Abstract
The thrust profiles of solid rocket motors are usually determined ahead of time by propellant composition and grain design. Traditional techniques for active thrust modulation use a moveable pintle to dynamically change the nozzle throat diameter, increasing the chamber pressure and therefore thrust. With this approach, high chamber pressures must be endured with only modest increases in thrust. Alternatively, it has been shown that spinning a solid rocket motor on its longitudinal axis can increase the burning rate of the propellant and therefore the thrust without the resulting high chamber pressures. Building on prior experience modelling pressure-dependent, low-dependent and acceleration-dependent burning in solid rocket motors, an internal ballistic simulation computer program is modified for the present study where the use of the pintle nozzle and spin-augmented solid rocket motor combustion approaches, for a reference cylindrical-grain motor, are compared. This study confirms that comparable thrust augmentation can be gained at lower chamber pressures using the novel spin-acceleration approach, relative to the established pintle-nozzle approach, thus potentially providing a significant design advantage.
Highlights
A solid propellant rocket motor (SRM) is nominally one of the simpler chemical rocket propulsion systems
By dynamically adjusting one of these mechanisms, the thrust of the SRM may be adjusted over the baseline thrust profile
It was suggested that the effect of spinning on the rate of combustion was due to a compressed combustion zone under a normal acceleration field and that this was the dominant effect for the burning rate augmentation seen in spinning solid rocket motors
Summary
Nozzle throat cross-sectional area, m2 al Longitudinal (or lateral) acceleration, m s−2 an Normal acceleration, m s−2. Lateral/longitudinal acceleration burning rate displacement orientation angle coefficient. Local gas Reynold’s number based on core hydraulic diameter rb Overall burning rate, m s−1 re Erosive burning rate positive component, m s−1 ro. Solid phase, reference conditions, K ue Nozzle exit gas or exhaust jet velocity, m s−1 ueff. M s−1 vf Normal gas flow velocity of flame, m s−1 αp Particle mass loading fraction δo Reference energy zone thickness, m δr Resultant energy zone thickness, m. Kg m−3 ρp Density, particles within gas flow volume, kg m−3 ρs Density, solid phase, kg m−3 σp Pressure-dependant burning rate temperature sensitivity, K−1. Mega-Newton Nitrocellulose, (solid monopropellant) Nitroglycerine, (liquid monopropellant/explosive; solid when combined with NC) Polybutadiene acrylic acid (solid fuel) Polybutadiene-acrylic acid-acrylonitrile terpolymer (solid fuel) Polysulfide Polyurethane QUasi-steady ROCket (code) Solid propellant rocket motor xv
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