A Delta II rocket launches from Cape Canaveral carrying the Dawn spacecraft.
|Manufacturer||United Launch Alliance (Boeing IDS)|
|Country of origin||United States|
|Cost per launch (1987)||US$51 million (7920-10 mod.)|
|Height||38.2 - 39 m (125.3 - 127 ft)|
|Diameter||2.44 m (8 ft)|
|Mass||151,700 - 231,870 kg
(334,300 - 511,180 lb)
|Stages||2 or 3|
|2,700 - 6,100 kg
(5,960 - 13,440 lb)
|900 - 2,170 kg
(1,980 - 4,790 lb)
|1,000 kg (2,200 lb)|
|Launch sites||Cape Canaveral SLC-17
Vandenberg AFB SLC-2W
Delta 6000: 17
Delta 7000: 129
Delta 7000H: 6
Delta 6000: 17
Delta 7000: 127
Delta 7000H: 6
|Failures||1 (Delta 7000)|
|Partial failures||1 (Delta 7000)|
|First flight||Delta 6000: 14 February 1989
Delta 7000: 26 November 1990
Delta 7000H: 8 July 2003
|Last flight||Delta 6000: 24 July 1992
Delta 7000H: 10 September 2011
|Boosters (6000 Series) - Castor 4A|
|Thrust||478.3 kN (107,530 lbf)|
|Specific impulse||266 sec|
|Burn time||56 seconds|
|Boosters (7000 Series) - GEM 40|
|No. boosters||3, 4 or 9|
|Thrust||492.9 kN (110,800 lbf)|
|Specific impulse||274 sec|
|Burn time||64 seconds|
|Boosters (7000 Heavy) - GEM 46|
|Thrust||628.3 kN (141,250 lbf)|
|Specific impulse||278 sec|
|Burn time||75 seconds|
|First stage - Thor/Delta XLT(-C)|
|Engines||1 RS-27 (6000 series) or RS-27A (7000 series)|
|Thrust||1,054.2 kN (237,000 lbf)|
|Specific impulse||302 sec|
|Burn time||265 seconds|
|Second stage - Delta K|
|Thrust||43.6 kN (9,800 lbf)|
|Specific impulse||319 sec|
|Burn time||431 seconds|
|Third stage - PAM-D (optional)|
|Engines||1 Star 48B|
|Thrust||66.0 kN (14,837 lbf)|
|Specific impulse||286 sec|
|Burn time||87 seconds|
Delta II is an American space launch system, originally designed and built by McDonnell Douglas. Delta II is part of the Delta rocket family and entered service in 1989. Delta II vehicles included the Delta 6000, the Delta 7000, and two 7000 variants ("Light" and "Heavy").
After McDonnell Douglas merged with Boeing in 1997, Delta II rockets were built by Boeing Integrated Defense Systems, until Delta rocket production became the responsibility of United Launch Alliance (ULA) on December 1, 2006. ULA now markets Delta II to U.S. government customers, and Boeing Launch Services (BLS) markets Delta II to commercial companies.. Delta II production has ceased; three more launches are scheduled and one additional vehicle remains unsold.
All United States expendable launch vehicles were planned to be phased out in favor of the Space Shuttle. After the Challenger disaster of 1986, President Reagan announced that commercial satellites were to be launched by private industry. A contract to provide 20 launch vehicles for the U. S. Air Force, beginning in 1989, brought Delta back into production with Delta II. Delta II was specifically designed to accommodate the GPS Block II series of positioning satellites. Additionally, the Delta II launched 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, Spirit and MER-B, Opportunity) in 2003
- Mars Phoenix Lander in 2007
Deltas are expendable launch vehicles (ELVs), which means they can only be used once. Each Delta II launch vehicle consists of:
- Stage I: RP-1 and liquid oxygen tanks that feed the Rocketdyne RS-27 main engine for the ascent. The first stage is technically referred to as the "Extra-Extended Long Tank Thor", a derivative of the Thor ballistic missile as were all Delta rockets until the Delta IV.
- Solid rocket booster motors: Used to increase thrust during the initial two minutes of flight. The medium-capacity Delta II has nine motors total (six fire on the ground, three in flight); the other models use only three or four.
- Interstage: A spacer between stage I and stage II. The first friction stir welded interstage module was launched in 1999.
- Stage II: Delta-K stage featuring a restartable hypergolic Aerojet AJ10-118K engine to insert the vehicle-spacecraft stack into low Earth orbit. This propellant mixture is highly corrosive, so once loaded the launch must occur within approximately 37 days, or the stage will have to be refurbished or replaced. This stage also contains the vehicle's "brains", a combined inertial platform and guidance system that controls all flight events.
- Stage III: Optional ATK-Thiokol solid rocket motor for payloads bound for higher energy orbits such as GTO or to reach Earth escape velocity for trans-Mars injection or other destinations beyond Earth. It is connected to the payload until it is done firing, and then separates. This stage is spin-stabilized and depends on the second stage for proper orientation prior to Stage II/III separation, but could be equipped with a nutation control system to maintain proper spin axis. It also includes a yo-weight system to induce tumbling in the third stage after payload separation to prevent recontact, or a yo-yo de-spin mechanism to slow the spin before spacecraft release, as many spacecraft cannot handle the high spin rates needed for stability of this stage.
- Payload fairing: Thin metal or composite payload fairing (aka "nose cone") to protect the spacecraft during the ascent through Earth's atmosphere.
The Delta II family uses a four-digit system to generate its technical names:
- The first digit is either 6 or 7, denoting the 6000- or 7000-series Deltas. The 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-cased Castors. In addition, two LR101-NA-11 vernier engines provide guidance for the first stage.
- The second digit indicates the number of boosters, usually 9. In such cases, six are lit at liftoff and three are lit one minute into flight. On vehicles with 3 or 4 boosters, all are ignited 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 Payload Assist Module (PAM) stage with Star 48B solid motor, 6 indicates a Star 37FM 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 used the larger GEM-46 boosters, originally designed for the Delta III. These are designated 79xxH. The Heavy variant could be launched only from Cape Canaveral, and was retired with the closure of that launch site in 2011.
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.
|This section requires expansion. (May 2011)|
- Launch vehicle build-up
- A Delta II launch vehicle is assembled vertically on the launch pad. Assembly starts by hoisting the first stage into position. The solid rocket boosters are then hoisted into position and mated with the first stage. Launch vehicle build-up then continues with the second stage being hoisted atop the first stage.
- It takes approximately 20 minutes to load the first stage with 37,900 litres (10,000 US gal) of fuel.
Delta II launches
The Delta II system has been used for 152 launches. On September 18, 2007, Delta II completed its 75th consecutive successful launch. This is a record for modern launch vehicles. As of 2012, it is the most reliable launch vehicle in service, which it has been since the presumed retirement of the Tsyklon 2 in 2006. With the launch of OCO-2 in 2014, the Delta II has enjoyed 97 consecutive successful launches. Should the remaining three scheduled launches be successful, the Delta II could achieve 100 consecutive launch successes.
However, the Delta II system does not have a perfect success record. One mission, the launch of Koreasat-1 in 1995, was a partial failure in which the satellite payload was able to compensate when the launch system placed the vehicle in an incorrect orbit.
Another failure, this time complete, occurred on January 17, 1997, when a Delta II 7925 carrying the first GPS Block IIR satellite, GPS IIR-1, exploded only 13 seconds after liftoff, raining flaming debris all over Launch Complex 17 at Cape Canaveral Air Force Station. No one was injured, and the launchpad itself was not seriously damaged, though several cars were destroyed and a few buildings were damaged. It was later determined that a "17-foot crack" in the rocket booster had caused the failure.
- 2001 Mars Odyssey
- Deep Impact
- Deep Space 1
- Gravity Probe B
- Mars Climate Orbiter
- Mars Exploration Rovers
- Mars Global Surveyor
- Mars Pathfinder
- Mars Phoenix
- Mars Polar Lander
- Polar (satellite)
- Spitzer Space Telescope (SIRTF)
- USA 193 (NROL-21)
- Genesis (spacecraft)
A 2007 article published by the Wall Street Journal speculated about the fate of the Delta II launch system after the U.S. Air Force discontinues its use of the Delta II. Thomas Young, who was director of Goddard Space Flight Center from 1980 to 1982, is quoted as saying, "It's definitely an item people are quite worried about."
As of July 2014, three further Delta II launches are scheduled; carrying the SMAP satellite in November 2014 and the JPSS-1 and ICESat-2 satellites in 2017 and 2018. ULA had previously indicated that it had "around half a dozen" unsold Delta II rockets on hand. A spokesperson indicated that ULA will change some aspects of the Delta II system once the current Medium Launch Vehicle 3 contract with the Air Force ends and requirements imposed by the contract are lifted. The Air Force contract required that Delta II be kept ready to launch within 40 days of call up, which led ULA to maintain two launch pads at Cape Canaveral. ULA indicated it would not continue to operate two launch pads.
In August 2009, the NASA assistant associate administrator for the Launch Services Program stated that NASA might purchase additional Delta II launches beyond those it had planned at that time. However on September 30, 2011, NASA modified the NASA Launch Services II (NLS-II) contract to allow for the continuing order of Delta II launchers in agreement with ULA. Components for five additional Delta II vehicles had been built and two now remain unassigned to planned flights. Under the terms of the revised NLS-II contract, only three Delta II configurations are available – the 7320-10, 7420-10 and 7920-10 – and launches are only available from SLC-2W at Vandenberg Air Force Base. ULA has continued to update its product website and continues to state that the vehicle is available for order for commercial or government offices.
On July 16, 2012 NASA selected the Delta II for the launch of Soil Moisture Active Passive (SMAP), Orbiting Carbon Observatory-2 (OCO-2) and Joint Polar Satellite System-1 (JPSS-1) spacecraft. The spacecraft will launch in October 2014, July 2014 and November 2016, respectively, aboard Delta II rockets from Complex 2 at Vandenberg Air Force Base in California.
- United Launch Alliance Transaction completed
- Delta rocket history, Boeing. Accessed 14 June 2008.
- "United Launch Alliance Restructures Delta II Program for Long Term Viability". ULA. January 29, 2008.
- Graham, William (July 2, 2014). "ULA Delta II successfully lofts OCO-2 to orbit". NASASpaceflight.com. Retrieved July 23, 2014.
- "Reagan Orders NASA To Halt Launch of Commercial Payloads". AP. Aug 16, 1986.
- "Mars Surveyor 98 Delta II Launch Vehicle". NASA/JPL.
- "Delta II, Atlas II". U.S. Air Force. May 2003. Retrieved 28 June 2013.
- Dr. Marc D. Rayman (2007-07-15). "DAWN Journal". JPL NASA. Retrieved 2008-09-06.
- "Delta II Payload Planner's Guide 2007". ULA. Retrieved 24 July 2014.
- Forsyth, Kevin S. (2007-08-10). "Vehicle Description and Designations". History of the Delta Launch Vehicle. Retrieved 2008-03-15.
- "Expendable Launch Vehicle Status Report". NASA. June 6, 2007.
- "Swift Launch Pad Activities". 2004-11-18.
- "DigitalGlobe Successfully Launches Worldview-1". DigitalGlobe.
- Ray, Justin. "Mission Status Center (Delta 326)". Spaceflight Now. Retrieved 2007-09-26.
- Space Launch Report - Active Launch Vehicle Reliability Statistics[dead link]
- "Workhorse Delta 2 returns to launch NASA observatory". Spaceflight Now. Retrieved July 2014.
- "Delta II Data Sheet". Space Launch Report. Retrieved 24 July 2014.
- Krebs, Gunter Dirk. "Koreasat 1, 2 (Mugungwha 1, 2) / Europe*Star B".
- "Unmanned rocket explodes after liftoff". CNN.com. 1997-01-17. Retrieved 2009-03-31.
- The Deadly Aftermath of a Rocket Explosion Seconds After Launch
- "Boeing Delta II to Launch New Additions to Iridium Constellation". Boeing.
- Pasztor, Andy (2007-05-29). "Delta II's Fate Worries Nonmilitary Users". WSJ.
- "NASA Selects Launch Services Contract For Three Missions". MarketWatch. 16 July 2012. Retrieved 16 July 2012.
- "NASA Selects Launch Services for ICESat-2 Mission". NASA Kennedy Space Center. 22 February 2013. Retrieved 15 March 2013.
- Berger, Brian (2008-06-30). "Delta 2 Rockets to Remain Competitive Until 2015". Space News.
- Stephen Clark (August 29, 2009). "NASA looking to solve medium-lift conundrum".
- "NASA Launch Services Program Update".
- Ray, Justin. "NASA gives the Delta 2 rocket a new lease on life". SpaceFlightNow. Retrieved 17 July 2012.
- "NASA Launch Services Program".
- "Delta II website".
- "2010 Delta II product card".
- "NASA Selects Launch Services Contract for Three Missions". NASA. 16 July 2012.
Media related to Delta II at Wikimedia Commons
- Delta II page at Boeing.com
- Delta I, II und III launch data at Skyrocket.de
- History of the Delta launch vehicle