Operational characteristics of the thermally choked ram accelerator

TLDR

The projectile functions as a ramjet centerbody, moving through a high‑pressure tube of premixed fuel and oxidizer. The study investigates the operational characteristics of a thermally choked ram accelerator for ultrahigh‑velocity projectile launch. The device uses a combustion wave that thermally chokes to generate a pressure field thrusting the projectile, and the study examines staged propellants, mixture transitions, and velocity limits. Experiments with 45–75 g projectiles in a 12.2 m, 38 mm accelerator using methane mixtures achieved 1150–2350 m/s, matching theoretical predictions closely.

Abstract

Operational characteristics of the thermally choked ram accelerator, a ramjet-in-tube device for accelerating projectiles to ultrahigh velocities, are investigated theoretically and experimentally. The projectile resembles the centerbody of a conventional ramjet and travels through a stationary tube filled with premixed gaseous fuel and oxidizer at high pressure. The combustion process travels with the projectile, its thermal choking producing a pressure field which results in thrust on the projectile. The results of experiments with 45-75 gm projectiles in a 12.2 m long, 38 mm bore accelerator, using methane-based propellant mixtures, are presented in the velocity range of 1150-2350 m/s. Acceleration of projectiles with staged propellants and transitions between different mixtures are investigated and the velocity limits in several propellant mixtures are explored. Agreement between theory and experiment is found to be very good.