majuro is the capital of the Marshall Islands. To give some idea of scale; it is 539 miles from Bikini to Ebon, the same distance as from London to Leipzig. The circular calculator in the bottom left is a Time Conversion Computer [see this post].
Testing began on Bikini in 1946 with the Crossroads tests Two 21 kiloton atomic bombs were detonated. ‘Able’ was an atmospheric test [video] and ‘Baker” an underwater test [video]. The Baker bomb was exploded at a depth of 27 meters in the middle of a small fleet of ex WW2 vessels. The dangers of radioactivity were not fully understood then and sailors were sent to try a scrub ‘clean’ the highly contaminated vessels.
Testing then moved to Enewetok Atoll for the Sandstone, Greenhouse and Ivy series of tests. After that testing took place on both Enewetok and Bikini until Operation Dominic in 1962 which involved 36 bombs being detonated above and near Johnston Atoll and Christmas Island.
Both Enewetok and Bikini remain heavily contaminated. Bikini is now a UNESCO World Heritage site. The natives of the Marshall Islands suffered form American operations in the Pacific Proving Ground, but not as badly as the natives of Utah and the mid west suffered from the operations in the Nevada Proving Ground.
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