Effect of Rocket Engine Layouts on Jet Flowfield Inside a Launch Pad

Abstract

A numerical analysis is conducted to understand the flowfield inside a launch pad affected by the layouts of clustered rocket engines for the first stage. The Japanese H3 launch vehicle with typical rocket engines and a launch pad is selected for analysis. In a configuration having three clustered liquid-propellant rocket engines at a core stage, the exhaust jets from adjacent engines are found to interact with each other after impinging on the flame deflector, resulting in side jet reversal in the upstream direction along the flame deflector. An investigation of the layouts of solid rocket boosters around the core stage reveals that exhaust jets from the solid rocket boosters interfere with those from liquid-propellant rocket engines spreading on the flame deflector. This interference also causes reversed jets. Guidelines for suppressing such jet reversal are proposed for designing a launch vehicle and a launch pad for clustered rocket engines at the first stage.