
Silverplate was the code reference for the
United States Army Air Forces
The United States Army Air Forces (USAAF or AAF) was the major land-based aerial warfare service component of the United States Army and ''de facto'' aerial warfare service branch of the United States during and immediately after World War II ...
' participation in the
Manhattan Project
The Manhattan Project was a research and development program undertaken during World War II to produce the first nuclear weapons. It was led by the United States in collaboration with the United Kingdom and Canada.
From 1942 to 1946, the ...
during
World War II
World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
. Originally the name for the aircraft modification project which enabled a
B-29 Superfortress
The Boeing B-29 Superfortress is a retired American four-engined Propeller (aeronautics), propeller-driven heavy bomber, designed by Boeing and flown primarily by the United States during World War II and the Korean War. Named in allusion to ...
bomber
A bomber is a military combat aircraft that utilizes
air-to-ground weaponry to drop bombs, launch aerial torpedo, torpedoes, or deploy air-launched cruise missiles.
There are two major classifications of bomber: strategic and tactical. Strateg ...
to drop an
atomic weapon
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission or atomic bomb) or a combination of fission and fusion reactions (thermonuclear weapon), producing a nuclear expl ...
, "Silverplate" eventually came to identify the training and operational aspects of the program as well. The original directive for the project had as its subject line "Silver Plated Project," but continued usage of the term shortened it to "Silverplate".
Testing began with scale models at the
Naval Proving Ground in
Dahlgren, Virginia, in August 1943. Modifications began on a prototype Silverplate B-29 known as the "Pullman" in November 1943, and it was used for bomb flight testing at
Muroc Army Air Field in
California
California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...
commencing in March 1944. The testing resulted in further modifications to both the bombs and the aircraft.
Seventeen production Silverplate aircraft were ordered in August 1944 to allow the
509th Composite Group to train with the type of aircraft they would fly in combat, and for the
216th Army Air Forces Base Unit to test bomb configurations. These were followed by 28 more aircraft that were ordered in February 1945 for operational use by the 509th Composite Group. This batch included the aircraft which were used in the
atomic bombings of Hiroshima and Nagasaki
On 6 and 9 August 1945, the United States detonated two atomic bombs over the Japanese cities of Hiroshima and Nagasaki, respectively, during World War II. The aerial bombings killed between 150,000 and 246,000 people, most of whom were civili ...
in August 1945. Including the Pullman B-29, 46 Silverplate B-29s were produced during and after World War II. An additional 19 Silverplate B-29s were ordered in July 1945, which were delivered between the end of the war and the end of 1947. Thus, 65 Silverplate B-29s were made. The use of the Silverplate codename was discontinued after the war, but modifications continued under a new codename, Saddletree. Another 80 aircraft were modified under this program. The last group of B-29s was modified in 1953 but never saw further service.
Origin
The Silverplate project was initiated in June 1943 when
Norman Ramsey Jr. from the
Los Alamos Laboratory
The Los Alamos Laboratory, also known as Project Y, was a secret scientific laboratory established by the Manhattan Project and overseen by the University of California during World War II. It was operated in partnership with the United State ...
's E-7 Group identified the
Boeing B-29 Superfortress
The Boeing B-29 Superfortress is a retired American four-engined propeller-driven heavy bomber, designed by Boeing and flown primarily by the United States during World War II and the Korean War. Named in allusion to its predecessor, the Bo ...
as the only airplane in the United States inventory capable of carrying either type of the proposed weapons shapes: the tubular shape of the
Thin Man, or the oval shape of the
Fat Man
"Fat Man" (also known as Mark III) was the design of the nuclear weapon the United States used for seven of the first eight nuclear weapons ever detonated in history. It is also the most powerful design to ever be used in warfare.
A Fat Man ...
.
Prior to the decision to use the B-29, serious consideration was given to using the British
Avro Lancaster
The Avro Lancaster, commonly known as the Lancaster Bomber, is a British World War II, Second World War heavy bomber. It was designed and manufactured by Avro as a contemporary of the Handley Page Halifax, both bombers having been developed to ...
with its cavernous
bomb bay
The bomb bay or weapons bay on some military aircraft is a compartment to carry bombs, usually in the aircraft's fuselage, with "bomb bay doors" which open at the bottom. The bomb bay doors are opened and the bombs are dropped when over the ...
to deliver the weapon. It would have required much less modification but would have necessitated additional training for the
United States Army Air Forces
The United States Army Air Forces (USAAF or AAF) was the major land-based aerial warfare service component of the United States Army and ''de facto'' aerial warfare service branch of the United States during and immediately after World War II ...
(USAAF) crews.
Major General Leslie R. Groves Jr., the director of the
Manhattan Project
The Manhattan Project was a research and development program undertaken during World War II to produce the first nuclear weapons. It was led by the United States in collaboration with the United Kingdom and Canada.
From 1942 to 1946, the ...
, and
General
A general officer is an Officer (armed forces), officer of high rank in the army, armies, and in some nations' air force, air and space forces, marines or naval infantry.
In some usages, the term "general officer" refers to a rank above colone ...
Henry H. Arnold, the chief of USAAF, wished to use an American plane if this was at all possible. The superior range and high-altitude performance of the B-29 made it a much better choice, and after the B-29 began to be modified in November 1943 for carrying the atomic bomb, the suggestion for using the Lancaster never came up again.
The first B-29 was delivered to the USAAF on 1 July 1943, and Groves met with Arnold later that month. Groves briefed Arnold on the Manhattan Project and asked for his help in testing the
ballistics
Ballistics is the field of mechanics concerned with the launching, flight behaviour and impact effects of projectiles, especially weapon munitions such as bullets, unguided bombs, rockets and the like; the science or art of designing and acceler ...
of the project's proposed bomb shapes. Arnold and the head of the Ordnance Division at Los Alamos,
Captain
Captain is a title, an appellative for the commanding officer of a military unit; the supreme leader or highest rank officer of a navy ship, merchant ship, aeroplane, spacecraft, or other vessel; or the commander of a port, fire or police depa ...
William S. Parsons, arranged for tests to be carried out at the
Naval Proving Ground in
Dahlgren, Virginia, in August 1943. No aircraft was available that could carry the long Thin Man, so a scale model was used. The results were disappointing – the bomb fell in a
flat spin – but the need for a thorough test program was demonstrated.
Groves met with Arnold again in September 1943. He informed Arnold that there was now a second bomb shape under consideration, the Fat Man, and he formally requested that further tests be carried out, that not more than three B-29s be modified to carry the weapons, and that the USAAF form and train a special unit to deliver the bombs. Arnold delegated responsibility for this to Major General
Oliver P. Echols. In turn, Echols designated
Colonel
Colonel ( ; abbreviated as Col., Col, or COL) is a senior military Officer (armed forces), officer rank used in many countries. It is also used in some police forces and paramilitary organizations.
In the 17th, 18th, and 19th centuries, a colon ...
Roscoe C. Wilson as the project officer.
Codename
Originally the name for the aircraft modification project for the B-29 to enable it to drop a
nuclear weapon
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission or atomic bomb) or a combination of fission and fusion reactions (thermonuclear weapon), producing a nuclear exp ...
, Silverplate eventually came to identify the training and operational aspects of the program as well. The airplane modification project fell under the purview of the Manhattan Project's
Project Alberta after March 1945. The original codename for the project was "Silver Plated," but continued usage of the term shortened it to the one word "Silverplate". For security reasons, the codename "Silverplate" was not officially registered. Confusion then resulted when the
War Department allocated "Silverplate" to another project. Arnold's office had to order the other agency to discontinue its use of the codename.
Los Alamos' Thin Man and Fat Man code names were adopted by the USAAF for the weapons. A cover story was devised that Silverplate was about modifying a
Pullman car for use by President
Franklin Roosevelt
Franklin Delano Roosevelt (January 30, 1882April 12, 1945), also known as FDR, was the 32nd president of the United States, serving from 1933 until his death in 1945. He is the longest-serving U.S. president, and the only one to have served ...
(Thin Man) and United Kingdom Prime Minister
Winston Churchill
Sir Winston Leonard Spencer Churchill (30 November 1874 – 24 January 1965) was a British statesman, military officer, and writer who was Prime Minister of the United Kingdom from 1940 to 1945 (Winston Churchill in the Second World War, ...
(Fat Man) on a secret tour of the United States.
Initial experiments

The USAAF sent instructions to its
Army Air Forces Materiel Command at
Wright Field,
Ohio
Ohio ( ) is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Lake Erie to the north, Pennsylvania to the east, West Virginia to the southeast, Kentucky to the southwest, Indiana to the ...
, on 30 November 1943 for a highly classified B-29 modification project. The Manhattan Project would deliver full-sized mockups of the weapons shapes to Wright Field by mid-December, where Army Air Forces Materiel Command would modify an aircraft and deliver it for use in bomb flight testing at
Muroc Army Air Field in
California
California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...
. B-29-5-BW 42-6259 (referred to as the "Pullman airplane" from an internal code name assigned it by the Engineering Division of Army Air Forces Materiel Command) was delivered to the
468th Bombardment Group
The 468th Bombardment Group was a World War II United States Army Air Forces combat organization. The unit served primarily in the Pacific Ocean theater of World War II, Pacific Ocean theater and China Burma India Theater of World War II as p ...
at
Smoky Hill Army Airfield in
Kansas
Kansas ( ) is a landlocked U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Nebraska to the north; Missouri to the east; Oklahoma to the south; and Colorado to the west. Kansas is named a ...
on 30 November 1943 and was flown to Wright Field on 2 December.
Modifications to the bomb bays of 42-6259 were extensive and time-consuming. Its four bomb bay doors and the
fuselage
The fuselage (; from the French language, French ''fuselé'' "spindle-shaped") is an aircraft's main body section. It holds Aircrew, crew, passengers, or cargo. In single-engine aircraft, it will usually contain an Aircraft engine, engine as wel ...
section between the bays were removed and a single bomb bay configured. The length of the initial
gun-type bomb shape was approximately , necessitating that it be carried in the aft bomb bay, with some of its length protruding into the forward bay. The implosion-type bomb was mounted in the forward bay. New bomb suspensions and bracing were attached for both shape types, and separate twin-release mechanisms were mounted in each bay, using modified glider tow-cable attach-and-release mechanisms.
Testing of bomb shapes
The Pullman B-29 flew into Muroc on 20 February 1944, and testing began on 28 February. Twenty-four drops were carried out before tests were discontinued so that improvements could be made to Thin Man. The bombs failed to release immediately, frustrating
calibration
In measurement technology and metrology, calibration is the comparison of measurement values delivered by a device under test with those of a calibration standard of known accuracy. Such a standard could be another measurement device of known ...
tests. In what turned out to be the last test flight of the series on 16 March, a Thin Man was prematurely released while the B-29 was still en route to the test range and fell onto the bomb bay doors, severely damaging the aircraft. The modified glider mechanisms had apparently caused all four malfunctions, because of the weight of the bombs, and were replaced with British Type G single-point attachments and Type F releases used on the
Lancaster B.I Special to carry the
Tallboy bomb.

After repair of the Pullman B-29 at Wright Field, testing resumed with three Thin Man and nine Fat Man shapes dropped in the last two weeks of June 1944. High-speed photographs revealed that the tail fins folded under pressure, resulting in an erratic descent. Various combinations of stabilizer boxes and fins were tested on the Fat Man shape to eliminate its persistent wobble until an arrangement dubbed a "California Parachute"—a cubical tail box with eight fins within the sheetmetal box "frame", 45° apart from each other (four "
orthogonal
In mathematics, orthogonality (mathematics), orthogonality is the generalization of the geometric notion of ''perpendicularity''. Although many authors use the two terms ''perpendicular'' and ''orthogonal'' interchangeably, the term ''perpendic ...
" fins, and four more, one at each 45° angle to each corner)—was approved.
The Thin Man gun-type design was at that time based on the
fissibility of the very pure
plutonium-239
Plutonium-239 ( or Pu-239) is an isotope of plutonium. Plutonium-239 is the primary fissile isotope used for the production of nuclear weapons, although uranium-235 is also used for that purpose. Plutonium-239 is also one of the three main iso ...
isotope so far only produced in microgram quantities by the
cyclotron
A cyclotron is a type of particle accelerator invented by Ernest Lawrence in 1929–1930 at the University of California, Berkeley, and patented in 1932. Lawrence, Ernest O. ''Method and apparatus for the acceleration of ions'', filed: Januar ...
at
University of California, Berkeley
The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California), is a Public university, public Land-grant university, land-grant research university in Berkeley, California, United States. Founded in 1868 and named after t ...
. When the
Hanford Site
The Hanford Site is a decommissioned nuclear production complex operated by the United States federal government on the Columbia River in Benton County in the U.S. state of Washington. It has also been known as SiteW and the Hanford Nuclear R ...
production reactors came on-line in early 1944, the mix of plutonium-239 and
plutonium-240
Plutonium-240 ( or Pu-240) is an isotope of plutonium formed when plutonium-239 captures a neutron. The detection of its spontaneous fission led to its discovery in 1944 at Los Alamos and had important consequences for the Manhattan Project.
...
obtained was found to have a high rate of spontaneous fission. To avoid pre-detonation, the
muzzle velocity
Muzzle velocity is the speed of a projectile (bullet, pellet, slug, ball/ shots or shell) with respect to the muzzle at the moment it leaves the end of a gun's barrel (i.e. the muzzle). Firearm muzzle velocities range from approximately t ...
of the gun-type design needed to be greatly raised, making it impractically long.
Thin Man as a plutonium-based design was therefore abandoned, and the weapon was re-designed to use
uranium-235
Uranium-235 ( or U-235) is an isotope of uranium making up about 0.72% of natural uranium. Unlike the predominant isotope uranium-238, it is fissile, i.e., it can sustain a nuclear chain reaction. It is the only fissile isotope that exists in nat ...
. The muzzle velocity required was much lower, reducing the barrel length of the resulting bomb, code-named
Little Boy
Little Boy was a type of atomic bomb created by the Manhattan Project during World War II. The name is also often used to describe the specific bomb (L-11) used in the bombing of the Japanese city of Hiroshima by the Boeing B-29 Superfortress ...
, to less than . This allowed the device to fit into a standard B-29 bomb bay, so the Pullman was modified to its original configuration with the rear bomb bay of a standard B-29 design. All subsequent Silverplates were also configured in this manner. The Pullman B-29 was flown to
Wendover Army Air Field in
Utah
Utah is a landlocked state in the Mountain states, Mountain West subregion of the Western United States. It is one of the Four Corners states, sharing a border with Arizona, Colorado, and New Mexico. It also borders Wyoming to the northea ...
in September 1944. It carried out further drop testing with the
216th Army Air Forces Base Unit until it was damaged in a landing accident in December.
Wartime production versions
On 22 August 1944, to meet the requirements of the USAAF group about to be formed to train in the atomic mission, a production phase of Silverplate B-29s was ordered from the
Glenn L. Martin Company
The Glenn L. Martin Company, also known as The Martin Company from 1917 to 1961, was an American aircraft and aerospace industry, aerospace manufacturing company founded by aviation pioneer Glenn L. Martin. The Martin Company produced many impo ...
's
modification center at
Offutt Field, south of
Omaha, Nebraska
Omaha ( ) is the List of cities in Nebraska, most populous city in the U.S. state of Nebraska. It is located in the Midwestern United States along the Missouri River, about north of the mouth of the Platte River. The nation's List of United S ...
, under the designation Project 98146-S. The first three of these second increment Silverplate B-29s were delivered to the USAAF in mid-October and flown to Wendover. They were fitted with British single-point bomb releases mounted on a re-designed H-frame suspension rack fitted in the forward bomb bay, so that additional fuel tanks could be carried in the aft bay. A new crew position, called the "weaponeer station", was created in the
cockpit with a panel to monitor the release and detonation of the bomb during the actual combat drops. Fourteen production aircraft were assigned to the
393d Bombardment Squadron for training, and three to the 216th Army Air Force Base Unit for bomb drop testing.
By February 1945 the 17 aircraft of the second increment were in need of upgrades, particularly those of the 216th Army Air Force Base Unit. Four of the planes assigned to the 393d Bombardment Squadron (now part of the
509th Composite Group) were transferred to the 216th to meet an increase in its testing tempo. Rather than attempt to modify the existing aircraft a few at a time, a decision was made to start a new production series. The first five of this third increment, known as Project 98228-S, also went to the test unit. The order totaled an additional 28 aircraft, with delivery of 15 designated combat models for the 393d beginning in April. The final eight were not delivered until after the
two atomic bomb missions in August. Two were given to the 216th while the remaining six were assigned to the 509th at Wendover as replacements for any bombers lost while operating from
Tinian Naval Base. Ironically, no bombers were lost during operations from Tinian, but five of these six were lost in crashes over the next few years.
The final wartime Silverplates incorporated all technical improvements to B-29 aircraft, as well as the final series of Silverplate modifications that included Curtiss Electric
reversible-pitch propeller
A propeller (often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon a working flu ...
s and pneumatic actuators for rapid opening and closing of bomb bay doors. The British F-type bomb release and G-type attachment were installed, along with dual electrical and mechanical bomb release mechanisms. Early model B-29s were plagued by a host of engine problems, and the early Silverplate bombers were no exception. One was written off after being badly damaged as a result of an engine fire in February 1945. The
fuel-injected
Fuel injection is the introduction of fuel in an internal combustion engine, most commonly automotive engines, by the means of a fuel injector. This article focuses on fuel injection in Reciprocating engine, reciprocating piston and Wankel eng ...
Wright R-3350-41 engines in the later model bombers delivered in July and August 1945 were greatly improved and far more reliable. This was an important factor in the success of the 509th Composite Group's operations.
The Fat Man and
Pumpkin bombs (high-explosive filled bombs that resembled and handled like a Fat Man) weighed over , so weight was a concern, even with the more powerful engines. Weight reduction was accomplished by removal of all
gun turret
A gun turret (or simply turret) is a mounting platform from which weapons can be fired that affords protection, visibility and ability to turn and aim. A modern gun turret is generally a rotatable weapon mount that houses the crew or mechanis ...
s and
armor plating. This work was done by the 509th Composite Group for the early Silverplate aircraft, but later models were delivered without them. These B-29s represented a significant increase in performance over the standard variants.
Flying at put the B-29s above the effective range of Japanese
flak. Each Pumpkin bomb mission was conducted by a formation of three aircraft in the hope of convincing the Japanese military that small groups of B-29s did not justify a strong response. This strategy proved successful, and Japanese fighters only occasionally attempted to intercept the 509th Composite Group's aircraft. One B-29 incurred minor battle damage in operations.
Silverplate operational units
Including the Pullman B-29, a total of 46 Silverplate B-29s were produced during World War II. Of these, 29 were assigned to the 509th Composite Group during World War II, with 15 used to carry out the
atomic bombings of Hiroshima and Nagasaki
On 6 and 9 August 1945, the United States detonated two atomic bombs over the Japanese cities of Hiroshima and Nagasaki, respectively, during World War II. The aerial bombings killed between 150,000 and 246,000 people, most of whom were civili ...
. An additional 19 Silverplate B-29s were ordered in July 1945, which were delivered between the end of the war, and the end of 1947. By this time only 13 of the original 46 were still operational. Thus, a total of 65 Silverplate B-29s were made, of which 32 were operational at the start of 1948. Martin-Omaha produced 57 Silverplate B-29s. The other eight were built by Boeing-Wichita. Of these 65 bombers, 31 were eventually converted to other configurations, 16 were placed in storage and later scrapped, and 12 were lost in accidents (including four of the Tinian bombers). The pair of historic weapons delivery aircraft, named ''
Enola Gay
The ''Enola Gay'' () is a Boeing B-29 Superfortress bomber, named after Enola Gay Tibbets, the mother of the pilot, Colonel (United States), Colonel Paul Tibbets. On 6 August 1945, during the final stages of World War II, it became the Atomi ...
'' and ''
Bockscar
''Bockscar'', sometimes called ''Bock's Car'', is the United States Army Air Forces Boeing B-29 Superfortress, B-29 bomber that dropped the Fat Man, Fat Man nuclear weapon over the Japanese city of Nagasaki during World War II in the secondand ...
'', are currently displayed in museums.
The only other
United States Air Force
The United States Air Force (USAF) is the Air force, air service branch of the United States Department of Defense. It is one of the six United States Armed Forces and one of the eight uniformed services of the United States. Tracing its ori ...
combat unit to use the Silverplate B-29 was the
97th Bombardment Wing at
Biggs Air Force Base
Biggs may refer to:
Arts and entertainment
* Biggs (TV channel), a Portuguese television channel formerly for kids, teens and youth and now for teens and youth.
* Biggs Darklighter, a character in ''Star Wars Episode IV: A New Hope''
* Biggs, a re ...
in
El Paso, Texas
El Paso (; ; or ) is a city in and the county seat of El Paso County, Texas, United States. The 2020 United States census, 2020 population of the city from the United States Census Bureau, U.S. Census Bureau was 678,815, making it the List of ...
. In mid-1949 it received 27 of the aircraft from the
509th Bombardment Wing when the latter transitioned to the
B-50D bomber, an upgraded revision of the B-29. The re-equipment of the 97th Bombardment Wing was part of an expansion of the atomic strike force to ten wings during 1949. Within a year all were converted to TB-29 trainers. One other Silverplate B-29, on temporary assignment in the United Kingdom, was converted into a weather reconnaissance aircraft (WB-29) and transferred to the
9th Bombardment Wing at
Travis Air Force Base
Travis Air Force Base is a United States Air Force base under the operational control of Air Mobility Command (AMC), located three miles (5 Kilometre, km) east of the central business district of the city of Fairfield, California, Fairfield, i ...
in California. The last Silverplate B-29 in service as a nuclear weapons carrier was reassigned to another role in November 1951, ending Silverplate after nearly eight years.
Saddletree
Use of the codename Silverplate was discontinued on 12 May 1947 because the codename had become compromised. It was superseded by a new codename, "Saddletree", which was applied to aircraft modifications only. Initially it was intended that Saddletree would refer only to modifications to the B-29s, but it came to be used for modifications to B-50 and
B-36 bombers as well. Saddletree modifications included a new bomb bay frame and hoist and replaced the British FG bomb release with the newly developed U-1 pneumatic bomb release mechanism. Due to delays in the delivery of the B-50s, Saddletree commenced in February 1948. In all, 6,000 hours of work was carried out on each of the 36 B-50s by Sacramento Air Materiel Area.
The
Joint Chiefs of Staff
The Joint Chiefs of Staff (JCS) is the body of the most senior uniformed leaders within the United States Department of Defense, which advises the president of the United States, the secretary of defense, the Homeland Security Council and ...
issued a directive in January 1948 for the modification of 225 B-29, B-50, and B-36 bombers to carry nuclear weapons, along with eight
C-97 Stratofreighter aircraft to carry bomb assembly teams. There were already 32 Silverplate B-29s in service with the
Strategic Air Command
Strategic Air Command (SAC) was a United States Department of Defense Specified Command and a United States Air Force (USAF) Major Command responsible for command and control of the strategic bomber and intercontinental ballistic missile compon ...
, so the Air Materiel Command was directed to carry out Saddletree modifications on a further 80 B-29s, 36 B-50As, 23 B-50Bs and 18 B-36Bs. The B-36A could not carry nuclear weapons without major modifications.
As the anticipated enemy was the
Soviet Union
The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...
, the aircraft also required "winterization" to allow them to operate from
Arctic
The Arctic (; . ) is the polar regions of Earth, polar region of Earth that surrounds the North Pole, lying within the Arctic Circle. The Arctic region, from the IERS Reference Meridian travelling east, consists of parts of northern Norway ( ...
bases. On 16 April 1948, the codeword "Gem" was allocated to all modifications and improvements to provide atomic strike capability. The project included 36 B-29s, and the modification of 36 others to have an
air refueling
Aerial refueling (American English, en-us), or aerial refuelling (British English, en-gb), also referred to as air refueling, in-flight refueling (IFR), air-to-air refueling (AAR), and tanking, is the process of transferring aviation fuel from ...
capability. With the addition of the 80 Saddletree B-29s, a total of 145 B-29s were modified to carry nuclear weapons, and 117 of these were assigned to operational units.
In October 1951, in anticipation of a major build-up of the USAF to 95 groups, and of delays in the
B-47 program, the Air Materiel Command was ordered to modify an additional 180 B-29s then in storage to carry the
Mark 4,
Mark 5,
Mark 6, and
Mark 8 nuclear bombs. Modifications were carried out in Oklahoma City and Sacramento. By the time the aircraft were all delivered in September 1953, the B-29 was being phased out, and the modified aircraft went back into storage without seeing further service.
Costs
In 1945, a B-29 bomber cost $782,000. It cost $32,000 to upgrade an aircraft to Silverplate configuration, so the total cost of a Silverplate bomber was $814,000. The total cost of the 65 wartime Silverplate B-29s was therefore $53 million. Adding $7 million for logistics, this put the estimated cost of the Silverplate project at around $60 million.
See also
*
Enstone Airfield - Location of Royal Air Force 'Black Lancaster' program in England
Notes
References
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{{Manhattan Project
Boeing B-29 Superfortress
History of the Manhattan Project
Military aviation
Nuclear warfare
Atomic bombings of Hiroshima and Nagasaki