Sputnik crisis
The Vanguard rocket was intended to be the first launch vehicle the United States would use to place a satellite into orbit. Instead, the Sputnik crisis caused by the surprise launch of Sputnik 1 led the U.S., after the failure of Vanguard TV-3, to quickly orbit the Explorer 1 satellite using a Juno I rocket, making Vanguard 1 the second successful U.S. orbital launch.