# 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 (DM-18A / MB-3-I engine). The second stage was the Delta (AJ-10-142 engine), which had been derived from the earlier Able stage. An Altair solid rocket motor (X-248A-7) 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.

## Thor-Delta launches

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.

### Launch list

| Date/time (UTC) | Rocket | S/N | Launch site | Payload | Function | Orbit | Outcome | Remarks |
| 1960-05-13 09:16:05 | 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 |
| 1960-08-12 09:39:43 | Thor DM-19 Delta | Thor 270 Delta 2 | CCAFS LC-17A | Echo 1A | Communications | MEO | Success | |
| 1960-11-23 11:13:03 | Thor DM-19 Delta | Thor 245 Delta 3 | CCAFS LC-17A | TIROS-2 | Weather | SSO | Success | |
| 1961-03-25 15:17:04 | Thor DM-19 Delta | Thor 295 Delta 4 | CCAFS LC-17A | Explorer 10 | Magnetospheric | HEO | Success | |
| 1961-07-12 10:25:06 | Thor DM-19 Delta | Thor 286 Delta 5 | CCAFS LC-17A | TIROS-3 | Weather | SSO | Success | |
| 1961-08-16 03:21:05 | Thor DM-19 Delta | Thor 312 Delta 6 | CCAFS LC-17A | Explorer 12 | Magnetospheric | HEO | Success | |
| 1962-02-08 12:43:45 | Thor DM-19 Delta | Thor 317 Delta 7 | CCAFS LC-17A | TIROS-4 | Weather | SSO | Success | |
| 1962-03-07 16:06:18 | Thor DM-19 Delta | Thor 301 Delta 8 | CCAFS LC-17A | OSO-1 | Solar | LEO | Success | |
| 1962-04-26 18:00:16 | Thor DM-19 Delta | Thor 320 Delta 9 | CCAFS LC-17A | Ariel 1 | Ionospheric | LEO | Success | |
| 1962-06-19 12:19:01 | Thor DM-19 Delta | Thor 321 Delta 10 | CCAFS LC-17A | TIROS-5 | Weather | SSO | Success | |
| 1962-07-10 08:35:05 | Thor DM-19 Delta | Thor 316 Delta 11 | CCAFS LC-17B | Telstar 1 | Communication | MEO | Success | |
| 1962-09-18 08:53:08 | Thor DM-19 Delta | Thor 318 Delta 12 | CCAFS LC-17A | TIROS-6 | Weather | SSO | Success | Final flight of Thor-Delta |

## Gallery

* Thor 245 Delta 3 launching TIROS-2
* Thor 286 Delta 5 launching TIROS-3
* Thor 295 Delta 4 launching Explorer 10
* Thor 316 Delta 11 launching Telstar 1
* Thor 317 Delta 7 launching TIROS-4
* Thor 320 Delta 9 launching Ariel 1