Ignition study for low pressure combustible mixture in a ram accelerator

An ignition tube as a new section is inserted between the prelauncher and the ram acceleration section of the ram accelerator facility in Hiroshima University to study the ignition process under a sub-detonative condition. Because of the low fill pressure (around 0.5MPa) in ram acceleration section, it’s hard to ignite the premixed combustible gas which has the appropriate mixing ratio to keep the combustion behind the projectile in thermal choking propulsion mode. For this reason, a short ignition tube is employed in which hot (energetic) combustible gas is included to help the ignition. In the ram acceleration section, gas mixture colder (less-energetic) than it in the ignition tube is used to accelerate the projectile in sub-detonative mode. A 56 m/s velocity gain has been observed in a 2 m long ram acceleration section with 1.4CH4+2O2+4.3CO2 mixture at 0.45 MPa.