nasa aries moon rocket may shake too_20

NASA Aries moon rocket may shake too much

Shaun Saunders sends in this article from Yahoo News:

NASA Engineers are concerned that the new rocket meant to send

astronauts to the moon could shake violently during the first few

minutes of flight, possibly destroying the entire vehicle. The shaking

originates in the first stage of the Ares I rocket, which will lift

the Orion crew capsule into orbit. The concern isn't the shaking on

the first stage, but how it affects everything that sits on top: the

Orion crew capsule, instrument unit, and a booster. 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. Those vortices happen to

match the natural vibrating frequencies of the motor's combustion

chamber, and the combination causes the shaking. NASA officials hope

to have a plan for fixing the design as early as March, and they do

not expect it to delay the goal of returning astronauts to the moon by

2020.