| Delta Family | |
|---|---|
 | |
 Delta II through Delta IV | |
| General information | |
| Type | Expendable launch system |
| Manufacturer |
|
| Status | Out of service |
| History | |
| Introduction date | 13 May 1960 (Echo 1) |
| First flight | May 13, 1960; 65 years ago (1960-05-13) |
| Retired | 9 April 2024 (NROL-70) |
TheDelta rocket family was a versatile range of Americanrocket-poweredexpendable launch systems that provided space launch capability in the United States from 1960 to 2024. Japan also launched license-built derivatives (N-I,N-II, andH-I) from 1975 to 1992. More than 300 Delta rockets were launched with a 95% success rate. The series was phased out in favor of theVulcan Centaur, with theDelta IV Heavy rocket's last launch occurring on April 9, 2024.[1]
The original Delta rockets used a modified version of thePGM-17 Thor, the firstballistic missile deployed by theUnited States Air Force (USAF), as theirfirst stage. The Thor had been designed in the mid-1950s to reach Moscow from bases in Britain or similar allied nations, and the first wholly successful Thor launch had occurred in September 1957. Subsequentsatellite andspace probe flights soon followed, using a Thor first stage with several different upper stages. The fourth upper-stage combination of the Thor was named the Thor "Delta", reflecting the fourth letter of the Greek alphabet. Eventually the entire Thor–Delta launch vehicle came to be called simply "Delta".[2][3]NASA intended Delta as "an interim general-purpose vehicle" to be "used forcommunication,meteorological, andscientific satellites andlunar probes during 1960 and 1961". The plan was to replace Delta with other rocket designs when they came on-line. The Delta design emphasized reliability rather than performance by replacing components that had caused problems on earlier Thor flights; in particular, the trouble-proneinertial guidance package made byAC Spark Plug was replaced by a radio ground guidance system, which was mounted to the second stage instead of the first. NASA made the original Delta contract to theDouglas Aircraft Company in April 1959 for 12 vehicles of this design:[citation needed]
These vehicles would be able to place 290 kg (640 lb) into a 240 to 370 km (150 to 230 mi)LEO or 45 kg (99 lb) intoGTO. Eleven of the twelve initial Delta flights were successful, and until 1968, no failures occurred in the first two minutes of launch. The high degree of success achieved by Delta stood in contrast to the numerous West Coast Thor failures. The total project development and launch cost came to US$43 million, US$3 million over budget. An order for 14 more vehicles was made before 1962.[citation needed]
TheDelta A used the MB-3 Block II engine, with 170,000 lbf (760 kN) of thrust versus 152,000 lbf (680 kN) for the Block I.[4][5]
13. 2 October 1962 –Explorer 14 (EPE-B).
14. 27 October 1962 –Explorer 15 (EPE-C).
TheDelta B introduced the upgradedAJ10-118D upper stage, a three-foot propellant tank extension, higher-energy oxidizer, and solid-state guidance system. With the Delta B the Delta program went from "interim" to "operational" status. Delta B could launch 200 lb (91 kg) to GTO.[5]
15. 13 December 1962.Relay 1, second NASA communications satellite, the NASAcommunications satellite first active one.
16. 13 February 1963. Pad 17B.Syncom 1;Thiokol CorporationStar-13B solid rocket asapogee motor.
20. 26 July 1963.Syncom 2; geosynchronous orbit, but inclined 33.0° due to the limited performance of the Delta rocket.
ForDelta C, the third stage Altair was replaced with Altair 2. The Altair 2 had been developed as theABL X-258 for theScout vehicle and was 3 in (76 mm) longer, 10% heavier, and with 65% more total thrust.OSO 4 is an example of a Delta C launch.[citation needed]
Delta D, also known as Thrust Augmented Delta, was a Delta C with the Thrust Augmented Thor core plus threeCastor 1 boosters.[citation needed]
25. 19 August 1964.Syncom 3, the firstgeostationarycommunications satellite.
30. 6 April 1965.Intelsat I.
FirstDelta E: 6 November 1965; launchedGEOS 1[citation needed]
This launch vehicle was not built.[6]
TheDelta G was a Delta E without the third stage. The two-stage vehicle was used for two launches:Biosatellite 1 on 14 December 1966 andBiosatellite 2 on 7 September 1967.[4]
TheDelta J used a larger ThiokolStar 37D motor as the third stage and was launched once on 4 July 1968 withExplorer 38.[4]
This launch vehicle was not built.[6]
TheDelta L introduced the Extended Long Tank first stage with a uniform 2.4 m (7 ft 10 in) diameter and used theUnited Technologies FW-4D motor as a third stage.[citation needed]
TheDelta M first stage consisted of a Long Tank Thor with MB-3-3 engine augmented with threeCastor 2 boosters. The Delta E was the second stage, with aStar 37D (Burner 2) third stage/apogee kick motor. There were 12 successful Delta M launches from 1968 until 1971.[7]
TheDelta N combined a Long Tank Thor (MB-3-3 engine) first stage augmented with threeCastor 2 boosters and a Delta E second stage. There were six successful Delta N launches from 1968 until 1972.[8]
The "Super Six" was a Delta M or Delta N with three additionalCastor 2 boosters for a total of six, which was the maximum that could be accommodated. These were respectively designatedDelta M6 orDelta N6. The first and only launch of the M6 configuration wasExplorer 43 (IMP-H, Magnetospheric research) on 13 March 1971.[9] Three launches of the N6 between 1970 and 1971 resulted in one failure.[10]
TheDelta 0100 series was the first stage of the initial numbered Delta was the Long Tank Thor, a version of theThor missile with extended propellant tanks. Up to nine strap-onsolid rocket boosters (SRBs) could be fitted. With three SRBs, the Delta was designated a 300 series, while the nine SRB variant was designated the 900 series. A new and improved Delta F second stage using the higher-thrust AerojetAJ 10-118F engine was also introduced. The first 900 series launch was the fourth Delta 0100.[citation needed] On 23 July 1972, Thor-Delta 904 launchedLandsat 1.[11] A license-built version of the Long Tank Thor stage with the MB-3 engine was also used for the JapaneseN-I launch vehicle.
TheDelta 1000 series was nicknamed theStraight-Eight and combined an Extended Long Tank first stage with an 8 ft-diameter (2.4 m) payload fairing, up to nineCastor 2 SRBs, and the newMcDonnell DouglasDelta P second stage using theTRWTR-201 engine. Payload capacity increased to 1,835 kg (4,045 lb) to LEO or 635 kg (1,400 lb) to GTO.[citation needed] The first successful 1000 series Thor-Delta launchedExplorer 47 on 22 September 1972.[11] The Extended Long Tank Thor stage was also used in the JapaneseN-II andH-I launch vehicles.
TheDelta 2000 introduced the newRocketdyneRS-27 main engine on an Extended Long Tank first stage with the same constant 8-foot diameter. A Delta 2310 was the vehicle for the first three-satellite launch ofNOAA-4,Intasat, andAMSAT-OSCAR 7 on 15 November 1974.[citation needed] Delta 2910 boosters were used to launch bothLandsat 2 in 1975 andLandsat 3 in 1978. On 7 April 1978, a Delta 2914 launched "Yuri 1", the first Japanese BSEBroadcasting Satellite.[12]
TheDelta 3000 combined the same first stage as 1000-series and 2000-series with upgradedCastor 4 solid boosters and was the last Delta series to use theMcDonnell DouglasDelta P second stage withTRWTR-201 engine. Delta 3000 introduced the PAM (Payload Assist Module) /Star 48B solid-fueled kick motor, which was later used as Delta II third stage.[citation needed] The Delta 3914 model was approved for launching United States government payloads in May 1976[11] and was launched 13 times between 1975 and 1987.
TheDelta 4000-series and 5000-series were developed in the aftermath of theChallenger disaster and consisted of a combination of 3000-era and Delta II-era components. The first stage had the MB-3 main engine and Extended Long Tank of the 3000-series and mounted upgradedCastor 4A motors. The new Delta K second stage was also included. A total of three were launched in 1989 and 1990, carrying two operational payloads.[citation needed]
TheDelta 5000 series featured upgradedCastor 4A motors on an Extended Long Tank first stage with the newRS-27 main engine and only launched one mission.[citation needed]
TheDelta II series was developed after the 1986Challenger accident and consisted of the Delta 6000-series and 7000-series, with two variants (Light and Heavy) of the latter.
The Delta 6000-series introduced the Extra Extended Long Tank first stage, which was 12 ft (3.7 m) longer, and theCastor 4A boosters. Six SRBs ignited at takeoff, and three ignited in the air.[citation needed]
The Delta 7000-series introduced theRS-27A main engine, which was modified for efficiency at high altitude at some cost to low-altitude performance, and the lighter and more powerfulGEM-40 solid boosters fromHercules. TheDelta II Med-Lite was a 7000-series with no third stage and fewer strap-ons (often three, sometimes four) that was usually used for small NASA missions. TheDelta II Heavy was a Delta II 792X with the enlargedGEM-46 boosters fromDelta III.[citation needed]
TheDelta III 8000-series was a McDonnell Douglas / Boeing-developed program to keep pace with growing satellite masses:
Of the three Delta III flights, the first two were failures, and the third carried only adummy (inert) payload.
As part of the Air Force'sEvolved Expendable Launch Vehicle (EELV) program,McDonnell Douglas /Boeing proposedDelta IV. As the program name implied, many components and technologies were borrowed from existing launchers. BothBoeing andLockheed Martin were contracted to produce their EELV designs. Delta IVs were produced in a new facility inDecatur, Alabama.
The first stage was referred to as aCommon Booster Core (CBC); aDelta IV Heavy attached two extra CBCs as boosters.
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TheDelta IV Heavy (Delta 9250H) was anexpendableheavy-lift launch vehicle, the largest member of theDelta IV family. Following the retirement of the Space Shuttle in 2011, it was the most capable operational launch vehicle until theFalcon Heavy's debut in 2018. At the time of its retirement in 2024, it ranked third among active rockets in payload capacity.[13][14][15] Developed byBoeing and later manufactured byUnited Launch Alliance (ULA), it first flew in 2004. The Delta IV Heavy was retired after its 16th and final launch on 9 April 2024 and was succeeded by ULA'sVulcan Centaur rocket, which can offer similar heavy-lift capabilities at a lower cost with a single-core and six solid rocket boosters.[16][17]
The vehicle consisted of threeCommon Booster Cores (CBCs), each powered by anRS-68 engine. Two served as strap-on boosters attached to a central core. During ascent, all three engines ignited at liftoff, with the central engine throttling down partway through flight to conserve propellant before throttling up again after booster separation.[18][19]
A distinctive feature of Delta IV Heavy launches was the hydrogen-fueled ignition sequence, which often produced a large fireball that scorched the booster’s exterior surface.[20]From 1969 through 1978 (inclusive), Thor-Delta was NASA's most used launcher, with 84 launch attempts. (Scout was the second-most used vehicle with 32 launches.)[21] Satellites for other government agencies and foreign governments were also launched on a cost-reimbursable basis, totaling 63 satellites. Out of the 84 launch attempts there were 7 failures or partial failures, a 91.6% success rate.[22]
The Delta was a launch success, but it has also been a significant contributor to orbital debris, as a variant used in the 1970s was prone to in-orbit explosions. Eight Delta second stages launched between 1973 and 1981 were involved in fragmentation events between 1973 and 1991 usually within the first 3 years after launch, but others have broken apart 10 or more years later. Studies determined that explosions were caused by propellant left after shutdown. The nature of the propellant and the thermal environment occupied by the derelict rockets made explosions inevitable. Depletion burns were started in 1981, and no fragmentation events for rockets launched after that have been identified. Deltas launched before the 1970s variant have had fragmentation events as long as 50 years after launch.[23]
In 1972,McDonnell Douglas introduced a four-digit numbering system to replace the letter-naming system. The new system could better accommodate the various changes and improvements to Delta rockets and avoided the problem of a rapidly depleting alphabet. The digits specified (1) the tank and main engine type, (2) number ofsolid rocket boosters, (3) second stage (letters in the following table refer to the engine), and (4) third stage:[24]
| Number | First digit (first stage/boosters) | Second digit (number of boosters) | Third digit (second stage) | Fourth digit (third stage) | Letter (Heavy configuration) |
|---|---|---|---|---|---|
| 0 | Long Tank Thor MB-3 engine Castor 2SRBs | No SRBs | Delta F*, withAerojetAJ-10-118F engines. *References upratedAerojet AJ-10-118 engine | No third stage | N/A |
| 1 | Extended Long Tank Thor MB-3 engine Castor 2 SRBs | N/A | Delta P*,Douglas built withTRWTR-201 engines. *Exception:AJ-10-118F engine forAnik-A1 launch.[25] | N/A | |
| 2 | Extended Long Tank Thor RS-27 engine Castor 2 SRBs | 2SRBs (orCBCs in the case of the Delta IV Heavy) | Delta K*, withAJ-10-118K engines. *References uprated Aerojet AJ-10-118 engine | FW-4D (unflown) | |
| 3 | Extended Long Tank Thor RS-27 engine Castor 4 SRBs | 3 SRBs | Delta III cryogenic upper stage,RL-10B-2 engine | Star 37D | |
| 4 | Extended Long Tank Thor MB-3 engine Castor 4A SRBs | 4 SRBs | Delta IV 4m diameter cryogenic upper stage,RL-10B-2 engine | Star 37E | |
| 5 | Extended Long Tank Thor RS-27 engine Castor 4A SRBs | N/A | Delta IV 5 metre diameter cryogenic upper stage,RL-10B-2 engine | Star 48B /PAM-D | |
| 6 | Extra-Extended Long Tank Thor RS-27 engine Castor 4A SRBs | 6 SRBs | N/A | Star 37FM | |
| 7 | Extra-Extended Long Tank Thor RS-27A engine GEM 40 SRBs | N/A | N/A | GEM 46 SRBs | |
| 8 | Strengthened Extra-Extended Long Tank Thor RS-27A engine GEM 46 SRBs | N/A | |||
| 9 | Delta IV Common Booster Core (CBC) RS-68 engine | 9 SRBs | 2 additional CBC parallel first stages |
This numbering system was to have been phased out in favor of a new system that was introduced in 2005.[26] In practice, the new system was never used, as all but theDelta II have been retired:
| Number | First digit (first stage/boosters) | Second digit (number of boosters) | Third digit (second Stage) | Fourth digit (third stage) | Letter (Heavy configuration) |
|---|---|---|---|---|---|
| 0 | N/A | No SRBs | N/A | No third stage | N/A |
| 1 | N/A | N/A | |||
| 2 | Extra-Extended Long Tank Thor RS-27A engine GEM 40 SRBs | 2 SRBs (or LRBs in the case of theDelta IV Heavy) | Delta K, withAJ-10-118K engines | GEM 46 SRBs | |
| 3 | Strengthened Extra-Extended Long Tank Thor RS-27A engine GEM 46 SRBs | 3 SRBs | N/A | ||
| 4 | Delta IV CBC RS-68 engine | 4 SRBs | Delta IV 4 metre diameter cryogenic upper stage,RL-10B-2 engine | 2 additional CBC parallel first stages | |
| 5 | N/A | N/A | Delta IV 5 metre diameter cryogenic upper stage,RL-10B-2 engine | Star 48B /PAM-D | N/A |
| 6 | N/A | Star 37FM | |||
| 7 | N/A | ||||
| 8 | |||||
| 9 | 9 SRBs |
This article incorporates text from this source, which is in thepublic domain. This article incorporates text from this source, which is in thepublic domain. This article incorporates text from this source, which is in thepublic domain.The Falcon Heavy is capable of lifting 140,000 pounds to low Earth orbit, more than any other rocket today.
The ULA Delta 4-Heavy is currently the world's largest rocket, providing the nation with reliable, proven, heavy lift capability for our country's national security payloads from both the east and west coasts.
This article incorporates text from this source, which is in thepublic domain. This article incorporates text from this source, which is in thepublic domain.
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