The Delta D, Thrust Augmented Delta or Thor-Delta D was an American

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 expendable launch system

Expendable launch system

An expendable launch system is a launch system that uses an expendable launch vehicle to carry a payload into space. The vehicles used in expendable launch systems are designed to be used only once , and their components are not recovered for re-use after launch...

 used to launch two communications satellites in 1964 and 1965. It was derived from the Delta C

Delta C

The Delta C, or Thor-Delta C was an American expendable launch system used for thirteen orbital launches between 1963 and 1969. It was a member of the Delta family of rockets....

, 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

PGM-17 Thor

Thor was the first operational ballistic missile of the U.S. Air Force . Named after the Norse god of thunder, it was deployed in the United Kingdom between 1959 and September 1963 as an intermediate range ballistic missile with thermonuclear warheads. Thor was in height and in diameter. It was...

 missile in the DSV-2A

Thor DSV-2

The Thor DSV-2 was a series of sounding rockets, test vehicles, and anti-satellite weapons derived from the Thor Intermediate-range ballistic missile. It was also used as the first stage of several Thor-derived expendable launch systems-Thor DSV-2D:...

 configuration, and the second stage was the Delta D, which was derived from the earlier Delta. An Altair-2

Altair (rocket stage)

The Altair was a solid-fuel rocket with a fiberglass casing, initially developed for use as the third stage of Vanguard rockets. It was manufactured by Allegany Ballistics Laboratory as the X-248. It was also sometimes called the Burner 1.-Uses:...

 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 booster

Solid rocket booster

Solid rocket boosters or Solid Rocket Motors, SRM, are used to provide thrust in spacecraft launches from the launchpad up to burnout of the SRBs. Many launch vehicles include SRBs, including the Ariane 5, Atlas V , and the NASA Space Shuttle...

s, clustered around the first stage.

Both Delta D launches were conducted from Cape Canaveral Air Force Station

Cape Canaveral Air Force Station

Cape Canaveral Air Force Station is an installation of the United States Air Force Space Command's 45th Space Wing, headquartered at nearby Patrick Air Force Base. Located on Cape Canaveral in the state of Florida, CCAFS is the primary launch head of America's Eastern Range with four launch pads...

 Launch Complex 17A

Cape Canaveral Air Force Station Launch Complex 17

Cape Canaveral Air Force Station Space Launch Complex 17 , previously designated Launch Complex 17 , was a launch site at Cape Canaveral Air Force Station, Florida used for Thor and Delta rocket launches between 1958 and 2011....

. The first, on 19 August 1964, carried the Syncom 3 satellite. The last, on 6 April 1965, carried the first commercial communications satellite, Intelsat I

Intelsat I

Intelsat I was the first communications satellite to be placed in geosynchronous orbit, on April 6, 1965...

.