Government and military secrets can range from terrifying to amusing to downright absurd, but most are nothing short of intriguing. From a secret U.S. Air Force project to build a supersonic flying saucer to a now-famous World War II-era research program that produced the first atomic bombs, here are seven declassified military or CIA secrets.
In late 2012, the U.S. Air Force declassified a trove of documents, including records of a secret program to build a flying saucer-type aircraft designed to shoot down Soviet bombers. The ambitious program, called Project 1794, was initiated in the 1950s, and a team of engineers was tasked with building a disc-shape vehicle capable of traveling at supersonic speeds at high altitudes.
The declassified documents reveal plans for the plane to reach a top speed of Mach 4 (four times the speed of sound), and reach an altitude of 100,000 feet (30,480 meters). The project's estimated cost was more than $3 million, which in today's dollars would be more than $26 million.
Project 1794 was canceled in December 1961 after tests suggested the flying saucer design was aerodynamically unstable and would likely be uncontrollable at high speeds (let alone supersonic speeds).
In the 1960s, the U.S. Army embarked on a secret mission to build a series of mobile nuclear missile launch sites under the Greenland ice sheet. The objective was to house medium-range missiles close enough to strike targets within the Soviet Union.
The program was codenamed Project Iceworm, but to test its feasibility, the Army launched a cover research project called "Camp Century" in 1960. Under this guise, engineers built a network of underground buildings and tunnels, including living quarters, a kitchen, a recreation hall, infirmary, laboratories, supply rooms, a communications center and a nuclear power plant.
The base, which was kept secret from the Danish government, operated for seven years. The program was canceled in 1966 after shifting ice created unstable conditions. Today, the crushed remains of Project Iceworm are buried beneath Arctic snow.
During the Cold War, the CIA initiated Project MK-ULTRA, a secret and illegal human research program to investigate potential mind-control systems. The program's operators examined the effects of hypnosis, biological agents and drugs, such as LSD and barbiturates, on human subjects. Some historians suggest the program was designed to develop a mind-control system that could be used to "program" the brains of potential assassins. [The 10 Craziest Military Experiments]
In 1973, then-CIA director Richard Helms ordered that all documents from Project MK-ULTRA be destroyed, but a formal investigation into the program was launched several years later. The project became the basis for several movies, such as "The Manchurian Candidate" and "The Men Who Stare at Goats."
Almost no other site has garnered as much attention from conspiracy theorists and UFO-enthusiasts as Area 51, a remote desert tract near Groom Lake in Nevada, roughly 83 miles (134 kilometers) northwest of Las Vegas. The intense secrecy surrounding the base sparked peoples' imaginations, and Area 51 was commonly linked to paranormal activities, including pervasive theories that suggested Area 51 hid aliens and UFOs.
In July 2013, declassified documents from the CIA acknowledged the existence of Area 51 for the first time, and confirmed that the top-secret site was used to test a variety of spy planes, including the well-known U-2 reconnaissance aircraft.
While Area 51, which operates as a detachment of Edwards Air Force Base in neighboring California, has never been declared a covert base, the research and activities conducted there were some of the nation's most closely guarded secrets.
While Area 51 was not a top-secret base designed to study extraterrestrials, the U.S. Air Force did study the existence of UFOs. Project Grudge was a short-lived program launched in 1949 to study unidentified flying objects. The mission followed an earlier program, known as Project Sign, which published a report in early 1949 stating that while some UFOs seemed to be actual aircraft, there was not enough data to determine their origins. [Top 10 States for UFO Sightings]
Critics of Project Grudge said the program solely set out to debunk UFO reports, and very little actual research was conducted. In his book on the topic, Edward J. Ruppelt, Air Force Captain and director of Project Grudge, wrote: "[I]t doesn't take a great deal of study of the old UFO files to see that standard intelligence procedures were not being followed by Project Grudge. Everything was being evaluated on the premise that UFOs couldn't exist. No matter what you see or hear, don't believe it."
In September 1946, President Harry Truman authorized a program called Operation Paperclip, which aimed to lure scientists from Nazi Germany to the United States following World War II. Officials at the Office of Strategic Services (the predecessor to the CIA) recruited German scientists to America to aid the country's postwar efforts, which would also ensure that valuable scientific knowledge would not end up in the hands of the Soviet Union or the divided East and West Germany.
One of the most well-known secret research programs is the Manhattan Project, which eventually produced the world's first atomic bombs. The project began in 1939, and was cloaked in secrecy as physicists investigated the potential power of atomic weapons. From 1942 to 1946, Major General Leslie Groves of the U.S. Army Corps of Engineers led the Manhattan Project.
The first nuclear bomb was detonated at 5:30 a.m. on July 16, 1945, during the so-called Trinity test at the Alamogordo Air Base, 120 miles (193 km) south of Albuquerque, N.M. The explosion created a mushroom cloud that stretched 40,000 feet (12,200 m), and the bomb's explosive power was equivalent to more than 15,000 tons of TNT.
A month after the Trinity test, two atomic bombs were dropped on Hiroshima and Nagasaki in Japan in the waning stages of World War II. To date, the bombings of Hiroshima and Nagasaki remain the only uses of nuclear weapons in war.