Statistics – Methodology
Scientific paper
Aug 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004esasp.558...19l&link_type=abstract
Proceedings of the 5th International Symposium on Environmental Testing for Space Programmes Noordwijk, The Netherlands (ESA SP-
Statistics
Methodology
Scientific paper
The Ariane5 structures qualification methodology has recently been improved especially in the frame of low frequency dynamic environments encountered during Ariane flights. For example, the 3D dynamic behaviour of the launcher taking into account all possible load cases at a given moment during flight, obliged us to modify our dynamic dimensioning rules so as to combine excitations coming from different launcher's axes: lateral and longitudinal. Therefore, standard monoaxial sine tests are no more considered as "direct qualifying tests". On top of that, more and more non linear systems are integrated in the launcher's stages. The objective is either to reduce the dynamic stresses locally (i.e. by using dampers or mechanical filters in order to prevent high amplification factors) or, to optimise the dynamic behaviour at the "system" launcher level (i.e.: the liquid oxygen tank friction damper system of Ariane new upper stage which has been developed in order to reduce the dynamic levels on the spacecrafts). The dynamic models have been improved consequently. And the dynamic tests, at different levels (several and single stages levels, elementary level), are necessary to validate these dynamic models including nonlinear elements. This paper presents, through some examples, the testing philosophy for Ariane5 structures qualification. It will show the necessary links between tests and theoretical models approaches. Vibration environments will mainly be covered. Nevertheless, acoustic and static testing philosophy for qualification will also be briefly mentioned. For these later cases, the mathematical models are necessary to justify the test configuration by providing correction factors so as to cover the different effects: adjacent structures, loading conditions, thermal gradients, temperatures, pressure... At the very end of the qualification process, the first flight results must validate the methodology. For that, the flight measurement plan is particularly improved for the qualification flight. An important effort is made to verify the most critical flight phases (i.e.: microphones outside and inside the stages for lift- off phase, unsteady pressure transducers on the rear part of the launcher for atmospheric "buffeting" phase...). A quick view of a typical first flight measurement plan will be finally shown.
Chemoul B.
Louaas E.
Mourey P.
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