Vinci – tests on the high-thrust, cryogenic, restartable upper stage engine for Ariane 5 gather pace
28 April 2010
The Vinci upper stage propulsion unit en route to test stand P4.1
Europe's Ariane 5 launcher depends greatly on the capability and reliability of its propulsion systems. Their ongoing development lays the groundwork for sustained competitiveness and ensures Europe's independent access to space. The new Vinci upper stage engine continues this policy. It is a cryogenic (ultra-cold propellant) engine; it can be restarted several times and has a deployable nozzle extension.
Engineers from the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) in Lampoldshausen are developing Vinci on behalf of the French engine manufacturer Snecma. Test items are being installed in the P4.1 altitude simulation test bench of the European Space Agency (ESA), marking the start of a six-month programme of trials on Europe's most powerful upper stage.
These will include the first ever test of an engine in 'flight configuration' – the engine with its long expansion nozzle deployed. Trials will also be conducted on the propulsion system's ability to restart – exceptionally important for many mission profiles, but also an immense challenge for the test stand. This will be a major step in validating Vinci.
Installation of the Vinci propulsion unit in the vacuum chamber of test stand P4.1
Highly capable test stand technology vital in Vinci development
Never before has Europe tested a cryogenic upper stage propulsion system at thrust levels of 180 kilonewtons in a vacuum. To accomplish this, a completely new altitude simulation system was required. With the first four test campaigns held between 2005 and 2008, development engineers at Snecma gained some fundamental insights into the operating characteristics of their new rocket engine, especially during the critical phases of ignition and shutdown.
Forthcoming tests will be challenging. "With this campaign, we are undergoing a gradual process of approaching the later, realistic thrust levels and propulsion system conditions. The propulsion system cannot receive final approval for operational flights until the technology is fully understood and has been thoroughly tested," states Lars Ohlenmacher, who is in charge of tests on the P4.1 test stand.
Before the first Vinci propulsion unit is signed off for flight, a vast array of development cycles needs to be performed. During development, detailed investigations into individual components, such as turbopumps, the thrust chamber and expansion nozzle, are of central importance. Engineers at DLR are currently running tests on the Vinci's thrust chamber – the heart of the propulsion system - at the P3.2 test stand in Lampoldshausen. Development of this component is managed by Astrium Space Transportation.
Vinci – Cryogenic propellants
Vinci uses a high-energy combination of liquid hydrogen and liquid oxygen. It will power the upper stage of the performance-enhanced and more competitive version of Europe's launcher – Ariane 5 ME (Midlife Evolution). Astrium is managing its development, having been assigned this task in December 2009 by the European Space Agency. Ariane 5 ME is expected to enter service in 2017.
The payload will be increased by 20 percent, enabling it to place twelve tons in geostationary transfer orbit (GTO). A key development priority is to improve the all-round performance profile of the propulsion systems. For example, the ability of Vinci to re-ignite will allow injection straight into geostationary orbit (GEO). This will give satellites longer lives because they will no longer need their own propulsion units to reach their orbital positions. They can therefore use all their on-board fuel for station keeping, extending their operational lifetime.
Altitude simulation test rig P4.1
Simulation of great altitudes
Vinci will be used in the vacuum of space. This affects the firing characteristics of the propulsion unit. In a vacuum, much greater thrust is achieved and temperatures are very different since no heat convection takes place. That is why it is so important to simulate such conditions for the propulsion unit during tests.
Extraction of propulsion unit exhaust gases from the test chamber is performed by steam-powered ejectors. The steam is delivered by generators developed at DLR Lampoldshausen. These convert water into steam through combustion of a mixture of alcohol and liquid oxygen.