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Delta rocket
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Delta is a family of expendable launch systems that have provided space launch capability in the United States since 1960. There have been over 300 Delta rockets launched, with a 95% success rate. Two Delta launch systems -- Delta II and Delta IV -- are in active use. Delta rockets are currently manufactured and launched by the United Launch Alliance.
Delta origins
The original Delta rockets used a modified version of the PGM-17 Thor, the first ballistic missile deployed by the United States, as their first stage.
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Delta is a family of expendable launch systems that have provided space launch capability in the United States since 1960. There have been over 300 Delta rockets launched, with a 95% success rate. Two Delta launch systems -- Delta II and Delta IV -- are in active use. Delta rockets are currently manufactured and launched by the United Launch Alliance.
Delta origins
The original Delta rockets used a modified version of the PGM-17 Thor, the first ballistic missile deployed by the United States, as their first stage. The Thor had been designed in the mid-'50s 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."
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. The Delta design emphasized reliability rather than performance by replacing components which had caused problems on earlier Thor flights. NASA let the original Delta contract to the Douglas Aircraft Company in April of 1959 for 12 vehicles of this design:
- Stage 1: Modified Thor IRBM with a Block I MB-3 engine producing 152,000 lbf (676 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 7700 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 2800 lbf (12 kN) of thrust for 28 seconds. The stage weighed 500 lb (230 kg) and was largely constructed of wound fiberglass.
These vehicles would be able to place 650 lb (295 kg) into a 150 to 230 mile (241 to 370 km) LEO or 100 lb (45 kg) into GTO. Eleven of the twelve initial Delta flights were successful. The total project development and launch cost came to $43 million, $3 million over budget. An order for 14 more vehicles was let before 1962.
Early Delta flights
Delta Evolution
Delta A
Block II MB-3 engine, 170,000 lbf (756 kN) vs. 152,000 lbf (676 kN)
13. EPE2
14. EPE3
Delta B
- Upgraded AJ10-118D upper stage--3 foot tank stretch, higher energy oxidizer, solid-state guidance system.
- Delta program goes from 'interim' to 'operational' status.
- 200 lb (90 kg) to GTO.
15. 13 Dec 1962. Relay 1, second NASA communications satellite, NASA's first active one.
16. 13 Feb 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
- Third stage Altair replaced with Altair 2—its engine having been developed as the ABL X-258 for the Scout vehicle; 3 in (76 mm) longer, 10% heavier, but 65% more total thrust.
- Sample mission: OSO-4
Delta D
- Also known as Thrust Augmented Delta.
- A Delta C with the Thrust Augmented Thor core plus three Castor 1 boosters.
25. 19 Aug 1964. Syncom 3, the first geostationary communications satellite.
30. 06 Apr 1965. Intelsat I
Delta E
- Also known as Thrust Augmented Improved Delta.
- 1965.
- 100 lb (45 kg) more to GTO than Delta D.
- Castor 2 vs. Castor 1 boosters. Same thrust, longer duration.
- MB-3 Block III core engine, 2000 lbf (9 kN) more thrust.
- AJ10-118E second stage widened from to diameter. Double burn time.
- Additional helium tanks allow for almost unlimited restarts.
- Two available third stages: Altair 2 or FW-4D. The latter caused the Delta to be known as a Delta E1.
- New payload fairing from Agena.
First Delta E. 6 Nov 1965. Launched GEOS 1.
Delta G
- Two stage Delta Es.
- used for Biosatellite 1 and 2 flights.
1. 14 Dec 1966. Biosatellite 1.
2. 7 Sep 1967. Biosatellite 2
Delta J
- Used larger Thiokol Star 37D motor as third stage.
4 Jul 1968. Explorer 38.
Delta L
- Introduced Extended Long Tank first stage- diameter throughout.
- FW-4d motor for third stage.
Delta M
Delta N
- Two stage version of Delta M.
- There were nine Delta N launch attempts from 1968 until 1972; eight were successful.
'Super Six'
- Delta M or Delta N with three extra strap ons.
- 1000 lb (450 kg) to GTO.
Launch Reliability
From 1969 through 1978 (inclusive), Thor-Delta was NASA's most popular launcher, with 84 launch attempts. (Scout was the second most used vehicle with 32 launches.)
NASA used it to launch its own satellites, and also to launch satellites for other government agencies and foreign governments on a cost reimbursable basis. 63 of the satellites NASA attempted to launch were provided by other parties. Out of the 84 attempts there were 7 failures or partial failures (91.6% successful).
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). It specified (1) the tank and main engine type, (2) number of solid boosters, (3) second stage, and (4) third stage.
This numbering system was phased out in favor of a new system that was introduced in 2005. In practice, vehicles designated by the new system will not launch before 2007 at the earliest.
Delta 904
On July 23, 1972, the launch of Landsat 1 marked the first use of nine strap-on boosters, and the new uprated second-stage engine (AJ 10-118F). This Thor-Delta model was designated the 904.
Delta 1000-Series
- Extended Long Tank with eight-foot diameter payload fairing; nicknamed "Straight-Eight".
- Nine Castor II strap-on solid boosters.
- The first successful 1000 series Thor-Delta launched Explorer 47 on September 22, 1972.
Delta 2000-Series
- Features new Rocketdyne RS-27 main engine on Extended Long Tank. Same constant eight-foot diameter.
- Delta 2910 boosters were used to launch both Landsat 2 in 1975 and Landsat 3 in 1978.
- A Delta 2914 was used 1978-04-07 to launch the Japanese BSE Broadcasting Satellite, also known as "Yuri 1".
Delta 3000-Series
- Introduced upgraded Castor IV solid motors. Same first stage as 1000- and 2000-series.
- Also introduced PAM (Payload Assist Module)/Star 48B solid-fueled kick motor. Later used as Delta II third stage.
- The Delta 3914 model was approved for launching U.S. government payloads in May 1976.
Delta 4000-Series
- Used old MB-3 main engine on Extended Long Tank with Castor IV motors.
- Only launched two missions.
- First use of a Delta-K second stage.
Delta 5000-Series
- Featured upgraded Castor IVA motors on Extended Long Tank first stage with RS-27 main engine.
- Only launched one mission.
Delta II series
The Delta II series consists of the retired Delta 6000, the active Delta 7000, and two variants (Lite and Heavy) of the latter.
Delta 6000-Series
When in 1986 the Challenger accident demonstrated that Delta launches would continue, the Delta II was developed.
- Introduced Extra Extended Long Tank first stage. 12 additional feet provide more propellant.
- Introduced Castor IVA boosters. Six ignite at takeoff, three ignite in flight.
Delta 7000-Series
- Introduces RS-27A main engine, modified for efficiency at high altitude, at some cost to low-altitude performance.
- Introduces GEM-40 (Graphite-Epoxy Motor) solid boosters from Hercules (now Alliant). Besides being longer, their lighter casings allow higher payload capability.
Delta II Med-Lite
A 7000-series with no third stage and fewer strap-ons (often three, sometimes four). Usually used for small NASA missions.
Delta II Heavy
A Delta II 792X with the enlarged GEM-46 boosters from Delta III.
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.
Future Development
Currently development is focused on the Delta 4 Heavy, which uses three Common Booster Cores to lift higher masses to orbit and escape velocity.
See also
External links
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