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.
|