Delta (rocket family)


Delta Family
Delta EELV family.svg
Delta II through Delta IV
Role Expendable launch system with various applications
Manufacturer United Launch Alliance
Introduction 1960
Status active

Delta is an American versatile family of expendable launch systems that has provided space launch capability in the United States since 1960. More than 300 Delta rockets have been launched with a 95% success rate. Only the Delta IV Heavy rocket remains in use as of August 22, 2019. Delta rockets are currently manufactured and launched by the United Launch Alliance.

Delta origins

Delta rocket on display at the Goddard Space Flight Center in Maryland

The original Delta rockets used a modified version of the PGM-17 Thor, the first ballistic missile deployed by the United States Air Force, as their first 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. Subsequent satellite and space probe flights soon followed, using a Thor first stage with several different upper stages. The fourth upper stage used on the Thor was the Thor "Delta," delta being the fourth letter of the Greek alphabet. Eventually the entire Thor-Delta launch vehicle came to be called simply, "Delta."[1][2]

NASA intended Delta as "an interim general purpose vehicle" to be "used for communication, meteorological, and scientific satellites and lunar probes during '60 and '61". The plan was to replace Delta with other rocket designs when they came on-line. From this point onward, the launch vehicle family was split into civilian variants flown from Cape Canaveral which bore the Delta name and military variants flown from Vandenberg Air Force Base which used the more warlike Thor name. The Delta design emphasized reliability rather than performance by replacing components which had caused problems on earlier Thor flights; in particular the trouble-prone inertial guidance package made by AC 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 the Douglas Aircraft Company in April 1959 for 12 vehicles of this design:[citation needed]

  • Stage 1: Modified Thor IRBM with a Block I MB-3 engine producing 152,000 lbf (680 kN) thrust. (LOX/RP1 turbopump, gimbal mounted engine, two verniers for roll control)
  • Stage 2: Modified Able. Pressure fed UDMH/nitric acid powered Aerojet AJ-10-118 engine producing 7,700 lbf (34 kN). This reliable engine cost $4 million to build and is still flying in modified form today. Gas jet attitude control system.
  • Stage 3: Altair. A spin-stabilized (via a turntable on top of the Able) at 100 rpm by two solid rocket motors before separation. One ABL X-248 solid rocket motor provided 2,800 lbf (12 kN) of thrust for 28 seconds. The stage weighed 500 pounds (230 kg) and was largely constructed of wound fiberglass.

These vehicles would be able to place 650 pounds (290 kg) into a 150 to 230 miles (240 to 370 km) LEO or 100 pounds (45 kg) into GTO. 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 endless parade of failures that dogged West Coast Thor launches. The total project development and launch cost came to $43 million, $3 million over budget. An order for 14 more vehicles was made before 1962.[citation needed]

Thor-Delta flights

[citation needed]

No. Date Payload Site Outcome Remarks
1 May 13, 1960 Echo 1 CCAFS LC 17A failure Launch at 9:16 p.m. GMT. Good first stage. Second-stage attitude control system failure. Vehicle destroyed.
2 August 12, 1960 Echo 1A success Payload placed into 1,035 miles (1,666 km), 47 degree inclination orbit.
3 November 23, 1960 TIROS-2 success
4 March 25, 1961 Explorer-10 success 78 pounds (35 kg) payload placed into elliptical 138,000 miles (222,000 km) orbit.
5 July 12, 1961 TIROS-3 success
6 August 16, 1961 Explorer-12 success Energetic Particle Explorers. EPE-A.[3] Highly elliptical orbit.
7 February 8, 1962 TIROS-4 success
8 March 7, 1962 OSO-1 success Orbiting Solar Observatory. 345 miles (555 km), 33 degree orbit.
9 April 26, 1962 Ariel 1 success Ariel 1 was later seriously damaged by the Starfish Prime nuclear test.
10 June 19, 1962 TIROS-5 success
11 July 10, 1962 Telstar 1 success Also later damaged by the Starfish Prime high altitude nuclear event.
12 September 18, 1962 TIROS-6 success

Delta evolution

Launch of the first Skynet satellite by Delta rocket (Delta M) in 1969 from Cape Canaveral

Delta A

The Delta A used the MB-3 Block II engine, with 170,000 lbf (760 kN) of thrust vs. 152,000 lbf (680 kN) for the Block I.[4] [5]
13. EPE2
14. EPE3

Delta B

The Delta B introduce the upgraded AJ10-118D 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 pounds (91 kg) to GTO.[5]

15. 13 December 1962. Relay 1, second NASA communications satellite, NASA's first active one
16. 13 February 1963. pad 17b. Syncom 1; Thiokol Star 13B solid rocket as apogee kick motor
20. July 26, 1963. Syncom 2; geosynchronous orbit, but inclined 33° due to the limited performance of the Delta

Delta C

For Delta C, the third stage Altair was replaced with Altair 2. The Altair 2 had been developed as the ABL X-258 for the Scout 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

Delta D, also known as Thrust Augmented Delta, was a Delta C with the Thrust Augmented Thor core plus three Castor 1 boosters.[citation needed]

25. 19 August 1964. Syncom 3, the first geostationary communications satellite
30. 6 April 1965. Intelsat I

Delta E

First Delta E. 6 November 1965; Launched GEOS 1[citation needed]

Delta F

This launch vehicle was not built.[6]

Delta G

The Delta G was a Delta E without the third stage. The two-stage vehicle was used for 2 launches: Biosatellite 1 on 14 December 1966 and Biosatellite 2 on 7 September 1967.[4]

Delta J

The Delta J used a larger Thiokol Star 37D motor as the third stage and was launched once on 4 July 1968 with Explorer 38.[4]

Delta K

This launch vehicle was not built.[6]

Delta L

Delta L introduced the Extended Long Tank first stage with a uniform 8 feet (2.4 m) diameter and used the United Technologies FW-4D motor as a third stage.[citation needed]

Delta M

The Delta M first stage consisted of a Long Tank Thor with MB-3-3 engine augmented with 3 Castor 2 boosters. The Delta E was the second stage, with a Star 37D (Burner 2) third stage/apogee kick motor. There were 12 successful Delta M launches from 1968 until 1971.[7]

Delta N

The Delta N combined a Long Tank Thor (MB-3-3 engine) first stage augmented with 3 Castor 2 boosters and a Delta E second stage. There were six successful Delta N launches from 1968 until 1972.[8]

'Super Six'

The 'Super Six' was a Delta M or Delta N with three additional Castor 2 boosters for a total of six, which was the maximum that could be accommodated. These were respectively designated M6 or N6. The first and only launch of the M6 configuration was Explorer 43 (IMP-H, Magnetospheric research) on 13 March 1971.[9] Three launches of the N6 between 1970 and 1971 resulted in one failure.[10]

  • 1,000 pounds (450 kg) to GTO

Launch reliability

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.)[11] Satellites for other government agencies and foreign governments were also launched on a cost-reimbursable basis, totaling sixty-three satellites. Out of the 84 launch attempts there were seven failures or partial failures, a 91.6% success rate.[12]

Delta numbering system

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 of solid rocket boosters, (3) second stage (letters in the following table refer to the engine), and (4) third stage:[13]

Number First Digit
(First stage/boosters)
Second Digit
(Number of boosters)
Third Digit
(Second Stage)
Fourth Digit
(Third stage)
(Heavy configuration)
0 Long Tank Thor
MB-3 engine
Castor 2 SRBs
No SRBs Delta F*, with Aerojet AJ-10-118F engines.
*References uprated Aerojet 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 with TRW TR-201 engines.
*Exception: AJ-10-118F engine for Anik-A1 launch.[14]
2 Extended Long Tank Thor
RS-27 engine
Castor 2 SRBs
2 SRBs (or CBCs in the case of the Delta IV Heavy) Delta K*, with AJ-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 5m 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
8 Strengthened Extra-Extended Long Tank Thor
RS-27A engine
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.[15] In practice, the new system was never used, as all but the Delta IV Heavy have been retired:[citation needed]

Number First Digit
(First stage/boosters)
Second Digit
(Number of boosters)
Third Digit
(Second Stage)
Fourth Digit
(Third stage)
(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
2 SRBs (or LRBs in the case of the Delta IVH) Delta K, with AJ-10-118K engines GEM 46 SRBs
3 Strengthened Extra-Extended Long Tank Thor
RS-27A engine
3 SRBs N/A
4 Delta IV CBC
RS-68 engine
4 SRBs Delta IV 4m diameter cryogenic upper stage, RL-10B-2 engine 2 additional CBC Parallel first stages
5 N/A N/A Delta IV 5m diameter cryogenic upper stage, RL-10B-2 engine Star 48B/PAM-D N/A
6 N/A Star 37FM
7 N/A
9 9 SRBs

Delta 0100

The first stage of the initial numbered Delta was the Long Tank Thor, a version of the Thor missile with extended propellant tanks. Up to nine strap-on solid 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 Aerojet AJ 10-118F engine was also introduced. The first 900 series launch was the fourth Delta 100.[citation needed] On 23 July 1972, Thor-Delta 904 launched Landsat 1.[16]

Delta 1000-Series

The Delta 1000 series was nicknamed the Straight-Eight and combined an Extended Long Tank first stage with an 8-foot-diameter (2.4 m) payload fairing, up to nine Castor II SRBs, and the new McDonnell-Douglas Delta-P second stage using the TRW TR-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 launched Explorer 47 on 22 September 1972.[16]

Delta 2000-Series

The Delta 2000 introduced the new Rocketdyne RS-27 main engine on an Extended Long Tank first stage with the same constant eight-foot diameter. A Delta 2310 was the vehicle for the first three-satellite launch of NOAA 4, Intesat, and Amsat Oscar 7 on 15 November 1974.[citation needed] Delta 2910 boosters were used to launch both Landsat 2 in 1975 and Landsat 3 in 1978. On 7 April 1978, a Delta 2914 launched "Yuri 1", the first Japanese BSE Broadcasting Satellite.[17]

Delta 3000-Series

The Delta 3000 combined the same first stage as 1000- and 2000-series with upgraded Castor IV solid boosters and was the last Delta series to use the McD Delta-P second stage with TRW TR-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 U.S. government payloads in May 1976[16] and was launched 13 times between 1975-1987.

Delta 4000-Series

The Delta 4000 and 5000 series were developed in the aftermath of the Challenger 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 upgraded Castor IVA 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]

Delta 5000-Series

The Delta 5000 series featured upgraded Castor IVA motors on an Extended Long Tank first stage with the new RS-27 main engine and only launched one mission.[citation needed]

Delta II (6000 and 7000 series)

The Delta II series was developed after the 1986 Challenger accident and consisted of the Delta 6000 and 7000 series, with two variants (Lite and Heavy) of the latter. The Delta 6000 series introduced the Extra Extended Long Tank first stage, which was 12 feet longer, and the Castor IVA boosters. Six SRBs ignited at takeoff and three ignited in the air.[citation needed]

The Delta 7000 series introduced the RS-27A main engine, which was modified for efficiency at high altitude at some cost to low-altitude performance, and the lighter and more powerful GEM-40 solid boosters from Hercules. The Delta 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. The Delta II Heavy was a Delta II 792X with the enlarged GEM-46 boosters from Delta III.[citation needed]

Delta III (8000-Series)

A McDonnell Douglas/Boeing-developed program to keep pace with growing satellite masses:

  • The two upper stages, with low-performance fuels, were replaced with a single cryogenic stage, improving performance and reducing recurring costs and pad labor. Engine was a single Pratt & Whitney RL10, from the Centaur upper stage. The hydrogen fuel tank, 4 meters in diameter in orange insulation, is exposed; the narrower oxygen tank and engine are covered until stage ignition. Fuel tank contracted to Mitsubishi, and produced using technologies from Japanese H-II launcher.
  • To keep the stack short and resistant to crosswinds, the first-stage kerosene tank was widened and shortened, matching the upper-stage and fairing diameters.
  • Nine enlarged GEM-46 solid boosters attached. Three have thrust-vectoring nozzles.

Of the three Delta III flights, the first two were failures and the third carried only a dummy (inert) payload.

Delta IV (9000-series)

As part of the Air Force's EELV (Evolved Expendable Launch Vehicle) program, McDonnell Douglas/Boeing proposed Delta IV. As the program implies, many components and technologies were borrowed from existing launchers. Both Boeing and Lockheed Martin were contracted to produce their EELV designs. Delta IVs are produced in a new facility in Decatur, Alabama.

  • First stage changed to liquid hydrogen fuel. Tank technologies derived from Delta III upper stage, but widened to 5 meters.
  • Kerosene engine replaced with Rocketdyne RS-68, the first new, large liquid-fueled rocket engine designed in the US since the Space Shuttle Main Engine (SSME) in the '70s. Designed for low cost; has lower chamber pressure and efficiency than the SSME, and a much simpler nozzle. Thrust chamber and upper nozzle is a channel-wall design, pioneered by Soviet engines. Lower nozzle is ablatively cooled.
  • Second stage and fairing taken from the Delta III in smaller (Delta IV Medium) models; widened to 5 meters in Medium+ and Heavy models.
  • Medium+ models have two or four GEM-60 60-inch diameter solid boosters.
  • Revised plumbing and electric circuits eliminate need for a launch tower.

The first stage is referred to as a common booster core (CBC); a Delta IV Heavy attaches two extra CBCs as boosters.

Delta IV Heavy

The Delta IV Heavy (Delta 9250H) uses two additional CBCs as boosters. These are strap-on boosters which are separated earlier in the flight than the center CBC.
The initial demonstration flight on December 21, 2004 was a partial failure, due to the premature cutoff of CBCs.[18][19] The DemoSat reached incorrect orbit and the 3CS satellites entered orbit at a height of only 105 km, which led to a rapid decay.
The cause of the problem was a premature first-stage LOX depletion sensor signal that resulted when LOX cavitation occurred in the LOX feedline. The LOX feedline/sensor design was modified and the problem did not recur on subsequent Delta IV Heavy missions.[20]

  • Features a stretched 5-meter composite payload fairing.[21]
  • An aluminum trisector (3 part) fairing derived from the Titan IV fairing is also available.[22] This was first used on the DSP-23 flight.
  • First successful launch from Space Launch Complex 37 (SLC-37) at the Cape Canaveral Air Force Station on November 11, 2007.[18][19]
  • First successful launch from Vandenberg Air Force Base's Space Launch Complex 6 (SLC-6) on January 20, 2011.
  • On June 29, 2012, the first Delta IV using the upgraded RS-68A engines launched from SLC-37 in the Heavy configuration, carrying the National Reconnaissance Office's NROL-15 mission. The new upgraded variant produced a total of 2.106 million pounds of thrust at liftoff. [23]
  • In December 2014, the Delta IV Heavy was used to launch an uncrewed test flight of the Orion Multi-Purpose Crew Vehicle, designated EFT-1.
  • A Delta IV Heavy was used to launch the Parker Solar Probe mission on August 12, 2018.[24] This Delta IV Heavy launch implemented the Star 48BV third stage (Delta 9255H), the first use of a third stage on a Delta IV.

See also


  1. ^ "Origins of NASA Names - Ch. 1: Launch Vehicles". NASA. Archived from the original on 2004-11-04.
  2. ^ Helen T. Wells; Susan H. Whiteley; Carrie E. Karegeannes. Origin of NASA Names. NASA Science and Technical Information Office. pp. 14–15.
  3. ^ "Explorer 12". NASA.
  4. ^ a b c Kruse, Richard. "Thor and Delta Rockets Overview". Historic Spacecraft. Retrieved 8 March 2020.
  5. ^ a b Kyle, Ed. "Thor-Agena A & B: Photospy Launcher". Space Launch Report. Retrieved 8 March 2020.
  6. ^ a b Jos Heyman (January 8, 2008). "Delta beyond 1974 (incl. Delta 2)". Directory of U.S. Military Rockets and Missiles. Retrieved 8 June 2012.
  7. ^ "Delta M". Encyclopedia Astronautica. Archived from the original on 2012-06-18.
  8. ^ "Delta N". Encyclopedia Astronautica. Archived from the original on 2008-03-05.
  9. ^ "Delta M6". Encyclopedia Astronautica. Archived from the original on 2012-06-19.
  10. ^ "Delta N6". Encyclopedia Astronautica. Archived from the original on 2012-06-18.
  11. ^ "NASA Historical Data Book, Vol. III". NASA. Archived from the original on 2004-11-02.
  12. ^ "Listing of Thor-Delta Vehicles". NASA. Archived from the original on 2004-11-18.
  13. ^ Forsyth, Kevin S. "Vehicle Description: Four Digit Designator". History of the Delta Launch Vehicle. Retrieved 2008-05-07.
  14. ^ "Delta P". Encyclopedia Astronautica. Archived from the original on 2012-06-17.
  15. ^ Wade, Mark. "Delta". Encyclopedia Astronautica. Archived from the original on 2008-03-29. Retrieved 2008-05-07.
  16. ^ a b c "Chronology of Thor-Delta Development and Operations". NASA. Archived from the original on 2004-11-18.
  17. ^ "Delta Chronology". Encyclopedia Astronautica. Archived from the original on 2008-07-24.
  18. ^ a b Justin Ray (December 22, 2004). "Delta 4-Heavy hits snag on test flight". Spaceflight Now. Retrieved December 12, 2010.
  19. ^ a b Justin Ray (December 22, 2004). "Air Force says plenty of good came from Delta 4 test". Spaceflight Now. Retrieved December 12, 2010.
  20. ^ Ed Kyle (January 24, 2012). "Delta IV Data Sheet". Space Launch Report. Retrieved June 6, 2012.
  21. ^ "Delta Launch 310 – Delta IV Heavy Demo Media Kit - Delta Growth Options" (PDF). Boeing. Archived from the original (PDF) on 2011-05-24.
  22. ^ US Air Force - EELV Fact Sheets Archived April 27, 2014, at the Wayback Machine
  23. ^ "Delta IV Data Sheet". Space Launch Report. 22 August 2019. Retrieved 8 May 2020.
  24. ^
  • Forsyth, Kevin S. (2002). Delta: The Ultimate Thor. In Roger Launius and Dennis Jenkins (Eds.), To Reach The High Frontier: A History of U.S. Launch Vehicles. Lexington: University Press of Kentucky. ISBN 0-8131-2245-7

External links

  • History of the Delta Launch Vehicle
  • Delta Launch Record
  • The Satellite Encyclopedia - Thor Delta