Critical Assembly: A Technical History of Los Alamos during the Oppenheimer Years, 1943–1945

Hoddeson, Henriksen, Meade & WestfalCritical Assembly, ISBN 0-521-54117-4Cambridge University Press, 2004 The title of the book has double meaning. It denotes the critical assembly of uranium 235, or plutonium 239 to start the chain reaction in an atomic bomb. But it also points to the »critical« assembly of numerous scientists, engineers, technicians and US Army personnel. The authors described how in a race with time all these experts were pursuing a single objective: to make an atomic bomb before the Nazi scientists could (supposedly) do it. Each of them was working in his or her special field, but only a handful of the privileged ones knew they were making an atomic bomb. The resolute, competent and mercilessly hard driving conductor of this huge orchestra was General Leslie R. Groves; its concertmaster was the physicist J. Robert Oppenheimer. To carry on this parable, the musicians - with rare exceptions - were obliged to play their scores with plugged ears. The conductor allowed them to know only their own score, because the whole composition named MED (Manhattan Engineering District) must not become known before the end of the war. Though the fission was discovered in Germany (in the winter 1938/39) many Jewish scientists, being suppressed under Nazi-fascist reign, had left Europe as soon as they could. Among them A. Einstein, H. Bethe, R. Peierls, C. Fuchs (unfortunately also a soviet spy), N. Bohr, E. Teller, E. Wiegner, L. Szilard, E. Fermi and J. von Neumann, to name just the most important ones, arrived in the USA, where they contributed essentially to MED. When Groves began leading the project, it started advancing like an avalanche. What in 1939 was deemed to be a science fiction has become a real bomb within just six years. To quench the thirst for information after the first bomb was dropped on Hiroshima in August 6, 1945, Henry de Wolf Smyth of MED had prepared the book "Atomic Energy for Military Purposes". In it the most basic knowledge of how an atomic bomb works, as well as the enormous effort of MED to make it, was made public. But in its preface Groves attached a latch, telling us this is all, which can be released at the time; take it, do not ask any further questions - or else! Though many books published after this date had disclosed this or that, the book "Critical Assembly" has definitely broken that latch by disclosing many minute details, which were classified almost up to present time. In the book we learned how the scientists and other personnel, forced to work under the circumstances as outlined above, starting with micrograms of highly enriched uranium 235 and (up to then non existent) plutonium, have gradually extended the production up to kilogram quantities, determined the critical masses, avoided the nuclear explosion, and had managed to build two combat-ready weapons, which ended the war. The details will certainly be interesting for physicists as well as for engineers of chemistry, electronics, metallurgy, mechanics, ordnance and some others. For the layman the minute descriptions would be mostly too difficult to understand and the same might be valid even for professionals, if the matter lies too far outside of their specialty. But as a whole, the book is a great work of reference, with an enormous collection of interesting data, not known so far. On top of all this the book has 74 pages of references. Unfortunately, the Department of Energy was too thorough when removing many "sensitive data" from the original text. Initially numerous details became gradually scarce when the discussion advanced toward August 1945. However, some common sense and simple calculations, based on the data published in many other books, magazines and films, converge to the following conclusions: Approximately 10 lbs (4.53 kg) of plutonium was used in the Fat Man and 70 lbs (31.75 kg) of 88 % enriched uranium 235 in the Little Boy bomb. In the uranium bomb the active material of about 3 critical masses was divided into 4 projectiles and one equilateral cylindrical target, with holes to fit the projectiles, placed inside the massive tungsten steel tamper. When three critical masses are assembled, the chain reaction starts spontaneously within about 0.1 s; so an initiator (with dangerously radioactive polonium 210) is basically not needed. Why was such data not mentioned in the book, which is full of less important details? Today nobody would waste so much precious, highly enriched uranium by not resorting to implosion, which needs less than one critical mass. On the other hand, the metallurgy of plutonium is a science in itself and so is the implosion. So why be so scared?Peter Staric, PhD, BSEELjubljana, Slovenia

This is a remarkable book, truly a labor of love, which details the work at Los Alamos during the A bomb development.It is a great gift for the A bomb aficionado, the kind of reader that is likely to have a copy of 'Atom Bombs' by John Coster-Mullen in his/her library.It reconstructs the flow of discoveries and decisions that resulted in the two very different bomb designs realized at the lab.There has not been a more detailed, more comprehensively referenced study produced outside of possibly classified internal histories.The true value of this book however will be to the management student.The lab was able to juggle its limited resources spectacularly effectively, ruthlessly cutting off lines of development that had been bypassed or that could not meet required deadlines, while feeding less obvious but promising approaches such as implosion that eventually became critical to the success of the mission. This example of a combination of effective goal setting and informed scientific leadership remains a model for managing large scale efforts with many unknowns.Critical Assembly fills in the gaps and lays out the story, without neglecting the impact of the different personalities that were all drawn together to make it happen.There is plenty of material here for construction of a really useful management training tool, which would be another worthwhile contribution from the Los Alamos effort.

Textbook printing is the only thing that lets this excellent book down. Dry, but if you are after the science, then this hits the mark.If you are looking for a story with less math and physics then try what is in many peoples opinion the best book ever written on the subject, the pulitzer prize winning 'Making of the Atomic Bomb' by Richard Rhodes. I read it first. One of my top ten all time on any subject.

An excellent account of the great efforts made at Los Alamos to develop the atomic bomb. This book was written by people who had full access to the still secret documents stored at the lab. It is a detailed history of the many avenues and blind alleys they explored to reach their goal.

The author has written a very detailed account of the making of the atomic bomb. It has some gems of insight into the chemistry, physics, and engineering that was done to achieve this war time goal of a workable weapon. Unfortunately it doesn't flow well. The book is written in chronological order, but jumps around from one problem to another so you can't be sure where you are in time. Manufacturing of Putonium is interspersed with separation of Uranium and and the design of the explosive lenses. A great deal of effort is spent on naming all the scientists on each project, but unless you are an historian, most of the names are meaningless. Claus Fuchs and Ted Hall are named, but their significance to the spying for the Russians is hardly mentioned. There are some fascinating details in the book, but if a good editor worked on it, the length could be cut in half, and the story would read much better. I found myself skimming paragraphs to speed up the book and locating the really interesting parts.

I recommend it for those who have a minimum of science backround