The opportunity of performing many tests in a single working day makes it possible to partially overcome one of the limitations in the field of hypervelocity impact testing, i.e. the lack of experiments. The special LGG set-up does not use components that are destroyed during gun operations: high-pressure helium is used instead of powder as piston driver, special automatic valves have been designed to replace rupture disks between the pump tube and the barrel, and the piston extrusion in the pump tube high pressure section is avoided.
The gun has been designed to be a very flexible system to be applied on different problems, from low speed to hypervelocity. It can be used in a single-stage mode (500 grams accelerated up to 300 m/s) and in a two-stage mode (100 mg up to 5.5 km/s).
The gun can launch saboted projectiles allowing the acceleration of particles having different shape and size.
Speed measurement equipment:
The sabot and projectile velocity is measured by recording the time distance between two subsequent break-ups of two laser blades crossing the flight path. A third signal comes up from a photodetector that is sensitive to the light emitted during the impact. The combined use of these methods makes it possible to achieve accuracy below 2% in the velocity measurements.
Photographic equipment is available to catch 4 shadowgraphs with a minimum time delay of 1 microsecond between subsequent pictures. This can be used to verify the projectile integrity before the impact or to study the evolution of the debris cloud resulting from the perforation of a target. Three different fields of view are obtainable (80, 110 and 160 mm). The system adopts a trigger that synchronizes automatically the light flashes to the impact, without the need of trial tests.
Acceleration measurement equipment
A measurement system is available to record vibration and deformation signals from different locations on targets. Shock accelerometers (up to 200000 g, resonance frequency 1.2 MHz) can be employed to measure the near-field environment resulting from hypervelocity impacts. Moreover, standard piezoeletric accelerometers and laser vibrometer are available for acceleration measurements in the mid and far-field.