Design and analysis of orbital debris protection for spacecraft composite pressure vessels
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Being parts of spacecraft systems, composite overwrapped pressure vessels (COPVs) are exposed to orbital debris environment. In the case of impact of orbital debris on a composite vessel, the vessel may fail non-catastrophically, possibly resulting in the loss of spacecraft, or catastrophically, producing numerous non-trackable fragments, which may result in the loss of spacecraft and also affect and destroy other active and future spacecraft in neighbor orbits. Consequences of orbital debris impacts, therefore, must be minimized with the use of an appropriate design strategy. For a weight-efficient design providing high level of protection for spacecraft composite pressure vessels, the following design strategy is suggested in this study: • Exclude any involvement of the pressure wall in resisting orbital debris impacts by means of an external shielding designed for the same tolerable risk of penetration as the shielding of any other critical subsystem of the spacecraft (R1tol; typically, 1-5%); • Ensure that the shielded COPV will not fail catastrophically under conditions corresponding to even stricter tolerable risk of penetration (R2tol), such that R2tol < R1tol, which can correspond to the tolerable risk of accidental explosion during mission operations in Orbit (typically, 0.1%). Implementation of the proposed design paradigm required 1) weight-efficient shielding systems to be designed against highly probable impacts of small-size orbital debris; and 2) a procedure capable of predicting the behavior of a shielded COPV subjected to perforating orbital debris impacts to be developed. Correspondingly, this study focused on these two aspects. First, five different external shielding systems were analysed for their weight efficiency when designed against small-size (1 mm) orbital debris impacts, including a novel orbital debris shield with ceramo-metallic bumper. Conducted evaluation made it possible to identify and recommend weight-efficient shielding designs in such categories as “Single purpose orbital debris shields” and “Multipurpose structural panels”. In this part, the results are mainly applicable to the spacecraft in low Earth Orbit. Second, a two-step modeling procedure was proposed to simulate behavior of shielded composite overwrapped pressure vessels when subjected to perforating impacts by large-size hypervelocity projectiles. The procedure can be used to evaluate vulnerability of a shielded vessel to catastrophic failure.