Date of Award

9-18-2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Department of Aeronautics and Astronautics

First Advisor

Jonathan T. Black, PhD.

Abstract

The goal of the Dual-Expander Aerospike Nozzle, a modification to traditional engine architectures, is to find those missions and designs for which it has a competitive advantage over traditional upper stage engines such as the RL10. Previous work focused on developing an initial design to demonstrate the feasibility of the Dual-Expander Aerospike Nozzle. This research expanded the original cycle model in preparation for optimizing the engine's specific impulse and thrust-to-weight ratio. The changes to the model allowed automated parametric and optimization studies. Preliminary parametric studies varying oxidizer-to-fuel ratio, total mass flow, and chamber length showed significant improvements. Drawing on modeling lessons from previous research, this research developed a new engine simulation capable of achieving a specific impulse comparable to the RL10. Parametric studies using the new model verified the Dual-Expander Aerospike Nozzle architecture conforms to rocket engine theory while exceeding the RL10's performance. Finally, this research concluded by optimizing the Dual-Expander Aerospike Nozzle engine for three US government missions: the Next Generation Engine program, the X-37 mission, and the Space Launch System. The optimized Next Generation Engine design delivers 35,000 lbf of vacuum thrust at 469.4 seconds of vacuum specific impulse with a thrust-to-weight ratio of 127.2 in an engine that is one quarter the size of a comparable RL10. For the X-37 mission, the optimized design operates at 6,600 lbf of vacuum thrust and has a vacuum specific impulse of 457.2 seconds with a thrust-to-weight ratio of 107.5. The Space Launch System design produces a vacuum thrust of 100,000 lbf with a vacuum specific impulse of 465.9 seconds and a thrust-to-weight ratio of 110.2. When configured in a cluster of three engines, the Dual-Expander Aerospike Nozzle matches the J2-X vacuum thrust with a 4% increase in specific impulse.

AFIT Designator

AFIT-ENY-DS-14-S-06

DTIC Accession Number

ADA609649

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