This Cratering Prediction Rule [CRG – 1] was designed for the Defense Nuclear Agency by Horizons Technology Inc. of San Diego in 1984. The 8″ diameter rule is made of plastic and was produced by Perrygraf. The rule was used to calculate what craters would be produced by nuclear weapons.
The inputs to the rule are weapon yield, height or depth of burst and target geology. One side of the rule was used to estimate crater radius, volume and depth [and debris thickness] in dry soil. The other side was used for wet soil, soft dry rock, soft wet rock and hard rock. The weapon yield could be in the range 1 kiloton to 100 megaton.
I assume the rule was used to calculate the results of using nuclear weapons on rail and road transport bottlenecks and airfields. For such targets cratering could have a significantly disruptive effect.
During the Cold War potential targets were given vulnerability numbers [see this post]. Most targets were given QVN or PVN numbers depending on whether the target should be best attacked using overpressure [crushing pressure] or dynamic pressure [horizontal pressure]. PVN targets are best destroyed by crushing, QVN targets are destroyed by being knocked over. Both RAND and the DNA produced rules to assist in planning attacks on such targets and these are covered in separate posts..
It was hard to cause difficult to repair damage to targets such as rail track, roads or runways with either overpressure or dynamic pressure. Cratering was the most effective form of attack. Such targets were given ZVN numbers. For example, roadbed and rail tracks were given a VN of 45Z0. The Cratering Prediction Rule could be used to plan attacks on such targets. A cratering prediction computer program was also available.
By 1984 desktop computers and hand held programmable calculators were available and a newsletter that was distributed with the rule mentioned that the DNA was currently supporting the HP-41/HP-71, IBM PC, IBM PC/XT and Zenith Z-100. The IBM PC had been introduced in 1981 and was rapidly becoming the standard for personal computing. Before then each computer manufacturer has their own hardware, operating system and storage. There was a great deal of incompatibility and it was hard for software developers to know what system to support.
The newsletter mentioned that the DNA had supported the Texas Instruments TI-59 programmable calculator. but that device was no longer produced. The DNA had produced programs on Fallout, X-Ray Effects and Aircraft Vulnerability for the TI-59. At the time air to air and ground to air nuclear missiles were used to attack incoming bombers and it may be that the Aircraft Vulnerability program was used to estimate the vulnerability of NATO and Warsaw Pact bombers to such weapons.
The newsletter mentioned that the DNA was working on programs for Atmospheric Effects, EMP, Thermal Effects and Underwater Effects. It was not clear if rules like the CRG – 1 were ever produced for these effects.
This rule is very rare. For more posts about Cold War calculators click on the Cold War Calculators category on the right.