On 1 June , an attempted launch of a Zenit photo reconnaissance satellite ended with the booster crashing near the pad . One of the strap-ons had also fallen back onto LC-1 and burned , resulting in extensive damage that took over a month to repair . By mid-July , the pad had been restored to use , but another delay occurred when the United States carried out a high-altitude nuclear test on 9 July known as Starfish Prime . The test had unexpected consequences in that it released high levels of radiation into the upper atmosphere and space , knocking out several satellites and making any crewed space launch unsafe for at least a month . By the second week of August , radiation levels had diminished enough that the Vostok 3/4 mission could go ahead
Starfish Prime
Starfish Prime
Vostok 3