Performance Modeling of the Baffled Tube Ram Accelerator

Abstract

The baffled tube ram accelerator is a hypervelocity mass driver theoretically capable of accelerating axisymmetric projectiles up to 3 km/s. Researchers at the UW have investigated the baffled tube ram accelerator since 2015 achieving projectile velocities over 1.4 km/s. The device is based on the smooth bore ram accelerator developed at the UW in the 1980s and consists of washer-like inserts normal to the flow that are used to prevent unstart and enable the use of axisymmetric projectiles and more energetic propellants. With baffled tubes, the ram accelerator is theoretically capable of achieving 2-3 times more thrust than the smooth bore ram accelerator. Theoretical performance models including three drag models with combustion effectiveness were developed and compared with experiment. The results show that only 35-65\% of the theoretical thrust is observed in baffled tube ram accelerator experiments, although thrust is still improved over the smooth bore ram accelerator. Performance losses may be attributed to momentum lost to baffle drag, which hinders performance in most experiments, but may provide a boost to performance at low Mach numbers.