Hypervelocity debris impact damage of space composite structures

The increasing amount of debris in Earth orbit poses a danger to users of the orbital environment.During the design phase of a spacecraft, an important requirement may be specified for the survivabilityof the spacecraft against Meteoroid / Orbital Debris (M/OD) impacts throughout the mission; moreover,the spacecraft structure is designed to guarantee its integrity and reliability during the launch and, if it isreusable, during descent, re-entry and landing. In addition, the structure has to provide required rigidityfor exact positioning of experiments and antennas, and it has to protect the payload against the spaceenvironment. In this frame, in order to decrease the probability of spacecraft failure caused by impacts,for M/OD with dimensions less than 1cm, shields are needed for every spacecraft. It is therefore necessaryto determine the impact-related failure mechanisms and associated ballistic limit equations (BLEs) fortypical spacecraft components and subsystems. In order to obtain the ballistic limit equations, numericalsimulations and laboratory experiments are required. A high energy ballistic characterization of layeredstructures has been carried out by means of a new advanced electromagnetic accelerator, called railgun,that has been assembled and tuned. A railgun is an electrically powered linear electromagnetic projectilelauncher. Such device consists of a couple of parallel conducting rails, that allow sliding metallic armatureto be accelerated along, by the electromagnetic effect (Lorentz force) of a current flowing down one rail,into the armature and then back along the other rail, thanks to a high power pulse given by a capacitorsbank. A tunable power supplier is used to set the capacitors charging voltage at the desired level: inthis way the Railgun energy can be tuned as a function of the desired bullet velocity. In such a way thisfacility is able to analyze both low and high velocity impacts. A numerical simulation is also carried out,using the Ansys Autodyn code, in order to analyze the exposed structures and verify the correct behaviorof the facility. The experimental and numerical simulations results show that the railgun device can beused to perform impact testing of materials in the space debris energy range.