Rocket

About: Rocket is a research topic. Over the lifetime, 14018 publications have been published within this topic receiving 95852 citations. The topic is also known as: rockets.

A shock wave model of unstable rocket combustors

Abstract: A periodic solution describing the nonlinear waveform of the fundamental longitudinal mode of combustion instability has been obtained. The waveform consists of shock discontinuities followed by exponential decays in pressure and gas velocity. The theory predicts an explicit relationship between the functional nature of the combustion laws and the functional form of the wave shape in the combustion chamber. Therefore, this allows the possibility of investigating the forcing function or driving mechanism of the instability in a quantitative manner by experimentally determining the wave shape in the chamber. The theory applies to any instability where the physical phenomenon that provides that the forcing function contains no phasing effect. Specifically, a model of the combustion zone dynamics has been studied which considers chemical kinetics as the important factor in the forcing function. The results of the analysis on this model have been compared with the experimental results on the Princeton gas rocket research program. The method may be applied to other forms of the forcing function as well.

Launch Vehicle Acoustics Part 2: Statistics of the Time Domain Data

Abstract: Skewness and kurtosis coefficients were investigated as a means of quantifying the shock content and non-Gaussian characteristics of rocket noise. Rocket noise data measured at 3-5 locations during the launches of four different vehicles with thrusts ranging from 440 to 10,700 kN were analyzed. The kurtosis coefficients of the acoustic pressure data showed no discernible pattern of variation about the Gaussian value of 3. The skewness coefficients ranged from 0.02 to 0.55, all of them greater than the value of 0 expected for Gaussian data. Both the skewness and kurtosis coefficients for the derivative of the acoustic pressure showed much greater deviations from the values expected for Gaussian noise. This study has confirmed that the coefficient of skewness is a useful metric for the characterization of rocket noise. The statistics of the pressure gradient have been shown to be more sensitive indicators of shock content, and these metrics are much less sensitive to low-frequency instrumentation limits.

Electron energy measurements in pulsating auroras.

Abstract: Electron spectra were obtained during two rocket flights into pulsating aurora from Southend, Saskatchewan. The first rocket launched at 1143:24 UT, on February 15, 1980 flew into an aurora of back...

Parietal vortex shedding as a cause of instability for long solid propellant motors - Numerial simulations and comparisons with firing tests

Abstract: This paper describes a new mechanism leading to vortex shedding instabilities in long (large L/D) solid propellant motors. This mechanism is termed "parietal vortex shedding" and has been discovered thanks to numerical simulations of the unsteady, 2D, compressible, Navier-Stokes equations. It seems to involve hydrodynamic instabilities of the mean flow velocity profiles, corresponding to injection induced internal flow (so called Culick or Taylor profiles), that couple with the acoustic frequencies of the chamber. Although this mechanism is found to be very powerful, it seems to need some background noise to feed it. The presented simulations can explain observed instabilities in configurations, without segmentation or without protruding inhibitor rings, of a simplified subscale setup of the Ariane 5 MPS P230 solid propellant motor. Detailed comparisons are proposed and the influence of the propellant combustion response and of the turbulence of the flow field are analyzed by means of recently developed models. INTRODUCTION-OBJECTIVES not precisely known if inhibitor rings are or not destroyed or completely slack; on the other hand non segmented motors have also given rise to a same type of instability as vortex shedding : this is the case of one of the configuration (LP3D) of the LP3 set up presented in a preceding paper. As it is known ' ' , classical linear acoustic balance computations do not give reliable stability predictions in complex internal geometries (such as in the P230 motor), and then an effort was carried out to perform full numerical simulations of the unsteady, compressible internal flow fields. On the other hand, motor internal flows are mostly non-observable, and without numerical simulations it is not possible to describe the path of the aerodynamic instability development. The object of the present paper is to show hydrodynamic instabilities (which drive pressure oscillations) in configurations without shear flows induced by inhibitor rings, and to explain how these instabilities occur by means of numerical simulations. LP3D AND LP3E TEST CASES This work is part of the overall research effort, supported by CNES, accompanying the development of the Ariane 5 P230 MPS solid propellant motor (program ASSM for Aerodynamics of Segmented Solid Motors) and makes use of experimental results obtained during the combustion stability assessment program carried out for BPD and CNES, by delegation of ESA. In this scope, it is the continuation of earlier works about numerical simulations in solid propellant rocket motors ". The Ariane 5 motor, as other large segmented motors (U.S. Space Shuttle and Titan SRM) has been reported to exhibit pressure and thrust oscillations. Until recently, it was believed that such instability was exclusively due to the segmented design : inhibitor rings induce shear layers and vortex shedding driven oscillations. Nevertheless it is * Research scientist, Energetics Dept. 1 Project manager, Energetics Dept., Member AIAA Copyright © 1996 by the American Institute of Aeronautics and Astronautics, Inc., All rights reserved. The test cases are based on two configurations of the LP3 motor. The LP3 motor, which has been presented in reference , is a simplified 1/15 subscale set-up of the Ariane 5 P230 motor used to test several inter-segment arrangements. The configurations of interest here, called LP3D and LP3E, have no prominent obstacles at the mid chamber point, see figure 1. Both configurations have a cylindrical chamber of length 1632 mm and inner diameter 203 mm. At ignition, the main propellant burning surface is cylindrical, inner diameter 90 mm, with a chamfered surface near the aft end. The supersonic outlet nozzle is submerged, with a throat diameter of 56.5 mm, then the total length of the motor is 1650 mm. LP3D and LP3E have a small forward segment of 225 mm length, cylindrical for LP3D (169.5