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Strangelove Slide Rule
Nuclear Bomb Effects Computer

Online Edition
by John Walker
Tumbler Charlie detonation 1952-04-22 17:30 UTC 31 kt airdrop, Nevada Test Site, Area 7

Effects of Nuclear Weapons and Computer (1962 Edition)

Strangelove Showdown

Back when I was in college in the 1960s, there was no better way for a larval engineer or scientist to stand out from those pursuing more mushy majors than swaggering around with a fancy slide rule in a spiffy leather holster dangling from his belt. “Well now mister phil-oss-a-pher, I don't rightly cotton to your kind of fuzzy thinkin'. How about we settle this, just you and me—logarithms at ten paces.” Then there were the peaceniks…. Now, I'm for peace as much as the next fellow, but it's always seemed to me a clear lesson of history that unilateral disarmament in the face of aggressive tyranny is not the way to peace. Maybe it's one of those slippery concepts which an understanding of feedback systems and differential equations helps one to grasp more firmly than an encyclopedic knowledge of the works of nineteenth century political theorists.

Anyway, when some champion of human liberty in a Che Guevara T-shirt and Mao jacket was haranguing his audience with claims like “A single Hiroshima bomb set off downtown would annihilate this university and all of us in the blink of an eye”, what better way to burnish one's Strangelovian credentials than to whip out a handy-dandy nuclear bomb computer slide rule, whip—slip—slide, and interrupt, “Naaah…fifteen kilotons at five miles? Surface burst? Why, that's only a quarter to a third of a pound per square inch overpressure—it'll probably break some window glass but that's about it.” Flipping the slide rule over, “The flash isn't even enough to cause sunburn, and the immediate radiation is next to nothing.” For some unfathomable reason, this never seemed to either carry the argument or suitably impress chicks.

Collectible Computer

Back in those psychedelic days of yore, you could order your own fantastic pastel plastic nuclear bomb effects computer directly from the U.S. Government Printing Office for a single green dollar, and for three dollars more, obtain the authoritative 730 page book, The Effects of Nuclear Weapons, upon which it was based. With the winding down of the nuclear arms race and eventual end of the Cold War, interest in the actual consequences of setting off nuclear weapons waned. The book and computer were last updated in 1977, and subsequently went out of print. By the 1990s they had become something of a collectors' item, with mint copies of the book and computer selling for hundreds of dollars, although bargains remained available if you were patient and looking for a copy to read, not store away in the hope of eventually reselling it to a greater fool.

Since these were publications of the U.S. federal government, which does not assert copyright on its documents, they have been in the public domain since inception, but interest to date has not motivated anybody to republish them. Fortunately, a copy of the 1977 third edition of the book has been scanned and is now available online. The existence of this Web resource (in PDF files for each chapter, which can be printed if a paper copy is required), seems to have restored some sanity to the prices quoted for used copies of the original books, but that still leaves the bomb effects slide rule a difficult item to obtain.

Internet Implementation

My nostalgia for this particular relic of the Cold War was such that I've had a project to produce an online edition on my to-do list for more than five years. Like many items on this embarrassingly long and all too infrequently shortened list of unrealised ambitions, it's something I half expected someone else to do long before I got to it. This would be perfectly fine with me—I undertake these projects because I want to see them done, and crossing off an item without the wear and tear of doing it myself couldn't make me happier. In fact, scanning (and possibly OCR-ing) The Effects of Nuclear Weapons was an item on my list before the fine folks at Princeton got the job done.

I originally envisioned an online interactive calculator, along the lines of a spreadsheet, either in JavaScript or, to be really super-cool, as a server based CGI application written entirely in Ada (doubly appropriate, not just as a programming language associated with military applications, but because the Lady after which it is named also shares a name with the creators of the bomb calculator: the Lovelace Foundation—better known for devising the diabolical medical torture tests for the Project Mercury astronauts chronicled by Tom Wolfe in The Right Stuff). I've used this model for various other Web resources, for example the Fourmilab Calendar Converter, but every time I looked into the details, I found that the fit between the bomb effects slide rule and a cell-and-number based calculator was rather poor. As users of slide rules and nomograms (which excludes almost everybody under the age of forty) will appreciate, once you've “set up” the inputs to a calculation, a whole range of solutions can often be obtained for varying inputs just by reading numbers which line up along a scale. Further, it's usually possible to work backwards from a result to discover families of inputs which produce it. The bomb computer takes superb advantage of both of these characteristics. For example, when you're computing the decay of fallout from a detonation, setting up the dose rate at a single time permits the relative dose for any time between 12 minutes and 30 days after the burst to be read directly from the scale, or inverse questions answered like how long one must wait before the radiation declines to a specified level. Or, suppose you're interested in the tradeoff between yield and accuracy to attack a buried, steel-reinforced bunker which requires an overpressure of 100 pounds per square inch (PSI) to bust. Setting the overpressure scale of the bomb computer to 100 PSI (opting here for an optimum height as opposed to a surface burst), one finds that with the roughly 100 metre accuracy of state of the art intercontinental missiles, a bomb on the order of one kiloton will do the deed, but with the “general vicinity” accuracy available with early ballistic missiles like the Atlas (2000 foot / 600 metre circular error probable), a yield in excess of 100 kilotons, almost five times that of the Nagasaki bomb, would be required. Working numbers like these brings home the extent to which technological progress in metre-accuracy precision guided munitions, not the efforts of disarmament activists, have rendered nuclear weapons, as the man said (albeit in a different context) “impotent and obsolete”.

Reflecting on the design advantages of the original calculator, I ended up concluding the best way to bring it to the Web would be in its original form—an interactive graphical reincarnation of the original plastic slide rule. Many were the obstacles, due in part to the fact that I have only a single prototype and would never destroy the authenticity of such an artefact by disassembling it. I will spare you the technical details—the result is now yours to explore. (If you're really interested in how this Web application was built, please see the production notes. Basing the online edition on the graphics of the original slide rule also made it easy to provide what's needed for those interested to build their own replica slide rule.)

Detonation Definition

Enter yield and range for complete weapon effects, or time since detonation and relative dose rate for a fallout computation, into the forms below, click the “Calculate” button, and you'll see the results on the bomb effects computer set to the specified values. (The two kinds of calculations have nothing to do with one another and simply happen to share the same slide rule; hence, they are requested on separate forms below). To understand the results, refer to the bomb computer instructions, which are transcribed from the sheet which accompanied the slide rule, with illustrations added to show how values are read from the various scales. You can change the size of the calculator image by entering the desired size (up to a limit of 1575 pixels—that's all the resolution there is in the scan and, for that matter, detail on the plastic slide rule), and rotate the slide rule image either by entering an angle or clicking on the portion of the image you wish to appear at the top.

Weapon Effects Calculation
Yield:  Kilotons  Megatons
 Surface burst thermal effects?
Range:  Miles  Kilometres
Rotate: Degrees counterclockwise
Image size: Pixels

Fallout Rate Calculation
Time after detonation:  Hours  Days
Relative dose rate: Arbitrary units
Rotate: Degrees counterclockwise
Image size: Pixels

Why the 1962 Edition?

This interactive Web-based implementation of the quintessential Cold War weaponeer's vade mecum is based on the 1962 revised edition. Since I can already hear the vintage whiners and hate kiddies spooling up through the octaves and decibels to decry this choice over the most recent 1977 third edition (as far as I know, there were no editions between these two), please permit me to explain. First and foremost, the 1962 slide rule is the one I have, and however spiffy I considered this project to be, I wasn't about to spend a wad of money and a lot of time chasing down the newer edition (which, to be equally authentic, would have to come with the matching version of the accompanying instructions, which, as a single folded sheet of paper, is easily lost and missing from many copies offered for sale.) But also, this is an artefact of the Cold War, and 1962 is the very heart of that epoch. Herman Kahn's On Thermonuclear War was published in 1960, and his Thinking about the Unthinkable hit the shelves in 1962. On the fiction front, the novel Red Alert came out in 1958, followed by Fail-Safe in 1962, with the films they inspired, Dr. Strangelove and Fail-Safe both debuting in 1964. In the real world, in late 1961, the Soviet Union exploded the most powerful nuclear weapon ever developed, a 50 megaton three stage thermonuclear device capable of 100 megatons (with vastly more fallout) were its lead tampers replaced by uranium. The United States responded to the resumption of Soviet atmospheric testing with its own test series both in Nevada and the Pacific (including the Operation Fishbowl nukes in space), which continued throughout 1962. In February 1960, France exploded its first nuclear bomb and continued testing in Algeria through 1966, and China got into the game with its first detonation at Lop Nor in October 1964. The British deployed their first strategic nuclear missile, the megaton class air-to-surface Blue Steel, in December 1962. And in October 1962, the world came as close to the brink as it ever has during the eyeball-to-eyeball Cuban missile crisis, while Civil Defence pamphlets encouraged U.S. homeowners to turn a corner of their basement into a family fallout shelter.

Yes, 1962 was the very high point of the High Cold War, so it's entirely fitting and proper that this twenty-first century re-creation be based on a relic dating from that year, not 1977, which cannot help but summon images of the effete and pusillanimous Carter administration, absurd MX peekaboo racetrack deployment schemes, and the nascent nuclear freeze movement in the U.S.

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by John Walker
June 2005