UGA engineering prof, grad student will test NASA rocket part

A University of Georgia professor and his graduate student will test a critical engine part for a new space rocket the National Aeronautics and Space Administration plans to deploy in its new Space Launch System.

It's the next generation after the old space shuttles, and engineers hope the system eventually carries astronauts to asteroids and even the planet Mars.

Professor Ben Davis and graduate student Stephen Higgins got a grant from the space agency to test a part called a bellows expansion joint, a kind of big pipe fitting with ridges, or convolutes, that look sort of like bendable electric tubing, but a lot larger.

During rocket launches, fluids such as rocket fuel or oxygen flow through the joints at variable speeds and pressures; the joints expand and contract in response not only to differing pressure but changes in temperature. The joints also flex as the direction of the engine's thrust changes.

As liquid fuel and oxygen flow through the joints, the fluids don't move uniformly. The corrugated interiors create eddies, with pressure variations causing vibrations. Those flow-induced vibrations can interact with the vibrations of the structural vibrations as the rocket powers into space.

That interaction can cause structural fatigue and possibly joint failure, Davis explained.

Bellows expansion joints are nothing new, but with the bigger engines of the new system, and with costs that could reach $1 billion or more per launch, the space agency wants to make sure the joints can withstand the additional stress, he said.

"The RS-25 is pretty much the same as the old space shuttle, but a little more powerful," he said.

Davis worked at NASA before coming to UGA last August, conducting similar research in structural and flow-induced vibration.

He and Higgins aim to first develop a new computer program to model the forces at play in the joints - a simplified model that won't require the huge computing power it now takes to model the forces that come to bear on the bellows expansion joints.

After that phase is completed sometime next year, they'll run actual laboratory tests on the joints, testing how well their model works.

Follow education reporter Lee Shearer at www.facebook.com/LeeShearerABH or https://twitter.com/LeeShearer.