Notes Saturn V Program Also Experienced Issue

NASA engineers told Congress last week they're working on the first-stage vibration problem foreseen for the agency's upcoming Ares I booster rocket, but as of yet no clear solution has been found.

The Huntsville (AL) Times reports engineers at Marshall Space Flight Center continue to work on the issue, which was first disclosed in January. The problem is due to accelerating gas vortices from the rocket, which happen to match the natural vibrating frequencies of the motor's combustion chamber. 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 were aware of the problem since last October, categorizing the seriousness of the problem as a "four" on a risk scale of five.

Since Ares is still under development, engineers are working to solve the problem in the theoretical mindsent, before flight testing of the new booster begin in 2009. NASA has called upon retired agency managers and academic consultants to assist in finding a solution.

The agency is exploring a number of solutions for the problem, including use of a vibration damper system to insulate astronauts riding atop the rocket in the Orion space capsule. Engineers hope to find a design solution, however... as in addition to the complexity of vibration damping, such systems would also add weight, robbing Ares of needed payload capabilities.

"We are going to run across these type of issues and run them down," said Rick Gilbrech, associate administrator, Exploration Systems Mission Directorate at NASA Headquarters.

Despite misgivings expressed by some in the scientific community, and lawmakers, NASA stresses its scientists are up to the task of coping with the problem -- noting the Saturn V rocket program also suffered similar vibrations at the beginning, which led to severe problems on that rocket's second test flight, Apollo 6, in April 1968.

This time around, NASA engineers also have the benefit of the "off-the-shelf" nature of the Ares program, as many of its systems coming directly from the space shuttle program.

FMI: www.nasa.gov/constellation