Thor Delta rocket.
On August 15th, 1961 NASA managed to launch Explorer 12 into a highly eliptical orbit around the Earth. When we think of orbiting the Earth, we usually think of a circular pattern, but this craft followed a more egg-shaped path around the planet. The orbit ranged from 50,000 miles to 170,000 miles from the Earth, studying a number of physical properties of energetic particles found in space.
The rocket was launched from the Atlantic Missile Range at Cape Canaveral on a Thor-Delta rocket. Blast-off occurred from Launch Complex 17, where Delta rocket launches are made even to this day.
Because of the strange orbit, it took several days for scientists to confirm that Explorer 12 had reached its intended path. Data for the experiment stopped arriving in December of 1961, and the satellite re-entered the atmosphere in 1963.