Redesigned Solid Rocket Motor Research Articles

Constitutive Equations for Solid Propellants

Mechanical behavior of the Space Shuttle redesigned solid rocket motor (RSRM) propellant is studied from a phenomenological point of view. Motivated by the study of the experimental data three initially isotropic constitutive models have been developed. All models represent the effect of strain rate, superimposed hydrostatic pressure, and cyclic loading on the stress and dilatation response of the material. A particular emphasis is given to the prediction of volume dilatation. The model resulting in the best representation of the available data is calibrated using only a few tests. The predictions of the model are compared with experiments for several loading conditions not used in the calibration.

Al2O3 collection and sizing from solid rocket motor plumes

A unique dart system has been designed and built to collect aluminum oxide particles from the plumes of large-scale solid rocket motors, such as the Space Shuttle redesigned solid rocket motor (RSRM). The capability of this system to collect clean samples from both the vertically fired modified NASA (MNASA) (18.3% scaled version of the RSRM) motors and the horizontally fired RSRM motor has been demonstrated. The particle mass-averaged diameters d& measured from the samples for the different motors, ranged from 8 to 11 fun and were independent of the dart collection surface and the elapsed time during motor burn. The measured d& results agreed well with those calculated using the industry standard Hermsen's correlation within the standard deviation of the correlation. For each of the samples analyzed from both MNASA and RSRM motors, the distribution of the cumulative mass fraction of the plume oxide particles as a function of the particle diameter was best described by a monomodal log-normal distribution with a standard deviation between 0.13-0.17. This distribution agreed well with the theoretical prediction by Salita using the one-dimensional three phase code for the RSRM motor at the nozzle exit plane; this seems to confirm that droplet collision-coalescence removes most of the smoke mass from the plume flowfield.

Large-scale nonlinear structural analysis simulation on CRAY parallel/vector supercomputers

Two large-scale nonlinear structural analysis simulations of a nine degree model of the Space Shuttle Redesigned Solid Rocket Motor (RSRM) factory joint are described. The first analysis simulates a burst pressure test where a pressure load was incrementally applied from 0 to 1500 p.s.i. This simulation was used to assist in evaluating and defining an error criterion based on correlation of the finite element analysis with experimentally determined failure points from an actual burst pressure test of a metal case containing the tang and clevis joint. The second part of the analysis is used to show the cyclic stress-strain behavior of the joint assembly and is used to evaluate low cycle fatigue in the local yield zones. The finite element analysis of the RSRM factory joint was conducted using the ANSYS structural analysis code and the computer runs were made using CRAY Y-MP 81 and CRAY C90 supercomputers at Cray Research Inc. Performance aspects of this large-scale analysis are described, including both parallel/vector algorithms used within the ANSYS code and a new I/O software layer under development at Cray Research designed to reduce I/O wait time for engineering applications. Key features of the finite element model are discussed, including features to improve accuracy and efficiency.

Negatively Buoyant Flow Along Vertical Cylinders at High Rayleigh Numbers

Conditions that must be satisfied before the launch of a Space Transportation System (STS) include combinations of ambient temperature and wind speed that are intended to prevent ice formation on the External Tank (ET) and a local air temperature around the STS of 33°F (0.56°C) or less. Nineteen effluent gases are purged or vented from the STS into the launch pad environment, the most significant of these being the cold and negatively buoyant boil-off gaseous oxygen (GOX) from the oxygen tank. Vented into the ambient, this GOX can be wind-carried toward the STS, where it will cool the launch pad environment. This article described a combined three-dimensional (3D) and two-dimensional (2D) computational fluid dynamics (CFD) analysis that investigated this cooling effect. The results of this analysis for a 6-knot (3.09 m/s) west wind and an ambient temperature of 38°F (3.33°C) indicate that the GOX could cool, relative to the ambient, the local air in the vicinity of the STS and the surface of the east Redesigned Solid Rocket Motor (RSRM) by as much as 28°F (15.56°C) and 5 to 6°F (2.78 to 3.33°C), respectively. The large lengths associated with the ET and the east RSRM resulted in Rayleigh numbers that were one to three orders of magnitude larger than those found in literature.

Gaseous oxygen cooling of the Space Transportation System launch padenvironment

The external tank (ET) of the Space Transportation System (STS) contains liquid oxygen and hydrogen as oxidizer and fuel for the Space Shuttle main engines (SSMEs). During and subsequent to the loading of the ET prior to the launch of an STS, the cryogens boil in the near atmospheric conditions existing within their respective tanks. The gaseous oxygen (GOX) formed as a result of this boiling is vented overboard, mixes with air, and may, under certain wind conditions, be transported toward the STS to cause a cooling of its environment. This paper describes a two-dimensional computational fluid dynamics analysis to determine the magnitude of this cooling effect by determining the temperature depression and stratification caused by this GOX/air mixture in the region around the east redesigned solid rocket motor (RSRM), the ET, and below the STS assembly. For a severe wintertime launch temperature of 24°F (-4.44°C), the maximum local temperature depression of the mixture was calculated to be 58°F (32.22°C) in the inboard region next to the ET surface, and a surface temperature on the east RSRM was found to be as much as 25°F (13.89°C) colder than ambient. The computed average surface temperatures on either side of the RSRM were in excellent agreement with a temperature determined from a correlation of prelaunch temperature measurements.

Predicting redesigned solid rocket motor joint volume pressurization, temperature transients, and ablation

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