The Ariane 5 launch vehicle is the new addition
(as of 1998) to the Arianespace family of
launchers. With this new vehicle, Arianespace
brings the next generation of heavy lift launch
services to the global satellite launch
marketplace. Ariane 5 is designed to be even more
successful and reliable than Europe's launch
workhorse, the Ariane 4. Its simple, clean,
modular design provides reliability and
performance that is unsurpassed in its class.
Ariane 5 is not so much a single vehicle as it is
a modular collection of reliable, well proven
parts. Modularity allows maximum versatility for
different sizes and styles of payloads, and
ensures that Ariane 5 can continue the philosophy
of improvement and innovation that began with its
predecessors. Future improvements to the launch
vehicle will allow the delivery of larger and more
diverse payloads to a wide range of possible
orbits. Future enhancements will become
particularly useful as large satellite
constellations become more commonplace.
Ariane 5 was originally proposed as the next in
the Ariane line in 1977. The project was
approved in 1985, and the design of a new
cryogenic engine began. The resulting engine,
Vulcain, was first tested in 1990, and has since
proven to be a reliable foundation for Ariane
5. The Aestus engine, which is used in the upper
stage of the launch vehicle to put payloads in
the required orbits, was first tested in 1992 and
completed testing in 1994. Development of the
solid rocket boosters culminated in the first
full scale test in 1993. The combined vehicle made
its maiden voyage on June 4th, 1996. The test flight ended 37
seconds after liftoff, when a software error
caused it to veer off course and breakup. The
second test flight occurred on October 27th, 1997,
and the third, completely successful flight flew
on October 28th, 1998.
The heart of the Ariane 5 launch vehicle is the
main cryogenic stage. This stage houses the
equipment bay, the cryogenic propellant, and the
Vulcain engine. The vehicle equipment bay contains
the electronics that monitor and control the
vehicle during its flight. Redundant computers and
flight guidance systems help make Ariane 5 as
reliable as possible. The cryogenic propellant
consists of 132.27 metric tons of liquid oxygen
and 25.84 metric tons of liquid hydrogen, which is
burned by the Vulcain engine. The cryogenic stage
is 30.5 meters long, from the engine bell to the
forward skirt, and has a dry mass of 12.2 metric
tons. Fully fueled, this stage has a mass of 170.3
metric tons. This stage operates for 589 seconds,
at which point it separates from the remaining
upper stage. The cryogenic stage then falls back
into the atmosphere and is destroyed as it falls
back into the ocean.
Solid rocket boosters provide 90% of the enormous
thrust required to break free of Earth's
gravitational field. The boosters are 30 meters
long, and contain 237.8 metric tons of
propellant. Both boosters together provide 1,370
metric tons of thrust at liftoff. They burn for
130 seconds, after which they separate from the
vehicle and fall into the ocean. The boosters may
then be recovered, and post flight analysis can be
performed.
The upper, or stored propellant stage, is the part
of the vehicle that actually puts the payload into
orbit. This stage carries 9.7 metric tons of fuel,
and is powered by the Aestus engine. This
restartable engine can provide 3 metric tons of
thrust, with flight control provided by electrical
actuators controlling the engine nozzle.
A number of payload configurations are available
for Ariane 5. The vehicle can be configured with
one of two fairings, one of nine payload adapters,
and, optionally, either a Speltra or a Sylda 5
structure. The Speltra and Sylda 5 structures
allow two primary payloads to be launched at the
same time. Ariane 5 can also be fitted with the
Ariane structure for auxiliary payloads, which can
accommodate up to eight micro satellites.
The fairings provided by Ariane 5 protect the
payload as it is launched. The acoustic, thermal,
and atmospheric protection provided by the fairing
ensure that the payload is not damaged during its
ascent. The vehicle can be fitted with one of two
payload fairings. The short fairing is 12.7 meters
long and accommodates payloads up to 11.5 meters
long. The long fairing is 17 meters in length and
allows for payloads as long as 15.5 meters
long. Both the long and the short fairings have a
useful interior diameter of 4.57 meters.
To provide maximum versatility, Ariane 5 has nine
different payload adapters, allowing payloads
ranging in mass from 1,000 kg to 18,000 kg. These
adapters give Ariane 5 the ability to launch
satellites based on all current satellite
platforms.
The Speltra and Sylda 5 structures allow two
primary payloads to be launched on the same
flight. The Speltra structure is mounted on the
stored propellant stage and contains one of the
primary payloads. The second primary payload is
mounted on top of the Speltra structure and is
enclosed in the payload fairing. Speltra comes in
three versions, tall, standard, and short. The
standard version is seven meters in length and all
Speltra structures can house payloads 4.57 meters
in diameter. The Sylda 5 structure is similar to
the Speltra structure, except that it is entirely
enclosed by the payload fairing. The Sylda 5
structure comes in six different versions, and can
carry payloads from 2.9 meters to 4.4 meters in
length, with a maximum diameter of 4 meters.
All in all, Ariane 5 is a modern, reliable, heavy lift
launcher. It is operated by France based
Arianespace, and is flown from the Guiana Space Center
in French Guiana.
Resources
Arianespace, Jan 17th 2001, http://www.arianespace.com/
Arianespace,
Ariane 5 Technical Information, 1999,
http://www.arianespace.com/interior/ARIANE5\_tech\_GB.pdf
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