September-October 1982:the Ariane launcher

Introduction

Following the successful launch of Ariane L04 last December, the new European launcher has now been declared to be operational. For the first time, Europe has direct access to space. NASA now has to face an independent challenger for customers, thus introducing a new factor into the design and marketing of launch vehicles.

Ariane was designed as a low cost, high capacity rocket using proven technology and was aimed at the lucrative communications satellite market. This philosophy has affected the design; for example, performance had to be traded against low production costs. This article presents a technical description of Ariane.

Viking Engines

The Viking motors of the first and second stages are devel¬opments of motors used 20 years ago for the French Veronique and Vesta sounding rockets, and later the Diamant (first stage)- and Europa (second stage) satellite launchers. Their evolution includes:

1966: first studies on 40 tonnes thrust, turbopump-driven engines (based on Diamant B first stage engine).

1968: studies for stage to replace Blue Streak in the Europa II. Four Viking engines.

1970: Europa III studies; cluster of four of five Vikings considered with up to 60 tonnes thrust each (for Viking II).

1972: CNES, the French space agency, propose the L-3S launcher after the cancellation of Europa III. Called for four Viking II in first stage and one in second. L-3S became Ariane.

1974: Viking II improved by extending nozzle; renamed Viking IV.

Ariane uses four Viking V (thrust 66 tonnes at altitude) and one Viking IV (thrust 71 tonnes at altitude) in the first and second stages, respectively. The nitrogen tetroxide (NtO) and Unsymmetrical Dimethylhydrazine (UDMH) propellant require less sophisticated engine design and handling than liquid hydrogen and oxygen. A portion of the propellants are fed into a gas generator to drive the turbopump. There, the resultant gases are cooled to 600°C by using water vapour from, in the first stage, a 3000 litre toroidal tank. The gases can also be used, when further cooled, to pressurize the tanks and provide power for gimballing the nozzles. The Viking IV and V designs are identical except for the gimbal and nozzle systems.

Third Stage Engine

The HM7 is the first operational cryogenic engine in Europe, using liquid hydrogen and oxygen. Its development by SEP (Societe Europeene de Propulsion) included:

1962: studies for 4 tonnes thrust four-chamber HM4 for Diament A second stage.

1967: first tests.

1968: cancellation following successful tests.

1969: cancellation of studies for 6 tonnes thrust version of HM4.

1969: Europa IIIN second stage: called for 7 tonnes thrust single-chamber HM7 using HM4 turbopump.

1970: Europa III second stage: design developed from HM7 with increased chamber pressure.

1972: cancellation of Europa.

1973: studies for L-3S third stage. Based on HM7, resulted in Ariane H8 third stage.

Future Ariane Versions

It was clear from the beginning that the Ariane I version was not powerful enough to compete with American launchers (1780 kg into geostationery transfer orbit.) Ariane II and III were approved in 1978 and in january this year ESA gave approval for the IV version. A possible Ariane V will be considered later.

Ariane II

The first II launch will be the 12th vehicle. The first stage has 9 per cent more thrust, achieved by raising chamber pressure to 58.5 atmospheres. Thrust per engine: 66 tonnes (sea level); 76 tonnes (vacuum). It is hoped to recover the first stage (tests will be carried out during the seventh I launch) in order to reuse some of the components. If successful, total launch cost could be reduced by 10 per cent.

The second stage Viking IV will be increased in thrust from 71.3 to 76 tonnes (vacuum).

The HM7 third stage engine will use a lengthened nozzle and increased chamber pressure to raise its specific impulse from 442.4 to 444.2 s. The third stage will be lengthened by 1.3 m to carry 10.5 tonnes more propellants.

Ariane III

Ariane III is identical to its predecessor except that it will include boosters and a modified fairing to allow larger payloads. Its first launch is schedule to be LI3 in December next year although the lengthy delays caused by the L5/Marecs satellite modifications may push it further back.

Ariane IV

Ariane IV will form a whole family by itself by using a variety of liquid and solid strap-on boosters and different payload shrouds. First launch is planned for L26 in October 1985. Modifications include:

Stage 1: tanks lengthened from 10.63 to 16.83 m, propellants from 148 to 210 tonnes. Reinforced structure.

Stages 2 & 3: identical to earlier versions but with reinforced structure.

Ariane V

The form of Ariane V is by no means certain. During 1980/81 CNES produced a variety of designs based on uprating the Ariane IV, including new third and fourth stages and a 4 m diameter second stage (which was later reduced to the same diameter as Stage 1). The third stage would be developed from MBB’s H10 Ariane IV third stage and housed inside a 4.2 m diameter fairing. The fourth stage (apogee) motor would be a modular design based on the cancelled Space Tug. This 1981 project included four basic versions (with/without third or fourth stages) and was used as the basis for the preliminary design of the CNES Hermes manned shuttle study. More recently, studies have included the Ariane IV first and third stages but with a cryogenic second stage built around a new HM60 (Vega) 60/80 tonnes thrust engine.

Ariane V will be required around 1995 for the large payloads expected by then. There would be three main versions:

Ariane VB: for low Earth orbits.

Ariane VG; for geostationary payloads; with H9 cryogenic third stage, 9 tonnes thrust.

Ariane VH: a two stage version for use with Hermes manned shuttle.

Payload volume would be half that of the Space Shuttle, and similarly for the payload mass. Other possibilities include reusable first stages.