This volume brings together international scientists in the field of solid rocket propulsion. Thirty-nine papers present in-depth coverage on a wide range of topics including: advanced materials and non-traditional formulations; the chemical aspects of organic and inorganic components in relation to decomposition mechanisms, kinetics, combustion and modelling; safety issues, hazards and explosive characteristics; and experimental and computational interior ballistics research, including chemical information and the physics of the complex flow field.

Solid propellant chemistry, combustion, and motor interior ballistics

An approximation that can be used to determine how swirl affects the choking constraint on flow through the throat of a nozzle is obtained. The flow model is consistent with an experimentally observed flow pattern that contains a recirculating internal cell upstream of the throat. Results of the approximation are applied to three different flow situations. First, it is found that the choking constraint imposes a limit on the maximum tangential Mach number that can be achieved in a vortex tube even when an infinite pressure ratio is available. Next, analytic expressions are derived for the variation of rocket mass flow in a spinning rocket. The last application is the prediction of a performance curve for a fluidic vortex valve that is consistent with limited experimental data.

Transonic swirling flow.

This paper presents results obtained from testing double-base (BUU), polyurethane (E-107), and polybutadiene (PBAA) propellants at acceleration levels up to 300 g with various orientations of the acceleration vector with respect to the burning surface. The tests were conducted using a unidirectional-burning propellant slab (4 in. wide by 6 in. long by 0.5-in. web thickness) motor mounted on a ballistic centrifuge. Extinction tests demonstrated the transient nature of the combustion process. The burning rate r at 500 psi was increased 27% by a normal acceleration of 280 g into the surface for the PBAA propellants with 16% 6yu or 13/z aluminum; for 26fji Al, the increase in r was 60% at 280 g. However, the effect of aluminum content on r varied with acceleration level. For the E-107 propellant, r increased by 173% at 300 g. With the PBAA propellant, the burning-rate augmentation was eliminated by changing the orientation of the acceleration vector from 90° to 60° relative to the surface; thus, longitudinal acceleration of a rocket will diminish the effect on r due to spin. Results are compared with data from strand tests and motor spin tests.

On the effects of acceleration upon solid rocket performance.

Effects of acceleration upon solid-rocket performance.

This work explores the use of surface-mesh flow solvers to model solid rocket internal ballistics with arbitrary grain geometry. Specifically, a surface-vorticity approach, originally intended for external flow applications, is adapted for internal flow analysis using boundary conditions that are suitable for solid rocket motors. In this study, an enhanced panel code is shown to be capable of resolving internal rocket flowfields with a striking level of fidelity and with such a degree of computational efficiency to make it valuable in the conceptual and preliminary design of rocket motors. In this process, the vortex paneling approach embodied within FlightStream® is refined using boundary conditions appropriate for solid rocket rotational flows. The simulation results are then compared to existing analytical solutions for cylindrical and planar chamber configurations exhibiting small taper angles and uniform headwall injection. For a more realistic validation case, the space shuttle's reusable solid rocket motor (RSRM) is examined. Guided by the analytical models, simple rotational and compressibility corrections are incorporated into the solver, and the results are subsequently compared to two other computational models and experimental measurements gathered from qualification motors. For the basic configurations, our results are shown to agree well with theoretical predictions. For the RSRM case, the corrected solution agrees well with the validation data in the first half of the motor; however, it becomes less robust in the aft region unless a recirculation zone boundary patch is applied; the latter approximates the added vorticity introduced by intersegmental gaps and the submerged nozzle effects.

Solid rocket motor internal ballistics using an enhanced surface-vorticity panel technique

Ballistic propellant combustion alteration and thermal effects due to dynamic spinning observed on solid propellant sounding rockets

Melvin H. Lucy

Papers

Spin acceleration effects on some full-scale rocket motors.