Following several delays, full-scale nuclear detonations began on 28 May. Shot BOLTZMANN, a 12-kiloton blast, was fired from a 500-foot tower on northern Yucca Flat. After more delays, two minor blasts, FRANKLIN and LASSEN, were fired during the first week of June. These tests came near the intended end of Watertown's existence as an active installation.
The base had always been considered a temporary facility. As U-2 testing began to wind down and CIA pilot classes finished their training, Watertown became a virtual ghost town. By mid-June 1957, the U-2 test operation had moved to Edwards and operational U-2 aircraft were assigned to the 4028th Strategic Reconnaissance Squadron at Laughlin, Texas.
On 18 June 1957, a test code-named WILSON deposited fallout on Watertown. The AEC measured radiation exposure inside the evacuated buildings and vehicles at the base to study the effectiveness of various materials in shielding against fallout. In effect, Watertown served as a laboratory to determine the shielding qualities of typical building materials that might be found in any American town. WILSON was followed by the 37-kiloton PRISCILLA shot at Frenchman Flat on 24 June.
HOOD, the sixth nuclear shot of Plumbbob, was truly spectacular. It also caused substantial damage to the Groom Lake airbase. The device was lofted by balloon to a height of 1,500 feet over Yucca Flat, about 14 miles southwest of Watertown. On 5 July 1957, HOOD exploded with a yield of 74 kilotons. It was the most powerful airburst ever detonated within the continental United States. HOOD's shockwave shattered windows on two buildings at Watertown, and broke a ventilator panel on one of the dormitories. A maintenance building on the west side of the base and the supply warehouse west of the hangars suffered serious damage as their metal roll-up doors buckled.
Despite the end of U-2 operations and the near constant rain of fallout, security at the Watertown facility remained tight. On 28 July 1957, a civilian pilot was detained after making an emergency landing at Watertown airstrip. Edward K. Current Jr., an employee of Douglas Aircraft Company, had been on a cross-country training flight when he became lost, ran low on fuel, and decided to land at Groom Lake. He was held overnight and questioned before being released.
On 20 June 1958, 38,400 acres of land encompassing the Watertown base was officially withdrawn from public access under Public Land Order 1662. This rectangular addition to the Nevada Test Site was designated Area 51. Shortly after this, the National Aeronautics and Space Administration (NASA) secured permission to designate Groom Lake as a contingency landing site for the X-15 rocket plane. It was, however, never needed for this purpose.
For two years following the departure of the U-2 fleet from Watertown, the base was fairly quiet.
New Lease on Life
Dramatic changes came to Area 51 with the advent of Project OXCART, through which Lockheed's proposed successor to the U-2 was developed. The OXCART aircraft was a sleek, powerful looking aircraft with a long tapered forward fuselage with blended chines. A rounded delta wing supported two turbo-ramjet engines capable of boosting the aircraft to Mach 3.2 at altitudes in excess of 90,000 feet.
Twin, inwardly canted tails and a sawtooth internal structure in the wing edges contributed to a low overall RCS. The airframe was constructed mostly of titanium, with asbestos-fiberglass and phenyl silane composites in the leading and trailing edges, chines, and tails for RCS reduction. The final designation for the OXCART aircraft was A-12, with the "A" standing for "Archangel."