Thor-Delta

{{Short description|Expendable Rocket developed by USA during the Cold War to launch satellites}}

{{Use American English|date=November 2021}}

{{Use dmy dates|date=November 2021}}

{{Infobox Rocket

| image = 19620426 Delta 9-Ariel 1 LC-17A.jpg

| caption = Thor 320 Delta 9 rocket with UK first satellite Ariel 1, 26 April 1962

| upright = 1

| function = Expendable launch system

| country-origin = United States

| sites = Cape Canaveral, LC-17

| launches = 12

| success = 11

| fail = 1

| status = Retired

| first = 13 May 1960

| last = 18 September 1962

|stage1engines=DM-18A / MB-3-I|stage2engines=AJ-10-142|stage3aengines=X-248A-7|stage1name=Thor DM-19|stage2name=Delta|stage3name=Altair|LEO-payload=270 kg}}

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.{{cite web|url=http://www.astronautix.com/lvs/delta.htm |title=Delta|last=Wade|first=Mark|publisher=Encyclopedia Astronautica|access-date=2009-02-09|url-status=dead|archive-url=https://web.archive.org/web/20130817180906/http://astronautix.com/lvs/delta.htm |archive-date=2013-08-17}}

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.{{cite web|url=http://space.skyrocket.de/doc_lau_fam/thor.htm|title=Thor family|publisher=Gunter's Space Page |access-date=2009-02-09}}{{Cite web |title=Delta |url=https://space.skyrocket.de/doc_lau_det/delta.htm |access-date=2024-11-29 |website=Gunter's Space Page |language=en}}

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.