Delta DM-19 | Explorer 12

The Delta DM-19, or Thor-Delta was an early launch system used for 12 launches in the early '60s in the US. The first stage was a Thor missile with the second stage being the Delta, hence the name Thor-Delta. Of 12 flights, it failed only once and put 11 satellites into orbit between 1960 and 62.

The United States Air Force (USAF) is the air service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part of the United States Army Signal Corps, the USAF was established as a separate branch of the United States Armed Forces in 1947 with the enactment of the National Security Act of 1947.