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Countdown! NASA Launch Vehicles and Facilities
PMS 018-B (KSC)
October 1991
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In 1989 NASA implemented a mixed fleet concept,
under which the agency launches manned Space Shuttles and unmanned expendable
Scouts, and contracts for launch services on other expendable launch vehicles (ELVs).
This has encouraged the growth of the U.S. commercial launch industry. It also
ended a tradition that began with the birth of the agency -- assuming the
primary responsibility for the launch of all unmanned space vehicles under
contract to NASA. Except for some Scout vehicles to be launched from the West
Coast over the next few years, NASA has turned launch operations over to the
manufacturers of the vehicles and the U.S. Air Force.
All ELVs use the same basic technology to get
into space -- two or more rocket-powered stages which are discarded when their
engine burns are completed. The only U.S. manned space vehicle is the Space
Shuttle, which is a unique design and in a class by itself.
The payload weight, destination and purpose
determine what vehicle capabilities are required for each mission. A low-weight
spacecraft designed to operate in near-Earth orbit might be flown aboard the
comparatively small Scout. Sending a manned Apollo spacecraft to the Moon
required the massive Saturn V. The powerful Titan-Centaur combination carried
large and complex unmanned scientific explorers such as the Vikings and Voyagers
to examine other planets. Atlas/Agenas sent several spacecraft to photograph and
then impact on the Moon. Atlas/Centaurs and Deltas have launched more than 260
spacecraft for a wide variety of purposes, covering the broad range of the
national space program.
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| NASA has used eight major space vehicles over the
years. |
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The Space Shuttle fleet of three vehicles will launch the
ground-assembled segments of the International Space Station until the end of the program.
The first Space Shuttle lifted off from Pad A on
Launch Complex 39, Kennedy Space Center, on April 12, 1981. After a two-day,
test-flight mission that verified the ability of the Orbiter Columbia to
function in space, it landed at Edwards AFB in California. The vehicle was
piloted by John Young and Robert Crippen. The STS-1 mission marked the first
time that a new space vehicle carried a crew on its initial flight.
A Space Shuttle consists of a reusable
delta-winged space plane, called an orbiter; two solid-propellant booster
rockets, which are recovered and also reused; and an expendable tank containing
liquid propellant for the orbiter’s three main engines. Only the orbiters have
names, and an orbiter alone is not a full Space Shuttle.
An assembled Space Shuttle is approximately 184
feet (56 meters) long, 76 feet (23 meters) high to the tip of the orbiter’s
vertical tail, and 78 feet (24 meters) wide, measuring across the orbiter’s
wingtips. Liftoff weight is usually about 4,500,000 pounds (2,041,200
kilograms).
An orbiter’s three liquid fueled engines --
drawing propellants from the external tank -- and the two solid-propellant
rocket boosters burn simultaneously for the first two minutes. Together, they
produce about 7.3 million pounds (32.4 million newtons) of thrust at liftoff.
After two minutes of flight a Space Shuttle
reaches an altitude of 32 miles (48 kilometers) and the boosters have burned all
their propellant. They then detach and parachute into the ocean. Two waiting
ships recover them, for refurbishment and reuse on later missions.
The orbiter and external tank continue on toward
Earth orbit. When the orbiter’s main engines cut off, just before achieving
orbit, the external tank is jettisoned, to re-enter the atmosphere and break up
over a remote ocean area. On most missions the orbiter continues to coast until
it reaches the other side of the Earth from where the external tank was
discarded. The on-board orbital maneuvering engines are then fired to place the
vehicle in a near-circular low-Earth orbit. Most operational missions last from
four to seven days, though longer ones are sometimes required.
When the mission has been completed, the orbiter
re-enters the atmosphere and returns to Earth, gliding to an unpowered landing
at either KSC or Edwards AFB.
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The Scout launch vehicle, which became
operational in 1960, has undergone systematic upgrading since 1976. The current
Scout is a solid-propellant, four-stage booster system, approximately 75 feet
(23 meters) in length, with a launch weight of 46,620 pounds (21,147 kilograms)
and a liftoff thrust of 132,240 pounds (588,203 newtons). It can boost an
average payload of 400 to 465 pounds (181 to 211 kilograms) into low Earth
orbit.
A total of 113 Scouts were launched through 1990.
They were used to place a variety of U.S. and international payloads into
inclined, equatorial and polar orbit, for orbital, probe and re-entry missions.
LTV Aerospace and Defense Missiles
Division currently produces the Scout vehicle for NASA. LTV also provides
systems management and support for launches. Scouts can lift off from Vandenberg
AFB in California; the NASA Wallops Flight Facility at Wallops Island, Virginia;
and the Italian San Marco launch platform off the east coast of Kenya, Africa.
The only firm launches NASA has scheduled at present are from Vandenberg.
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Time-proven launch vehicles formerly purchased
and put into space by NASA are now launched by the vehicle manufacturers. NASA
contracts with either the U.S. Air Force or the individual company to procure
both vehicles and launch services. These vehicles are the Delta II (McDonnell
Douglas Space Systems Co.); Atlas I and Atlas II (General Dynamics Space Systems
Division); and Titan 34D and Titan IV (Martin Marietta Space Launch Systems).
KSC/NASA retains oversight responsibilities for those vehicles which carry NASA
payloads. |
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The Delta rocket has been called the workhorse of
the space program. Since 1960, NASA has been the responsible agency in the
launch of more than 180 scientific, weather, and communications spacecraft,
along with some military satellites. These spacecraft include the TIROS, Nimbus,
ITOS, LANDSAT, and Westar series, and over 30 scientific Explorers.
The Delta II is the newest version of this
rocket. The U.S. Air Force and McDonnell Douglas first launched this vehicle
from Complex 17 at Cape Canaveral Air Force Station in February 1989, carrying
the first of 21 upgraded Navstar Global Positioning Satellites into orbit. NASA
relinquished control of this launch area to the Air Force in 1988. Delta
commercial launches also take place here.
The Delta family of vehicles has been upgraded
several times over the years. Currently, the most powerful version is the Delta
II, which stands 128 feet (39 meters) tall. Nine Castor IV-A strap-on solid
rocket boosters augment its first stage. Six of them ignite at liftoff. The
remaining three Castors ignite after the first six burn out. All of them burn
for approximately 1 minute.
The average first-stage thrust with the main
engines and the six solid-propellant boosters is 873,400 pounds (3.9 million
newtons). The Delta has liquid-fueled first and second stages and a
solid-propellant third stage. For most launches today, the third stage has been
replaced by a more powerful Payload Assist Module (PAM) solid-propellant stage
attached to the spacecraft.
The newest version of the PAM upper stage, the
PAM-DII, also has been used on Shuttle launches. It can boost spacecraft from
the low Earth orbit achieved by the Shuttle orbiter into higher ones. Many
spacecraft, especially communications satellites, operate in a geosynchronous
orbit some 22,240 miles (35,792 kilometers) above the equator. The Delta II and
the PAM-DII together can lift some 3,190 pounds (1,447 kilograms) into a highly
elliptical orbit for eventual transfer into geosynchronous orbit by a motor
built into the payload spacecraft. This is more than double the 1,500 pounds
(680 kilograms) that a Delta built in 1980 could manage.
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The Atlas I and Atlas II are the latest versions
of the Atlas/Centaur vehicle that first became operational in 1966. General
Dynamics uses these two vehicles to launch military, commercial, and scientific
payloads into space from Launch Complex 36 on Cape Canaveral.
The Atlas I can place a 13,000-pound
(5,897-kilogram) payload into low Earth orbit. It can also propel 5,150 pounds
(2,336 kilograms) into a geosynchronous transfer orbit, or 3,350 pounds (1,520
kilograms) into an Earth escape trajectory.
The Atlas II is 150 feet (45.6 meters) high. The
first stage produces 468,500 pounds (2,084,000 newtons) of thrust at liftoff.
The Centaur stage has the same thrust as on the Atlas I, but carries 6,600
pounds more propellant, and so can burn longer for more total power. An Atlas II
can place a 14,950-pound (6,780-kilogram) payload into low Earth orbit. The
amounts for geosynchronous transfer orbit and Earth escape trajectory are 6,100
pounds (2,770 kilograms) and 4,270 pounds (1,940 kilograms).
While launched by NASA, the Atlas/Centaur was the
standard vehicle for intermediate payloads. The Centaur was the nation’s first
high-energy, liquid-hydrogen/liquid-oxygen launch vehicle stage.
The Atlas/Centaur was the launch vehicle for
Surveyor 1, the first U.S. spacecraft to soft-land on the Moon. Some of the
other spacecraft launched by NASA Atlas/Centaurs include the Orbiting
Astronomical Observatories; Applications Technology Satellites; the Intelsat IV,
IV-A and V series of communications satellites; Mariner Mars orbiters; a Mariner
spacecraft which made a flyby of Venus and three of Mercury; Pioneers which
accomplished flybys of Jupiter and Saturn; and Pioneers that orbited Venus and
plunged through its atmosphere to the surface.
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Martin Marietta, builder of the Titan family of
vehicles, now launches the Titan IV from pads 40 and 41 on Cape Canaveral, and
from Vandenberg AFB in California. Pad 40 also has the capability to launch the
smaller Titan 34D. The U.S. Air Force is the primary customer for these launch
vehicles, but Titans are also used for NASA scientific missions - usually
planetary launches - and for commercial payloads.
In 1974 NASA launched the first of seven vehicles
that combined the Titan III-E, a two-stage liquid- propellant rocket with two
large solid-propellant boosters attached, with a Centaur from the Atlas-Centaur
vehicle replacing the original third stage. At liftoff the two solids, burning
alone, produced 2.4 million pounds (10.7 newtons) of thrust; the first liquid
propellants stage ignited when the solids burned out, followed by the second
stage. Then the Centaur, which produced 30,000 pounds (133,440 newtons) of
thrust from two main engines, ignited and burned for up to 7-1/2 minutes, an
unusually long burn time for an upper stage.
The Titan-Centaur combination vehicle, which had
a new and wider fairing, had an overall height of 160 feet (48.8 meters). It was
used in the interval between the last launches in the Saturn family and the
first flight of the Space Shuttle. Titan-Centaur gave the United States an
extremely powerful and versatile rocket which successfully launched six large
spacecraft on interplanetary missions.
The seven Titan-Centaur flights were of a test
vehicle, two Helios spacecraft to the Sun, two Vikings to Mars, and two Voyager
spacecraft to Jupiter and Saturn. The Vikings were two-part spacecraft; each
first orbited Mars, and then sent a lander to its surface. The second Voyager
went on past Saturn to Uranus and Neptune. All provided remarkable new
scientific data on our solar system. The Vikings and Voyagers also produced
spectacular color photographs of the planets they explored.
Today the Titan IV is the primary launch vehicle
for Martin Marietta. It has longer and more powerful solid rocket boosters,
longer first and second liquid propellant stages, and an upgraded version of the
Centaur. When used with an 86-foot (26.2-meter) fairing over the Centaur and
payload, this vehicle is 204 feet (62 meters) in height. It is capable of
placing 39,000 pounds (17,690 kilograms) into an east-west orbit - a payload
approaching that of the Space Shuttle. It can also place a 32,000 pound (14,515
kilogram) payload into a low polar orbit from Vandenberg AFB in California,
where the Shuttle has no launch facilities.
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The Atlas/Agena was a multipurpose two-stage
liquid-propellant rocket. It placed unmanned spacecraft in Earth orbit, or
inserted them into the proper trajectories for planetary or deep space probes.
Several programs used the versatile Atlas/Agena.
They included early Mariner probes to Mars and Venus, Ranger photographic
missions to the Moon, the Orbiting Astronomical Observatory, and early
Applications Technology Satellites. The Agena upper stage also was the
rendezvous target vehicle for the Gemini spacecraft during this series of
two-man missions in 1965-1966. In preparation for the manned lunar landings,
Atlas/Agena launched Lunar Orbiter spacecraft which went into orbit around the
Moon and took photographs of most of the lunar surface.
The Atlas/Agena D stood about 100.4 feet (30.6
meters) high and developed a total thrust at liftoff of approximately 376,000
pounds (1.67 million newtons). It carried an Orbiting Geophysical Observatory (OGO)
for its last launch in 1968.
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The Saturn V, America’s most powerful staged
rocket, carried out the ambitious task of sending astronauts to the Moon. The
first Saturn V vehicle, Apollo 4, lifted off on November 9, 1967. Apollo 8, the
first manned flight of the Saturn V, was also the first manned flight to the
Moon. Launched in December 1968, Apollo 8 orbited the Moon but did not land.
Apollo 11, launched on a Saturn V on July 16, 1969, achieved the first lunar
landing.
Saturn V began its last manned mission on
December 7, 1972, when it sent Apollo 17 on a final lunar exploration flight.
For its last mission, on May 14, 1973, it lifted the unmanned Skylab Space
Station into Earth orbit, where it was later occupied by three crews for a total
period of 171 days.
All three stages of the Saturn V used liquid
oxygen as the oxidizer. The first stage burned kerosene with the oxygen, while
the fuel for the two upper stages was liquid hydrogen. Saturn V, with the Apollo
spacecraft and its small emergency escape rocket on top, stood 363 feet (111
meters) tall and developed 7.75 million pounds (34.5 million newtons) of thrust
at liftoff.
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The Saturn 1B originally launched Apollo lunar
spacecraft into Earth orbit to train for manned flights to the Moon. The first
launch of a Saturn 1B with an unmanned Apollo spacecraft took place in February
1966. A Saturn 1B launched the first manned Apollo flight, Apollo 7, on October
11, 1968.
After the completion of the Apollo program, the
Saturn 1B launched three missions to man the Skylab space station in 1973. In
1975, it launched the American crew for the Apollo/Soyuz Test Project, the joint
U.S./Soviet Union docking mission. Saturn 1B was 223 feet (68 meters) tall with
the Apollo spacecraft atop, and developed 1.6 million pounds (7.1 million
newtons) of thrust at liftoff.
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