By Cliff Lethbridge

Delta D Launch, Photo Courtesy NASA

Delta D Launch, Photo Courtesy NASA

Classification: Space Launch Vehicle

Length: 92 feet, 11 inches

Diameter: 8 feet

Date of First Cape Canaveral Launch: August 19, 1964

Date of Final Cape Canaveral Launch: April 6, 1965

Number of Cape Canaveral Launches: 2

Originally called the Thrust Augmented Delta (TAD), the Delta D added a major improvement that has become the trademark of Delta launch vehicles. The Delta D significantly improved payload capacity by incorporating three Castor solid-propellant rocket boosters to “augment” the thrust of the first stage engine. This strap-on booster configuration was not unique, as it had already been successfully applied to the U.S. Air Force Thrust Augmented Thor-Agena D space launch vehicle. Although the Thrust Augmented Thor-Agena D was never launched from Cape Canaveral, it preceded the Delta D by about two years. The three Castor solid rocket boosters were ignited at liftoff, and provided a total thrust of 156,600 pounds. The boosters were jettisoned during flight. An upgraded Rocketdyne first stage engine produced 175,000 pounds of thrust at launch. The total vehicle could carry a 1,275-pound payload to low-Earth orbit or a 230-pound payload to geostationary transfer orbit. This effectively doubled the payload capability of the Delta launch vehicle in a period of just four years.