Mercury-Atlas 4 was an unmanned spaceflight of the Mercury program. It was launched on September 13, 1961 at 14:09 UTC from Launch Complex 14 at Cape Canaveral, Florida. A Crewman Simulator instrument package was aboard. The craft orbited the Earth once. Further delays happened when it was discovered that the brand of transistor used in both the Atlas and Mercury were prone to forming solder balls, thus the entire last week of August was spent laboriously repairing them.