NASA's Moon Rocket Looks Less Shaky

HUNTSVILLE, Ala., Aug. 23, 2008 — -- The nation's new moon rockets will be outfitted with shock absorbers to buffer astronauts from jackhammer-like vibrations during rocky rides into orbit.

A spring-and-damper ring will separate the first and second stages of Ares 1 rockets, which NASA is developing for missions to the International Space Station, the moon and later Mars.

Sixteen actuators that act like shock absorbers also will be added to the bottom of the rockets, significantly reducing the gravitational forces and vibrations astronauts will be exposed to in flight.

"The good news here is we've got a solution that will solve the thrust oscillation phenomenon," said Steve Cook, manager of Ares Projects at NASA's Marshall Space Flight Center in Huntsville, Ala.

NASA's Ares 1 rocket is being developed to launch Apollo-style Orion crew capsules.

The rocket's first stage will comprise a five-segment solid rocket booster derived from the four-segment boosters that help propel shuttles into orbit. The second stage will be powered by a liquid-fueled engine.

NASA design engineers found the Ares 1 -- dubbed the "single stick" due to its slender shape -- would shake violently near the end of a two-minute firing of the rocket's first stage.

This "thrust oscillation" is induced as solid fuel in the first stage depletes, leaving a long, empty metal case that takes on the characteristics of a pipe organ, resonating at frequencies between 12 and 14 hertz.

The resulting vibrations could shake the Orion crew capsule enough to make it difficult for astronauts to read cockpit displays. In a worst case, astronauts might be injured or critical components of the spacecraft could be damaged.

An internal NASA task force determined the second stage of the vehicle and the Orion crew capsule would naturally dampen resulting pressure pulses.

The astronauts, however, would be subjected to forces five or six times that of normal gravity -- or about double the three G's shuttle crews are exposed to during nine-minute climbs into orbit.

The task force recommended NASA add the shock absorber system, which will reduce gravitational forces to 0.25 G, or about the same level that Mercury and Gemini astronauts were exposed to.

The system will reduce the lift capacity of the Ares 1 rockets by 1,200 to 1,400 pounds. But Cook said the rockets still will be powerful enough to fly missions to the space station and moon.

NASA aims to debut the Ares 1 rocket and Orion spacecraft by March 2015 — five years after the agency's shuttle fleet is retired. The target for the first moon mission is 2020.