Delta (rocket family)

The Delta 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.[3][4]
13. 2 October 1962 - Explorer 14 (EPE-B)
14. 27 October 1962 - Explorer 15 (EPE-C)

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 lb (91 kg) to GTO.[4]

15. 13 December 1962. Relay 1, second NASA communications satellite, the NASA communications satellite first active one.
16. 13 February 1963. Pad 17B. Syncom 1; Thiokol Corporation Star-13B solid rocket as apogee motor.
20. 26 July 1963. Syncom 2; geosynchronous orbit, but inclined 33.0° due to the limited performance of the Delta rocket.

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.

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

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

First Delta E: 6 November 1965; launched GEOS 1

This launch vehicle was not built.[5]

The Delta G was a Delta E without the third stage. The two-stage vehicle was used for two launches: Biosatellite 1 on 14 December 1966 and Biosatellite 2 on 7 September 1967.[3]

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.[3]

This launch vehicle was not built.[5]

The Delta L introduced the Extended Long Tank first stage with a uniform 2.4 m (7 ft 10 in) diameter and used the United Technologies FW-4D motor as a third stage.

The Delta M first stage consisted of a Long Tank Thor with MB-3-3 engine augmented with three 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.[6]

The Delta N combined a Long Tank Thor (MB-3-3 engine) first stage augmented with three Castor 2 boosters and a Delta E second stage. There were six successful Delta N launches from 1968 until 1972.[7]

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 Delta M6 or Delta N6. The first and only launch of the M6 configuration was Explorer 43 (IMP-H, Magnetospheric research) on 13 March 1971.[8] Three launches of the N6 between 1970 and 1971 resulted in one failure.[9]

• 450 kg (990 lb) to GTO

The Delta 0100 series was 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 0100. On 23 July 1972, Thor-Delta 904 launched Landsat 1.[16] A license-built version of the Long Tank Thor stage with the MB-3 engine was also used for the Japanese N-I launch vehicle.

The Delta 1000 series was nicknamed the Straight-Eight and combined an Extended Long Tank first stage with an 8 ft-diameter (2.4 m) payload fairing, up to nine Castor 2 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. The first successful 1000 series Thor-Delta launched Explorer 47 on 22 September 1972.[16] The Extended Long Tank Thor stage was also used in the Japanese N-II and H-I launch vehicles.

The Delta 2000 introduced the new Rocketdyne RS-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 of NOAA-4, Intasat, and AMSAT-OSCAR 7 on 15 November 1974. 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]

The Delta 3000 combined the same first stage as 1000-series and 2000-series with upgraded Castor 4 solid boosters and was the last Delta series to use the McDonnell Douglas 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. The Delta 3914 model was approved for launching United States government payloads in May 1976[16] and was launched 13 times between 1975 and 1987.

The Delta 4000-series 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 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.

The Delta 5000 series featured upgraded Castor 4A motors on an Extended Long Tank first stage with the new RS-27 main engine and only launched one mission.

The Delta II series was developed after the 1986 Challenger accident and consisted of the Delta 6000-series 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 4A boosters. Six SRBs ignited at takeoff and three ignited in the air.

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.

The Delta III 8000-series was 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. The engine was a single Pratt & Whitney RL10, from the Centaur upper stage. The hydrogen fuel tank, 4 metre 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 were 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.

As part of the Air Force's Evolved Expendable Launch Vehicle (EELV) 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.

• The first stage changed to liquid hydrogen fuel. Tank technologies derived from Delta III upper stage, but widened to 5 metre.
• The kerosene engine replaced with Rocketdyne RS-68, the first new, large liquid-fueled rocket engine designed in the United States 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.
• The second stage and fairing taken from the Delta III in smaller (Delta IV Medium) models; widened to 5 metre in Medium+ and Heavy models.
• Medium+ models have two or four GEM 60, 60-inch diameter solid boosters.
• The plumbing was revised and electrical 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.

The Delta IV Heavy consists of a central Common Booster Core (CBC), with two additional CBCs as liquid rocket boosters instead of the GEM-60 solid rocket motors used by the Delta IV Medium+ versions. At lift off, all three cores operate at full thrust, and 44 seconds later the center core throttles down to 55% to conserve fuel until booster separation. The boosters burn out at 242 seconds after launch and are separated as the core booster throttles back up to full thrust. The core burns out 86 seconds later, and the second stage completes the ascent to orbit.[18]

The rocket uses three RS-68 engines, one in the central core and one in each booster.[19]

On 24 September 2022, the last Delta IV flight from Vandenberg launched the NROL-91 mission from SLC-6.[20]