Nike Hercules was the Army's only deployed nuclear-armed surface-to-air weapon, created to defend major urban centers against enemy bombers and later against enemy missiles. Developed in the early 1950s as a replacement for Nike Ajax after concerns that Ajax could not stop a massed Soviet air attack, it was initially pursued as the Nike B program, authorized in July 1953 to design a missile capable of intercepting aircraft flying 1,000 miles per hour at 60,000 feet and a horizontal range of 50,000 yards, and it was renamed Nike Hercules in December 1956. Essentially an Ajax with four of each component, it used a cluster of four solid-fuel rocket boosters and four liquid-propellant engines to carry the warhead to its target, though the engine fuel was later changed to solid propellant. Although designed to use the supporting components of the Nike Ajax system, its greater capability required added ground equipment, including a High-Powered Acquisition Radar, Alternate Battery Radars, and a Target Ranging Radar to improve range, provide backup, and counter enemy radar jamming. Testing began in 1955 at White Sands Proving Ground, where on September 30, 1955, a liquid-fueled engine undergoing static test exploded, collapsing a protective bunker, injuring five people, and killing one person, the only missile-testing death in the history of White Sands Missile Range; after this, the engine fuel was changed from liquid to solid propellant. At White Sands Missile Range, Nike Hercules achieved the first intercept of a drone on October 31, 1956, the first test using the new solid propellant sustainer engine on March 13, 1957, a direct hit on a Corporal missile on June 3, 1960, and an intercept of another Hercules in late 1960. The first production missiles were delivered in 1958 and quickly replaced Ajax on Nike sites, and in June 1961 Army Air Defense Command began phasing in Improved Hercules, mainly through radar improvements that made the High-Power Acquisition Radar, Target Tracking Radar, and Target Ranging Radar more capable and more compact for mobility. During the Cold War, the Army established 145 Nike Hercules sites in the continental U.S. to protect metropolitan areas and Strategic Air Command bomber bases, keeping them strategically deployed there until 1974, while the system continued in service abroad into the early 1990s. Although the Army originally planned to replace Hercules with Patriot, that was not implemented. More than 25,000 Nike Hercules missiles were manufactured, and at White Sands Missile Range 680 were fired, more than any other missile ever tested there. Nike Hercules measured 41 feet long, 31.5 inches in diameter, weighed 10,000 pounds, had a range greater than 75 miles, could reach an altitude of 30 miles, and was first fired in 1955.