The Soviet space program was tied to the USSR's Five-Year Plans and from the start was reliant on support from the Soviet military. Although he was "single-mindedly driven by the dream of space travel", Korolev generally kept this a secret while working on military projects—especially, after the Soviet Union's first atomic bomb test in 1949, a missile capable of carrying a nuclear warhead to the United States—as many mocked the idea of launching satellites and crewed spacecraft. Nonetheless, the first Soviet rocket with animals aboard launched in July 1951; the two dogs were recovered alive after reaching 101 km in altitude. Two months ahead of America's first such achievement, this and subsequent flights gave the Soviets valuable experience with space medicine.