Silverplate B-29 Straight Flush. Note lack of gun turrets and tail code of 444th BG painted on for security reasons.

Silverplate was the code reference for the United States Army Air Forces participation in the Manhattan Project during World War II. The United States Army Air Forces ( USAAF) was the military aviation arm of the United States of America during and immediately after World War II. The World War II Manhattan Project developed the first Nuclear weapon (atomic bomb World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including Originally the name for the aircraft modification project for the B-29 Superfortress to enable it to drop an atomic weapon, Silverplate eventually came to identify the training and operational aspects of the program as well. A nuclear weapon is an explosive device that derives its destructive force from Nuclear reactions either fission or a combination of fission and fusion. The airplane modification project fell under the purview of Project Alberta after March 1945. Project Alberta was a section of the Manhattan Project which developed the means of delivering the first atomic bombs, used by the United States Army The original directive for the project had as its subject line "Silver Plated Project" but continued usage of the term shortened it to the one word "Silverplate". ^[1]

Between February 1944 and December 1947 a total of 65 B-29s were modified to Silverplate specifications in five increments. Ultimately 53 of them served with the first nuclear weapons unit, the 509th Composite Group. The 509th Composite Group was an air combat unit of the United States Army Air Forces during the Second World War and as the 509th Operations Group, is ^[2]

Initial phase

The project was initiated in October 1943 when Dr. Year 1943 ( MCMXLIII) was a Common year starting on Friday (the link will display full 1943 calendar of the Gregorian calendar. Norman F. Ramsey, a member of the Los Alamos National Laboratory Group E-7, identified the B-29 Superfortress as the only airplane in the U. Norman Foster Ramsey Jr (born August 27, 1915, in Washington DC) is an American Physicist. Los Alamos National Laboratory (LANL (previously known at various times as Site Y, Los Alamos Laboratory, and Los Alamos Scientific Laboratory) is a S. inventory capable of carrying either type of the proposed weapons shapes: the uranium 235 "gun-type fission weapon" shape and the plutonium implosion weapon shape. Uranium (jʊˈreɪniəm is a silvery-gray Metallic Chemical element in the Gun-type fission weapons are fission -based Nuclear weapons whose design assembles their fissile material into a supercritical mass by the Nuclear weapon designs are physical chemical and engineering arrangements that cause the physics package of a nuclear weapon to detonate ^[3] Furthermore, because the attachment box for the main wing spars was located between the bomb bays on the B-29, the gun-type weapon could only be a maximum of two feet in diameter. In an aircraft the spar is the main structural member of the wing running widthways across the span of the wing at right angles (or thereabouts to the Fuselage. The older name of the Indian city of Mumbai, is correctly spelled " Bombay "

USAAF sent instructions to its Army Air Forces Materiel Command at Wright Field, Ohio, on November 30, 1943, for a highly-classified B-29 modification project. Air Force Materiel Command (AFMC is a major command of the United States Air Force. Wright-Patterson Air Force Base is a United States Air Force base located in Greene and Montgomery counties eight miles (13 km) northeast of Ohio ( is a Midwestern state of the United States. As part of the Great Lakes region, Ohio has long been a cultural and geographical crossroads Events 1700 - Battle of Narva — A Swedish army of 8500 men under Charles XII defeats Year 1943 ( MCMXLIII) was a Common year starting on Friday (the link will display full 1943 calendar of the Gregorian calendar. ^[4] The Manhattan Project would deliver full-sized mockups of the weapons shapes to Wright Field by mid-December, where AAFMC would modify an aircraft and deliver it for use in bomb flight testing at Muroc Army Air Field, California. Edwards Air Force Base is a United States Air Force base located on the border of Kern County and Los Angeles County California in the Antelope California ( is a US state on the West Coast of the United States, along the Pacific Ocean. ^[5]

B-29-5-BW 42-6259 (referred to as the "Pullman airplane" from an internal code name assigned it by the Engineering Division of AAF Materiel Command) was delivered to the 468th Bomb Group at Smoky Hill AAB, Kansas on November 30, 1943, and flown to Wright Field, Ohio, on December 2. Kansas ( is a Midwestern state in the central region of the United States of America, an area often referred to as the American " Events 1700 - Battle of Narva — A Swedish army of 8500 men under Charles XII defeats Year 1943 ( MCMXLIII) was a Common year starting on Friday (the link will display full 1943 calendar of the Gregorian calendar. Wright-Patterson Air Force Base is a United States Air Force base located in Greene and Montgomery counties eight miles (13 km) northeast of Ohio ( is a Midwestern state of the United States. As part of the Great Lakes region, Ohio has long been a cultural and geographical crossroads Events 1409 - The University of Leipzig opens 1755 - The second Eddystone Lighthouse is destroyed by fire ^[6] Modifications to the bomb bays were extensive and time-consuming. Its four 12-foot bomb bay doors and the fuselage section between the bays were removed and a single 33-foot bomb bay configured (the length of the gun-type shape was approximately seventeen feet). New bomb suspensions and bracing were attached for both shape types, with the gun-type suspension anchored in the aft bomb bay (although its length protruded into the forward bay) and the implosion type mounted in the forward bay. ^[7] Separate twin-release mechanisms were mounted in each bay, using modified glider tow-cable attach-and-release mechanisms. ^[8] To document the tests, motion picture camera mounts were installed in the rear bay. ^[5]

The modifications were made using the dummy bomb shapes as models, and the gun-type shape (code-named Thin Man) proved to be a very close fit. The "Thin Man" (formally Mark 2) nuclear bomb was a proposed Plutonium gun-type nuclear bomb which the United States was All modifications were made by hand and the process required more than 6000 man-hours of labor^[5] which could not be completed until February. Engine problems systemic to the B-29 delayed delivery of the Pullman B-29 for flight testing until February 20, 1944. Events 1472 - Orkney and Shetland are left by Norway to Scotland, due to a Dowry payment Year 1944 ( MCMXLIV) was a Leap year starting on Saturday (link will display full calendar of the Gregorian calendar.

The first test drop at Muroc on March 6 involved a Thin Man, followed on March 14 by two drops of an implosion device shape (codenamed Fat Man) fitted with a circular tail fin stabilizer designed by engineers at the National Bureau of Standards. Events 1079 - Omar Khayyám completes the Iranian calendar. 1454 - Thirteen Years' War: Delegates of Events 1489 - The Queen of Cyprus, Catherine Cornaro, sells her kingdom to Venice. "Fat Man" is the codename for the Atomic bomb that was detonated over Nagasaki, Japan, by the United States on August 9 The Thin Man performed without major problems but the Fat Man shapes exhibited significant wobble characteristics, apparently due to poor workmanship and misalignment of the tail fins. ^[5]

All three bombs had also failed to release immediately, frustrating calibration tests. Calibration is the process of establishing the relationship between a measuring device and the units of measure A fourth testing flight resulted in the premature release of a Thin Man shape while the B-29 was still enroute to the test range and severely damaged 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. ^[9]

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. Wright-Patterson Air Force Base is a United States Air Force base located in Greene and Montgomery counties eight miles (13 km) northeast of 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",^[5] a cubical tail box with fins angled at 45 degrees to the line of fall, was approved.

The Thin Man gun-type design was based on the fissibility of the very pure Pu-239 isotope produced in microgram quantities by the Berkeley cyclotron. Plutonium-239 is an Isotope of Plutonium. Plutonium-239 is the primary Fissile isotope used for the production of Nuclear weapons although When the Hanford production reactors came on-line in the spring of 1944, the mix of Pu-239 and Pu-240 obtained was found to be much more fissile. The Hanford Site is a decommissioned nuclear production complex on the Columbia River in south-central Washington operated by the United States government To avoid pre-detonation, the muzzle velocity would need to be greatly raised, making the bomb impractically long. A gun's muzzle velocity is the speed at which the Projectile leaves the muzzle of the gun The weapon was re-designed to use uranium-235. Uranium-235 is an isotope of uranium that differs from the element's other common isotope Uranium-238, by its ability to cause a rapidly expanding fission The muzzle velocity required for a U-235 fission reaction is much lower, reducing the barrel length of the resulting bomb (now code-named Little Boy) to less than ten feet. Little Boy was the Codename of the Atomic bomb, developed via the "Manhattan Project" which was dropped on Hiroshima, on August 6 1945 by the This allowed the device to fit into a standard B-29 bomb bay.

The Pullman was modified to its original configuration with the rear bomb bay a standard B-29 design. ^[10] All subsequent Silverplates were also configured in this manner. The Pullman B-29 was flown to Wendover and assigned to further drop testing in September 1944 with the 216th Base Unit until it was damaged in a landing accident in December. Year 1944 ( MCMXLIV) was a Leap year starting on Saturday (link will display full calendar of the Gregorian calendar. ^[11]

Production versions

B-29 Enola Gay, 31st Silverplate Superfortress

On August 22, 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 under the designation Project 98146-S^[12] from the Glenn L. Martin Company's modification center at Omaha, Nebraska. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout Events 392 - Arbogast has Eugenius elected Western Roman Emperor. Year 1944 ( MCMXLIV) was a Leap year starting on Saturday (link will display full calendar of the Gregorian calendar. The Glenn L Martin Company was an early US Aircraft company founded by aviation pioneer Glenn Luther Martin. In mid-October the first three of these second increment Silverplate B-29s were delivered to the USAAF and flown to Wendover Army Airfield, Utah. Wendover Air Force Base is a former United States Air Force base in Utah now known as Wendover Airport. The State of Utah (ˈjuːtɔː or) is a western state of the United States. They were fitted with British single-point bomb releases mounted on a re-designed H-frame^[13] 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 393rd Bomb Squadron and three to the 216th Base Unit for bomb drop testing.

By February 1945 the seventeen aircraft of the second increment were themselves in need of upgrades, particularly those of the 216th Base Unit. Year 1945 ( MCMXLV) was a Common year starting on Monday (link will display the full calendar Four of the planes assigned to the 393rd Bomb Squadron (now a squadron of the 509th Composite Group) were immediately transferred to the 216th to meet an increase in its testing tempo. The 509th Composite Group was an air combat unit of the United States Army Air Forces during the Second World War and as the 509th Operations Group, is ^[14] Rather than attempt to modify the existing aircraft a few at a time, a decision was made to start a new production series. ^[15] The first five of this third increment, known as Project 98228-S, also went to the test unit. ^[16] The order totalled an additional 28 aircraft, with delivery of 15 designated combat models for the 393rd Bomb Squadron beginning in April; the final 8 were not delivered until after the atomic bomb missions in August.

The final war-time Silverplates incorporated all technical improvements to B-29 aircraft, as well as the final series of Silverplate modifications that included fuel-injected Wright R-3350-41 engines, Curtiss Electric reversible-pitch propellers, and pneumatic actuators for rapid opening and closing of bomb bay doors. Fuel injection is a system for mixing fuel with air in an Internal combustion engine. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout Thrust reversal, also called reverse thrust, is the temporary diversion of an Aircraft engine 's exhaust or changing of propeller pitch so that the thrust produced A propeller is essentially a type of fan which transmits power by converting Rotational motion into Thrust for propulsion of a vehicle such as an ^[17] Weight reduction was also accomplished by removal of all gun turrets and armor plating. In Architecture, a turret (from Italian: torretta, little tower Latin: turris, tower is a small Tower that For body armour see Armour, for armoured forces see Armoured warfare, for other uses see Armour (disambiguation. These B-29s represented a significant increase in performance over the standard variants.

Including the Pullman B-29, a total of 65 Silverplate B-29s were produced both during and after World War II. Twenty-nine of these were assigned to the 509th Composite Group during World War II, with 15 used to carry out the atomic bombings of Hiroshima and Nagasaki. The atomic bombings of Hiroshima and Nagasaki were nuclear attacks near the end of World War II against the Empire of Japan by the United States at An additional twenty-four were assigned to the group for post-war operations as the 509th Bomb Group. Fifty-seven Silverplates were produced by Martin-Omaha and 8 by Boeing-Wichita. Thirty-two 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). Two, the Enola Gay and Bockscar, are displayed in museums. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout Bockscar, sometimes called Bock's Car or Bocks Car, is the name of the United States Army Air Forces B-29 Bomber that

The only other USAF combat unit to use the Silverplate B-29 was the 97th Bomb Wing at Biggs Air Force Base, El Paso, Texas. Biggs Army Airfield, also known as Biggs AAF, is a military Airport located at Fort Bliss in El Paso Texas, USA. In the summer of 1949 it received 27 of the aircraft from the 509th Bomb Wing when the latter transitioned to B-50D bombers, but within a year all were converted to TB-29 trainers. This article is about the US Air Force B-2 Wing For the article on the World War II B-29 unit see 509th Operations Group. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout 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 Bomb Wing at Travis Air Force Base, California. The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located The 9th Bomb Group (Very Heavy was an air combat unit of the United States Army Air Forces during the Second World War and as the 9th Operations Group Travis Air Force Base is a United States Air Force air base under the operational control of the Air Mobility Command (AMC located three miles (5 California ( is a US state on the West Coast of the United States, along the Pacific Ocean. ^[18]

Followup program

The U. S. Joint Chiefs of Staff issued a directive in January 1948 for the modification of 225 B-29, B-50, and B-36 bombers to carry nuclear weapons. The Joint Chiefs of Staff ( JCS) is a group comprising the Chiefs of service of each major branch of the Armed services in the United States armed forces The project was intended to be completed by December 1948 and was known by the code name "Gem". The modification of 80 B-29s was authorized by Air Materiel Command project DOM-595C, known as Saddletree.

The project included "winterization" of 36 B-29s for operating from Arctic bases, and the modification of 36 others to have an air refueling capability under project DOM-599C ("Ruralist"). The Arctic is the Region around the Earth 's North Pole, opposite the Antarctic region around the South Pole. Aerial refueling, also called air refueling, in-flight refueling ( IFR) air-to-air refueling ( AAR) or tanking, is With the addition of the 80 Saddletree bombers, a total of 145 B-29s were modified to carry nuclear weapons, and 117 of these were assigned to operational units,^[19]

Notes

Sources

• Campbell, Richard H. , The Silverplate Bombers: A History and Registry of the Enola Gay and Other B-29s Configured to Carry Atomic Bombs (2005), ISBN 0-7864-2139-8 This source provided most of the information for this article, augmented and validated by the web site essay below.
• George Cully Article: Silverplate, the Aircraft of the Manhattan Project This source appears to draw material from Dr. Ramsey's History of Project A and from H. L. A. Bowen's A History of the Air Force Atomic Energy Program 1943-1953, Vol. I Silverplate, a U. S. Air Force publication.