VEGA launch vehicle upper stage re-entry survivability analysis

A key task in launch vehicle (LV) system design process consists in the estimation of upper stage fragmentation during atmospheric re-entry once accomplished the launcher mission, and the related probability of making on-ground casualties. According to international policy for space debris mitigation, VEGA upper stage AVUM re-entry from its final orbit is analyzed by means of numerical tools, in order to identify which objects are demised during atmospheric re-entry and which ones are able to withstand aerothermal loads impacting on ground. The logic is based on parent/child concept: initially the S/C is modelled as one parent object. The parent object virtually contains all other internal components of the S/C. The output of the analysis comprises the mass, cross-section, velocity, incident angle of the surviving fragments and their casualty area. Final casualty risk assessment is then performed starting from the survivability analysis results achieved and compared to applicable regulations. Application on Vega LV maiden flight provide practical results.