Like the 1979 Ariane 1, forerunner of Ariane 2, 3 and 4, Ariane 5 was conceived from the outset as the first in a new family of launchers that would maintain Europe with a sure and competitive means of access to space.

So, in October 1995, even before the new launcher's first flight, the ESA Member States decided at a Council meeting at ministerial level in Toulouse, to start work on an improved version of Ariane 5 with increased lift capability.

Commercial space transport, which represents most of the Ariane launchers' activity, depends to a large extent on developments in the satellite market. During the 1990s, that market saw a sharp increase in the power and capacity (thus also mass) of geostationary telecommunications satellites, which alone account for more than 95% of the commercial launch market.

In the course of 10 years, large satellites increased in mass from 2.5 to almost 5 tonnes. Since 2000, orders have also been placed for satellites weighing 6 tonnes or more.

At the same time, the competitive environment has changed. Orders for new satellites have slowed down, the communications sector is going through a phase of consolidation and rationalisation, and many launchers are now operating in competition with the Ariane system, resulting in overcapacity.

A response to new market needs
In order to provide competitive launch capabilities, the Ariane system has been geared since the beginning of the 1980s to dual launches of geostationary satellites. The new market conditions have made this even more imperative.

In 1995, ESA commissioned studies and predevelopment work to increase Ariane 5's lift capability even further and in May 1999, the ESA Council meeting at ministerial level approved a new plan to improve the Ariane 5 launcher so as to achieve the aim of placing 10 tonnes in geostationary transfer orbit in 2002 and 12 tonnes by 2006.

ESA has delegated the technical management of these Ariane 5 follow-on development programmes, like earlier ones in the series, to the French space agency, CNES, and Arianespace will continue to be responsible for the marketing side.

This new lift capability, and the strategy for achieving it while at the same time reducing the launcher production costs, means that Ariane 5 will be able to launch almost all the satellites on the market, from the largest to the smallest, in pairs. Also, its fairing, 5.4 m in diameter, will accommodate the most bulky satellites.

This release from pairing constraints is accompanied by greater flexibility in the requirements regarding occupancy. The launcher has been designed so as to achieve a very substantial reduction in the cost per kg in orbit, with the result that it will still be competitive even if it carries two satellites that together weigh less than 10 tonnes.

In practice, as a result of these improvements, Ariane 5 will have a powerful and at the same time standardised configuration enabling it to take satellites on board in pairs as they arrive in Kourou.

All these features represent prime assets that will secure the lasting success of Arianespace's commercial range in years to come.

Tried and tested architecture
The first Ariane 5 launcher with a lift capability of 10 tonnes will be used on Flight 157, the 14th Ariane 5 launch and the European launcher's 11th commercial mission since it was commissioned by Arianespace in 1999.

On 28 November, the launcher lifting off from Kourou in French Guiana, will orbit two satellites, the Hot Bird(TM) 7 communication satellite for Eutelsat, and the STENTOR space telecom technology satellite for the French Space Agency, CNES.

The "Ariane 10 tonnes" launcher or Ariane 5 ECA, to give it its official name, has the same general architecture as the Ariane 5 launcher, with two solid boosters (EAP) to lift it off the launch pad, a cryogenic main stage (EPC) to do most of the work of getting into orbit, and an upper stage to place the satellites in the target orbit, in most cases a geostationary transfer orbit of up to 36,000 km from which their on-board propulsion system will be able to help them into their final orbit.

To raise the lift capability from 5.9 tonnes to 10 tonnes for a dual launch, most of these features have been "beefed-up" to increase their performance.

"Beefed-up" engines
The solid booster engines -- made by Europropulsion (Italy, France) -- each comprise three segments and the smallest of these now carries 10%, or approximately 2.5 tonnes, more propellant. Because of its form, this segment is the one, which burns most quickly and gives the launcher its initial thrust. The extra load it now carries in fact provides an additional 50 tonnes of thrust in the first 20 seconds following lift-off.

So, between them, the solid boosters deliver a thrust of 1 400 tonnes, or 10 times that delivered by the engine of the central stage. At the end of the day, that means 400 kg more payload. Also, these boosters are equipped with a new nozzle, which has fewer parts and so is easier and cheaper to produce.

The cryogenic Vulcain engine of the main stage, produced by Snecma (France), has also been modified to increase its thrust by 20%, to 137 tonnes. The new version, Vulcain 2, burns a mixture of propellants enriched with 20% liquid oxygen under slightly higher pressure than the previous version.

As a result of this change in the mixture of propellants, FiatAvio (Italy) has had to develop a new oxygen turbopump, capable of rotating at 13,000 rpm and delivering a pressure of 161 bars.

It has also been necessary to increase the capacity of the liquid oxygen tank in this stage by 15 tonnes. This has been achieved, without altering the structure of the stage, simply by moving the common base of the liquid oxygen and hydrogen tanks 640mm.

Another improvement in Vulcain 2 is a new nozzle divergent, manufactured by Volvo Aero (Sweden), which enables the emissions from the turbopumps to be reinjected into the main system and improves the engine's performance at high altitudes.

All in all, the Vulcain 2 alone provides an additional lift capability of 1,300 kg to destinations in geostationary transfer orbit.

The legacy of Ariane 4
The most important new feature of "Ariane 10 tonnes" is the upper stage. The storable propellant stage (EPS) has been replaced by a cryogenic upper stage (ESC-A) carrying

14.6 tonnes of liquid oxygen and hydrogen. Produced in Bremen under the prime contractorship of Astrium (Germany), it makes extensive use of tried and tested technologies, including the liquid oxygen tank, thrust frame and propulsion assembly used in the third stage of Ariane 4, together with its HM-7B engine, supplied by Snecma.

The liquid hydrogen tank employs the technologies developed for the tank housed in the main stage. The only new feature is the dome-shaped bulkhead, which holds the liquid oxygen tank.

The stage rests on a composite cylindrical section 5.4m in diameter and 2.8m high, produced by EADS CASA Espacio (Spain).

The ESC-A is the crowning achievement among the improvements to Ariane 5. It alone accounts for 60% of the increase in performance compared with the preceding launcher in the series, with almost no change in the production cost. It is also responsible for deploying the satellites with maximum precision so as to ensure that they have an optimum operational life.

A rigorous qualification programme
All these modifications to the Ariane 5 launcher have been subjected to rigorous qualification procedures within the framework of the ESA development programmes and the Ariane Research and Technology Accompaniment programme, ARTA, which is also managed by ESA and funded by the European governments.

The increased propellant charge carried by the boosters and their new nozzle were qualified in two full-scale hot tests conducted at Kourou in May 2000 and November

2001. And the Vulcain 2 engine has undergone more than 130 test-stand firings at Vernon, in Normandy, and Lampoldshausen, in Baden-W�rtemberg, accumulating more than 50,000 seconds of operating time, equivalent to about 100 flights.

The ESC-A stage has been subjected to standard qualification with dynamic and vibration tests conducted at the IABG Centre at Ottobrunn (Germany).

The HM-7B engine, although it has already flown more than 130 missions, has undergone its own validation test campaign to ensure that it functions satisfactorily in Ariane 5 flight conditions and, in particular, with 200 seconds more burn time.

An operational test campaign has also been conducted at Kourou on a complete stage, to check the procedures and interfaces required for filling and activating the stage on the launch site, including the use of new retractable cryogenic arms mounted on the mobile launch table mast.

Objective: Re-ignition
The "Ariane 10 tonnes" will be the standard version of the Ariane 5 launcher for the next few years. However, its successor is already being planned within the framework of the Ariane 5 Plus programme adopted at the ESA Council meetings at ministerial level held in Brussels in 1999 and Edinburgh in 2001.

Ariane 5's development potential is by no means exhausted and this new version could increase its lift capability to the point of placing 12 tonnes in geostationary transfer orbit.

A new and more powerful upper stage is being studied. It will be equipped with a new engine, the Vinci, already under development, capable of delivering three times as much thrust and performing re-ignition and ballistic phases.

The re-ignition facility will give Ariane 5 added flexibility to meet the new market demand to place satellites in other orbits or to carry out complex tasks such as placing constellation clusters like Galileo in medium Earth orbit.

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