The last thing you want on a flight to the moon is a headache.

That's why NASA engineers have been working to figure out how to reduce vibrations predicted to occur in the Ares 1 rocket, a multi-stage launch vehicle that plays an early role in the space agency's Constellation program to return to the moon by 2020.

NASA plans to field the Ares 1 in 2015, using it to launch the Apollo-like Orion crew capsule into orbit (left). But engineers believe that combustion in the rocket's solid-fuel motor would likely set up vibrations across both vehicles for a few seconds during the ascent. These "thrust oscillations" could injure astronauts or make it hard for them to see the controls and respond to emergencies.

In a teleconference this morning, NASA project managers described their plan to limit the vibrations to one-quarter of a g force (the force of gravity on Earth). More than that, they said, and vibrations can affect vision and speech similar to the way a jackhammer might.

Part of the plan is to add 16 adjustable spring-mounted weights or actuators to the aft skirt—the flared structure at the bottom of the rocket that shields it from exhaust. The idea is that sensors would monitor the vibrations and adjust the position of these 100-pound weights to reduce the shaking.

The second proposed fix is a shock-absorber-like ring between the rocket's first and upper stages.

NASA managers said the system would reduce the payload capacity of Ares 1 by 1,200 to 1,400 pounds. But they said they wouldn't have to cut any critical systems because they had 8,000 pounds of excess lift capacity to play with.

The total cost of the Constellation program is estimated at $230 billion over 20 years.

Image credit: Lockheed Martin Corp.