From Wikipedia, the free encyclopedia
A Delta II rocket launches from Cape Canaveral
carrying the Dawn spacecraft.
||United Launch Alliance (Boeing IDS)
|Country of origin
|Cost per launch (1987)
||38.2 - 39 m (125.3 - 127 ft)
||2.44 m (8 ft)
||151,700 - 231,870 kg
(334,300 - 511,180 lb)
||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)
||Cape Canaveral SLC-17
Vandenberg AFB SLC-2W
Delta 6000: 17
Delta 7000: 123
Delta 7000H: 5
Delta 6000: 17
Delta 7000: 121
Delta 7000H: 5
||1 (Delta 7000)
||1 (Delta 7000)
||Delta 6000: 14 February 1989
Delta 7000: 26 November 1990
Delta 7000H: 8 July 2003
||Delta 6000: 24 July 1992
Boosters (6000 Series) - Castor 4A
||3, 4 or 9
Boosters (7000 Series) - GEM 40
||3, 4 or 9
Boosters (7000 Heavy) - GEM 46
stage - Thor/Delta XLT-C
stage - Delta K
||43.6 kN (9,800 lbf)
stage - PAM-D (optional)
||66.0 kN (14,837 lbf)
Delta II is a space launch system
originally designed and built by McDonnell Douglas. Delta II is part
of the Delta rocket family and has been in service
since 1989. Delta II vehicles include the retired Delta 6000, the
active Delta 7000, and two 7000 variants (light and heavy).
Delta II rockets were later 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.
All United States expendable launch vehicles were to be phased
out for the Space
Shuttle, but in 1986 the Challenger
accident restarted Delta development. The Delta II was
specifically designed to accommodate the GPS Block II series of satellites. Delta
IIs have successfully launched 125 projects (through August 2007),
including several NASA missions to
Delta II manufacturing, assembly and integration currently take
place in Decatur, Alabama; Harlingen,
Texas; San Diego,
California; and Denver,
Deltas are expendable
launch vehicles (ELVs), which means they are used only 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
- 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
- Interstage: A spacer between stage I and stage II.
- Stage II: Fuel and oxidizer tanks feeding a restartable, hypergolic Aerojet AJ10-118K engine that fires one or more
times to insert the vehicle-spacecraft stack into low Earth
orbit. This propellant mixture is highly corrosive and 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 (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
or other target beyond Earth orbit. It is connected to the
spacecraft until it is done firing, and 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. It also includes 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
- Naming system
The Delta II family is more technically named by a four-digit
- 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-case 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 has the larger GEM-46 boosters, originally
designed for the Delta III. These
are designated 79xxH.
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
- 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
10,000 US gallons (37,900 L) of fuel.
The Delta II system has been used for 146 launches. On September
18, 2007, Delta II completed its 75th consecutive successful
launch. This is
a record for modern launch vehicles. It is
the most reliable launch vehicle currently in service, behind the
(now retired) Tsyklon 2. Eight
launches took place in 2007.
However, the Delta II system does not have a perfect success
record. One mission, the launch of Koreasat-1, 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.
A third partial failure was an Iridium payload 77, which was "in
pieces" in orbit after launch (according to Don Gillies, Payload
Systems Engineer) in September 1998.
Between May 1997 and November 1998 Delta II vehicles placed 55
Iridium satellites into orbit.
Comparison of standard vs. heavy Delta II
An article published by the Wall Street
Journal speculates about the fate of the Delta II launch
system after U.S. Air Force discontinues its use of the Delta
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."
The final payload currently scheduled for Delta II is a NASA
moon mission in 2011. ULA
has indicated it has "around half a dozen" unsold Delta II rockets
A spokesperson indicated 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
launch services indicated NASA might purchase additional Delta II
launches beyond those it currently has planned. Seven
Delta II flights are planned through 2011. Five additional Delta II
vehicles have been built but remain unassigned to planned
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
Shuttle after 2010. The engine was chosen due to its restart
capabilities 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.
United Launch Alliance
Delta rocket history,
Boeing. Accessed 14 June 2008.
- ^ a
"United Launch Alliance
Restructures Delta II Program for Long Term Viability". ULA.
January 29, 2008. http://www.ulalaunch.com/news_deltaIIProgramDirector.html.
Dr. Marc D. Rayman (2007-07-15). "DAWN Journal". JPL
NASA. http://dawn.jpl.nasa.gov/mission/journal_7_15_07.asp. Retrieved
Forsyth, Kevin S. (2007-08-10). "Vehicle Description and
Designations". History of the Delta Launch
Vehicle. http://kevinforsyth.net/delta/vehicle.htm. Retrieved
"Expendable Launch Vehicle
Status Report". NASA. June 6, 2007. http://www.nasa.gov/centers/kennedy/launchingrockets/status/2007/elvstatus-20070606.html.
"Swift Launch Pad
Activities". 2004-11-18. http://www.nasa.gov/mission_pages/swift/launch/pad.html.
Launches Worldview-1". DigitalGlobe. http://media.digitalglobe.com/index.php?s=press_release_popup&item=135.
Ray, Justin. "Mission Status Center (Delta
326)". Spaceflight Now. http://www.spaceflightnow.com/delta/d326/status.html. Retrieved
Space Launch Report - Active
Launch Vehicle Reliability Statistics
Krebs, Gunter Dirk. "Koreasat 1, 2 (Mugungwha 1,
2) / Europe*Star B". http://www.skyrocket.de/space/doc_sdat/koreasat-1.htm.
"Unmanned rocket explodes
after liftoff". CNN.com. 1997-01-17. http://www.cnn.com/TECH/9701/17/rocket.explosion/index.html. Retrieved
"Iridium 77 Not in
Service". http://www.astronautix.com/project/iridium.htm. Retrieved
"Boeing Delta II to Launch New
Additions to Iridium Constellation". Boeing. http://www.boeing.com/news/releases/2002/q1/nr_020205s.html.
"Delta II's Fate Worries
Nonmilitary Users". WSJ. http://online.wsj.com/article/SB118039764439516631.html?mod=googlenews_wsj.
"Launch team packs rockets'
timetable". Florida Today. 2008-05-25.
http://www.floridatoday.com/apps/pbcs.dll/article?AID=/20080525/BUSINESS/805250328/1007/news02. Retrieved 2008-06-09.
"United Launch Alliance piled up a half-dozen new payloads for
Atlas and Delta rockets during the first half of the year,
including a NASA moon mission that will extend Delta 2 launch
- ^ a
Berger, Brian (2008-06-30). "Delta 2 Rockets to Remain
Competitive Until 2015". Space News. http://www.space.com/businesstechnology/080630-busmon-delta-2.html.
Stephen Clark (August 29, 2009). "NASA looking to solve
medium-lift conundrum". http://www.spaceflightnow.com/news/n0908/29mediumlift/.