Vibration Problem Plagues SRB Design

NASA experts are wrestling with a propulsion vibration problem in its new moon rocket design. Engineers are working to develop options to address a "thrust oscillation" issue in the Ares I rocket, The Associated Press reports.

The Ares I rocket and the Orion crew capsule attached to it are NASA's planned replacements for the aging space shuttle, which is due to retire in 2010.

The vibration problem was disclosed Friday, although NASA declined requests for interviews. Spokeswoman Beth Dickey provided a lengthy statement identifying the problem as "thrust oscillation", a pulsing of thrust late in the burn of the rocket's first stage.

NASA officials say the accelerating gas vortices from the rocket happen to match the natural vibrating frequencies of the motor's combustion chamber, and the combination causes the shaking.

Thrust oscillation is a phenomenon found in all solid rocket motors, including those used on the space shuttle -- which are also being used on Ares.

Program managers have been aware of the problem since last October, categorizing the seriousness of the problem as a "four" on a risk scale of five. Outside experts have been called upon to assist NASA personnel in finding a solution.

NASA Administrator Michael Griffin expressed confidence the issue will be resolved.

"This is a development project like Apollo. I hope no one would be so ill-informed as to believe we would be able to develop a system to replace the space shuttle without facing any challenges in doing so." He added, "NASA has an excellent track record of resolving technical challenges. We're confident we'll solve this one as well."

NASA officials hope to have a plan for fixing the design as early as March, and they don't anticipate it delaying the planned goal of returning astronauts to the moon by 2020.

FMI: www.nasa.gov/ares