In-Tube Photography of Ram Accelerator Projectiles

Abstract

Techniques for photographing ram accelerator projectiles operating in a transparent tube section are currently being developed at the University of Washington. The shock waves and intense pressure pulses generated in these flowflelds necessitate relatively thick-walled tubes to allow for the safe observation of accelerating projectiles. Short transparent tube inserts made from polycarbonate and acrylic have sufficient strength for ram accelerator operation in propellant mixtures at reduced fill pressures (< 10 bar) and are transparent enough for direct observation of the projectile. In-tube photographs of strobe-illuminated projectiles in a 38 mm bore facility, taken with image intensifying cameras, have shown that many flow characteristics are discernible.