Review of Dr Harold L. Brode’s new book, "Nuclear Weapons in the Cold War"
After the unpleasantness of the previous post about the EU policy to allow war refugees no protection or adequate search and rescue so that thousands drown, here's some good news, our review of Dr Harold L. Brode, Nuclear Weapons in the Cold War, Montgomery Publishing, 2014, 544 pages
“In the 1950s, at the RAND Corporation, Leon Goure, a political scientist who was born in Russia and was particularly familiar with the USSR, proposed an idea his professional peers considered ridiculous. He pointed out that the Soviet Union was actually a union of many disparate peoples and made up of numerous distinct ethnic groups. In his mind, it was conceivable that this union would quickly fail if the iron fist of Stalin was ever relaxed.”
– Dr Brode, Nuclear Weapons and the Cold War, page 16.
Hal Brode, RAND Corporation’s legendary nuclear effects expert and editor of the 1992 edition of effects manual EM1, “Capabilities of Nuclear Weapons”, has cut no corners and omitted no gripping controversy in the entire field of nuclear weapons and cold warfare. Topics covered, in entertaining style and great depth of research, span from nuclear bomb effects during tests and combat use in Japan, to the failure of deterrence in the different wars since 1945, and from nuclear accidents and beneficial effects of low dose rate radiation. He discloses new facts about secret research at RAND Corporation by people like neutron bomb inventor Sam Cohen.
The illustration of the French nuclear test Licorne on the front cover is appropriate, since Dr Brode deals with nuclear weapons and accidents by all countries, not just the USA. The book includes 19 pages of references, including this blog, which is quoted on pages 242-5. In a nutshell, Brode has produced a more logical, better organized, better researched textbook on nuclear weapons and cold war history than the populist, “politically correct” books by Richard Rhodes and renowned academic historians.
Dr Brode explains on pages 27-8 that his first involvement with the arms industry was as a sheet metal machinist with North American Aviation at Mines Field in Los Angeles in 1941, assembling the B-25 bombers used in the very first American air strike on Tokyo, Japan, April 18, 1942. Brode explains on page 30 that 250,000 Chinese civilians were “assassinated” by Japan in retaliation for that air raid. He remembers the announcement that Japan bombed Pearl Harbor, December 7, 1941 (page 28):
“I was listening to the Sunday morning radio broadcast of the Mormon Tabernacle Choir in my parent’s living room when the broadcast was interrupted with the news of that attack. At the time, I had been working nights, building bombers and fighters at North American Aviation and was attending junior college during the day. The next day, Monday, the United States declared war on Japan. Then four days later, Germany declared war on the United States.”
Brode spent the year 1943-4 at the University of Minnesota cramming two years of maths and physics into one, before serving in the US Army Air Corps as a 2nd Lieutenant. On page 44 he lists the 52 million casualties of World War II by country, dividing the mortality into civilian and military deaths. Poland, the country whose invasion triggered off Britain’s declaration of war on Germany, lost 17.2% of its population, many in concentration camps, with only 2% of the fatalities being military deaths. The USSR lost 20.6 million, 10.4% of its population, half of which were civilians. Germany lost 6.85 million or 9.5% of its population, with again about half of the deaths civilian. By using nuclear weapons, America kept its casualties to half a million, 0.4% of the population, all military personnel.
He quotes Nagasaki nuclear bomber pilot Major General Charles W. Sweeny’s testimony (page 45):
“Today, millions of people in America and Japan are alive because we ended the war when we did. This is not to celebrate the use of atomic weapons. Quite the contrary. It is my fervent hope that my mission is the last such mission ever flown. But that does not mean that back in 1945, given the events of war and the recalcitrance of the enemy, President Truman was not obliged to use all the weapons at his disposal to end the war.”
Harold Brode thanks Hiroshima and Nagasaki and resulting rapid surrender for sparing his life as a 22-year-old scheduled for the second D-Day of World War II, planned for 1 November 1945 (pages 84-5):
“Invasion of the Japanese home islands … had been estimated to lead to the probable deaths of between 400,000 and one million U.S. soldiers and sailors. In addition, as many as half a million British troops would have been at risk … 800,000 Japanese defenders and civilians were expected to be casualties. I personally have always been grateful that the war in the Pacific was brought to a conclusion when it was. At the time that the first atom bomb was dropped on Hiroshima, I was … a 22-year-old second lieutenant in the Army Air Forces … in charge of a small detachment of 18-year-old draftees who were destined (but ill-prepared and totally inexperienced) to join the invasion … We were scheduled to land on D-day-plus-one and immediately scatter into the interior of that likely hostile country ... Those two nuclear weapons destroyed many lives in Hiroshima and Nagasaki – but, by ending the war, they saved a great many others … possibly including my own.”
After a detailed review of German nuclear weapons research, Brode details the science of implosion type nuclear weapons during the American Manhattan Project of World War II. Gun type assembly (used at Hiroshima) was not feasible for the heavy plutonium isotope 239 contaminated by isotope Pu-240 which has a high spontaneous fission rate because (page 69):
“To get the plutonium to a super-critical state before it blew itself apart required a critical mass assembly at speeds of more than 6 miles/sec (~ 31,700 ft/sec) – much faster than simple howitzer devices could have managed.”
He adds that John von Neumann’s Mach wave reflection theory (pages 70-1):
“… convinced his fellow scientists at Los Alamos that the blast from a nuclear burst would be greatly enhanced if its shock wave were to reflect off the ground from a burst height high above the target … the four radars in each weapon were wired in pairs, so either one pair of the other could trigger the weapon when both radars in one pair or the other agreed that the right altitude had been reached, so they would not detonate prematurely. In addition … a barometric fuse, set to go off at a somewhat lower altitude, was included as a further backup.” (The detail about the radar fuses comes because his uncle, Robert B. Brode, was on the Manhattan Project and developed the bomb’s radar fuse systems.)
John von Neumann’s second contribution, after selecting the air burst altitude, was to apply mathematics to Seth Neddermeyer’s implosion theory for the Trinity and Nagasaki weapons (pages 71-2):
“In fact, von Neumann and Robert Richtmyer invented (and later published) a numerical scheme that proved essential to many such subsequent calculations, and has been in wide use at weapons laboratories and elsewhere ever since. Subsequently, in doing my own calculations of both nuclear and high explosive blast waves, I employed von Neumann’s and Richtmyer’s ingenious ‘artificial viscosity’ scheme. Their technique allowed computer programs to numerically integrate right through shock wave discontinuities, and still accurately represented the physics and hydrodynamics of explosive phenomena.”
Brode points out that the Neumann-Richtymer technique for computing implosion system behavior (with smothing over discontinuities by the use of artificial viscosity) was published openly by Pergamon Press of New York under the heading “The point source solution” in volume 6 of a compilation of von Neumann’s works edited by A. J. Taub in 1963. So much for the secrecy of computer models of implosion bomb physics. Anyone can numerically integrate the Neumann-Richtymer equations for any implosion system in Fortran on any modern computer!
The major British contribution to the Manhattan Project was James Tuck’s argument in April 1944 to use high explosive “lenses” to focus point source detonation waves by modifying the speed of the detonation wave by the use of shaped charges of fast and slow-burning explosive. The effect is exactly the same as the way light is refracted by the effect of a shaped lens of glass slowing down light relative to its speed through the air. (Being denser, glass has a higher electron charge density than air, thus “loading” the photons passing through glass with more electromagnetic field interactions, which slows down light.) Explosive lenses reduce the number of detonators needed for implosion and make the compression of the core more uniform (page 82): “… X-ray images showed successful compressions of the heavy metal cores without any of the devastating jetting that had been feared and was so important to avoid.”
THE COLD WAR PERIOD
Dr Brode begins this with a review of the Russian spying in the Manhattan Project. He explains that, apart from the well-known spies like Alan Nunn May, Hlaus Fuchs, David Greenglass, and the Rosenbergs, who sold the principles of bomb design, others like George Koval – finally recognised by Putin in 2002 for stealing American secrets – gave Stalin the vital U235 gaseous diffusion barrier design used at Oak Ridge (pages 92-3)
“In recent times, Russian President Putin awarded posthumously the highest Russian award to George Koval … Koval was born in Iowa in 1913 … his parents emigrated to a Siberian establishment … he was then trained by the GRU for his role as a spy. And he returned to the US in 1940. As an American citizen, with no trace of a foreign accent, he was subsequently drafted … Koval was sent back to school at the City College of New York in the Army Specialized Training Program … Later … assigned … to support the Manhattan Project. While in that assignment, he also learned details of the Oak Ridge operations … Koval continued to spy in the US from 1940 to 1948 … Only years later did his spying activity become known in the United States.”
Dr Brode points out on page 119 that 63% of the total cost of the Manhattan Project ($1.89 billion in 1944 dollars, or $27.3 billion in 2006 dollars, allowing for inflation) was spent on the massive Oak Ridge plants for U235 separation by the gaseous diffusion process, pumping acidic UF6 gas at high pressure through porous nickel barriers. The plant was the first wide scale use of teflon, which coated all the compressor pumps to avoid corrosive destruction from UF6. The barriers themselves were acid etched from a tin-nickel alloy, and later by fusing powdered nickel together, developed to optimally withstand the gas pressure while allowing the lighter and faster U-235F6 molecules to diffuse through, without dissolving due to the acidity over a 6 month operational life. (There are some minor typographical errors in the book like commas out of place occasionally, and on page 129 the error occurs that 5% of natural uranium is U235, but everyone knows that 0.71% natural uranium is U-235.)
After discussing the spies, Brode moves on to secrecy during the hydrogen bomb program, and his personal interactions with Robert Oppenheimer, Director of wartime Los Alamos, who was a personal friend of Brode’s uncle, the Manhattan Project physicist Robert B. Brode, 1900-86 (page 134):
“I first met Robert Oppenheimer and his wife Kitty at my Uncle’s home in Berkeley. My aunt and uncle were close friends of the Oppenheimers and the Fermis, and, of course, with the many other scientists who had been a part of that wartime effort. In 1948 I attended Oppenheimer’s graduate seminar on nuclear physics … I found him impatient and even rather sarcastic, especially with students who dared to ask questions.”
Dr Brode did his PhD in Theoretical Nuclear Physics at Cornell from 1948-51 under supervision of his thesis advisor and PhD Committee Chairman, the celebrated Nobel Laureate Hans A. Bethe. It was Bethe who first tried to calculate the nuclear fusion rates in stars prior to WWII, and who with Freeman Dyson in 1947 persuaded Oppenheimer of the validity of Feynman’s path integral approach to calculating the Lamb shift in the hydrogen atom’s ground state energy level. Brode points out that Bethe had been the theoretical group leader at Los Alamos (leading to lifelong friction between Teller and Bethe, stemming from the low priority of H- bomb research during WWII). While minimising H-bomb research during WWII to the irritation of Teller, Bethe did authorize several detailed theoretical studies of nuclear weapons effects while at Los Alamos, including nuclear fireballs, blast wave pressures, and thermal radiation pulses (see Bethe’s Los Alamos report LA-2000, or LA-1020).
RICHARD P. FEYNMAN
During Brode’s PhD research at Cornell, he had a job as a graduate assistant, grading papers from students of Bethe, Richard Feynman, and others (page 142):
“In my job as a graduate assistant … I seldom got much guidance from Professor Feynman. For him, I had to define the ‘correct’ answers for myself and then defend them with no help from him. My problem was that his exam questions were often a bit obtuse and seldom led to simple answers.”
After discussing Edward Teller’s testimony to the 1954 Oppenheimer security hearings, in which Teller cast doubt on Oppenheimer’s motivations because of his resistance to the H-bomb even after Russian exploded a nuclear weapon in 1949, Brode suggests (pages 145-6):
“… Dr Teller was credited with influencing then-President Reagan to sponsor research into advanced technology for shooting down Soviet ICBMs [Strategic Defense Initiative, SDI; or “Star Wars” in President Reagan’s language] … So, perhaps the world should also give some credit to Edward Teller for his contribution to the successful end to the Cold War, because that SDI or Star Wars effort did force the USSR to pursue vastly more expansive and expensive research … These efforts placed inordinate demands on the Soviet defenses and further strained their already overburdened military budgets. …
“Edward Teller was a frequent consultant at RAND … Teller would hold daily marathon seminars, where he probed ideas for new thermonuclear weapons designs. These were rather informal gatherings that frequently went on all day long … He would often suggest as many as half a dozen or more ideas during the course of a single day, and one or more of us would inevitably be designated to go off and more thoroughly investigate his suggested innovations. … this man was a true genius, and some of his ideas proved invaluable. Unfortunately, out of his plethora of concepts and suggested avenues of research, only a few proved worth further pursuit, but, as that old hand put it: ‘Who among us has even one good idea per day, or per week, for that matter?’”
JOHN VON NEUMANN
Brode describes on how he at RAND Corporation beat computer innovator John von Neumann in 1955 publish (Journal of Applied Physics, v26, n6, pp766-75) the first full electronic computer solutions to point source, free air blast waves, using von Neumann’s own artificial viscosity equation (page 147):
“… with excellent support at RAND, I managed to produce results that von Neumann was still trying to squeeze out of an early electronic computer at Princeton for the Institute for Advanced Studies. I had scooped the one true expert!”
ISADOR RABI AND EUGENE WIGNER
After the Cuban Missiles Crisis of 1962, Harold Brode was recruited by Nobel Laureate Eugene Wigner to determine the efficiency of civil defence countermeasures against nuclear weapons effects, in Project Harbor, which was ignored by people like Bethe and was opposed by Isador Rabi (page 148):
“After the war, Rabi was appointed to the General Advisory Council for the first Atomic Energy Commission, and subsequently served as a member of The Presidential Science Advisory Committee (PSAC). In 1963, during a review of the National Civil Defense Program before the PSAC … in a conference room in the White House Executive Office Building … right after the Cuban Missile Crisis, when many citizens felt the imminent threat of nuclear war … Dr Rabi did not favor the Civilk Defense findings that Wigner, Teller and others of us were espousing. Thus, while Wigner made his presentation, Rabi sat at the opposite end of that great PSAC conference table and read a newspaper, loudly turning papers while he held the paper up in front of himself, thereby making certain everybody could see … Wigner was deeply offended by Rabi’s obvious scorn.”
THE SAFETY SYSTEMS OF THE FIRST NUCLEAR WEAPONS
Brode deals with permissive action links to physically prevent unauthorised use of nuclear weapons, and the safety of nuclear weapons in accidents. He begins with a detailed discussion of the safety of the Hiroshima and Nagasaki weapons, both of which used special radar circuits and a backup barometric circuit developed by a team led by his uncle, Robert B. Brode (pages 153-4):
“… it is not surprising that the fusing of each weapon was designed with a succession of safety and redundancy measures: First, a safety tape was pulled out when the bomb was released from the bomb bay, and that started a timer set for fifteen seconds. That was to avoid premature detonation … That mechanism also turned on the power to each bomb’s radar fuses. Secondly, a barometric sensor delayed the functioning of the radar sensors … Thirdly, a set of four radar fuses were set to sense the appropriate distance to the ground … Each pair was wired in series so both radars in either pair had to agree that the selected altitude had been reached before the weapon would detonate, thus assuring a high probability … There was, of course, also a non-radar backup, another barometric fuse …”
MICROCHIP, COMPUTER, INTERNET, GPS, TEFLON, ETC. FROM WAR RESEARCH
Brode explains how hydrogen bomb improvements financed early computer development (page 163):
“In a kind of synergism, the development of high-speed computers had been stimulated by the computational needs of the nuclear weapons developers. The ability to carry out complex and repetitive numerical calculators was vital to their weapon research. Consequently, for some years, nearly all the first new electronic computers went directly to the Los Alamos Laboratory …”
The space race of course was driven by the fear of the Russian ICBM, which Russia successful tested first (in adition to the first satellite in orbit, Sputnik). Brode explains how carbon-based plastic ablation shields proved vital to protect ICBM warheads during re-entry. These plastics were used by Edward Teller as sheet type “radiation mirrors” to protect the inside of the casing of a nuclear weapon from destruction by X-rays, while reflecting X-rays from the fission stage to the fusion stage. The surface of the plastic is an insulator so it absorbs X-ray or heat, re-radiates from the surface layer, and ablates, without transmitting heat or the recoil pressure that a dense metal produces in ablation (pages 190-1):
“Only after years of experimentation did the missile designers develop lightweight ablative carbon phenolic heat shields. These light plastics, being poor conductors of heat, i.e., good insulators, protected the inner workings of the missiles, even while getting so hot on their surfaces as to vaporize. Their outer surfaces would evaporate and blow away, thus effectively carrying off the heat generated by re-entry.”
As noted, Teflon was first manufactured for the Oak Ridge UF6 gas pumps, high-speed computers for H-bomb design and military code breaking, internet to RAND’s Arpanet to allow communications after an EMP in nuclear war by routing messages by any available cables (without a single central hub). Microchips and GPS were first funded to develop miniature guidance systems for accurate missiles (pages 195-6):
“Our first true ICBM, the ATLAS, became operational in 1959 … In the beginning, this long-range missile was unreliable, inaccurate, and extremely vulnerable. … In October of 1959 the first ATLAS missiles went on combat alert, armed with its 3.8-MT nuclear warhead. … IRBMS were added to our Armed Forces to augment the shrinking roles and diminished capabilities of the tactical bombers. … submarine-launched ballistic missiles (SLBMs) such as Polaris and Poseidon missiles also became operational.”
Brode explains on page 197 that ATLAS-D and –E missiles were hardened to 25 psi peak overpressure by simply storing them “horizontally in covered underground pits” before launch. (This caused delays because ATLAS was liquid fuelled, but all modern missiles use solid fuel and can easily be stored sideways.) The first unlined vertical silos gave the ATLAS an impressive 100 psi peak overpressure protection (roughly survival at the fireball radius and near the crater edge for wet soil and small yields). Later silo development using linings of shock absorbers gave really increases to missile hardness. This increasing hardness meant that to destroy the missile in the silo by a first strike, you needed either a much higher yield or a much more accurate missile delivery system, thus driving the development of satellite GPS missile guidance and tiny high-speed computers, employing integrated circuits. By 1963, Brode reports on page 198, TITAN-II missile silos were capable of surviving inside a nuclear fireball, at a peak overpressure of 300 psi. The silo would be sited in rock to minimize crater shock effects. Finally, MINUTEMAN missiles arrived which were designed to take 1,000 psi peak overpressure.
It was this survivability of close-in nuclear weapons effects, as calculated by Brode, that guaranteed American retaliation capability and so deterred Russia, in the event that the submarines were tailed and torpedoed. As the Russians surged ahead in the arms race, the thousand MINUTEMAN missiles were upgraded with additional shock absorbers in the silos and multiple independently targetable (MIRV) and decoy warheads like chaff wire and metal foil balloons shaped like warheads to statistically saturate Russia’s Galosh ABM system around Moscow.
BRODE ON SAM COHEN’S HIGH ALTITUDE BURST IDEA
Dr Brode gives a personal account of his own accidental over-exposure to 200 rads of dental X-rays to his head, which stopped his beard growing for a month. Personal experiences too of attending nuclear weapons tests in the Nevada desert helped to motivate his studies of fellow RAND Corporation physicist Sam Cohen’s neutron bomb and high altitude bursts for defensive shields without blast damage (pages 220-221):
“But Sam was an ever-imaginative contributor to the nuclear weapons business. And later, when thermonuclear weapons of megaton yields became a reality, he also envisioned the use of very large-yield weapons … high above the atmosphere … He reasoned correctly that the blast from such a space burst, detonated at such a high altitude, would cause little or no blast damage on the ground.”
Sam Cohen was arguing for space burst nuclear weapons to shoot down Russian bombers or missiles while they were still airborne, a question that ultimately led to the Starfish test and the high altitude EMP discovery, and to Edward Teller’s Star Wars project that precipitated the end of the USSR.
Brode also includes numerous summary tables of nuclear weapons data, listing nuclear crises, nuclear accidents, nuclear tests, etc. There is no mathematical physics included, but you can find Brode's reports online at RAND Corp., the Annual Review of Nuclear Science v18, and by searching the DTIC database for Harold Brode. The printing, type setting and text size and paper quality is excellent.
Links to some newly-released declassified nuclear weapons effects reports vital for civil defense:
Louis Costrell, Operation JANGLE: Nevada Proving Grounds, October-November 1951, Gamma Radiation Measurements, ADA078575 (PDF of document downloadable from the DTIC page is linked here):
Gamma ray dosage rates were determined as a function of time and distance. The method of measurement and the equipment used is described. Dose rates as a function of time were obtained for 27 stations on the surface burst and for 29 stations on the underground burst. Total dose data was obtained by integration of the dose rates. Dose rate and integrated dose as a function of time are presented for all of the stations. One hour dose rate contours are presented as well as 10 minute, 1 hour, and 10 hour integrated dose contours. All of the above mentioned data is presented in the form of curves. In addition 10 second dose versus distance curves for the surface and underground bursts are presented on a single graph for ready comparison.
Gamma-ray intensity vs. time data in the range from a few milliseconds to about 20 sec were obtained on tests C and E of Operation Buster and the underground test (Shot F) of Operation Jangle. The equipment consisted of a detector consisting of a solution of terphenyl in toluene surrounding a coaxial phototube, the output of which was fed into a 5.5-decade pseudo-log circuit which in turn was direct-coupled to the plates of a 3-in. battery-operated scope tube. The face of the scope was photographed with a 16-mm strip-film camera. The data seem to indicate that the source of the gamma radiation for these times is due to neutron capture in the nitrogen of the air, followed in about 0.2 sec by gamma rays from the decay of fission fragments, the latter modified by shock hydrodynamics and rise of the fireball.
Richard K. Laurino and I. G. Poppoff, Contamination Patterns at Operation JANGLE, ADA078578 (PDF of document downloadable from the DTIC page is linked here):
The distributions of contamination resulting from bursts at Operation JANGLE have previously been represented on maps as iso-intensity contours. This report uses the data and maps of three projects, and combines this information. The result is two modified iso-intensity maps-one for the surface burst at Operation JANGLE, and one for the underground burst. These modified iso-intensity patterns are believed to be more useful than the maps which were previously made because a wider range of intensities is presented.There are also some declassified British documents on nuclear weapons at the U.K. National Archives. For example ES 1/495 gives high quality Trinity nuclear test photos sent to AWRE at Aldermaston by Los Alamos, which are not always easy to obtain elsewhere, and there is an interesting declassified Top Secret paper called The Rationale for the United Kingdom Strategic Nuclear Deterrent Force, DEFE 5/192:
|The Rationale for the United Kingdom Strategic Nuclear Deterrent Force, DEFE 5/192|
|The Rationale for the United Kingdom Strategic Nuclear Deterrent Force, DEFE 5/192|
The British declassified report has deleted sections justified by the comment: "Retained under section 3(4)", which is the British equivalent to the use of sub-section (b)(3) of the title 5 of the U.S. Code, Section 552, which defines matters exempt from disclosure, presumably because of the continuing secrecy concerning what target damage to enemies is judged to be adequate deterrence. How that secrecy of the details of the deterrent threat is supposed to be compatible with a credible deterrent to a potential adversary is not explained, but judging by President Putin's invasion of Ukraine last year despite the Budapest Memorandum guaranteeing Ukraine's security by the UK and USA, it is clear that it's not a very strong deterrent. If the basis of the UK's deterrence is causing destruction to soft civilian targets, rather than debunking hard targets under the Kremlin or at least military bases, tank depots, etc., then it's not adequate and we need to get tactical nuclear deterrence against military targets.
The best deterrent, judging from the opposition to it generated by the USSR during the Cold War, is the neutron bomb. If you deter massed invasions and troop or tank concentrations by the neutron bomb, then you force the enemy to disperse and that in itself prevents Blitzkrieg. It completely destroys the credibility of their plans for invasions, thus making the world safer.
According to Figures 6.41a and 3.94a in Glasstone's 1957 Effects of Nuclear Weapons, it takes a peak overpressure of 70 psi to demolish (i.e. "severe" or "type A" damage) a British WWII type reinforced concrete surface shelter, regardless of bomb yield. According to Figures 6.41b and 3.94a in the same book, it takes a peak overpressure of 50 psi for 1 kiloton (terrorist or neutron bomb) yield or 15 psi for 1 megaton yield to collapse a typical modern city "multistory reinforced concrete frame building with light walls" (emphasis added). These figures are justified by the survival of multistory concrete buildings with typical large window areas, near ground zero in Hiroshima and Nagasaki.
But when you look at chapter 11, Damage to Structures, in the declassified 1972 Secret American effects manual EM1, Capabilities of Nuclear Weapons (which is the basis for the 1977 edition of Glasstone and Dolan's Effects of Nuclear Weapons), severe damage to reinforced concrete building (building type 11-3) is predicted at only 17 psi peak overpressure for 1 kt, and 11 psi for 1 megaton (above 1 megaton, peak overpressures are independent of the yield: a wall isn't pushed over regardless of the impulse or how long you push for, if the peak overpressure is too low to cause it to crack). It turns out that the difference is due to the fact that the 1972 EM1 book absurdly assumes "small window area", which is defined as 5% window area, which maximises the loading on the building. In reality, modern city concrete buildings tend to have much larger areas of glass which breaks easily, reducing the blast loading.
In the earlier 1962 edition of the Capabilities of Nuclear Weapons (then designated TM 23-200, and just renamed from Capabilities of Atomic Weapons), reinforced concrete buildings are severely damaged at a peak overpressure of 24.5 psi for 10 kt and 14 psi for 1 Mt. The November 1957 edition of Capabilities of Atomic Weapons, Figure 7-20 shows that simple US Army field command posts with 4 feet of earth cover require a peak overpressure of 80 psi for fail, for surface bursts; Figure 7-22 shows that simple unrevetted open foxholes and trenches (similar to the standard protection against shelling in the American Civil War, in WWII and in England during the 1938 Munich crisis) in the dry soil of Nevada resists 20 psi.
The shameful thing is that the application of such effective, simple, cheap field-tested countermeasure effectiveness data remained secret for so long, and remains obscured from discussions of nuclear weapons. Modern concrete city buildings and simple trenches for rural areas offer immense, low cost protection.