Delta (rocket family)

The Delta rocket family was a versatile range of American rocket-powered expendable 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, and H-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 the Vulcan Centaur, with the Delta IV Heavy rocket's last launch occurring on April 9, 2024.[1]

Origins

The original Delta rockets used a modified version of the PGM-17 Thor, the first ballistic missile deployed by the United States Air Force (USAF), 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 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]

Evolution

[[Image:Delta-M with Skynet-1A.jpg|thumb|Launch of the first [[Skynet (satellite)|Skynet]] satellite by Delta M

launch vehicle in 1969 from Cape Canaveral.]]

Delta A

Delta B

Delta C

Delta D

Delta E

Delta F

Delta G

Delta J

Delta K

Delta L

Delta M

Delta N

"Super Six"

Delta 0100-series

Delta 1000-series

Delta 2000-series

Delta 3000-series

Delta 4000-series

Delta 5000-series

Delta II (6000-series and 7000-series)

The Delta II series was developed after the 1986 Challenger 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 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.

Delta III (8000-Series)

The Delta 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 a dummy (inert) payload.

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 metres in diameter is exposed, showing its orange insulation; 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 of them have thrust-vectoring nozzles.

Delta IV (9000-series)

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

The first stage was referred to as a Common Booster Core (CBC); a Delta IV Heavy attached two extra CBCs as boosters.

The first stage changed to liquid hydrogen fuel. Tank technologies derived from Delta III upper stage, but widened to 5 metres.
The kerosene engine replaced with Rocketdyne RS-68

type	Expendable launch system
manufacturer	Douglas Aircraft Company (1960–1967) McDonnell Douglas (1960–1997) Boeing (1997–2006) United Launch Alliance (2006–2024)
first flight	May 13, 1960
introduction	13 May 1960 (Echo 1)
retired	9 April 2024 (NROL-70)
status	Out of service