Thor 320 Delta 9 rocket with UK first satellite Ariel 1, 26 April 1962
FunctionExpendable launch system
Country of originUnited States
Launch history
Launch sitesCape Canaveral, LC-17
Total launches12
First flight13 May 1960
Last flight18 September 1962

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

See also: List of Thor and Delta launches (1960–1969)

This section is transcluded from List of Delta DM-19 launches. (edit | history)

Rocket S/N Launch Site Payload Function Orbit Outcome Remarks
Thor DM-19 Delta Thor 144
Delta 1
CCAFS LC-17A Echo 1 Communication MEO Failure Maiden flight of Thor-Delta, upper-stage attitude control system malfunctioned
Thor DM-19 Delta Thor 270
Delta 2
CCAFS LC-17A Echo 1A Communications MEO Success
Thor DM-19 Delta Thor 245
Delta 3
CCAFS LC-17A TIROS-2 Weather SSO Success
Thor DM-19 Delta Thor 295
Delta 4
CCAFS LC-17A Explorer 10 Magnetospheric HEO Success
Thor DM-19 Delta Thor 286
Delta 5
CCAFS LC-17A TIROS-3 Weather SSO Success
Thor DM-19 Delta Thor 312
Delta 6
CCAFS LC-17A Explorer 12 Magnetospheric HEO Success
Thor DM-19 Delta Thor 317
Delta 7
CCAFS LC-17A TIROS-4 Weather SSO Success
Thor DM-19 Delta Thor 301
Delta 8
CCAFS LC-17A OSO-1 Solar LEO Success
Thor DM-19 Delta Thor 320
Delta 9
CCAFS LC-17A Ariel 1 Ionospheric LEO Success
Thor DM-19 Delta Thor 321
Delta 10
CCAFS LC-17A TIROS-5 Weather SSO Success
Thor DM-19 Delta Thor 316
Delta 11
CCAFS LC-17B Telstar 1 Communication MEO Success
Thor DM-19 Delta Thor 318
Delta 12
CCAFS LC-17A TIROS-6 Weather SSO Success Final flight of Thor-Delta

1963 mystery cloud

On 28 February 1963, a Thor launch vehicle carrying a spy satellite into orbit was launched from Vandenberg Air Force Base. The rocket went off course and mission control detonated the rocket at an altitude of 44 km (27 mi) before it could reach orbit. The rocket detonation produced a large circular cloud that appeared over the southwestern United States. Due to its mysterious nature, appearing at a very high altitude and being visible for hundreds of miles, the cloud attracted widespread attention and was published by the news media. The cloud was featured on the cover of Science Magazine in April 1963, Weatherwise Magazine in May 1963, and had a full page image published in the May issue of Life Magazine.[3][4] Prof. James MacDonald at the University of Arizona Institute for Atmospheric Physics investigated the phenomena and linked it to the Thor rocket launch after contacting military personnel at Vandenberg Air Force Base. When the launch records were later declassified, the United States Air Force released a memo explaining that the cloud was the result of a military operation.[5][6]


See also

Delta (rocket family)


  1. ^ Wade, Mark. "Delta". Encyclopedia Astronautica. Archived from the original on 17 August 2013. Retrieved 9 February 2009.
  2. ^ "Thor family". Gunter's Space Page. Retrieved 9 February 2009.
  3. ^ MacDonald, James (19 April 1963). "Stratospheric Cloud Over Northern Arizona". Science Magazine. Vol. 140, no. 3564. pp. 292–294. doi:10.1126/science.140.3564.292.b.
  4. ^ "Mystery Cloud". Life Magazine. 14 May 1963. p. 73.
  5. ^ Jackson, Jeff G. (26 January 1995), 30th Space Wing History, Vandenberg AFB, California: Department of the Air Force, pp. 1–2
  6. ^ MacDonald, James (15 June 1963). "Cloud Ring In The Upper Stratosphere" (PDF). Weatherwise. pp. 99–148.