Ph.D. Thesis Defense

By

Michael J. Steffens

 (Advisor: Prof. Dimitri Mavris)

1:00 PM, Thursday, June 2, 2016

Weber Space Science and Technology Building (SST-II)

Collaborative Visualization Environment (CoVE)

Trajectory-Based Launch Vehicle Performance Analysis for

Design-Space Exploration in Conceptual Design

ABSTRACT:

Trajectory optimization is an important part of launch vehicle conceptual design.  It provides the link between a proposed vehicle and its performance.  Launch vehicle performance analysis is used to quantify how much payload a vehicle can put into the desired orbit and to compare vehicles against each other and against requirements.  This is especially important in early phases of design, where a large design space of vehicles may be considered and must be pared down to a few candidate vehicles.  Current methods for trajectory optimization do not allow for extensive design space exploration.  The methods involve numerical analysis, are computationally expensive, and require trajectory experts in the loop.  A simplified performance analysis, like the rocket equation, is much better suited to the types of studies desired in conceptual design, where thousands of vehicles can be considered and compared.  Unfortunately, the rocket equation does not take into account trajectory losses and therefore does not provide an accurate measure of performance.  The lack of a fast and accurate method to evaluate launch vehicle performance represents a gap in the current capability that will be addressed in this thesis.

The goal of this research is to formulate and implement a performance analysis method that is closed-form and takes into account the trajectory losses considered in a numerical trajectory analysis method.  Achieving this goal will result in a capability that enables rapid and accurate performance evaluation of launch vehicles.  In conceptual design, this can be used in the context of multi-disciplinary optimization, technology trade studies, probabilistic assessments, and Monte Carlo analysis for launch vehicles. 

In this thesis, the process is implemented for the Delta IV Heavy with an example design space.  The resulting surrogate model is able to accurately estimate the performance of a launch vehicle in the design space of interest virtually instantaneously.  This method is flexible and can be applied to any launch vehicle and any design space of interest.  The performance analysis capability that results from implementing the method proposed in this thesis meets the research objective of enabling rapid and accurate launch vehicle performance analysis in conceptual design.  This provides a way of estimating the performance for thousands of vehicles in the design space considered where previously only a few were considered.  

Committee Members:

Prof. Dimitri Mavris (Advisor)

Prof. Daniel Schrage

Prof. Marcus Holzinger

Dr. Brad St. Germain

Mr. Mark Rogers