Dr Norman Ramsey was the man tasked with designing the atomic bomb casings and in finding a suitable aircraft for testing and actual delivery. It is very clear from the historical record that Ramsey favoured the Lancaster, and that his research led him to conclude that only two Allied bombers were suitable to carry the proposed weapons, the B-29 and the Lancaster. Ramsey conferred with Roy Chadwick, the designer of the Lancaster and showed him drawings of the proposed bomb casings including FAT MAN, the implosion bomb, and was assured by Chadwick that the Lancaster could accommodate either bomb design:
"The person at Los Alamos with who, Wilson primarily worked was Norman F. Ramsey.
Ramsey, son of an army officer, received a Ph.D. in physics from Columbia in 1939, and
was drafted to work at the MTT Radiation Lab the following year."" After some time in
Cambridge he came to Washington to work in Stimson's office on Army Alr Forces
projects for Edward Lindley Bowles, a consultant to the secretary. Ramsey's combination of
expertise in physics and aerodynamics made him a prime candidate for Los Alamos. After
an effective recruitment appeal by Oppenheimer in March 1943, Ramsey agreed to foin the
project. Oppenheimer left t to Groves o get Stimson to agree to release Ramsey. This took
several months, because Bowles refused to let him go. Bowles and Groves were both used to
getting their way, and who would get Ramsey turned into a matter of prestige and power.
To men in powerful positions losing a bureaucratic battle, even a small one, could mean
Losing others in the future, and that must not be allowed to happen. Rather than push it to
the hilt, Bowles found a way out by asking Ramsey what he wanted to do. Ramsey said he
thought he should go to Los Alamos. To allow Bowles to save face Ramsey continued as a
consultant from the secretary of war's offce and was not an employee of the University of
California, Los Alamos's contractor.
Ramsey was assigned to head the Delivery Group of the Ordnance Division and later
served as deputy to Pasion." His immediate tasks were to design the bomb casings that
would carry the gun-assembly bomb and implosion bomb. By the end of 1943 it had
already been established that the gun-type bomb-Thin Man-would weigh on the order
of five tons. Ramsey assumed that the implosion bomb would weigh approximately the
same. Given their size and weight, there were only two possible choices for an aircraft to
deliver the weapons, the British Lancaster or the American B-29, which had begun
production in September.
Ramsey favored the Lancaster and traveled to Canada in early October 1943 to meet Roy
Chadwick, the plane's chief designer, Chadwick was in Canada to observe the initial
Lancasters coming off the production line at the Victory Aircraft Works, Milton Airdrome,
in Toronto. Ramsey showed Chadwick preliminary sketches of the large-thin-shaped and
stubby shaped-bombs and later wrote with more details.(12) Chadwick assured Ramsey that
the Lencaster could accommodate them.
When Ramsey returned, he wrote to Parsons suggesting that the Lancaster be seriously
considered and planned a memo to General Groves recommending that a modified
Lancaster be used.(13)The bomb bay was thirty-three feet long and sixty-one inches wide.
The depth was only thirty-eight inches, but this could be modified. The Lancaster's ceiling
was 27,000 feet, its speed 285 miles per hour, and takeoff required only 3,750 feet of runway
-a critical matter wherever it would be based.
Groves had not been Informed about Ramsey's preference and was at a loss for words
when he found out. It was beyond comprehension that Ramsey could consider using a
British plane to deliver an American atomic bomb. Needless to say, Groves found an ally in
General Arnold when he discussed. this matter with him. The new Boeing B29
Superfortress would carry the atomic bomb.
The first production B-29s were produced at the Boeing-Wichita plant beginning in
September 1943. One was chosen to be modified; by December 1 it was at Wright Feld for
two months of modifications. The modifications were originally called Silver Plated. but
this was soon shortened to Siverplate. On the same day General Arnold's office informed
the commanding general, Material Command, that Siverplate modifications should be
given "the greatest possible priority." The two bomb bays were made into one, and the four
twelve-foot bomb bay doors were replaced by two. twenty-seven-foot pneumatically
operated doors. At this point the length of the Thin Man bomb was expected to be at least
seventeen feet. Racks, bracing, and hoists were installed, long with the release mechanism
and mounts for a motion picture camera to record training drops.
On February 20, 1944, the first hand-modified Silverplate B-29 flew from Wright Fld to
Muros Army Air Base (now Edwards AFB) in the Mojave Desert of California. Drop tests
of the Thin Man and Fat Man dummy bombs began on March ."" Many problems were
encountered and corrected, The ballistics for the Thin Man had been partially worked out
at Dahlgren, where scale-model tests were conducted. The bulbous Fat Man shape was
another matter it proved more difficult over the next year to find the correct tall structure
design to prevent it from wobbling. As the analysts sought their solution, they made
another discovery The standard tailfins used on air force aerial bombs seemed to have a
flaw, which caused some of the fins to collapse as the bomb reached terminal velocity. This
had an obvious effect on accuracy and would have been of great interest to the Ordnance
Department. But when this information was passed on to Groves he suppressed it, not
wanting to compromise security It took another year for the Ordnance Department to find
out.
As the tests continued, further modifications and refinements were made to the aircraft
to arrive at a final standard. These mainly had to do with the bomb bay and the various
frames, hoists, braces, and release assemblies that could handle the four-and five-ton
bombs. One major change was to adopt a single lug to suspend the heavy bomb rather than
twin release lugs, which had caused problems. Once premature release of a seventy-three
hundred-pound Thin Man caused severe damage to the bomb bay doors of the single B-29
in March. After repairs were made, testing resumed in mid-June.
By the summer of 1944 the design was fairly firm, and on August 23 the Glenn L. Martin
-Nebraska Company received the contract to modify the first three B-29s of a total of
twenty-four-and selected its Fort Crook Modification Center in Omaha as the program
site. The delivery schedule was three planes by the end of September, the next eleven by
the end of the year, and the final en in January 1945, The initial fourteen were slated for
test and training, with the other ten assigned as the combat unit. As with most parts of the
Manhattan Project, schedules were accelerated and quantities increased. In February the
number of Silverplate B-29s was increased to forty-eight, and on April 18 to fifty-three-
fifty-four counting the hand-modified Muroc plane. As Los Alamos continued to change
and refine its design for the bombs, new instructions were repeatedly sent to modify the
bombers. By the end of the war forty-six planes had been completed.
(12). Norman F, Ramsey Jr. to Roy Chadwick, October 23, 1943, Folder Dr. Norman Ramsey, Box 6,
Tolman Files, RG 227/81, NARA.
(13). Memo, N. F, Ramsey to Capt. W. . Parsons, October 14, 1943, Lancaster Aircraft, Folder Dr Norman Ramsey... NARA
" (Norris, pages 316-317 Racing for the Bomb)