SHOCK ATTENUATION SYSTEM FOR SPACECRAFT AND ADAPTOR

摘要

Shock problematic – Attenuation performancerequirementThe coming on the launcher market of Ariane 5 hasallowed to launch heavier spacecraft but has alsointroduced new important shock levels at the base of thespacecraft. Specific test campaigns or expertises havebeen necessary to qualify the spacecraft and to acceptthe Flight Aptitude Review. The objective of theproposed SASSA (Shock Attenuation System forSpacecraft and Adaptor) is to limit the spacecraftqualification to shocks on the basis of a clamp-bandrelease test only (without any Shogun test). It meansthat the clamp band release event must be the sizingshock event in the whole frequency range compared tofairing jettisoning and VEB separation. With such anattenuation system, the same logic as ARIANE 4qualification campaign could be maintained.SASSA requirementIn addition of shock filtering, the main requirements ofSASSA is to hold the spacecraft during all launch phaseand to avoid large modifications in dynamic involved inattitude control law. In particular, the first frequenciesand associated loads are examined.At launcher system level, the SASSA will bring someadditional flexibility to the upper part of the launcher. Itis necessary to limit this extra-flexibility in order toensure the attitude control of the launcher, in particularduring the atmospheric phase. The stiffness of SASSAmust be such that the decrease of the first modefrequencies of the configuration:Adaptor + SASSA +rigid spacecraft is limited to 20% in lateral (typicallyfrom 10 Hz to 8 Hz). This requirement must be met forthe sizing spacecrafts (small with 2 tons, medium &large with 6 tons).Sizing of SASSA takes into account, the general loadsimposed by the spacecraft inertia and the over fluxes atthe launcher interface.The nominal interface is, on one side the ACU 1194 Hin place of the dismountable ring, and on the other side,the clamp band profile. Anyway, generic aspects mustalso drive the design and the SASSA must be easilymodified in order to be introduced at differentdiameters, for example ACU (2624 m or 1666 diameter)or above the clamp band to attenuate its release.Synthesis on concepts feasibiltyResults from this feasibility phase, in addition withexperience gathered on the reflectors or solar arraysshock attenuators, show that it is possible to fulfil therequirement with the same concept based on rubbershock attenuation. In this case for spacecraft andadaptor, the most efficient design is reduced to simplestform, with only one stage of rubber.