Extensions to analysis of ignition transients of segmented rocket motors

The analytical procedures described in NASA CR-150162 were extended for the purpose of analyzing the data from the first static test of the Solid Rocket Booster for the Space Shuttle. The component of thrust associated with the rapid changes in the internal flow field was calculated. This dynamic thrust component was shown to be prominent during flame spreading. An approach was implemented to account for the close coupling between the igniter and head end segment of the booster. The tips of the star points were ignited first, followed by radial and longitudinal flame spreading

Investigation of the starting transients of high performance solid-propellant motors

The starting transients of solid propellant engines were investigated to develop design principles for predicting transients in high performance igniter and engine configurations. Research and diagnosis were conducted on the processes affecting ignition transients, such as heat flux, igniter, flame spreading over the surface, and nonsteady combustion gas dynamics. Abstracts of published reports related to this research are presented. Topics discussed include: development of an analytical model, analytical prediction of the entire ignition transient, transient behavior of pressure and regression rate during reignition after shut-down, and problems associated with restarting hybrid rocket engines

Ignition Transients of Large Segmented Solid Rocket Boosters

A model is described which provides a means for analyzing the complexities of ignition transients and pressure peaks of large, high performance, segmented solid rocket boosters. The method accounts for: (1) temporal and spatial development of the flow field set up by the head end igniter discharge, (2) ignition and flame spreading coupled to chamber flow, (3) the steep velocity, pressure, and temperature gradients that occur during the early phases of ignition, and (4) the interactions that produce ignition spikes (i.e., compression of chamber gases during pressurization, erosive burning, and mass added effect of igniter discharge). The technique differs from earlier models in that the flow interactions between the slots and main chamber are accounted for, and the original computer program for monolithic motors is improved. The procedures were used to predict the ignition transients of the current design for the space shuttle booster

The starting transient of solid propellant rocket motors with high internal gas velocities

A comprehensive analytical model which considers time and space development of the flow field in solid propellant rocket motors with high volumetric loading density is described. The gas dynamics in the motor chamber is governed by a set of hyperbolic partial differential equations, that are coupled with the ignition and flame spreading events, and with the axial variation of mass addition. The flame spreading rate is calculated by successive heating-to-ignition along the propellant surface. Experimental diagnostic studies have been performed with a rectangular window motor (50 cm grain length, 5 cm burning perimeter and 1 cm hydraulic port diameter), using a controllable head-end gaseous igniter. Tests were conducted with AP composite propellant at port-to-throat area ratios of 2.0, 1.5, 1.2, and 1.06, and head-end pressures from 35 to 70 atm. Calculated pressure transients and flame spreading rates are in very good agreement with those measured in the experimental system

Evaluation of candidate metals in a simulated space shuttle main engine environment for application as turbine blade dampers

The high-pressure pumps for the space shuttle main engine are driven by combustion products which are 50 percent H2 and 50 percent H2O (by weight). The Haynes alloy 188, used in the dampers, experienced erosion. The erosion producing characteristics of wet H2 were evaluated using a controlled environment produced by a ballistic compressor. Four candidate materials were evaluated: H-188, A-286, Pt/Rh and Rh. Rh was clearly the most erosion resistant. Comparisons with AISI 4340 and Fe specimens of known uniformity indicate that metallurgical defects in the candidate materials are primary contributors to the higher than usual erosion

Revisiting Event Horizon Finders

Event horizons are the defining physical features of black hole spacetimes, and are of considerable interest in studying black hole dynamics. Here, we reconsider three techniques to localise event horizons in numerical spacetimes: integrating geodesics, integrating a surface, and integrating a level-set of surfaces over a volume. We implement the first two techniques and find that straightforward integration of geodesics backward in time to be most robust. We find that the exponential rate of approach of a null surface towards the event horizon of a spinning black hole equals the surface gravity of the black hole. In head-on mergers we are able to track quasi-normal ringing of the merged black hole through seven oscillations, covering a dynamic range of about 10^5. Both at late times (when the final black hole has settled down) and at early times (before the merger), the apparent horizon is found to be an excellent approximation of the event horizon. In the head-on binary black hole merger, only {\em some} of the future null generators of the horizon are found to start from past null infinity; the others approach the event horizons of the individual black holes at times far before merger.Comment: 30 pages, 15 figures, revision

Adaptive Event Horizon Tracking and Critical Phenomena in Binary Black Hole Coalescence

This work establishes critical phenomena in the topological transition of black hole coalescence. We describe and validate a computational front tracking event horizon solver, developed for generic studies of the black hole coalescence problem. We then apply this to the Kastor - Traschen axisymmetric analytic solution of the extremal Maxwell - Einstein black hole merger with cosmological constant. The surprising result of this computational analysis is a power law scaling of the minimal throat proportional to time. The minimal throat connecting the two holes obeys this power law during a short time immediately at the beginning of merger. We also confirm the behavior analytically. Thus, at least in one axisymmetric situation a critical phenomenon exists. We give arguments for a broader universality class than the restricted requirements of the Kastor - Traschen solution.Comment: 13 pages, 20 figures Corrected labels on figures 17 through 20. Corrected typos in references. Added some comment