From Ariane-1 to Ariane-5

G. Le Guern

Ariane-5 is the latest member of a family which has evolved to a large extent over the last 20 years. Its first member was built out of 'off-the-shelf' hardware and its last member embodies advanced technology. This evolution is worth recalling.

Introduction

The initial decision to ensure autonomous and affordable access to space for Europe was taken in Brussels in July 1973 by European ministers. This was a bold decision at a time when the prospect of Europe placing in orbit satellites other than those meeting its own needs (on average two per year) appeared remote indeed. Atthe European Space Conference, the ministers also approved the principle of establishing the European Space Agency.

The maiden flight of Ariane-1 on 24 December 1979 marked Europe's arrival on the international satellite launch market. Market prospects and changing payload mass requirements prompted, in the early 1980s, the Ariane-2/-3 and then Ariane-4 development programmes. In parallel, Europe's determination to gain a foothold in the international market was underlined in March 1980 by the formation of Arianespace to handle Ariane production and commercialisation.

The space transport market was henceforth a profitable proposition and within Europe's reach. European ministers meeting in Rome (January 1985) and The Hague (November 1987) therefore decided to develop a successor to Ariane-4 in order to preserve the launcher's technological strengths and international market share.

Ariane-1/-4 development programmes

Ariane-1
With a geostationary transfer orbit lift capability of 1835kg, Ariane-1 was used eleven times from 1979 to 1986. Of these, four qualification flights demonstrated the launcher's operational capability and six promoted the commercial use of Ariane (promotion phase approved in December 1977). The latter were carried out under ESA's responsibility and involved European and other satellites (e.g. Intelsat).

Ariane-2/-3
The Ariane-2/-3 programme was decided in 1979 with a view to increasing the lift-capability to about twice that of Delta-class satellites at the time, i.e. approx. 2 1140kg. No qualification launcher was required and GTO lift capabilities of 2275 kg (Ariane-2) and 2650kg (Ariane-3) were achieved. A further objective was to gear production facilities to a production rate of at least five launchers per year. Seventeen units were built and launched from 1986 to 1989.

The main modifications made to Ariane-1 to create an Ariane- 2 or Ariane-3 launcher were as follows:

• increase payload volume allocation (biconical nose fairing and lengthening of SYLDA: Ariane dual-launch system);

• improve third-stage performance (increase propellant capacity, HM7 B engine thrust and specific impulse);

• develop 7.35tonne solid propellant boosters and reinforce first-stage structures (thrust frame and inter-tank skirt for fastening the boosters);

• increase launch chamber pressure of first/second stage Viking engines.

Ariane-4
Ariane-4 development was given the go-ahead in April 1982, the three main components of the programme being:

• a new launcher meeting satellite market requirements, taking into account payload mass (to allow dual launches of 1140kg Delta-class and 2500kg Atlas Centaur-class satellites as well as launches of heavy satellites such as Intelsat-6 and -7 in the +4000kg class) and launch costs;

• a new launch pad (ELA-2) allowing for a rate of ten launches per year;

• a new payload preparation complex (EPCU-2) dedicated to Ariane-4 class spacecraft

The programme itself involved:

• development and ground qualification of the modifications made to Ariane-3 to create Ariane-4;

• adapting the launch facilities to the launcher and payloads;

• carrying out a demonstration flight, which took place in June 1988.

The new features of Ariane-4 compared to Ariane-3 were as follows:

• development of a new fairing (to increase the useful volume) and of a new dual launch structure (SPELDA Ariane dual-launch external bearing structure);

• development of a new equipment bay;

• structural stiffening (second stage, third stage and carbon fibre inter-stage skirt);

• lengthening of first stage (total propellant load 228tonnes) and addition of 39tonne liquid-propellant boosters or new solid-propellant boosters (stretched from 7.35 to 9.5 tonnes).

Ongoing development activities necessary to support the operational phase and consolidate launcher reliability have been combined under the Ariane complementary development programme.

After flight 86, the various versions of Ariane-4 will have chalked up 58 launches with 28 still to come.

Ariane's success

This is mainly due to Europe's political will to back the programme in order to achieve the best possible end result (launcher, launch base and services), developed and produced in a suitable structure fully geared to market requirements and capable of standing upto the competition.

Ariane's successes came thick and fast in the early eighties and today Ariane is the yardstick for success on the world launch services market, thanks to:

• its reliability (success rate of 95%);

• its great precision in injecting payloads into orbit (in GTO, standard deviation of 30km for apogee and 0.5km for perigee);

• its great flexibility as regards utilisation (six Ariane-4 versions, two launch tables and payload preparation complex adapted to launch rate);

• a constant drive to improve both product and performance in order to best meet the requirements of a constantly changing market (a 44L/GTO lift-capability gain of over 500kg has been achieved since the start of the programme, mainly by modifying the third stage and various other launcher structures).

The competition

The civil and commercial market accounts for about 30% of the world market; this is the sector which is accessible to Ariane. It can be divided into two main groups:

• telecommunication-related applications (over four-fifths of the civil/commercial market are undergoing deregulation);

• Earth observation, meteorology and science applications.

The number of commercial satellites launched each year since the start of the decade has basically remained constant (50), with the proportion of telecommunication satellite launches rising steadily.

This market, which is changing all the time, is characterised by:

• a significant increase in the number of satellites to be launched between now and the end of the century,

• the start of constellation launches in low or medium earth orbit,

• an increase in telecommunication satellite mass (not taking into account clusters), with an average of 3400kg by the year 2000 as opposed to 1000kg at the start of the eighties,

• international competition.

This competition, which can be expected to be increasingly fierce as from 2000 onwards, is characterised by:

• the emergence on the market of the CIS (Commonwealth of Independent States) and China which, given their non-market economies, can offer prices well below those of US and European competitors;

• the emergence of international joint ventures like the International Launch Services (Lockheed Martin/Khrunichev Energia for Proton-K) and Sea Launch (Boeing/NPO Yuzhnoye for Zenit-3);

• the undertaking of new programmes in the United States (Delta-3; Atlas- 2AR, new concept, less expensive than Atlas-2AS; Evolved Expendable Launch Vehicle, available in early 2000; Titan- 4B, improving on Titan-4 lift-capability with 50% recurrent cost decrease) and in Japan (H-IIA available around 2001 in 4, 6 and 8 tonne versions in GTO, above all with 50% cost reduction in relation to H-II).

The table below shows the launchers (with their GTO lift capability) which are or will be competing with Ariane in the near future.

US	Delta-7925 Delta-3 Atlas-2AS Atlas-2AR Titan-2	1800 kg 3000 kg (1998) 3800 kg 3870 kg (1998) 4900 kg
CIS	Proton-K Zenit-3	550 (2600/GEO) 5400 kg (1998)
Japan	H-II	4000 kg
China	CZ3A CZ2E CZ3B	2500 kg 3500 kg 4800 kg (1996)

Conclusion

After over 25 years of political commitment, Europe has secured autonomous access to space and conquered the international space market thanks to its industry's stringent technical and operational standards. With over half the world commercial satellite launch market, Europe looks set to maintain its position with the arrival of Ariane-5, which will outperform Ariane-4 and has a simpler design, leading to more competitive recurrent costs). Furthermore, given the decisions on Ariane-5 complementary programmes taken at the Ministerial Conference in Toulouse in October 1995, the prospects for Europe in the area of space transportation in which it has demonstrated its excellence are once again bright.