Delta launch family.

Delta launch.

Delta Expendable Launch Vehicle

The Delta rocket, derived from the Thor intermediate-range ballistic missile, was America's first launch vehicle designed and produced for space exploration.

Delta has an impressive list of client satellites and has a success rate in the 90th percentile. Its first successful launch for the National Aeronautics and Space Administration (NASA) was the Echo 1A satellite on August 12, 1960, and it launched the first Telstar and Itelsat satellites, giving rise to the phrase: "Live, via satellite!" Other launches include, Explorer, Telstar, Syncom, Pioneer, Skynet, Nimbus, Westar, Landsat, the Cosmic Background Explorer, both the polar-orbiting and geosynchronous meteorological satellites, and the Extreme Ultraviolet Explorer (EUVE).

Manufactured by Boeing (formerly McDonnell Douglas Space Systems Company), the modern Delta looks different from earlier versions. The Delta has been configured in various designs over the years, including the basic Delta, Models A through E, J, M, M-6, 900, 2914, and 3910/Payload Assist Module (PAM), and the Delta II model 7925. It has become larger and more advanced and can boost heavier satellites into orbit. Its payload capacity has grown from 100 pounds (45 kilograms) up to 50,800 pounds (23,040 kilograms) to low-Earth orbit. For geosynchronous transfer orbit, its capacity has increased to 28,950 pounds (13,130 kilograms) using the new Delta IV, currently under development.

The first external or strap-on motors, which provide more thrust, were added in 1964. In 1965, the booster propellant capacity was increased. The number of strap-ons increased to six in the 1970s and then to nine in 1972. The Delta II rocket is augmented by nine external solid rocket motors.

Up to the early 1980s, the Delta was NASA's primary launch vehicle. With the beginning of the Space Shuttle program, U.S. space policy changed, and the Shuttle became the primary launch vehicle. However, after the 1986 Challenger accident, policy again changed and expendable launch vehicles once again were used to launch commercial satellites. The newer, more powerful Delta II began to be used in 1989. In 1995, development of the larger Delta III began, with its first launch occurring in 1998.

Development of the Delta IV family of medium-to-heavy launch vehicles is currently underway, and the first launch of a Delta IV is planned for 2002.