50 Fun Facts About Manhattan Project

Which Army general directed the Manhattan Project from 1942 to 1946?

He was promoted to brigadier general before taking over because it was felt the title would carry more weight with the scientists.

Who was the director of the Los Alamos Laboratory that designed the bombs?

Compton recommended him even though he had no Nobel Prize, little administrative experience and communist associates.

The project took its name from what?

Colonel Marshall's temporary HQ was at 270 Broadway, and engineer districts were named for their cities; the earlier codename was 'Development of Substitute Materials'.

What was the code name of the British atomic bomb programme that the Manhattan Project absorbed?

The MAUD Committee's 1941 report had convinced the Americans a bomb was feasible; the Quebec Agreement later formalised cooperation.

Roughly how many people did the Manhattan Project employ at its peak?

In June 1944 that included 84,500 construction workers, 40,500 plant operators and 1,800 military personnel.

Which two physicists drafted the August 1939 letter Einstein signed and sent to Roosevelt?

It warned of 'extremely powerful bombs of a new type' and urged America to stockpile uranium ore.

Which two German chemists discovered nuclear fission in 1938?

Lise Meitner and Otto Frisch supplied the theoretical explanation, and fear of a German bomb drove the American effort.

Which Australian physicist found in 1941 that Lyman Briggs had locked the MAUD report in a safe?

He persuaded Ernest Lawrence at Berkeley, who in turn alerted Conant and Compton, and the American programme accelerated.

Why did Roosevelt hand the atomic project to the service he chose rather than the Navy?

He approved acceleration on 9 October 1941 and set up a Top Policy Group whose meetings he never attended.

On what date did Fermi's team achieve the first self-sustaining nuclear chain reaction?

Compton phoned Conant in code: 'The Italian navigator has just landed in the new world.'

Where was Fermi's first reactor pile built after delays at the planned forest site?

Delays at the planned Argonne 'Site A' forced the move on campus; the pile was dismantled and rebuilt in the forest in 1943.

What term did Fermi coin for the early prototype nuclear reactors built at Columbia?

The Navy had given Columbia $6,000 in 1940, most of it spent by Fermi and Szilard on graphite.

What was the official name of the uranium-enrichment site at Oak Ridge, Tennessee?

About 1,000 families were displaced from 56,000 acres bought by eminent domain for $3.5 million.

In which state was the Hanford Engineer Works, site of the first industrial-scale plutonium reactors?

DuPont wanted the site far from Oak Ridge after worries that Knoxville was too close in case of accident.

What did the name 'calutron', the electromagnetic separation device, derive from?

The process was inelegant and inefficient but proven; it was housed at the Y-12 plant at Oak Ridge.

What did the project borrow from the US Treasury to wind the calutron magnets, because copper was scarce?

The 1,000-troy-ounce bars from West Point were cast into billets and extruded into strips; silver replaced copper at an 11:10 ratio.

How long was the U-shaped K-25 gaseous diffusion building at Oak Ridge?

The four-storey structure held 54 contiguous buildings; production started in February 1945.

What was the code name of the plutonium plant designated S-50 designed to do?

By March 1945 all three enrichment methods, S-50, K-25 and Y-12, were run in series, each feeding the next.

What percentage of natural uranium is the fissile isotope uranium-235?

The rest is uranium-238, so the isotopes had to be physically separated by electromagnetic, gaseous or thermal means.

What occupied the New Mexico mesa Oppenheimer chose as the site of the bomb laboratory?

Oppenheimer owned a ranch near Albuquerque; the lab was known during the war as 'Site Y' or 'the Hill'.

Which institution operated the Los Alamos laboratory under contract to the War Department?

Robert Bacher and Isidor Rabi had balked at the idea of scientists being commissioned into the Army, so a compromise was found.

Who ran the Santa Fe branch office where new Los Alamos arrivals were met and issued passes?

Los Alamos was known as 'Site Y' or 'the Hill' during the war.

Which two bomb designs did Los Alamos produce for use in the war?

Fat Man was a fallback until 1944, when Hanford plutonium proved too rich in plutonium-240 for a gun-type bomb.

Why was the gun-type design abandoned for the Hanford-fuelled bomb in 1944?

That forced the switch to the complex implosion design with explosive lenses, and made a full-scale test necessary.

What was the code name Oppenheimer gave the first nuclear test?

Kenneth Bainbridge chose the Alamogordo Bombing Range, and the device itself was nicknamed 'the gadget'.

On what date and at what time did the first nuclear device explode?

It yielded around 20 kilotons, left a 250-foot crater of trinitite glass and was heard as far away as El Paso.

What cover story did Groves issue to explain the first test blast?

The shock wave was felt over 100 miles away and the mushroom cloud rose 7.5 miles.

What was 'Jumbo' at the Alamogordo site?

Confidence in implosion grew so high it was never used; it was stood on a tower 800 yards away and survived the blast.

From which Hindu scripture did Oppenheimer recall 'Now I am become Death, destroyer of worlds' at the Trinity test?

He cited verses XI,12 and XI,32; the gadget had been winched up a 100-foot tower two days earlier.

What was the code name for the modification of B-29 bombers to carry atomic bombs?

The British Avro Lancaster was the only Allied plane that could carry the bombs unmodified, but a British aircraft was politically awkward.

Which unit, formed in December 1944 at Wendover, Utah, was created to drop the atomic bombs?

It trained at Wendover, Utah, with 'pumpkin bombs' and deployed to North Field on Tinian in July 1945.

Which cruiser carried the uranium bomb's components from San Francisco to Tinian in July 1945?

They left on 16 July 1945 and arrived on 26 July.

What was the estimated yield of the uranium bomb dropped on Hiroshima on 6 August 1945?

Weaponeer William Parsons finished assembling the bomb in flight; it detonated at 1,750 feet and destroyed about 4.7 square miles.

What was Bockscar's primary target on 9 August 1945, before cloud cover sent it to Nagasaki?

After three runs with fuel running low, pilot Charles Sweeney turned to the secondary target, where a last-minute break in the clouds allowed a visual drop.

Which pilot flew the Enola Gay to Hiroshima?

The B-29 belonged to the 393rd Bombardment Squadron and took off from North Field on Tinian.

What did Truman order on 10 August 1945 after learning a third bomb was being prepared?

He told his cabinet 'the thought of wiping out another 100,000 people was too horrible'; Groves stopped the core's shipment on 13 August.

Who was the most successful Soviet spy inside the Manhattan Project?

A member of the British Mission working on the implosion design, he was exposed only in 1950 through the Venona decrypts.

Which mission sent Manhattan Project personnel into Europe to seize German nuclear materials and scientists?

Its teams rounded up Heisenberg, Hahn and others and interned them at Farm Hall in England, where they were secretly bugged.

Where were the captured German nuclear scientists interned and secretly surveilled?

Groves had also ordered the bombing of Oranienburg in March 1945 to keep its uranium plant from the Soviets.

How much had the Manhattan Project spent by 1 October 1945?

That was less than nine days of wartime spending; 84% went on the Oak Ridge and Hanford plants.

Which security principle did Groves call 'the very heart of security'?

'Each man should know everything he needed to know to do his job and nothing else'; the Office of Censorship called it the best-kept secret of the war.

How many potential employees did investigators vet for security risks in 1943 alone?

They also vetted 600 companies; the Army later called the project 'more drastically guarded than any other highly secret war development'.

Which physicist wrote the sanitised public history of the project released after the bombings?

Groves commissioned it in advance; releasing it was controversial.

Which agency took over American nuclear weapons research from the Manhattan Project in January 1947?

In between, the project tested bombs at Bikini Atoll in Operation Crossroads and laid the groundwork for the nuclear navy.

Which contractor built the Hanford plutonium reactors after Groves recruited it in November 1942?

DuPont insisted the site be far from Oak Ridge; production later fell as reactors B, D and F suffered graphite swelling from the Wigner effect.

What name was given to the radioactive green glass formed from desert sand at Trinity?

The blast dug a crater 88 yards wide and completely vaporized the 100-foot steel tower the device sat on.

Which Harvard physicist planned and directed the Trinity test?

After the blast he told Oppenheimer, 'Now we are all sons of bitches'; his biggest fear had been that nothing at all would happen.

Which physicist took bets at Trinity on whether the atmosphere would ignite?

Bethe had calculated that outcome as almost impossible, but the betting frightened the guards, some of whom asked to be relieved.

What was the nickname of the six Los Alamos cottages that were the only homes with bathtubs?

Oppenheimer lived there next door to Deak Parsons; the cottages had once housed the Ranch School's headmaster and faculty.

Which physicist chose the names Fat Man, Thin Man and Little Boy based on the bombs' shapes?

Thin Man borrowed its name from the Dashiell Hammett detective novel and film series; the plutonium gun design was abandoned in 1944.