Delta II

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A Delta II 7925 with the Deep Impact spacecraft on the launch pad
The first stage of a Delta II is erected. The rocket launched the ACE spacecraft .
Assembly of the GEM-40 solid booster on the first stage.
The second stage shortly before its installation.
This picture clearly shows how small the second stage is compared to the first and the boosters of the Delta II Heavy.
In a clean room: on the left the third stage, on the right behind the engineers the two packed STEREO room probes.
The payload fairing of a Delta II Heavy is mounted around the Mercury probe MESSENGER , which is already on the third stage.

The Delta II was an American launch vehicle . The rocket family developed by McDonnell Douglas and later manufactured by Boeing IDS has been in use since November 26, 1990, with an interruption from 2012 to 2013. The last launch took place on September 15, 2018.


Originally, the space shuttle was supposed to replace all American single-use launch vehicles, but after the Challenger disaster , the further development of the Delta rockets was resumed. The Delta II replaced the previously hastily developed Delta-6XXX missiles and compared to them has a slightly increased payload capacity. The Delta II was specially tailored to the payload requirements of the GPS Block II satellites. In the old numerical naming system, the Delta II is the Delta 7XXX. The Delta II has been used 145 times since its maiden flight (September 2009). Except for GPS satellites it was also used in the 1990s to communication satellites to start. However, these have usually been too heavy for the Delta II since the late 1990s. Until August 2009, the GPS satellites continued to launch with Delta II rockets until the last copy of the GPS IIR-M series. In addition, many were scientific satellites and space probes of NASA brought and some other satellites with Delta II rocket into space.

The last flight of the Delta II should take place on October 28, 2011, although five rockets (without solid fuel boosters) were still in stock. Production of the Delta II had already been discontinued beforehand. In July 2012, NASA announced that it would use the Delta II for three more launches, leaving only two missiles in stock without a planned mission. The solid fuel boosters were newly produced according to the respective version.

The stages of Delta II

Delta missiles are single-use missiles, which means they can only fly once. They consist of the following components:

Six boosters of the Delta 7920-8 burn after the start
  • Booster : The boosters consist of a very light carbon fiber housing (hence the name Graphite-Epoxy Motor abbreviated to GEM ) to reduce the empty mass and are filled with solid propellant made of HTPB (hydroxyl-terminated polybutadiene), aluminum, ammonium perchlorate and various additives. They increase the thrust during the initial two minutes of flight. The standard version of the Delta II has nine GEM-40 boosters, but the smaller versions only have three or four. The Delta II Heavy, on the other hand, uses nine of the larger GEM-46 boosters that were taken over from the Delta III , which is no longer built . The GEM-40 boosters have a diameter of 101.6 cm, the GEM-46 boosters 116.8 cm. In the standard and heavy version, six boosters are ignited immediately at take-off and the remaining three in flight just before the first six burn out. In the smaller versions with three or four boosters, all boosters ignite on the ground.
  • 1st stage: A Thor XLT (extra e x tended L ong T ank) with 2.44 m diameter. It contains RP-1 and liquid oxygen tanks that supply fuel to the Rocketdyne- built RS-27A engine. The Thor makes the largest share of the speed gain during the ascent.
  • 2nd stage: A small Delta K in relation to the first stage . Your pressure subsidized fuel and Oxididatortanks provide a wiederzündbares Aerojet -Triebwerk with hyper golem fuel. If the flight goes into near-earth orbit, this stage ignites for a long time, then switches off and flies with the satellite in an elliptical park orbit almost half the earth without propulsion. Then it ignites in the apogee of the park's orbit for the second time (shorter) and brings itself and the satellite into an almost circular orbit at this altitude. Then she suspends the satellite. Finally it moves away from the satellite and ignites for the third time after another half orbit around the earth. This ignition counter to the direction of flight is one hand to bring the second stage in an elliptical orbit with the lowest possible perigee to step out soon burn up to let other hand, all of the fuel to be consumed, so that the stage can not explode by the fuel residues. However, if the flight goes into a high earth orbit or an escape path to another planet, the second stage ignites for a long time, switches off, and flies with the satellite almost halfway around the earth without propulsion. Then it ignites a second time (shorter) until the airspeed planned for this point in time is reached. Now it releases the third stage with the payload sitting on it in the precisely specified spatial orientation. The second stage contains the control system of the Delta II, an inertial navigation system and the flight control computer.
  • 3rd stage: Is an optional solid rocket motor from ATK-Thiokol. It provides most of the speed change for exiting the parking orbit so that the payload can reach higher earth orbits or escape paths. Then the third stage is separated. The stage is spin stabilized and has no control systems for changing course or position. The step is aligned by the second step prior to launch.

The members of the Delta II rocket family and designation system

The individual members of the Delta II rocket family are identified by a four-digit number code:

  • The first digit: 7 denotes the 7000 series of the Delta. This series has an Extra Extended Long Tank Thor first stage with an RS-27A engine, with a longer thrust nozzle than the RS-27 engine of the Delta 6000 series. The longer nozzle provides greater expansion and higher thrust at high altitudes. The GEM-40 boosters are larger than the Castor 4A and 4B boosters of the Delta 6000 series. Their composite shell is also lighter than the steel shell of the Castor booster.
  • The second digit: indicates the number of boosters. Normally with nine boosters, six ignite when taking off and three after one minute of flight time (when the first six are already burned out). In versions with only three or four boosters, all boosters ignite when you take off.
  • The third digit: a 2 denotes the second stage Delta K with an Aerojet AJ10 engine. The engine can be re-ignited.
  • The fourth digit: Stands for the third level. 0 means there is no third stage, 5 stands for the PAM-D stage (Payload Assist Module) with a Star 48 solid motor and 6 stands for a Star 37 solid motor. The Star 37 engine is smaller and weaker than the Star 48 engine and was only used for launching particularly light space probes (and a satellite), which since the failure of the " Faster - Better - Cheaper " , which was strongly designed to reduce costs, Concept can no longer be built.
  • H: stands after the four-digit code if it is a Delta II Heavy. The Delta II Heavy uses larger GEM-46 boosters instead of the GEM-40 booster. These increase the take-off weight enormously, but at the same time only increase the payload slightly. The Delta Heavy is more expensive than a standard Delta II and is only used when the payload is a bit too heavy for the normal Delta II, but a larger type of missile is not yet economically viable. So far (July 2009) there are heavy versions with only nine boosters, the version names are 7925H and 7920H.

Examples: A Delta 7925 has the Thor XLT first stage with RS-27A engine, nine GEM-40 boosters, and the PAM as the third stage. A Delta 7320 is a small version with three boosters and no 3rd stage.

There are currently three payload fairings to choose from. Originally there was a smaller and another very large payload fairing.

  • The smallest, 8 feet in diameter, is the same diameter as the Delta and is no longer used. With it, the Delta II rocket had a constant diameter throughout. For them -8 was added to the name.
  • The next larger payload fairing is 2.9 m (9.5 feet) in diameter. It is made of aluminum. It is most commonly used as the standard payload fairing. For them either -9.5 is added to the name or the appendix is ​​omitted.
  • Then there are three payload fairings that are 10 feet in diameter. Two of them are made of a composite material . Depending on the payload, they are available as normal and long versions. For them, -10C is added to the name for the short version and -10L for the long version. Instead of the two payload fairings of different lengths, the Delta II first used a 10-foot metal payload fairing taken over from the Delta 6XXX. This is no longer used today. For them, they just added -10 to their name. Each version of the Delta-II can be equipped with any of the three available payload fairings.

For double launches, there are also two double launch devices of different lengths, inside of which one satellite has space while the other sits on it. The double launch device is always located inside a three-meter payload fairing.

An example of a complete designation: Delta 7925H-9.5

Launch ramps

The Delta II rocket carries the two GRAIL probes to their lunar mission

Delta II missiles, which put payloads into orbits with inclinations between 28 ° and 57 °, launched in Cape Canaveral , from Launch Complex 17 , which has two launch pads, 17A and 17B. However, only starting position 17B was suitable for the Delta II Heavy. Delta II rockets with payloads that had to reach orbits between 56 ° and 104 ° inclination are launched from the Space Launch Complex 2W (SLC-2W) at Vandenberg Air Force Base , California.

Some known payloads of the Delta II

Delta II start list (incomplete)

Start date
( UTC )
Type Ser.-No. Launch site Payload¹ Type of payload Orbit² Remarks
... ... ... ... ... ... ...
July 3, 2002 Delta II 7425-9.5 D-292 CC SLC-17A CONTOUR Comet probe Escape route Success  (probe later exploded in space)
January 12, 2003 Delta II 7320-10C D-294 VAFB SLC-2W ICESat , CHIPSat Earth observation satellite and astronomy satellite SSO success
January 29, 2003 Delta II 7925-9.5 D-295 CC SLC-17B GPS IIR-8, XSS 10 Military navigation satellite, technology testing satellite Transfer orbit to the GPS orbit success
March 31, 2003 Delta II 7925-9.5 D-297 CC SLC-17A GPS IIR-9 Military navigation satellite Transfer orbit to the GPS orbit success
June 10, 2003 Delta II 7925-9.5 D-298 CC SLC-17A Spirit (MER-A) Mars rover Escape route success
July 7, 2003 Delta II 7925H-9.5 D-299 CC SLC-17B Opportunity (MER-B) Mars rover Escape route success
August 25, 2003 Delta II 7920H-9.5 D-300 CC SLC-17B Spitzer Space Telescope (SIRTF) Space telescope Solar orbit success
December 21, 2003 Delta II 7925-9.5 D-302 CC SLC-17A GPS IIR-10 Military navigation satellite Transfer orbit to the GPS orbit success
March 20, 2004 Delta II 7925-9.5 D-303 CC SLC-17B GPS IIR-11 Military navigation satellite Transfer orbit to the GPS orbit success
April 20, 2004 Delta II 7920-10C D-304 VAFB SLC-2W Gravity Probe B Research satellite to review the general theory of relativity Polar orbit success
June 23, 2004 Delta II 7925-9.5 D-305 CC SLC-17B GPS IIR-12 Military navigation satellite Transfer orbit to the GPS orbit success
July 15, 2004 Delta II 7920-10L D-306 VAFB SLC-2W aura Earth observation satellite for monitoring the earth's atmosphere SSO success
August 3, 2004 Delta II 7925H-9.5 D-307 CC SLC-17B MESSENGER Mercury orbiter Escape route success
November 6, 2004 Delta II 7925-9.5 D-308 CC SLC-17B GPS IIR-13 Military navigation satellite Transfer orbit to the GPS orbit success
November 20, 2004 Delta II 7320-10C D-309 CC SLC-17A Swift Gamma ray satellite LEO success
January 12, 2005 Delta II 7925-9.5 D-311 CC SLC-17B Deep impact Comet probe Escape route success
May 20, 2005 Delta II 7320-10C D-312 VAFB SLC-2W NOAA-N Weather satellite SSO success
September 26, 2005 Delta II 7925-9.5 D-313 CC SLC-17A GPS IIR-M1 Military navigation satellite Transfer orbit to the GPS orbit success
April 28, 2006
10:02 am
Delta II 7420-10C D-314 VAFB SLC-2W CALIPSO , CloudSat Two satellites for exploring the earth's atmosphere SSO Success at the 7th start attempt
June 21, 2006
Delta II 7925-9.5 D-316 CC SLC-17A MiTEx Two military mini satellites with a fourth stage rocket GTO success
September 25, 2006
6:50 pm
Delta II 7925-9.5 D-318 CC SLC-17A GPS IIR-M2 Military navigation satellite Transfer orbit to the GPS orbit success
October 26, 2006
12:52 am
Delta II 7925-10L D-319 CC SLC-17B STEREO A and B Two solar observatories HEO with apogee at about 400,000 km altitude success
November 17, 2006
7:12 pm
Delta II 7925-9.5 D-321 CC SLC-17A GPS IIR-M3 Military navigation satellite Transfer orbit to the GPS orbit success
December 14, 2006
9:00 p.m.
Delta II 7920-10C D-322 VAFB SLC-2W NRO-L 21 (USA 193) Secret spy satellite LEO success
February 17, 2007
11:01 PM
Delta II 7925-10C D-323 CC SLC-17B THEMIS Five magnetospheric satellites HEO , perigee at 64,000 km and apogee at 190,000 km success
June 8, 2007
2:34 am
Delta II 7420-10C D-324 VAFB SLC-2W COSMO 1 Commercially. Military radar satellite SSO success
August 4, 2007
9:26 am
Delta II 7925-9.5 D-325 CC SLC-17A Phoenix Mars lander Escape route success
September 18, 2007
6:35 pm
Delta II 7920-10C D-326 VAFB SLC-2W WorldView-1 Commercial Earth Observation Satellite SSO success
September 27, 2007
11:34 am
Delta II 7925H-9.5 C-327 CC SLC-17B Dawn Probe to Vesta and Ceres Escape route success
October 17, 2007
12:23 PM
Delta II 7925-9.5 D-328 CC SLC-17 GPS IIR-M4 Military navigation satellite Transfer orbit to the GPS orbit success
December 9, 2007
2:31 am
Delta II 7420-10C D-330 VAFB SLC-2W COSMO 2 Italian X-band radar earth observation satellite SSO success
December 20, 2007
8:04 p.m.
Delta II 7925-9.5 D-331 CC SLC-17A GPS IIR-M5 Military navigation satellite Transfer orbit to the GPS orbit success
March 15, 2008
6:10 am
Delta II 7925-9.5 D-332 CC SLC-17A GPS IIR-M6 Military navigation satellite Transfer orbit to the GPS orbit success
June 11, 2008
4:05 pm
Delta II 7920H-10C D-333 CC SLC-17B GLAST Gamma ray observatory 565 km high circular orbit with 28.5 ° inclination to the equator success
June 20, 2008
7:46 am
Delta II 7420-10C D-334 VAFB SLC-2W Jason 2 Ocean floor mapping satellite SSO? success
September 6, 2008
Delta II 7420-10C D-335 VAFB SLC-2W GeoEye Earth observation satellite SSO success
October 25, 2008
2:28 am
Delta II 7420-10C D-336 VAFB SLC-2 COSMO 3 Earth observation satellite SSO success
February 6, 2009
10:22 am
Delta II 7420-10C D-338 VAFB SLC-2W NOAA N '(NOAA 19) Weather satellite SSO success
March 7, 2009
3:49 am
Delta II 7925-10L D-339 CC SLC-17B Kepler Space telescope Solar orbit success
March 24, 2009
8:34 am
Delta II 7925-9.5 D-340 CC SLC-17A GPS IIR-M7 Military navigation satellite Transfer orbit to the GPS orbit success
May 5, 2009
8:24 PM
Delta II 7920-10C D-341 VAFB SLC-2W STSS-ATRR formerly Block 2010 Risk Reduction Spacecraft Technology satellite lower polar orbit success
August 17, 2009
10:35 am
Delta II 7925-9.5 D-343 CC SLC-17A GPS IIR-M8 Military navigation satellite Transfer orbit to the GPS orbit success
September 25, 2009
12:20 pm
Delta II 7920-10C D-344 CC SLC-17B STSS demo Two satellites to test the detection of missile defense LEO success
October 8, 2009
6:51 p.m.
Delta II 7920-10C D-345 VAFB SLC-2W WorldView 2 Commercial Earth Observation Satellite LEO success
December 14, 2009 Delta II 7320-10C D-347 VAFB SLC-2W WISE Space telescope SSO success
November 6, 2010
2:20 am
7420-10C D-350 VAFB SLC-2W COSMO-Skymed 4 Earth observation satellite SSO success
June 10, 2011
2:20 pm
7320-10C D354 VAFB SLC-2W SAC-D Argentine Earth Observation Satellite LEO success
September 10, 2011
1:08 pm
7920H-10C D-356 CC SLC-17B GRAIL Lunar probe Lunar orbit success
October 28, 2011
9:48 am
7920-10C D-357 VAFB SLC-2W NPOESS Preparatory Project Earth observation satellite LEO success
July 2, 2014
9:56 am
7320-10C D-367 VAFB SLC-2W OCO-2 Research satellite SSO success
January 31, 2015
2:22 pm
7320-10C D-370 VAFB SLC-2W SMAP , FIREBIRD II-A , FIREBIRD II-B , GRIFEX , ExoCube Earth observation satellite and four small satellites SSO success
November 18, 2017
9:47 AM
7920-10C D-378 VAFB SLC-2W JPSS-1 Weather satellite SSO success
September 15, 2018
7420-10C D-381 VAFB SLC-2W ICESat-2 Earth observation satellite LEO (polar) Success  (last start of Delta II)

¹ The payloads are shown as they were placed one above the other or (in rare cases) next to each other in the payload fairing. The top payload first, then the second from the top, etc.

² NOT necessarily the target orbit of the payload - but the path on which the payload was deployed by the upper stage.

Web links

Commons : Delta II  - album with pictures, videos and audio files

Individual evidence

  1. a b Stephen Clark: Firefly's commercial satellite launcher to use Delta 2 pad at Vandenberg. In: Spaceflight Now. May 2, 2018, accessed May 3, 2018 .
  2. ^ Daniel Maurat, Klaus Donath: NPP started successfully - end of an era., October 28, 2011, accessed on October 28, 2011 : “The Delta II is no longer in production and there are currently no more planned launches. There are also only stored components for a maximum of five rockets. "
  3. Justin Ray: NASA gives the Delta 2 rocket a new lease on life. Spaceflight Now, July 16, 2012, accessed July 17, 2012 .
  4. ^ Launch Vehicle. NASA, October 4, 2011, accessed on October 28, 2011 (English): "SLC-17B is the only one of the two that can accommodate the larger Delta II 7925H."
  5. United Launch Alliance Successfully Launches Final Delta II Rocket with NASA's ICESat-2. Retrieved September 22, 2018 .