Thor-Delta
The Thor-Delta, also known as Delta DM-19 or just Delta was an early American expendable launch system used for 12 orbital launches in the early 1960s. A derivative of the Thor-Able, it was a member of the Thor family of rockets, and the first member of the Delta family.
The first stage was a Thor missile in the DM-19 configuration. The second stage was the Delta, which had been derived from the earlier Able stage. An Altair solid rocket motor was used as a third stage.
The basic design of the original Vanguard upper stages, featuring a pressure-fed nitric acid/UDMH, regeneratively cooled engine, was kept in place, but with an improved AJ10-118 engine. More significantly, the Delta stage featured cold gas attitude control jets allowing it to be stabilized in orbit for restart and more precise burns.
The Thor-Delta was the first rocket to use the combination of a Thor missile and a Delta upper stage. This configuration was reused for many later rockets, and a derivative, the Delta II, remained in service until 2018.
The Thor-Delta launched a number of significant payloads, including the first communications satellite, Echo 1A; the first British satellite, Ariel 1; and the first active direct-relay communications satellite, Telstar 1. All 12 launches occurred from Cape Canaveral Air Force Station Launch Complex 17. The launch of Telstar 1 used pad B, while all other launches were from pad A. All launches were successful except the maiden flight, which failed to place Echo 1 into orbit due to a problem with the second stage.
Thor-Delta launches
| No. | Date | Payload | Site | Outcome | Remarks |
| 1 | May 13, 1960 | Echo 1 | CCAFS LC 17A | Launch at 9:16 p.m. GMT. Good first stage. Second-stage attitude control system failure. Vehicle destroyed. | |
| 2 | August 12, 1960 | Echo 1A | CCAFS LC 17A | Payload placed into, 47 degree inclination orbit. | |
| 3 | TIROS-2 | CCAFS LC 17A | |||
| 4 | March 25, 1961 | Explorer-10 | CCAFS LC 17A | payload placed into elliptical orbit. | |
| 5 | July 12, 1961 | TIROS-3 | CCAFS LC 17A | ||
| 6 | August 16, 1961 | Explorer-12 | CCAFS LC 17A | Energetic Particle Explorers. EPE-A. Highly elliptical orbit. | |
| 7 | February 8, 1962 | TIROS-4 | CCAFS LC 17A | ||
| 8 | March 7, 1962 | OSO-1 | CCAFS LC 17A | Orbiting Solar Observatory., 33 degree orbit. | |
| 9 | April 26, 1962 | Ariel 1 | CCAFS LC 17A | Ariel 1 was later seriously damaged by the Starfish Prime nuclear test. | |
| 10 | June 19, 1962 | TIROS-5 | CCAFS LC 17A | ||
| 11 | July 10, 1962 | Telstar 1 | CCAFS LC 17B | Telstar 1 was later damaged by the Starfish Prime high altitude nuclear event. | |
| 12 | September 18, 1962 | TIROS-6 | CCAFS LC 17A |