AESTUS: Upper Stage Engine - EADS

Space Transportation
All the space you need
AESTUS: Upper Stage Engine

Bipropellant upper stage engine for the orbital insertion of heavy payloads
The Aestus rocket engine powers the Operation
Ariane 5 ES and GS version
bipropellant upper stage for the
insertion of payloads into LEO, SSO
and GTO. For the ES version, Aestus
uses its re-ignition capability to place
ESA's 21 tonne Automated Transfer
Vehicle (ATV) into a low Earth orbit.
The Aestus thrust chamber design is
based on the regenerative cooling
principle. Prior to combustion,
MMH fuel is pressurised into a
distribution manifold causing the
fuel to flow through narrow, closely
arranged channels in the
Aestus is a pressure fed engine that combustion chamber wall,
consumes up to 10 tonnes of the configured to cause a highly efficient
bipropellant combination cooling. The MMH then enters the
MMH/N2O4.
injector head which assures uniform
Aestus was developed at the
Ottobrunn Space Propulsion Centre
propellant flow rate distribution over
132 coaxial injection elements.
during the period 1988 - 1995. The The unique design of the injection
first operational flight of Aestus was element as well as the proper
on Ariane 5 flight 502, launched on element distribution along the
30th October 1997.
injector face cause swirl mixing and
Together with the Aestus engine,
EADS Astrium is responsible for the
complete Ariane 5/EPS upper stage,
under contract with ESA, with the
atomisation of the propellants
enabling combustion efficiencies in
the chamber in excess of 98% during
the remaining combustion process.
technical advice of CNES.
Upon leaving the injector elements
Major Sub-Assemblies
Injector with coaxial injection
elements for the mixing of
propellants.
and entering the combustion
chamber, the hypergolic propellants
spontaneously ignite and are burned
and accelerated up to sonic
conditions at the throat. The
Combustion chamber
regeneratively cooled by MMH fuel.
Nozzle extension, radiatively
cooled.
Propellant valves for fuel and
oxidiser, pneumatically operated by
pilot valves.
Gimbal joint mounted at the top of
the injector dome.
combustion temperature in the
combustion chamber reaches about
3000 K at a combustion pressure of
11 bar.
Controlling the hot gas wall and
MMH coolant temperature levels
under the high operating
combustion chamber heat fluxes
was one of the most challenging
tasks that had to be overcome during
Electromechanical gimbal
actuators for pitch and yaw engine
control.
Some subassemblies have been
subcontracted to partners including
the gimbal joint to NAMMO Raufoss
(Norway) , the nozzle extension to
Franke AG (Switzerland), the
propellant valves to MOOG
(Germany and USA), the flexible
propellant lines to Witzenmann
(Germany) and the helium filter to
Rellumix (France).
the development phase. A further
challenging task was the
development of a new injector
element for MMH /N2O4, using the
same, highly efficient, coaxial
injection principle used on all of our
cryogenic thrust chambers.
After leaving the combustion
chamber, the final acceleration of
hot gases up to supersonic velocities
is achieved by gas expansion in the
radiatively cooled nozzle extension,
thereby developing thrust.
AESTUS: Upper Stage Engine
Aestus/Ariane 5 upper stage engine
EPS/Ariane 5 Upper stage
with Aestus engine

Proven Design and Performance
Flexibility
The Aestus rocket engine has proven
to be a robust and flexible design,
evolving harmoniously with the
evolution of Ariane 5 and its various
missions, as shown in the Aestus
Development History below.
In addition, by varying the number of
coaxial injector elements, the basic
Aestus design can be used for higher,
or lower thrust applications.
A turbopump engine demonstrator
version,
known as the RS 72/Aestus
2, was
derived from the Aestus
engine. This so called Pathfinder
engine has been hot-fire tested in
cooperation with Boeing Rocketdyne
(Pratt & Whitney).
Aestus Development History
The Aestus rocket engine was
developed at the Ottobrunn Space
Propulsion Centre during the period
1988 - 1995. The first flight with
Aestus under operation was on
Ariane 5 flight 502, launched on 30th
October 1997.
In the frame of performance
improvements to the complete upper
stage, a delta-qualification
programme was performed in 1999 -
2002. Here, the propellant mixture
ratio of Aestus was adjusted from
2.05 to 1.9. Subsequently, the first
operational flight of the performance
enhanced Aestus was on Ariane 5
flight 518, launched on 26 February
2004.
During the period 2003 - 2007, the
Aestus engine underwent a reignition
qualification programme in
readiness for the first launch of the
Automated Transfer Vehicle. The inorbit
re-ignition capability of Aestus
was subsequently demonstrated
during the first launch of ATV
aboard Ariane 5 flight 528, launched
on 9 March 2008.
During ATV mission, the first Aestus
ignition occurs immediately after
separation of the upper stage
composite from the cryogenic main
stage. At the end of the first burn, a
ballistic phase commences for about
45 minutes. A second ignition then
provides a short duration burn for
injecting the ATV into its target Low
Earth Orbit after separation from the
upper stage. A third and final
ignition is then used to de-orbit the
depleted upper stage into a safe reentry
trajectory for burn-up in the
upper atmosphere.
With its proven flexibility and
multiple re-ignition capabilities, the
Aestus engine enables a
considerable range of mission
specific profiles for the Ariane 5
launcher. Ariane 5 ES (with Aestus)
is a suitable launcher also for low
earth operation missions, e.g.
Galileo.
Propellants
N2O 4\MMH
Specific impulse vacuum
324 s
Thrust vacuum
29.6 kN
Propellant mass flow rate 9.3 kg/s
Mixture ratio (TC)
1.9
Engine feed pressure 17.7 bar
Combustion chamber pressure
11 bar
Nozzle area ratio
84
Nozzle exit diameter
1.31 m
Overall engine length
2.2 m
Thrust chamber mass
111 kg
Nominal single firing 1100 s
Power 43,700 kW
59,400 hp
Re-ignition capability Multiple
AESTUS: Upper Stage Engine
Assembled Thrust Chamber of the
Aestus engine
Vacuum Test Platform P4.2 of
Aestus at DLR, Lampoldhausen

ASTRIUM Space Transportation
Propulsion & Equipment
D 81663 Munich, Germany
Phone: +49 89 607 32480
Fax: +49 89 607 85480
Hartwig.Ellerbrock@astrium.eads.net
www.space-propulsion.com
www.astrium.eads.net
Thanks to DLR and ESA for their information and pictures