Operation Hardtack I was a series of 35 nuclear tests conducted by the United States from April 28 to August 18, 1958, at the Pacific Proving Grounds. At the time of testing, the Operation Hardtack I test series included more nuclear detonations than the total of prior nuclear explosions in the Pacific Ocean. These tests followed the Project 58/58A series, which occurred from December 6, 1957, to March 14, 1958, and preceded the Operation Argus series, which took place in 1958 from August 27 to September 6.
Operation Hardtack I was directed by Joint Task Force 7 (JTF 7). JTF-7 was a collaboration between the military and many civilians, but was structured like a military organization. Its 19,100 personnel were composed of members of the US military, federal civilian employees, as well as workers affiliated with the Department of Defense (DOD) and the Atomic Energy Commission (AEC).
There were three main research directions. The first was the development of new types of nuclear weapons. This was undertaken by detonating experimental devices created by the AEC's Los Alamos Scientific Laboratory and the University of California Radiation Laboratory (UCRL). The DOD performed experiments and tests on these detonations that did not hamper the AEC's research. The second research direction was to examine how underwater explosions affected materiel, especially Navy ships, and was performed by the DOD. The Wahoo test was conducted in the open ocean, whereas Umbrella was in a lagoon. The final avenue of study was to analyze high-altitude nuclear tests to refine the detection of high-altitude nuclear tests and investigate defensive practices for combatting ballistic missiles. This research direction was composed of three individual tests and were the first high-altitude tests. The individual tests in the series were Orange, Teak, and Yucca. Orange and Teak were known collectively as Operation Newsreel and were rocket boosted. Yucca reached its altitude using balloons.
Historical background Many events and proceedings leading up to Operation Hardtack I, such as previous nuclear testing results and the global political atmosphere, influenced its creation and design. One such historical circumstance was that nuclear radiation concerns were mounting publicly and abroad by 1956. During the 1956 Presidential Election, ending nuclear testing was a campaign issue and nuclear safety was one part of that discussion. At the same time, the Union of Soviet Socialist Republics (USSR) was publicly proposing a moratorium on testing.
In 1956 during June, the National Academy of Sciences (NAS) recommended new radiation exposure limits for the general public in a report entitled: "The Biological Effects of Atomic Radiation". The AEC, which was the body that developed nuclear weapons, accepted the NAS recommended radiation exposure limits. Some AEC members asserted that the limits were reached incorrectly and should be reviewed in the future. Charles L. Dunham, AEC Director of the Division of Biology and Medicine (DBM), said that the new limits of nuclear radiation exposure would prevent them from continuing testing in Nevada. Dunham, in association with other AEC offices and officials, made recommendations to move further tests to the Pacific to eliminate the need to determine radiological fallout safety.
Also in 1956, the AEC was designing a test series that included nuclear detonations which would release significant amounts of nuclear fallout. The series came to be known as Operation Plumbbob and took place in 1957 from April 24 to October 7. Operation Plumbbob was followed by Project 58/58A and Operation Hardtack I. At the time of testing, Operation Plumbbob was the most extensive nuclear test series held at the Nevada Test Site. President Eisenhower was very cautious in approving Plumbbob due to public concern. Consequently, the AEC held brief and ultimately fruitless discussions of moving some of the tests in the Plumbbob series to the next planned Pacific Ocean series, Operation Hardtack I, to minimize radioactive fallout in and around the Nevada Test Site.
When Operation Plumbbob began in the spring of 1957, the planning process of Operation Hardtack I was well underway and the number of nuclear detonations planned were more than those in the Plumbbob series. At the same time, radiation and nuclear proliferation concerns around the world had led to formal discussions between the US, USSR, and other countries on the topic of instituting a global ban on nuclear testing as a path to disarmament. In 1957 on August 9 AEC chairman Lewis L. Strauss proposed to President Eisenhower a preliminary plan of Operation Hardtack I. President Eisenhower objected to the length of the four-month testing period and that the plan called for 25 shots, which was one more than in Plumbbob. As a result of the discussion, Eisenhower consented to yields no larger than , and ordered that the testing period be as brief as possible.
Project 58/58A followed Operation Plumbbob and began almost two months later starting in 1957 on December 6. Project 58/58A was composed of four safety tests; they were not supposed to result in nuclear radiation. All four took place at the Nevada Test Site. The safety tests were intended to ensure that the bombs would not malfunction. However, the test named Coulomb-C which took place in 1957 on December 9 did malfunction. It resulted in an unanticipated blast. The blast released a nuclear radiation fallout cloud that traveled toward Los Angeles and resulted in low levels of nuclear radiation. The bomb failure added to public concern over nuclear testing's safety.
Some tests were cut in an effort to meet Eisenhower's demands for a shorter testing period, but new tests quickly filled their place. AEC chairman Strauss remarked that the large number of shots was due to the "DOD's requirement for an increasing number of different nuclear weapons types". Eisenhower eventually approved the plan for Operation Hardtack I in late January, even though it still contained 25 shots. On March 31, 1958, the USSR announced a suspension of all tests and called on the US to do the same. On May 9 the leader of the Soviet Union, Nikita Khrushchev, accepted Eisenhower's invitation for technical discussions on a nuclear testing moratorium and negotiations began on July 1 of the same year. Eisenhower announced to the US on August 22, 1958, that the ban would begin October 31. US scientists responded by seeking to add more tests to the Hardtack Series in case it turned out to be the last chance. Consequently, Operation Hardtack I consisted of 35 tests.
There was public health concern with the number of shots in Operation Hardtack I. Studies released in March 1958 indicated that people as far as away could have severe retinal burns from two of the three high-altitude tests: Teak and Orange. It was then decided that they would be moved to Johnston Island, which was from the nearest inhabited island. The high-altitude nuclear tests delivered the first openly reported man-made high-altitude electromagnetic pulses (EMP). Teak, which was detonated at and was , produced an aurora-like effect that was visible from Hawaii, displaced from the detonation. Most radio communications immediately dropped across the Pacific Ocean. The blackout in Australia lasted for 9 hours and Hawaii's lasted for no less than 2 hours.
High-altitude tests
Operation Hardtack I contained three high-altitude tests called Operation Newsreel that were designed to study many effects that a nuclear explosion would have on materials and electronic systems. They were also used to test the energy of the explosion and what forms of energy they would produce. Yucca was the name of the first high-altitude test and it was performed near the Enewetak Atoll in the Marshall Islands. The other two high-altitude tests, Orange and Teak, were performed near the Johnston Atoll in the South Pacific Ocean about southwest of the Hawaiian Islands.
Impact on ozone layer There was some uncertainty on whether detonating a nuclear weapon at such high altitudes would cause a hole in the ozone layer. After multiple underwater tests there was evidence to show the energy created by the blast would create ozone. Project leads determined some destruction of ozone would occur which would then be replaced by the ozone created from the explosion. It was agreed that if this theory were wrong, the hole created in the ozone layer would be minuscule enough to cause no harm. Upon completion of Operation Newsreel, it was determined that there was very little evidence of any harm being caused to the natural ozone layer.
Yucca Yucca was the first high-altitude test performed during Operation Hardtack I and was detonated on April 28, 1958. It was lifted by a balloon to an altitude of and had a yield of .To achieve the altitude needed, the device was attached to a large helium-filled balloon which carried it to the detonation altitude. Due to issues with high winds on Enewetak Island, the balloon launches from ground were unsatisfactory, thus creating the need for a new method. The balloons were then deployed from an aircraft carrier which helped with deployment and the inflation. While the balloons were inflated, they were unable to take too much force from wind or the plastic material of the balloons would tear. While the balloons were inflating on the aircraft carrier, the ship could match and oppose the wind speed allowing for the balloon to be inflated in still air. To make sure the launch would be successful 86 balloon launches were tested.
Due to concerns of failures, many safety measures were employed. While on ground, the bomb used multiple pins to prevent certain safety features of the bomb from being deployed before liftoff. One such pin was used to stop the electrical systems so that the bomb would be unable to be armed. In case of a dud, the bomb would detach from the balloon and be allowed to drop into the ocean where many more safety features would come into action. Some of these features included probes which could detect saltwater which would destroy the electrical system so the conductive seawater could not cause a short which would detonate the bomb. Another concern was a nuclear device floating in the ocean should a misfire occur. To combat this, inserts were created which would dissolve in a few hours, thus scuttling the device.
On the day of the launch many meteorological aspects were taken into account and calculations were done to ensure the bomb would reach the correct altitude. The bomb was loaded onto an aircraft carrier and preparations began. As the balloon was inflated multiple testing devices were connected to the balloon. The readings from these devices would be sent to multiple ships and aircraft so nothing would need to be recovered after the explosion. After all the preparations were done and the balloon was inflated, the device was released and began to climb. After almost three and a half hours of climbing the bomb was detonated at an altitude of . The aircraft carrier which carried Yucca was approximately from the detonation site. The shock wave from Yucca reached the carrier 3 minutes and 16 seconds after detonation.