Thursday, August 10, 2006

Building a better rocket

Just thought I'd comment a little bit more on this bit of news that I found through a post over at RLV news. Some interesting excerpts from the article.

The NASA-funded research at Purdue focuses on liquid-fueled rockets. Specifically, the work deals with understanding how fuel and oxidizer interact inside the rocket engine's fuel injectors to cause unstable combustion. The instability results in extreme bursts of heat and pressure fluctuations that could lead to accidents and hardware damage.

a.k.a. Rapid Unscheduled Disassembly
"Combustion instability is a complex phenomenon that has hindered rocket development since the beginning of the Space Age," said Nicholas Nugent, a doctoral student in Purdue's School of Aeronautics and Astronautics. "We have to learn more about instability before future engines can be developed and used for space flight. Predicting combustion instability is one of the most difficult aspects of developing a rocket engine."

"The main purpose of the work is to generate combustion and instability data so that other researchers can develop better computational models for designing rocket engines," Nugent said. "We are generating benchmark data that will improve the design analysis of all types of rocket engines."

This work is actually just one small part of a much larger research effort aimed at improving the design and analysis tools available to rocket designers. The research is being conducted by a large consortium of university researchers which is referred to as the Constellation University Institute Program. The specific collaboration that these researchers, as well as myself and my advisor, are a part of is the Thrust Chamber Assembly (TCA) Virtual Institute. The aim of the research is to improve the state of the art in design tools and predictive simulation technology for engineers designing rocket engines.

For many engineering disciplines there exist some fairly reliable computational design tools which are employed regularly by engineers to refine their designs before being required to build and test actual physical prototypes. However due to the extreme environments and the complexity of the many coupled physical processes inside a rocket engine (fluid dynamics, chemical reactions, thermodynamics, acoustics, structural mechanics), it has been nearly impossible to develop similar tools for rocket designers. Consequently, rocket development must rely heavily on emperical models that have been developed through trial and error over the past few decades.

The part of this problem that we, and a few others, are working on is the development of a computational fluid dynamics solver capable of accurately modeling the extreme flow environment inside of a rocket engine. We're talking everything from the injection of cryrogenic propellants to the combustion of the fuel and oxidizer to the accurate simulation of unsteady turbulent high Reynolds number flows. This flow simulation will also be coupled with acoustic, thermal, and structural simulations to create the first predictive simulation tool for rocket designers. However, before we can trust the simulation, our code must be validated against the experimental results being generated by several other research groups. The researchers at Purdue are one of these groups.

In the end, we would like to provide rocket designers with a tool which they can use to determine the optimal configuration of a given thrust chamber assembly. By simulating the performance of their designs before testing them, it should be possible to eliminate many redundant or excessively over-designed features which have heretofore been necessary to ensure the engine will not fail. This could potentially allow the development of a whole new generation of lighter and more efficient rocket engines.

Back in May, I attended a workshop in Huntsville where we discussed the current state of TCA research and near term directions. I still have my notes around here somewhere. If I can find them, and a little spare time, I will try to post some highlights from the meeting.


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