9 July 1962: At 09:00:09 UTC, the United States detonated a thermonuclear warhead over the Pacific Ocean. This was part of the Operation Dominic-Fishbowl test series at Johnston Island, and was designated Starfish Prime.
At 08:46:28 UTC, a Douglas SM-75 Thor intermediate-range ballistic missile (IRBM) was launched from the Thor missile complex on Johnston Island, carrying a W-49 warhead in an AVCO Corporation Mk-2 reentry vehicle. The Mark 4/W-49 reached a peak altitude of 600 miles (965 kilometers) along a ballistic trajectory then began a descent.
The W-49 detonated 36 kilometers (22 miles) southwest of Johnston Island at an altitude of 400 kilometers (246 miles) with an explosive yield of 1.45 megatons. The point of detonation deviated from the planned Air Zero by 1,890 feet (576 meters) to the north, 2,190 feet (668 meters) east, and +617 feet (188 meters) in altitude. The fireball was clearly visible in the Hawaiian Islands, more than 800 miles (1,288 kilometers) away.
The electromagnetic pulse (EMP) damaged electrical systems in The Islands, cutting power, damaging equipment and interrupting telephone systems. Brilliant auroras were visible, lasting about 7 minutes. Telstar, an American communications satellite that was placed in Earth orbit the following day, was also damaged by residual radiation from the detonation.
The Starfish Prime experiment was for the purpose of, “Evaluation of missile kill mechanisms produced by a high altitude nuclear detonation.” The electromagnetic effects on communications were also studied.
The Douglas Aircraft Company SM-75 Thor (redesignated PGM-17A in 1963) was a single-stage nuclear-armed ballistic missile, 65 feet (19.812 meters) long and 8 feet (2.438 meters) in diameter. It weighed 6,890 pounds (3,125.3 kilograms) empty and 110,000 pounds (49,895.2 kilograms) when fueled.
The SM-75 was powered by one Rocketdyne LR79-NA-9 rocket engine which produced 150,000 pounds of thrust. Two Rocketdyne LR101-NA vernier engines of 1,000 pounds thrust, each, provided directional control and thrust adjustments. The Thor was fueled with kerosene and liquid oxygen sufficient for 165 seconds of engine burn time.
The Thor could reach a maximum speed of 11,020 miles per hour (17,735 kilometers per hour) and had a maximum range of 1,500 miles (2,414 kilometers).
The W-49 thermonuclear warhead was designed by the Los Alamos Scientific Laboratory (LASL) and is believed to be a development of the earlier B-28 two-stage radiation-implosion bomb. It incorporated a 10-kiloton W-34 warhead as a gas-boosted fission primary, and had a one-point-safe safety system. The warhead had a diameter of 1 foot, 8 inches (0.508 meters) and length of 4 feet, 6.3 inches (1.379 meters). It weighed 1,665 pounds (755 kilograms).
13 February 1950: Two Convair B-36B Peacemaker long-range strategic bombers of the 436th Bombardment Squadron (Heavy), 7th Bombardment Wing (Heavy), Strategic Air Command, departed Eielson Air Force Base, Fairbanks, Alaska, at 16:27 Alaska Standard Time, on a planned 24-hour nuclear strike training mission.
B-36B-15-CF 44-92075 was under the command of Captain Harold Leslie Barry, United States Air Force.¹ There were a total of seventeen men on board.
Also on board was a Mark 4 nuclear bomb.
The B-36s were flown to Alaska from Carswell Air Force Base, Fort Worth, Texas, by another crew. The surface temperature at Eielson was -40 °F. (-40 °C.), so cold that if the bomber’s engines were shut down, they could not be restarted. Crews were exchanged and the airplane was serviced prior to takeoff for the training mission. In addition to the flight crew of fifteen, a Bomb Commander and a Weaponeer were aboard.
After departure, 44-92075 began the long climb toward 40,000 feet (12,192 meters). The flight proceeded along the Pacific Coast of North America toward the practice target of San Francisco, California. The weather was poor and the bomber began to accumulate ice on the airframe and propellers.
About seven hours into the mission, three of the six radial engines began to lose power due to intake icing. Then the #1 engine, outboard on the left wing, caught fire and was shut down. A few minutes later, the #2 engine, the center position on the left wing, also caught fire and was shut down. The #3 engine lost power and its propeller was feathered to reduce drag. The bomber was now flying on only three engines, all on the right wing, and was losing altitude. When the #5 engine, center on the right wing, caught fire, the bomber had to be abandoned. It was decided to jettison the atomic bomb into the ocean.
The Mark 4 did not have the plutonium “pit” installed, so a nuclear detonation was not possible. The conventional explosive would go off at a pre-set altitude and destroy the bomb and its components. This was a security measure to prevent a complete bomb from being recovered.
The bomb was released at 9,000 feet (2,743 meters), north-northwest of Princess Royal Island off the northwest coast of British Columbia, Canada. It was fused to detonate 1,400 feet (427 meters) above the surface, and crewmen reported seeing a large explosion.
Flying over Princess Royal Island, Captain Barry ordered the crew to abandon the aircraft. He placed the B-36 on autopilot. Barry was the last man to leave 44-92075. Descending in his parachute, he saw the bomber circle the island once before being lost from sight.
Twelve of the crew survived. Five were missing and it is presumed that they landed in the water. Under the conditions, they could have survived only a short time. The survivors had all been rescued by 16 February.
It was assumed that 44-92075 had gone down in the Pacific Ocean.
On 20 August 1953, a Royal Canadian Air Force airplane discovered the wreck of the missing B-36 on a mountain on the east side of Kispiox Valley, near the confluence of the Kispiox and Skeena Rivers in northern British Columbia.
The U.S. Air Force made several attempts to reach the crash site, but it wasn’t until August 1954 that they succeeded. After recovering sensitive equipment from the wreckage, the bomber was destroyed by explosives.
The Mark 4 bomb was designed by the Los Alamos National Laboratory (LANL). It was a development of the World War II implosion-type Mark 3 “Fat Man.” The bomb was 10 feet, 8 inches (3.351 meters) long with a maximum diameter of 5 feet, 0 inches (1.524 meters). Its weight is estimated at 10,800–10,900 pounds (4,899–4,944 kilograms).
The core of the bomb was a spherical composite of plutonium and highly-enriched uranium. This was surrounded by approximately 5,500 pounds (2,495 kilograms) of high explosive “lenses”—very complex shaped charges designed to focus the explosive force inward in a very precise manner. When detonated, the high explosive “imploded” the core, crushing it into a smaller, much more dense mass. This achieved a “critical mass” and a fission chain reaction resulted.
The Mark 4 was tested during Operation Ranger at the Nevada Test Site, Frenchman Flat, Nevada, between 27 January and 6 February 1951. Five bombs were dropped from a Boeing B-50 Superfortress of the 4925th Special Weapons Group from Kirtland Air Force Base in New Mexico. The first four bombs were dropped from a height of 19,700 feet (6,005 meters) above ground level (AGL) and detonated at 1,060–1,100 feet (323–335 meters) AGL. Shot Fox was dropped from 29,700 feet (9,053 meters) AGL and detonated at 1,435 feet (437 meters) AGL. (Ground level at Frenchman Flat is 3,140 feet (957 meters) above Sea Level).
The Mark 4 was produced with explosive yields ranging from 1 to 31 kilotons. 550 were built.
Convair B-36B-15-CF Peacemaker 44-92075 was completed at Fort Worth, Texas, on 31 July 1949. It had been flown a total of 185 hours, 25 minutes.
The B-36B is 162 feet, 1 inch (49.403 meters) long with a wingspan of 230 feet (70.104 meters) and overall height of 46 feet, 8 inches (14.224 meters). The empty weight is 140,640 pounds (63,793 kilograms) and the maximum takeoff weight was 311,000 pounds (141,067 kilograms).
With a wing area of 4,772 square feet (443 square meters) and 21,000 horsepower, the B-36 could fly far higher than any jet fighter of the early 1950s.
The B-36B was powered by six air-cooled, supercharged and turbocharged 4,362.49 cubic-inch-displacement (71.488 liter) Pratt & Whitney Wasp Major B4 (R-4360-41) four-row, 28-cylinder radial engines placed inside the wings in a pusher configuration. These had a compression ratio of 6.7:1 and required 115/145 aviation gasoline. The R-4360-41 had a Normal Power rating of 2,650 horsepower at 2,550 r.p.m. Its Takeoff/Military Power rating was 3,500 horsepower at 2,700 r.p.m., with water injection. The engines turned three-bladed Curtiss Electric constant-speed, reversible propellers with a diameter of 19 feet, 0 inches (5.791 meters) through a 0.375:1 gear reduction. The R-4360-41 is 9 feet, 1.75 inches (2.788 meters) long, 4 feet, 6.00 inches (1.372 meters) in diameter, and weighs 3,567 pounds (1,618 kilograms).
The B-36B Peacemaker had a cruise speed of 202 miles per hour (325 kilometers per hour) and a maximum speed of 381 miles per hour (673 kilometers per hour) at 34,500 feet (10,516 meters). The service ceiling was 42,500 feet (12,954 meters) and its combat radius was 3,740 miles (6,019 kilometers). The maximum range was 8,175 miles (13,156 kilometers).
The B-36 was defended by sixteen M24A-1 20 mm automatic cannons. Six retractable gun turrets each each had a pair of 20 mm cannon, with 600 rounds of ammunition per gun. These turrets were remotely operated by gunners using optical sights. Two optically-sighted 20 mm guns were in the nose, and two more were in a tail turret, also remotely operated and aimed by radar.
The B-36 was designed during World War II and nuclear weapons were unknown to the Consolidate-Vultee Aircraft Corporation engineers. The bomber was built to carry up to 86,000 pounds (39,009 kilograms) of conventional bombs in the four-section bomb bay. It could carry the 43,600 pound (19,777 kilogram) T-12 Cloudmaker, a conventional explosive earth-penetrating bomb. When armed with nuclear weapons, the B-36 could carry several Mk.15 thermonuclear bombs. By combining the bomb bays, one Mk.17 25-megaton thermonuclear bomb could be carried.
Between 1946 and 1954, 384 B-36 Peacemakers were built by Convair. 73 of these were B-36Bs, the last of which were delivered to the Air Force in September 1950. By 1952, 64 B-36Bs had been upgraded to B-36Ds.
They were never used in combat. Only four still exist.
[Trivia enthusiasts might note that the U.S. military code for a lost nuclear weapon is “Broken Arrow.” In 1950, Academy Award-winning actor Jimmy Stewart, himself a Brigadier General, U.S. Air Force Reserve, and highly decorated World War II bomber commander, starred in the Delmer Daves western movie, “Broken Arrow.” In 1954, Stewart starred as a B-36 aircraft commander in Anthony Mann’s “Strategic Air Command.” Coincidence?]
¹ Captain Barry was killed along with other 11 crewmen, 27 April 1951, when the B-36D-25-CF on which he was acting as co-pilot, 49-2658, crashed following a mid-air collision with a North American F-51-25-NT Mustang, 44-84973, 50 miles (80 kilometers) northeast of Oklahoma, City, Oklahoma, U.S.A. The Mustang’s pilot was also killed.