Delta II

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A Delta II rocket launches from Cape Canaveral carrying a GPS satellite

The Boeing IDS Delta II family of launch vehicles 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:

Mars Global Surveyor in 1996
Mars Pathfinder in 1996
Mars Climate Orbiter in 1998
Mars Polar Lander in 1999
Mars Odyssey in 2001
Mars Exploration Rovers (MER-A and MER-B) in 2003

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 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 newer Med-Lite models use only three or four.
Stage II: Fuel and oxidizer tanks feeding a restartable, hypergolic Aerojet engine that fires one or more times to insert the vehicle-spacecraft stack into low Earth orbit. This stage also contains the vehicle's "brains", a combined inertial platform and guidance computer that controls all flight events.
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 shroud (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. Med-Lite vehicles, designated 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 Med-Lite 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.

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Launches of Delta II rockets (not complete)

List Date: September 07, 2005

Date	Type	Ser.-No.	Launch Site	Payload	Kind of Payload	Outcome
...	...	...	...	...	...	...
July 3 2002	7425	292	CC LC17A	CONTOUR	Comet probe	Success (payload later failed)
January 12 2003	7320-10	294	VAFB SLC-2W	ICESat, CHIPSat	Earth science satellite, Astronomical satellite	Success
January 29 2003	7925-9.5	295	CC LC17B	GPS IIR-8	Military navigation satellite	Success
March 31 2003	7925-9.5	297	CC LC17A	GPS IIR-9	Military navigation satellite	Success
June 10 2003	7925-9.5	298	CC LC17A	Spirit (MER-A)	Mars rover	Success
July 7 2003	7925H-9.5	299	CC LC17B	Opportunity (MER-B)	Mars rover	Success
August 25 2003	7920H-9.5	300	CC LC17B	Spitzer space telescope (SIRTF)	Infra-red telescope	Success
December 21 2003	7925-9.5	302	CC LC17A	GPS IIR-10	Military navigation satellite	Success
March 20 2004	7925-9.5	303	CC LC17B	GPS IIR-11	Military navigation satellite	Success
April 20 2004	7920-10C	304	VAFB SLC-2W	Gravity Probe B	Science satellite	Success
June 23 2004	7925-9.5	305	CC LC17B	GPS IIR-12	Military navigation satellite	Success
July 15 2004	7920-10L	306	VAFB SLC-2W	Aura	Atmospheric science satellite	Success
August 3 2004	7925H-9.5	307	CC LC17B	MESSENGER	Mercury probe	Success
November 6 2004	7925-9.5	308	CC LC17B	GPS IIR-13	Military navigation satellite	Success
November 20 2004	7320-10C	309	CC LC17A	Swift	Gamma-ray telescope	Success
January 12 2005	7925-9.5	311	CC LC17B	Deep Impact	Comet probe	Success
May 20 2005	7320-10C	312	VAFB SLC-2W	NOAA-N	Weather satellite	Success
September 26 2005	7925-9.5	313	CC LC17A	GPS IIR-M1	Military navigation satellite	Success

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Planned Launches

List Date: September 7, 2005

Date	Type	Serial Num.	Launch Site	Payload	Payload Type	Status
October 26 2005	7420-10C	?	VAFB SLC-2W	CloudSat, CALIPSO	Atmospheric science satellites	Planned
April 11 2006	7925	?	CC LC17	STEREO	Two solar observatories	Planned
June 17 2006	7925H	?	CC LC17	Dawn	Asteroid probe	Planned
October 19 2006	7425-10C	?	CC LC17	THEMIS	Five magnetosphere observatories	Planned