Tag Archives: LASL

9 July 1962, 09:00:09 UTC, T + 13:41

Fireball of Operation Dominc Starfish Prime, 248 miles ( kilometers) above the Pacific Ocean, 9 July 1962.
Fireball of Operation Dominic-Fishbowl Starfish Prime, 248 miles (399.1 kilometers) above the Pacific Ocean, 9 July 1962.

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.

Starfish Prime fireball was visible from Honolulu, Oahu. Hawaii.
Starfish Prime fireball was visible from Honolulu, Oahu, Hawaii, 898 miles (1,445.2 kilometers) from Ground Zero.

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.

A Douglas SM-75/PGM-17A Thor IRBM. (U.S. Air Force)
A Douglas SM-75 Thor IRBM. (U.S. Air Force)

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).

The flash from the Starfish-Prime detonation, photographed from Maui in the Hawaiian Islands 15 seconds after detonation. (Los Alamos National Laboratory)
The flash from the Starfish-Prime detonation, photographed from Maui in the Hawaiian Islands, 15 seconds after detonation. (Los Alamos National Laboratory)

© 2016, Bryan R. Swopes

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4 November 1962, 06:30 GMT

Dominic Tightrope fireball, 00:00 GMT, 4 November 1962. (Nuclear Weapons Archive)
Dominic Tightrope fireball, 06:30 GMT, 4 November 1962. (Nuclear Weapons Archive)

4 November 1962: A Western Electric M6 Nike Hercules air-defense guided missile was launched from Johnston Island in the North Pacific Ocean. The missile was armed with a W-31 Mod 1 nuclear warhead, and had been modified to include a command arm/fire capability, and an automatic disarm feature. At an altitude of 69,000 feet (21,031 meters), 2 miles (3.2 kilometers) south-southwest of the island, the warhead detonated with an explosive yield of 12 kilotons. This nuclear weapon effects test, Dominic Tightrope, was the final test of the Operation Dominic I test series, and was the last atmospheric nuclear test conducted by the United States.

The Nike Hercules was a long-range, high-altitude surface-to-air guided missile, designed and produced by Western Electric Company and the Douglas Aircraft Company. It was a two-stage missile with a cluster of four Hercules Powder Company M5E1 solid-fuel rocket engines as the boost stage. The second stage was powered by a Thiokol Chemical Corporation M30 solid-fuel rocket engine. The booster stage produced 173,600 pounds of thrust (772.211 kilonewtons)and burned for 3.4 seconds. The second stage engine produced 13,500 pounds of thrust (60.051 kilonewtons) and had a burn time of 29 seconds.

A Nike Hercules air defense missile launch. (U.S. Army)
A Nike Hercules air defense missile launch. (U.S. Army)

The Nike air defense missile system used multiple radars to track incoming target aircraft and the outgoing missile. Computer systems analyzed the data and signals were sent to guide the missile toward the target. This was a complex system and multiple missiles were based together at missile sites around the defended area.

The Nike Hercules was 41 feet (12.497 meters) long, with a maximum diameter of 2 feet, 6.5 inches (0.775 meters). The maximum wing span was 11 feet, 6 inches (3.505 meters). Its weight was 10,710 pounds (4,858 kilograms). The Hercules could reach an altitude of 100,000 feet (30,480 meters) and had a range of 90 miles (145 kilometers). The missile’s maximum speed was Mach 3.65.

The Hercules could be armed with either a M17 high explosive fragmentation warhead or a W-31 nuclear warhead. Although designed to attack jet aircraft, the Nike Hercules also successfully intercepted guided and ballistic missiles, and had a surface-to-surface capability.

The Western Electric SAM-A-25 Nike B was renamed Nike Hercules in 1956 while still in development. It was redesignated Guided Missile, Air Defense M6 in 1958, and MIM-14 in 1963. (“MIM” is Department of Defense terminology for a mobile, ground-launched interceptor missile.) About 25,000 Nike Hercules missiles were built. Initially deployed in 1958, it remained in service with the U.S. Army until 1984.

The W-31 was a boosted fission implosion warhead designed by the Los Alamos Scientific Laboratory. It weighed 900 pounds (408 kilograms) and had a selectable yield of from 2 to 40 kilotons. About 2,550 warheads were produced and remained in service until 1989.

A battery of U.S. Army Nike Hercules SAM-A-25 surface-to-air guided missiles. (U.S. Army)
A battery of U.S. Army Nike Hercules MIM-14 surface-to-air guided missiles. (U.S. Army)

© 2016, Bryan R. Swopes

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