FW: ESA Press Release - "ESA/CNES joint press release : ARIANE 502 - results of detailed data ana"

["Willmott, Paul" <paul.willmott@xxxxxxx>]

-----Original Message-----
From: ESA News/Document Server [mailto:esanews@esrin.esa.it] 
Sent: Wednesday, April 08, 1998 7:44 PM
Subject: ESA Press Release - "ESA/CNES joint press release : ARIANE 502
- results of detailed data ana"



                                         No. 14-98 - Paris, 8 April 1998


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ESA/CNES JOINT PRESS RELEASE                                            
----------------------------

Ariane-502 - results of detailed data analysis

The results of Ariane 502 flight data analysis - a detailed evaluation
covering all information gathered during the flight - were presented to
the Launcher Qualification Board on 1 April.

The analysis confirmed that the launcher performed well overall and did
not reveal any anomalies that had not previously been identified.

The most significant anomaly, namely excessive roll torque during
cryogenic main stage flight, has now been explained.

It will be remembered that the possible causes of the 900 Nm (Newton
metre) roll torque registered in flight were narrowed down to two :

- roughness of the internal surface of the Vulcain engine divergent
  causing the boundary layer of the main jet to spiral;
- snapping of one of the rods attaching the Vulcain engine turbine
  exhaust lines to the aft end of the divergent.


Three test firings of the Vulcain engine were performed on a teststand
equipped with a roll torque measurement device.  Throughout engine
running time on all three tests,  roll values very similar to those
encountered in flight 502 were recorded.  The first of the above
explanations is therefore confirmed.  The excess roll torque phenomenon
will now be countered by repositioning the turbine exhausts.

As a precautionary measure and to obtain in-flight confirmation of the
cause of the roll problem, the additional attitude control unit that has
already been developed will still be used on flight 503.

The studies and tests conducted since flight 502 have also shown that
the premature main stage shutdown that occurred during that flight was
caused by the excessive roll torque.  Action to overcome  the torque
problem will therefore also prevent a recurrence of the premature
shutdown.

Ariane-5 is an ESA programme for which ESA has delegated management
responsibility to CNES.

Flight 503, conducted under ESA responsibility, will be the last of the
Ariane-5 qualification flights.  The launcher used will be the first
production-series unit ordered by Arianespace from European industry.

Launch operations are managed by Arianespace at the ELA-3 launch site at
the Guiana Space Centre, Europe's space port.

For further information, please contact :

ESA Public Relations Division

Tel: +33(0)1.53.69.71.55

Fax: +33(0)1.53.69.76.90