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Ariane 503 total success
by Peter C Klanowski
The European heavylift launcher Ariane
5 completed its third and final demonstration
flight, which has been “outstandingly
successful” despite technical
problems that delayed the launch 37
minutes. Ariane 503 (Flight 112) was
carrying the European Space Agency’s
Atmospheric Re-entry Demonstrator
(ARD) capsule and the MaqSat-3 mockup
satellite.
ARD separated from the rocket 12 minutes
after lift-off. The dummy satellite MaqSat
3 was delivered almost exactly into the
planned orbit. Had it been a real satellite, it
would have separated from the launcher.
The Atmospheric Re-Entry Demonstrator
(ARD) splashed down only 5 km from its
target in the Pacific Ocean one hour and
forty-three minutes after launch.
Said Patrice Amadieu, head of the ARD programme:
“No other [launch] vehicle in the
world has performed such an manoeuvre.
It demonstrates the rocket’s guidance and
navigation system permit it to attain orbits
more exotic than the classic geostationary
missions.”
An important point was that the Ariane 5
used for this flight was the first in the series
of 14 production vehicles ordered by Arianespace.
It had been modified in accordance
with the recommendations of both the A501
inquiry and the analysis of the data from the
second qualification flight A502.
A501 exploded shortly after launch owing
to faulty control software. A502 was only
a partial success because it experienced
an excessively high roll torque, causing the
main engine to shut down some 10 or 20
seconds too soon. One of the test satellites
aboard was consequently delivered into a
wrong orbit.
Since the A502 mission,
improvements have been
made to Ariane 5’s attitude
control, flight control, guidance
and navigation. The roll
torque was to be corrected
by modifying the angular
setting of the Vulcain engine
turbine exhaust nozzles.
The power delivered by the
attitude control system has
also been largely increased
to counter any other disturbance
torque that may
occur.
Dummy satellite: MaqSat 3
The principal objective of A503 was to demonstrate
that the new launch vehicle is now
ready to place satellites in orbit with the precision
and quality of service that are required
of a commercial launch. As a real
satellite was unavailable, Kayser-
Threde of Munich, Bavaria, had
to build a dummy.
In contrast to the MaqSat-H and
B platforms on the A502 mission,
MaqSat-3 was not
fully equipped with
measuring instru-
MaqSat-3 ments. The number
of sensors was
limited to a dozen
shock transducers
and strain gauges
situated particularly
around the MaqSat-
3 interface with the payload
adapter. During the flight, it
was to precisely measure the
launcher environment on the
occasion of the different stage
separations.
After reaching its GTO orbital injection
point, MaqSat-3 was not separated from the
launcher in order to avoid undesired space
debris.
Get back: ARD
The vehicle looks like
the American Apollo
capsules that returned
from manned missions
to the moon. That’s
no coincidence: it was
designed to perform a
guided and controlled
re-entry of a (in this
case: European) space
vehicle.
The knowledge that
ARD
was expected be gained
from the ARD mission
should help confirm
many things: the correctness of aero-thermodynamic
models and predictions, the
efficiency of thermal protection design and
materials, the assessment of navigation, guidance
and control systems and software and
the behaviour of the parachute system that
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