Delta II was an

expendable launch system An expendable launch system (or expendable launch vehicle/ELV) is a launch vehicle that can be launched only once, after which its components are either destroyed during reentry or discarded in space. ELVs typically consist of several rocket sta ...

, originally designed and built by

McDonnell Douglas McDonnell Douglas was a major American aerospace manufacturing corporation and defense contractor, formed by the merger of McDonnell Aircraft and the Douglas Aircraft Company in 1967. Between then and its own merger with Boeing in 1997, it produ ...

. Delta II was part of the Delta rocket family and entered service in 1989. Delta II vehicles included the Delta 6000, and the two later Delta 7000 variants ("Light" and "Heavy"). The rocket flew its final mission

ICESat-2 ICESat-2 (Ice, Cloud, and land Elevation Satellite 2), part of NASA's Earth Observing System, is a satellite mission for measuring ice sheet elevation and sea ice thickness, as well as land topography, vegetation characteristics, and clouds. ICES ...

on 15 September 2018, earning the launch vehicle a streak of 100 successful missions in a row, with the last failure being GPS IIR-1 in 1997.

History

In the early 1980s, all United States

expendable launch vehicles An expendable launch system (or expendable launch vehicle/ELV) is a launch vehicle that can be launched only once, after which its components are either destroyed during reentry or discarded in space. ELVs typically consist of several rocket sta ...

were planned to be phased out in favor of the

Space Shuttle The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program na ...

, which would be responsible for all government and commercial launches. Production of Delta, Atlas-Centaur, and Titan 34D had ended. The ''Challenger'' disaster of 1986 and the subsequent halt of Shuttle operations changed this policy, and President

Ronald Reagan Ronald Wilson Reagan ( ; February 6, 1911June 5, 2004) was an American politician, actor, and union leader who served as the 40th president of the United States from 1981 to 1989. He also served as the 33rd governor of California from 1967 ...

announced in December 1986 that the Space Shuttle would no longer launch commercial payloads, and

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...

would seek to purchase launches on expendable vehicles for missions that did not require crew or Shuttle support. McDonnell Douglas, at that time the manufacturer of the Delta family, signed a contract with the U.S. Air Force in 1987 to provide seven Delta II. These were intended to launch a series of

Global Positioning System The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite sy ...

(GPS)

Block II Block or blocked may refer to: Arts, entertainment and media Broadcasting * Block programming, the result of a programming strategy in broadcasting * W242BX, a radio station licensed to Greenville, South Carolina, United States known as ''96.3 ...

satellites, which had previously been manifested for the

. The Air Force exercised additional contract options in 1988, expanding this order to 20 vehicles, and NASA purchased its first Delta II in 1990 for the launch of three Earth-observing satellites. The first Delta II launch occurred on 14 February 1989, with a Delta 6925 boosting the first GPS Block II satellite (

USA-35 USA-35, also known as Navstar 2-01, GPS II-1 and GPS SVN-14, was an American navigation satellite which formed part of the Global Positioning System. It was the first of nine Block II GPS satellites to be launched, which were the first operation ...

) from Launch Complex 17A (SLC-17A) at

Cape Canaveral , image = cape canaveral.jpg , image_size = 300 , caption = View of Cape Canaveral from space in 1991 , map = Florida#USA , map_width = 300 , type =Cape , map_caption = Location in Florida , location ...

into a high

medium Earth orbit A medium Earth orbit (MEO) is an geocentric orbit, Earth-centered orbit with an altitude above a low Earth orbit (LEO) and below a high Earth orbit (HEO) – between above sea level.

. The first Delta II 7000-series flew on November 26, 1990, replacing the

RS-27 The RS-27 was a liquid-propellant rocket engine developed in 1974 by Rocketdyne to replace the aging Rocketdyne_S-3D, MB-3 in the Delta. Incorporating components of the venerable MB-3 and the H-1 designs, the RS-27 was a modernized version of t ...

engine of the 6000-series with the more powerful

RS-27A The RS-27A is a liquid-fuel rocket engine developed in 1980s by Rocketdyne for use on the first stage of the Delta II and Delta III launch vehicles. It provides of thrust burning RP-1 and LOX in a gas-generator cycle. The engine is a modified ver ...

engine. Additionally, the steel-cased

Castor 4A The Castor family of solid-fuel rocket stages and boosters built by Thiokol (now Northrop Grumman) and used on a variety of launch vehicles. They were initially developed as the second-stage motor of the Scout rocket. The design was based on the ...

solid boosters of the 6000 series were replaced with the composite-cased GEM-40. All further Delta II launches except three were of this upgraded configuration, and the 6000-series was retired in 1992 with the last launch being on July 24. McDonnell Douglas began

Delta III Delta III was an expendable launch vehicle made by Boeing. The vehicle was developed from the highly-successful Delta II to help meet the launch demand of larger satellites. The first Delta III launch was on August 26, 1998. Of its three flights ...

development in the mid-1990s as increasing satellite mass required more powerful launch vehicles. Delta III, with its liquid hydrogen second stage and more powerful GEM-46 boosters, could bring twice as much mass as Delta II to

geostationary transfer orbit A geosynchronous transfer orbit or geostationary transfer orbit (GTO) is a type of geocentric orbit. Satellite, Satellites that are destined for geosynchronous orbit, geosynchronous (GSO) or geostationary orbit (GEO) are (almost) always put into ...

, but a string of two failures and one partial failure, along with the development of the much more powerful

Delta IV Delta IV is a group of five expendable launch systems in the Delta (rocket family), Delta rocket family introduced in the early 2000s. Originally designed by Boeing's Defense, Space and Security division for the National Security Space Launch, ...

, led to the cancellation of the Delta III program. The upgraded boosters would still find use on the Delta II, leading to the Delta II Heavy. On 28 March 2003, the Air Force Space Command began the process of deactivating the Delta II launch facilities and infrastructure at Cape Canaveral once the last of the second-generation GPS satellites were launched. However, in 2008, it instead announced that it would transfer all the Delta II facilities and infrastructure to NASA to support the launch of the Gravity Recovery and Interior Laboratory (GRAIL) in 2011. On 14 December 2006, with the launch of

USA-193 USA-193, also known as NRO Launch 21 (NROL-21 or simply L-21), was a United States military reconnaissance satellite (radar imaging) launched on 14 December 2006. It was the first launch conducted by the United Launch Alliance (ULA). Owned by ...

, was the first launch of the Delta II operated by

United Launch Alliance United Launch Alliance (ULA), legally United Launch Alliance, LLC, is an American spacecraft launch service provider that manufactures and operates a number of rocket vehicles that are capable of launching spacecraft into orbits around Earth, a ...

. The last GPS launch aboard a Delta II, and the final launch from SLC-17A at Cape Canaveral was in 2009. The GRAIL Launch in 2011 marked the last Delta II Heavy launch and the last from Florida. The final five launches would all be from Vandenberg Air Force Base in

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

. On 16 July 2012, NASA selected the Delta II to support the Orbiting Carbon Observatory (OCO-2),

Soil Moisture Active Passive Soil Moisture Active Passive (SMAP) is a NASA environmental monitoring satellite that measures soil moisture across the planet. It is designed to collect a global 'snapshot' of soil moister every 2 to 3 days. With this frequency, changes from spe ...

(SMAP), and Joint Polar Satellite System (JPSS-1 - NOAA-20) missions. This marked the final purchase of Delta II. OCO-2 was launched on 2 July 2014,

(SMAP) was launched on 31 January 2015, and JPSS-1 was launched on 18 November 2017. All three of these launches were placed into orbit from SLC-2 at Vandenberg. The Delta II family launched 155 times. Its only unsuccessful launches were Koreasat 1 in 1995, and GPS IIR-1 in 1997. The Koreasat 1 launch was a partial failure caused by one booster not separating from the first stage, which resulted in the satellite being placed in a lower than intended orbit. By using reserve fuel, it was able to achieve its proper

geosynchronous orbit A geosynchronous orbit (sometimes abbreviated GSO) is an Earth-centered orbit with an orbital period that matches Earth's rotation on its axis, 23 hours, 56 minutes, and 4 seconds (one sidereal day). The synchronization of rotation and orbital ...

and operated for 10 years. The GPS IIR-1 was a total loss as the Delta II exploded 13 seconds after launch. The explosion occurred when a damaged

solid rocket booster A solid rocket booster (SRB) is a large solid propellant motor used to provide thrust in spacecraft launches from initial launch through the first ascent. Many launch vehicles, including the Atlas V, SLS and space shuttle, have used SRBs to give ...

casing ruptured and triggered the vehicle's flight termination system. No one was injured, and the launch pad itself was not seriously impacted, though several cars were destroyed and a few buildings were damaged. In 2007, Delta II completed its 75th consecutive successful launch, surpassing the 74 consecutive successful launches of the Ariane 4. With the launch of

in 2018, Delta II reached 100 consecutive successful launches. While all completed Delta II rockets have launched, many flight-qualified spare parts remain. These spare parts were assembled to create a nearly-complete Delta II, for exhibition in its 7420-3 configuration. The rocket is displayed vertically at the

Kennedy Space Center Visitors Complex The Kennedy Space Center Visitor Complex is the visitor center at NASA's Kennedy Space Center on Merritt Island, Florida. It features exhibits and displays, historic spacecraft and memorabilia, shows, two IMAX theaters, and a range of bus tour ...

, and bears its popular "shark teeth" livery on its fairing, which was painted on past Delta II rockets for the GPS launches.

Vehicle description

The first stage of the Delta II was propelled by a Rocketdyne

main engine burning RP-1 and

liquid oxygen Liquid oxygen—abbreviated LOx, LOX or Lox in the aerospace, submarine and gas industries—is the liquid form of molecular oxygen. It was used as the oxidizer in the first liquid-fueled rocket invented in 1926 by Robert H. Goddard, an applica ...

. This stage was technically referred to as the "Extra-Extended Long Tank Thor", a derivative of the

Thor Thor (; from non, Þórr ) is a prominent god in Germanic paganism. In Norse mythology, he is a hammer-wielding æsir, god associated with lightning, thunder, storms, sacred trees and groves in Germanic paganism and mythology, sacred groves ...

ballistic missile as were all Delta rockets until the

. The RS-27 used on the 6000-series Delta II produced , while the upgraded RS-27A used by the 7000-series produced . The stage was long and wide, weighted over when fueled, and burned for 260 seconds. In addition, two LR101-NA-11 vernier engines provided guidance for the first stage. For additional thrust during launch, the Delta II used solid boosters. For the 6000-series, Delta II used Castor 4A boosters, while the 7000-series used Graphite-Epoxy Motors manufactured by ATK. The vehicle could be flown with three, four, or, most commonly, nine boosters. When three or four boosters were used, all ignited on the ground at launch, while models that used nine boosters would ignite six on the ground, then the remaining three in flight after the burnout and jettison of the first six. The second stage of Delta II was the Delta-K, powered by a restartable

Aerojet Aerojet was an American rocket and missile propulsion manufacturer based primarily in Rancho Cordova, California, with divisions in Redmond, Washington, Orange and Gainesville in Virginia, and Camden, Arkansas. Aerojet was owned by GenCorp. ...

AJ10 The AJ10 is a hypergolic rocket engine manufactured by Aerojet Rocketdyne (previously Aerojet). It has been used to propel the upper stages of several launch vehicles, including the Delta II and Titan III. Variants were and are used as the servic ...

-118K engine burning

hypergolic A hypergolic propellant is a rocket propellant combination used in a rocket engine, whose components spontaneously ignite when they come into contact with each other. The two propellant components usually consist of a fuel and an oxidizer. The ...

Aerozine-50 __NOTOC__ Aerozine 50 is a 50:50 mix by weight of hydrazine and unsymmetrical dimethylhydrazine (UDMH), originally developed in the late 1950s by Aerojet General Corporation as a storable, high-energy, hypergolic fuel for the Titan II ICBM rocket e ...

and . These propellants are highly toxic and corrosive, and once loaded the launch had to occur within approximately 37 days or the stage would have to be refurbished or replaced. This stage also contained a combined

inertial platform An inertial platform, also known as a gyroscopic platform or stabilized platform, is a system using gyroscopes to maintain a platform in a fixed orientation in space despite the movement of the vehicle that it is attached to. These can then be used ...

and

guidance system A guidance system is a virtual or physical device, or a group of devices implementing a controlling the movement of a ship, aircraft, missile, rocket, satellite, or any other moving object. Guidance is the process of calculating the changes in po ...

that controlled all flight events. The Delta-K stage was long and wide, containing up to of propellant, and burned for up to 430 seconds. For low Earth orbit, Delta II was not equipped with a third stage. Payloads bound for higher energy orbits such as GTO or to reach Earth escape velocity for trans-Mars injection or other destinations beyond Earth used a solid propellant third stage. This stage was

spin-stabilized Spin stabilization is the method of stabilizing a satellite or launch vehicle by means of spin, i.e. rotation along the longitudinal axis. The concept originates from ballistics, where the spin is commonly obtain by means of rifling. For most sate ...

and depended on the second stage for proper orientation prior to stage separation, but was sometimes equipped with a nutation control system to maintain proper spin axis. It also included a yo-weight system to induce tumbling in the third stage after payload separation to prevent recontact, or a

yo-yo de-spin A yo-yo de-spin mechanism is a device used to reduce the spin of satellites, typically soon after launch. It consists of two lengths of cable with weights on the ends. The cables are wrapped around the final stage and/or satellite, in the manne ...

mechanism to slow the rotation before payload release.

Naming system

The Delta II family used a four-digit system to generate its technical names: * The first digit was either 6 or 7, denoting the 6000- or 7000-series Delta. * The second digit indicated the number of boosters. Most Delta II rockets flew with 9 boosters, but some flew with 3 or 4. * The third digit was always 2, denoting a second stage with an Aerojet AJ10 engine. Only Deltas prior to the 6000-series used a different engine, the

TR-201 The TR-201 or TR201 is a hypergolic pressure-fed rocket engine used to propel the upper stage of the Delta rocket, referred to as Delta-P, from 1972 to 1988. The rocket engine uses Aerozine 50 as fuel, and as oxidizer. It was developed in the ...

. * The last digit denoted the third stage. 0 denoted no third stage, 5 indicated a Payload Assist Module (PAM) stage with Star 48B solid motor, and 6 indicated a Star 37FM motor. * An H following the four digits denoted that the vehicle used the larger Delta III GEM-46 boosters. The Heavy variant could be launched only from Cape Canaveral (as Vandenberg's pad wasn't modified to handle the larger SRBs), and was retired with the closure of that launch site in 2011. * Numbers and letters following those indicate the type of fairing. -9.5 means that the vehicle had a diameter fairing, -10 means a diameter fairing, and -10L indicates a lengthened diameter fairing. In a few rare circumstances, an 8-foot diameter fairing (from older Delta rockets) was flown, and those vehicles had a -8 designation. For example, a Delta 7925H-10L used an RS-27A, nine GEM-46 boosters, a PAM third stage, and a lengthened diameter fairing. A Delta 6320–9.5 is a two-stage vehicle with an RS-27 first stage engine, three Castor 4A boosters, a diameter fairing, and no third stage.

Launch profile

;

Launch vehicle A launch vehicle or carrier rocket is a rocket designed to carry a payload (spacecraft or satellites) from the Earth's surface to outer space. Most launch vehicles operate from a launch pad, launch pads, supported by a missile launch contro ...

build-up: A Delta II launch vehicle was 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. ; Fueling: It took approximately 20 minutes to load the first stage with of fuel. : At T-45 minutes, fueling completion is confirmed. At T-20 minutes, the FTS pyros are armed. At T-20 minutes and T-4 minutes, there are built in holds. During these holds, final checkouts are performed. At T-11 seconds SRB igniters are armed. Ignition is at T-0.4 seconds. The ascent profile varies between missions. ; SRB staging: If 9 solid rocket boosters were used, only six were ignited at launch. Once the first six were depleted, three air-start motors would ignite and the ground-start motors would separate. The air-start motors had nozzles optimized for high-altitude as they operated mostly in a near-vacuum during the flight profile. : If 3 or 4 boosters were used, all were ignited on the ground and jettisoned at the same time.

Delta II launches

Lancement Spirit fusee Delta IIs 10062003

Notable payloads

Earth-orbiting * GLAST *

Gravity Probe B Gravity Probe B (GP-B) was a satellite-based experiment to test two unverified predictions of general relativity: the geodetic effect and frame-dragging. This was to be accomplished by measuring, very precisely, tiny changes in the direction of ...

* 24 GPS satellites * 60

Iridium Iridium is a chemical element with the symbol Ir and atomic number 77. A very hard, brittle, silvery-white transition metal of the platinum group, it is considered the second-densest naturally occurring metal (after osmium) with a density of ...

satellites *

Kepler space telescope The Kepler space telescope is a disused space telescope launched by NASA in 2009 to discover Earth-sized planets orbiting other stars. Named after astronomer Johannes Kepler, the spacecraft was launched into an Earth-trailing heliocentric orb ...

OSTM/Jason-2 OSTM/Jason-2, or Ocean Surface Topography Mission/Jason-2 satellite, was an international Earth observation satellite, Earth observation satellite altimeter joint mission for sea surface height measurements between NASA and CNES. It was the t ...

* Radarsat-1 * Polar (satellite) * ROSAT * Spitzer Space Telescope (SIRTF) * STSS-ATRR * Swift * THEMIS * USA 193 (NROL-21) *

WIND Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few hou ...

WISE WISE may refer to: Arts, entertainment, and media * WISE (AM), a radio station licensed to Asheville, North Carolina *WISE-FM, a radio station licensed to Wise, Virginia * WISE-TV, a television station licensed to Fort Wayne, Indiana Education * ...

WMAP The Wilkinson Microwave Anisotropy Probe (WMAP), originally known as the Microwave Anisotropy Probe (MAP and Explorer 80), was a NASA spacecraft operating from 2001 to 2010 which measured temperature differences across the sky in the cosmic mic ...

Extra-planetary *

2001 Mars Odyssey ''2001 Mars Odyssey'' is a robotic spacecraft orbiting the planet Mars. The project was developed by NASA, and contracted out to Lockheed Martin, with an expected cost for the entire mission of US$297 million. Its mission is to use spectr ...

CONTOUR Contour may refer to: * Contour (linguistics), a phonetic sound * Pitch contour * Contour (camera system), a 3D digital camera system * Contour, the KDE Plasma 4 interface for tablet devices * Contour line, a curve along which the function has a ...

Dawn Dawn is the time that marks the beginning of twilight before sunrise. It is recognized by the appearance of indirect sunlight being scattered in Earth's atmosphere, when the centre of the Sun's disc has reached 18° below the observer's horizo ...

* '' Deep Impact'' * Deep Space 1 *

Genesis Genesis may refer to: Bible * Book of Genesis, the first book of the biblical scriptures of both Judaism and Christianity, describing the creation of the Earth and of mankind * Genesis creation narrative, the first several chapters of the Book of ...

* GRAIL * Mars Climate Orbiter * Mars Exploration Rovers * Mars Global Surveyor *

Mars Pathfinder ''Mars Pathfinder'' (''MESUR Pathfinder'') is an American robotic spacecraft that landed a base station with a roving probe on Mars in 1997. It consisted of a lander, renamed the Carl Sagan Memorial Station, and a lightweight, wheeled robot ...

Mars Phoenix ''Phoenix'' was an uncrewed space probe that landed on the surface of Mars on May 25, 2008, and operated until November 2, 2008. ''Phoenix'' was operational on Mars for sols ( days). Its instruments were used to assess the local habitability ...

* Mars Polar Lander *

MESSENGER ''MESSENGER'' was a NASA robotic space probe that orbited the planet Mercury between 2011 and 2015, studying Mercury's chemical composition, geology, and magnetic field. The name is a backronym for "Mercury Surface, Space Environment, Geoche ...

* NEAR *

STEREO Stereophonic sound, or more commonly stereo, is a method of sound reproduction that recreates a multi-directional, 3-dimensional audible perspective. This is usually achieved by using two independent audio channels through a configuration ...

The last Delta II launch was the

satellite in September 2018. In 2008, ULA indicated that it had "around half a dozen" unsold Delta II rockets on hand, but ULA CEO Tory Bruno stated in October 2017 that there are no complete, unbooked Delta II rockets left in the ULA inventory; and though there are leftover Delta II parts, there are not enough to build another launch vehicle. The remaining pieces will be used to create a museum piece for the Smithsonian.

Comparable rockets

* Antares * Ariane 4 (retired) *

GSLV Geosynchronous Satellite Launch Vehicle (GSLV) is an expendable launch system operated by the Indian Space Research Organisation (ISRO). GSLV was used in fourteen launches from 2001 to 2021. Even though GSLV Mark III shares the name, it is an ...

* Long March 4B * PSLV * Soyuz * Tsyklon-3 (retired) *

Vega Vega is the brightest star in the northern constellation of Lyra. It has the Bayer designation α Lyrae, which is Latinised to Alpha Lyrae and abbreviated Alpha Lyr or α Lyr. This star is relatively close at only from the Sun, an ...

Space debris

The only person on record ever hit by space debris was hit by a piece of a Delta II rocket. Lottie Williams was exercising in a park in Tulsa on 22 January 1997 when she was hit in the shoulder by a piece of blackened metallic material.

U.S. Space Command United States Space Command (USSPACECOM or SPACECOM) is a unified combatant command of the United States Department of Defense, responsible for military operations in outer space, specifically all operations 100 kilometers (62 miles) and grea ...

confirmed that a used Delta II rocket from the April 1996 launch of the

Midcourse Space Experiment The Midcourse Space Experiment (MSX) is a Ballistic Missile Defense Organization (BMDO) satellite experiment (unmanned space mission) to map bright infrared sources in space. MSX offered the first system demonstration of technology in space t ...

had crashed into the atmosphere 30 minutes earlier. The object tapped her on the shoulder and fell off harmlessly onto the ground. Williams collected the item and NASA tests later showed that the fragment was consistent with the materials of the rocket, and Nicholas Johnson, the agency's chief scientist for orbital debris, believes that she was indeed hit by a piece of the rocket.

References

External links

Delta II page
at Boeing.com

at Skyrocket.de
History of the Delta launch vehicle

Delta II Launch Weather Commit Criteria
{{Navboxes , title = Articles related to Delta II , list= {{United Launch Alliance {{Thor and Delta rockets {{Expendable launch systems {{US launch systems {{USAF space vehicles {{USAF Weapons Boeing spacecraft and space launch systems Delta (rocket family) United Launch Alliance space launch vehicles Vehicles introduced in 1989