Thor Delta with Explorer 10 Mar 25 1961.jpg
Thor-Delta prior to the launch of Explorer 10
FunctionExpendable launch system
Country of originUnited States
Launch history
Launch sitesCape Canaveral LC-17
Total launches12
First flight1960-05-13
Last flight1962-09-18

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.[1]

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.[2]

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 Failure 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 Success Payload placed into 1,035 miles (1,666 km), 47 degree inclination orbit.
3 November 23, 1960 TIROS-2 CCAFS LC 17A Success
4 March 25, 1961 Explorer-10 CCAFS LC 17A Success 78 pounds (35 kg) payload placed into elliptical 138,000 miles (222,000 km) orbit.
5 July 12, 1961 TIROS-3 CCAFS LC 17A Success
6 August 16, 1961 Explorer-12 CCAFS LC 17A Success Energetic Particle Explorers. EPE-A.[3] Highly elliptical orbit.
7 February 8, 1962 TIROS-4 CCAFS LC 17A Success
8 March 7, 1962 OSO-1 CCAFS LC 17A Success Orbiting Solar Observatory. 345 miles (555 km), 33 degree orbit.
9 April 26, 1962 Ariel 1 CCAFS LC 17A Success Ariel 1 was later seriously damaged by the Starfish Prime nuclear test.
10 June 19, 1962 TIROS-5 CCAFS LC 17A Success
11 July 10, 1962 Telstar 1 CCAFS LC 17B Success Telstar 1 was later damaged by the Starfish Prime high altitude nuclear event.
12 September 18, 1962 TIROS-6 CCAFS LC 17A Success

See also

Delta (rocket family)


  1. ^ Wade, Mark. "Delta". Encyclopedia Astronautica. Archived from the original on 2013-05-22. Retrieved 2009-02-09.
  2. ^ Krebs, Gunter. "Thor family". Gunter's Space Page. Retrieved 2009-02-09.
  3. ^ "Explorer 12". NASA.