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The Delta II family of launch vehicles built by Boeing's Integrated Defense Systems division and has been in service since 1989.
All United States expendable launch vehicles were to be phased out for the Space Shuttle, but the Challenger accident restarted Delta development. The Delta II, specifically, was designed to accommodate the GPS Block II series of satellites. Delta IIs have successfully launched 115 projects (through August 2004), including several NASA missions to Mars:
Deltas are expendable launch vehicles (ELVs), which means they are only used once. Each launch vehicle consists of:
Stage I: Kerosene and liquid-oxygen tanks that feed the Rocketdyne RS-27 main engine for the ascent.
Solid rocket booster motors: Used to increase thrust during the initial two minutes of flight. The medium-capacity Delta II has nine motors total; the other models use only three or four.
Stage III: Optional ATK-Thiokol solid rocket motor (some Delta II vehicles are two-stage only, and generally used for Earth-orbit missions) provides the majority of the velocity change needed to leave Earth orbit and inject the spacecraft on a trajectory to Mars; connected to the spacecraft until done firing, then separates. This stage is spin-stabilized and has no active guidance control; it depends on the second stage for proper orientation prior to Stage II/III separation.
Payload fairing: Thin metal or composite payload faring (aka "nose cone") to protect the spacecraft during the ascent through Earth's atmosphere.
The Delta II family is more technically named by a four-digit system:
The first digit is either 6 or 7, denoting the 6000- or 7000-series Deltas. 6000-series, last flown in 1992, had an Extra Extended Long Tank first stage with RS-27 main engine, plus Castor IVA solid rocket boosters. The current model 7000-series have an RS-27A engine, with a longer nozzle for higher expansion ratio and better high-altitude performance, and GEM (Graphite-Epoxy Motor) boosters. GEMs are larger, and have a composite casing to reduce mass versus the steel-case Castors.
The second digit indicates the number of boosters, usually 9. In such cases, six are lit at liftoff, three lit one minute into flight. Vehicles with a 3 or 4, ignite all boosters at liftoff.
The third digit is 2, denoting a second stage with an Aerojet AJ10 engine. This engine is restartable, for complex missions. Only Deltas prior to the 6000-series used a different engine, the TR-201.
The last digit denotes the third stage. 0 denotes no third stage, 5 indicates a PAM (Payload Assist Module) stage with Star 48 solid motor, 6 indicates a Star 37 motor.
For example, a Delta 7925 has the later first stage, nine GEM boosters, and a PAM third stage. A Delta 7320 is a two-stage vehicle with three boosters.
A Delta II-Heavy has the larger GEM-46 boosters, originally designed for the Delta III. These are designated 7xxxH.
Three payload fairings are available. The original aluminum fairing, seen above, is 9.5 feet in diameter. A 10-foot fairing is made of composite, and can be distinguished by its tapering front and rear. A lengthened 10-foot fairing is used for the largest payloads.
Delta II
Delta II launches
Future Applications
| | Name | Delta II | | image |  | | Caption | A Delta II rocket launches from Cape Canavera... | | Function | Launch vehicle | | Manufacturer | Boeing Boeing Integrated Defense Systems | | Country | USA | | Cpl-year | 1987 | | Cpl | 1987 | | Height | 38.2 - 39 metre | | Alt-height | 125.3 - 127 foot (unit) | | Diameter | 2.44 m | | Alt-diameter | 8 ft | | Mass | 151,700 - 231,870 kg
| | Alt-mass | 334,300 - 511,180 pound (mass) | | Stages | 2 or 3 | | Leo-payload | 5,100 kg | | Payload-location | GTO | | Payload | 5,100 kg | | Payload-location2 | Escape trajectory | | Payload2 | 1,000 kg | | Status | Active | | Sites | Cape Canaveral Air Force Station | | First | Delta 6000: 14 February 1989
Delta 7000: 2... | | Last | Delta 6000: 24 July 1992
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Delta II launches
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Future Applications
The Aerojet-built second-stage engine has been chosen by NASA to be used as the main propulsion engine for the Orion spacecraft that will replace the Space Shuttle after 2010. The engine was chosen due to its restart capabilites along with a switch from the original liquid oxygen/liquid methane (LOX/LCH4) application to hypergolic fuel and oxidizer similar to that in use on the Shuttle's OMS and RCS systems.
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