Ariane 5 Reaches for the Skies
By Vincent Canu and Gilles Lebiez, Fluent France and Keith Hanna, Fluent News
 Ariane 5 (last heavy version) qualification flight in February 2005. The launch was |
Europe's access to space today depends on the Ariane family of heavy-duty(6–10 ton) launchers and the future Soyouz and Vega launchers for medium and small payloads (1–3 tons). Since their inception, Ariane rockets have been the most successful commercial satellite launcher systems ever, with Ariane 4 alone being responsible for the launch of 182 satellites of all kinds in 14 years before its retirement in 2003 – over 450 tons in all.
The space industry in Europe today employs thousands of men and women in hundreds of companies across the continent. Space-related systems contribute a tremendous amount to our scientific knowledge and technological development in the modern world. They are responsible for the hundreds of satellites launched since the 1970s that have paved the way for global positioning systems in our cars, improved weather forecasting and global climate monitoring, detailed mapping of our land masses and ocean depths, modern high speed telecommunications, and increasingly sophisticated defense and security aids.
The Ariane 5 rocket was first put on the drawing board in 1987 and subsequently had its first successful launch in 1997 from the Guiana Space Center near Kourou, French Guiana. Its success is the result of a unique collaboration between many European companies who all make different parts of the launcher system. Over the years, engineers have faced immense technological challenges, including cryogenic propulsion systems, aerothermodynamics, fluid-structure interaction, thermal protection, and aeroacoustics to name a few. A variety of in-house and commercial CFD codes, including FLUENT, have been used to successfully model these diverse phenomena. In fact,CFD has been used to model nearly every part of the launcher and launch process [1], such as:
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By comparison with the Ariane 4 rocket, which relied little on CFD, Ariane 5 has made widespread use of this technology for understanding, refining, and ultimately accelerating the space transportation design process, within the constraints of safety and quality assurance demanded of such a unique system. Of the many companies involved with Ariane 5, CNES, the French governmental space agency, led its technological development in association with commercial and academic partners such as EADS Space Transportation, Air Liquide, Snecma, Sener, Fiat Avio Spa, and Cryospace, among others. CNES was formed in 1962 to assist the French government in shaping France’s space policy. It leads the programs funded by the French government and represents France at the European Space Agency (ESA) and in international space activities and partnerships. It has about 2,500 personnel at four sites across the world, and in addition, it promotes and encourages space applications and industrial space related R&D. For 40 years it has been involved in driving the design and development of European Launchers with respect to safety, production, quality assurance and launch ground facilities.
 Classical launch in geostationary transfer orbit (GTO) (with reentry of the main stage into the sea), followed by satellite maneuvers to reach geostationary orbit (GEO); solar arrays are then unfolded to get the operative configuration of the spacecraft |
“Real tests to validate or compare CFD results for Ariane 5 are expensive, hard to do (especially for cryogenic liquids), and limited in generating useful data. Actual Ariane flight data is best for CFD validation, but it, too, is very expensive to generate. That’s why we need reliable CFD codes.
Currently, CNES uses some 90 different pieces of simulation software, most of which need to be ISO 9001 certified. For future space systems, CNES is interested in using validated software (including CFD codes) to evaluate reusable launcher components; electrical, nuclear and solar propulsion systems in space; as well as miniaturization and nanotechnology, using lighter materials with different compositions. Ultimately, performing virtual launches with simulation software will be a challenge.”
“EADS carries out most of the construction of the Ariane 5 Launcher, and uses FLUENT for aerothermal analysis and aerodynamics. Each Ariane launcher is unique because each payload is different. CFD is used to give technical confidence and reliability to the design team. In their planning it helps to cut costs and it also yields technical insights that would not otherwise be available. However, senior engineering experience also plays a major role in the design process in terms of checking the CFD predictions rigorously.”
The civil space industry has become highly competitive in the post cold war world and the Ariane space program wants to keep its dominance in the satellite launching arena by constantly updating its technology. However, as with NASA’s recent space shuttle troubles, the modern Ariane 5-ECA rocket also had a failed mission. On December 11, 2002, the cooling tubes in the central Vulcain 2 liquid fuel rocket failed, ultimately leading to the rocket’s mission being aborted. This caused a major reevaluation of the Ariane 5 launcher and CFD was used extensively for the next two years to identify the source of the failure and fix the cooling problem. The changes, many of which were simulated and later tested, led to a successful launch of a new rocket with enhancements to its third stage in February, 2005. In honor of this achievement, all of the stories in this supplement focus on Ariane 5 applications that have made use of FLUENT software. Cryogenics applications are featured in stories by Air Liquide and Cryospace (page s3), Snecma (s4) and CNES (s5), and heat transfer in pressure-controlled cavities is described in an article by EADS (s6). The complex flow characteristics of gaseous combustion products in solid rocket motors are shown on the supplement cover, and described in the article by Fiat Avio Spa on page s7.
Reference
- Launch-Vehicle Modeling, European Space Agency (ESA) Bulletin 120, November, 2004.
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