An engineering model to describe fragments clouds propagating inside spacecraft in consequence of space debris impact on sandwich panel structures

All spacecraft in Earth orbit are exposed to the risk of impact with micrometeoroids and orbital debris. When such particles have enough energy to penetrate the hull of the vehicle, clouds of fragments are ejected into spacecraft and they can eventually compromise the functionality of various components encountered in their flight path. Knowledge of the clouds' properties (e.g. fragments mass and velocity) is therefore a key factor to obtain accurate predictions of the response of interior equipment to space debris threat. However, generation and evolution of debris clouds from hypervelocity impact is a complex phenomenon governed by a large number of parameters, and existing models mostly refer to fragments originated by impact on simple aluminium plates only, while the few models available for sandwich panels do not provide information on the fragments mass. In such context, this paper presents an engineering model describing debris clouds created by space debris impacts on honeycomb sandwich panels representative of satellites structural bodies. The model consists of a set of empirical equations providing three pieces of information, i.e. the geometric description of the cloud, the velocity distribution and the mass distribution of the fragments. The proposed equations are derived from analogous formulas for debris clouds originated by impacts on simple aluminium plates, by applying proper corrections to account for different materials effects and different behaviour of sandwich panels compared to plates of same material. The model is finally evaluated by comparing its predictions with few experimental data on triple wall structures (sandwich panel plus internal equipment cover plate), where debris clouds exiting the panels’ rear skin are used to assess the failure of the third wall. In this latter case, the proposed model is also compared with the SRL equations.