New NASA Rocket Has Vibration Problems

Over the weekend, we learned the U.S. space agency's new rocket for the next generation of space vehicles has a design problem that could seriously undermine its progress. Still on the drawing board, the proposed Ares class of main propulsion engines has an engineering flaw that will most likely lead to severe vibrations upon launch, according to a report from the Associated Press.

The new Ares rockets are being developed to lift the spacecraft that will replace the shuttle into orbit. They are designed to take advantage of successful technology modified from the shuttle program and are officially designated as Shuttle-Derived Launch Vehicle prototypes. NASA plans to use them to return to the Moon by the year 2020--and keep on going from there to Mars ultimately.

Relying on solid-fuel engines, the first of their class, Ares I, is to be the rocket that will serve to propel the astronauts onboard the proposed Orion crew launch vehicle into space. Engineers are now pointing out that the current design of the Ares I shows flaws in the use of the first-stage solid rocket boosters (SRBs) that could lead to significant shaking of the units, possibly transmitting vibrations up the rocket. Should the vibration problem be severe enough during ascent to cause damage to the upper stages of the craft, it could prove to be catastrophic.

Reached by the AP after it had learned of the flaw through a Freedom of Information Act petition, NASA managers said they were fully aware of the problem and expected to have it fixed by as early as March, posing no delay to the overall schedule of the pending Project Constellation program.

"I hope no one was so ill-informed as to believe that we would be able to develop a system to replace the shuttle without facing any challenges in doing so," Administrator Michael Griffin said in a statement to the AP. "NASA has an excellent track record of resolving technical challenges. We're confident we'll solve this one as well."

One of the outside experts recruited by the news service to examine the design of the Ares I agreed with others that the SRBs' tendency to vibrate at lift-off posed a serious hazard, but he was also confident that NASA would be able to overcome it.

"NASA has developed one of the safest and risk-controlled space programs in engineering history," Professor Jorge Arenas of the Institute of Acoustics in Valdivia, Chile, told the AP.

As the report explains:

The shaking problem, which is common to solid rocket boosters, involves pulses of added acceleration caused by gas vortices in the rocket similar to the wake that develops behind a fast-moving boat, said Arenas, who has researched vibration and space-launch issues. Those vortices happen to match the natural vibrating frequencies of the motor's combustion chamber, and the combination causes the shaking.

The SRBs for the Ares I are being built by ATK Launch Systems of Brigham City, Utah.

The first launch of the Ares I to carry astronauts into space is scheduled for March 2015.

That gives NASA a good size window to make sure every possible bug in the system has been identified and eliminated. Historically, it is an agency that understands just how much is at stake.


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