Delta II

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

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.

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

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

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Delta rocket evolution (U.S. Govt.)
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Delta rocket evolution (U.S. Govt.)
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