Aerospike Engine Performance Tool
John J. Korte
Multidisciplinary Optimization Branch, NASA Langley Research Center
September, 1998
RTA 243-33-03-05
Research Objective. Our objective is to develop an accurate and efficient method to predict aerospike rocket engine performance. The tool is intended for use in the trajectory optimization and the conceptual analysis and design of reusable launch vehicles.
Approach. For conceptual design of a launch vehicle using a rocket engine with a conventional bell nozzle, all that has to be specified is the vacuum performance. For an aerospike engine, the exhaust flow field adjusts to the atmospheric pressure with a performance improvement at low altitudes when compared to a bell nozzle. The altitude compensation of the aerospike engine requires that the complete operating envelope be specified for conceptual vehicle design. A tool is needed to predict the thrust components, pitching moment, and specific thrust of an aerospike rocket engine as a function of engine fuel to oxygen mixture ratio, engine power level, and altitude.
Accomplishment Description. An aerospike engine performance tool has been developed which includes an algebraic model of the gas generator cycle, combustor analysis, one-dimensional analysis of the thruster nozzle, two-dimensional computational fluid dynamic analysis of the aerospike nozzle flow field, and a simple base flow model. The tool correctly models the altitude compensation effect of the exhaust flow field as a function of altitude (see top-left of
figure). The pressure contours on the lower side of the engine represent the hot exhaust plume at an altitude of 5000 ft. while the contour on the top half is at 50,000 ft. At the lower altitudes, the engine exhaust plume does not expand significantly which minimizes over-expansion losses. The predicted engine performance compares favorably with Rocketdyne prediction as shown on the bottom left hand side of the figure. The aerospike engine performance tool can be used to either simulate one operation point or generate an engine table for performance across the operational envelope in POST (program to optimize simulate trajectories) format. The flow chart showing the process is given on the right-hand side of the figure.Significance. Propulsion information is needed early in conceptual design to improve the accuracy of the vehicle performance estimates. The aerospike engine performance tool was developed to fill a critical and timely need for performance data that was not available for the Langley multidisciplinary design optimization task on the VentureStar reusable launch vehicle. To date, three different aerospike engine performance tables for the VentureStar have been developed for use in POST.
Future Plans. In the near future, we plan to develop a parametric form of this tool for integrating with a design optimization procedure. Ultimately, we would like to optimize the aerospike engine design and a vehicle trajectory simultaneously.
Figure: Aerospike Engine Performance Tool
NASA POC: John J. Korte
Telephone: (757) 864-6920E-Mail: j.j.korte@larc.nasa.gov
Page Curator: D. H. Rudy
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Date last updated: April 21, 2006
