A two-tiered system of shock absorbers can quell dangerous vibration problems on NASA鈥檚 future Ares I rocket, agency officials announced on Tuesday.
NASA aims to use Ares I to carry the Orion crew capsule to orbit beginning in 2015. The system will replace the space shuttles, which are set to retire in 2010.
Officials announced last week that they would install springs in the rocket to combat vibrations that could build up to destroy the vehicle.
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On Tuesday, more details of that plan were revealed. Two different systems will be used to reduce the vibrations in Ares I from five to six times the force of gravity (5 to 6 Gs) down to 0.25 Gs.
That vibration level should be low enough for astronauts to read their onboard computer consoles. And it feels like nothing more than driving over the on the side of a highway, says Ares project manager Steve Cook of NASA鈥檚 Marshall Space Flight Center in Huntsville, Alabama.
Mass movement
Ares I will consist of two stages. The first will contain a five-segment solid-rocket booster, similar to the space shuttle鈥檚 four-segment booster. The second stage will be powered by a liquid-fuelled engine.
To combat vibrations, engineers plan to install two systems 鈥� a 鈥榩assive鈥� and an 鈥榓ctive鈥� one 鈥� on the rocket.
The passive system will use a spring and a damper ring 鈥� essentially acting as a cushion 鈥� between the rocket鈥檚 first and second stages.
The active system is called a 鈥榯uned mass absorber鈥�. It will consist of a ring of 16 cylinders containing 100-pound weights around the inside of the skirt-like base of the rocket鈥檚 first stage. Sensors will move these weights so they actively cancel out the vibration.
Human centrifuge
Should all of the actuators designed to move the 16 masses fail, NASA officials say, the vibrations on the craft should only reach 1 G. 鈥淲e would still be well under the health limits on the crew,鈥� says Garry Lyles, associate director for technical management at Marshall.
Ares engineers plan to test the effects of 0.25-G vibrations, combined with the acceleration of launch, at a human centrifuge at NASA鈥檚 Ames Research Center in Moffett Field, California.
Accelerometers will also be attached to astronauts鈥� seats on a shuttle mission scheduled for February 2009. The devices will measure the vibration effects of the shuttle鈥檚 solid rocket boosters on current crews.
The results of those tests may eventually raise the acceptable acceleration limit, potentially eliminating the need for the actively controlling the tuned mass absorber system.
