Delta is a versatile family of expendable launch systems that has
provided space launch capability in the United States since 1960. There have
been more than 300 Delta rockets launched, with a 95% success rate. Two
Delta launch systems – Delta II and Delta IV – are still in use, though the
Delta II will soon be retired. 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 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."
The Delta name stems from its position as the fourth, or D version, of the Thor
based rocket combination. The vehicle has been known both as Thor-Delta and
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 1959 for 12 vehicles of
this design: Stage 1: Modified Thor IRBM with a Block
I MB-3 engine producing 152,000 lbf thrust.
Stage 2: Modified Able. Pressure fed UDMH/nitric acid powered Aerojet
AJ-10-118 engine producing 7,700 lbf. 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 at
100 rpm by two solid rocket motors before separation. One ABL X-248 solid
rocket motor provided 2,800 lbf of thrust for 28 seconds. The stage weighed
500 pounds and was largely constructed of wound fiberglass.
These vehicles would be able to place 650 pounds into a 150 to 230 miles LEO
or 100 pounds 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. = Thor-Delta flights=
Delta evolution = Delta A=
MB-3 Block II engine, 170,000 lbf vs. 152,000 lbf
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 pounds to GTO 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=
Third stage Altair replaced with Altair 2—its engine having been developed as
the ABL X-258 for the Scout vehicle; 3 in 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 August 1964. Syncom 3, the first geostationary communications satellite
30. 6 April 1965. Intelsat I = Delta E=
Also known as Thrust Augmented Improved Delta
1965 100 pounds more to GTO than Delta D
Castor 2 vs. Castor 1 boosters; Same thrust, longer duration
MB-3 Block III core engine, 2,000 lbf more thrust
AJ10-118E second stage widened from 2.75 feet to 4.58 feet 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 November 1965; Launched
GEOS 1 = Delta F=
This launch vehicle was not built = Delta G=
Two-stage vehicle. Only used for 2 launches: Biosatellite 1
on 14 December 1966 and Biosatellite 2 on 7 September 1967.
= Delta J= Used larger Thiokol Star 37D motor as
third stage. Only one launch of this configuration on
4 July 1968. = Delta K=
This launch vehicle was not built = Delta L=
Introduced Extended Long Tank first stage- 8 feet diameter throughout
Used the United Technologies FW-4D motor for third stage
= Delta M= Three-stage configuration.
Long Tank Thor augmented with 3 Castor 2 boosters; Delta E second stage
Star 37D for third stage There were 12 successful Delta M
launches from 1968 until 1971. = Delta N=
Two-stage configuration Long Tank Thor augmented with 3 Castor 2
boosters; Delta E second stage There were 6 successful Delta N launches
from 1968 until 1972. = 'Super Six'=
Delta M or Delta N with three additional Castor 2 boosters, these were designated
as either M6 or N6. 1 launch of the M6 configuration -
Explorer 43 on 13 March 1971. 3 launches of the N6 configuration, one
failure. 1,000 pounds to GTO
Launch reliability From 1969 through 1978, Thor-Delta was
NASA's most used launcher, with 84 launch attempts.
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. Sixty-three of the satellites NASA
attempted to launch were provided by other parties. Out of the 84 attempts
there were seven failures or partial failures.
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. It specified the tank and main engine
type, number of solid rocket boosters, second stage, and third stage.
This numbering system was to have been phased out in favor of a new system that
was introduced in 2005. In practice, this system has never been used.
= Delta 904= The Long Tank Thor, a stretched version
of the Thor missile First use of nine strap-on boosters for
Landsat 1 launch on July 23, 1972. First use of new uprated Delta F
second-stage using Aerojet AJ 10-118F engine.
This Thor-Delta model was designated the 904.
= Delta 1000-Series= Nicknamed Straight-Eight.
Extended Long Tank with 8-foot-diameter payload fairing.
Nine Castor II strap-on solid boosters. The first successful 1000 series
Thor-Delta launched Explorer 47 on September 22, 1972.
Introduction of McDonnell-Douglas Delta-P second stage using TRW TR-201
engine. = 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.
First time three satellites launched simultaneously on Delta 2310
model—November 15, 1974. 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.
Introduced PAM/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.
The Delta 3914 model was launched 13 times between 1975-1987.
Last Delta series to use the McD Delta-P second stage with TRW TR-201 engine.
= Delta 4000-Series= Used old MB-3 main engine on Extended
Long Tank with Castor IV motors.. First use of a Delta-K second stage.
Only launched two missions. = 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 of the latter. It
was developed by Boeing at Chatsworth and Canoga Park, California, and its
engines were tested at Boeing's Santa Susana Field Laboratory,, located
northwest of Los Angeles in the Simi hills.
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, 3 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 solid boosters from
Hercules. 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. Usually used for small
NASA missions. Delta II Heavy
A Delta II 792X with the enlarged GEM-46 boosters from Delta III.
= Delta III= 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 payload. = Delta IV=
As part of the Air Force's 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. 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 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 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; a Delta IV Heavy attaches two extra CBCs as boosters.
Delta IV Heavy The Delta IV Heavy 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. 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 faulty 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. Features a stretched 5-meter composite
payload fairing. An aluminum trisector fairing derived
from the Titan IV fairing is also available. This was first used on the
DSP-23 flight. First successful launch from Space
Launch Complex 37 at the Cape Canaveral Air Force Station on November 11, 2007.
First successful launch from Vandenberg Air Force Base's Space Launch Complex 6
on January 20, 2011. On August 28, 2013 A Delta IV Heavy was
launched from Vandenberg Air Force Base's Space Launch Complex of the
National Reconnaissance Office's the top secret NROL-65 payload successfully into
orbit. http:www.youtube.com/watch?v=gL1dEBZ6Vyc
See also Comparison of orbital launchers families
Comparison of orbital launch systems List of Thor and Delta launches
HoloVID Contribution to space debris
Echo 1 Project Echo
References Forsyth, Kevin S.. Delta: The Ultimate
Thor. In Roger Launius and Dennis Jenkins, 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