Delta D

{{Short description|American expendable launch vehicle}}

{{Use American English|date=November 2020}}

{{Infobox Rocket

|image = Delta D Intelsat1.jpg

|caption = Launch of a Delta D with Intelsat I

|function = Expendable launch system

|country-origin = United States

|sites = Cape Canaveral LC-17

|launches = 2

|success = 2

|status = Retired

|first = 19 August 1964

|last = 6 April 1965

}}

The Delta D, Thrust Augmented Delta or Thor-Delta D was an American expendable launch system used to launch two communications satellites in 1964 and 1965. It was derived from the Delta C, and was a member of the Delta family of rockets.

The three-stage core vehicle was essentially the same as the Delta C. The first stage was a Thor missile in the DSV-2A configuration, and the second stage was the Delta-D, which was derived from the earlier Delta-A. An Altair-2 SRM was used as a third stage. The main difference between the Delta C and Delta D was the presence of three Castor-1 solid rocket boosters, clustered around the first stage.

Both Delta D launches were conducted from Cape Canaveral Air Force Station Launch Complex 17A. The first, on 19 August 1964, carried Syncom 3, the first satellite in a geostationary orbit. The last, on 6 April 1965, carried the first commercial communications satellite, Intelsat I.{{Cite web|last=Wade|first=Mark|title=Delta|url=http://www.astronautix.com/lvs/delta.htm|url-status=dead|archive-url=https://web.archive.org/web/20080724064027/http://www.astronautix.com/lvs/delta.htm|archive-date=2008-07-24}}{{Cite web|last=Krebs|first=Gunter|title=Thor Family|url=https://space.skyrocket.de/doc_lau_fam/thor.htm|url-status=live|access-date=2021-12-21|website=Gunter's Space Page|language=en|archive-url=https://web.archive.org/web/20070806202728/http://space.skyrocket.de:80/doc_lau_fam/thor.htm |archive-date=2007-08-06 }}