Listen to the soundtrack accompanying this image and you may think
it reminiscent of some avant-garde music. The sound is, in fact,
representative of the vibration the Mars Express spacecraft will
experience during launch.
“The machine the spacecraft is sitting on moves up and down like a
po-go,” explains Don McCoy, assembly, integration and verification
manager from ESTEC, who accompanied the spacecraft during recent tests
at Intespace, the company responsible for testing the Mars Express
spacecraft, in Toulouse, France. The tests were designed to check
that Mars Express will be able to withstand the incredible noise and
vibration generated during launch.
The po-going machine starts off at very low frequency, six cycles per
second or 6 Hz, and gradually increases to 100 Hz. At first, the
frequency is too low to be heard, but it quickly increases until the
spacecraft begins to resonate, and make a lot of noise, at about 45 Hz.
As the frequency increases further, the spacecraft begins to vibrate so
rapidly that it appears stationary. At 73 Hz there’s a second resonance
and the noise builds to a crescendo. Then from 75-100 Hz it quietens
down. In the background, throughout the piece, is the rhythmical swish
of a valve opening and closing periodically, like the brush of cymbals
keeping the beat.
During resonances, the acceleration of the spacecraft walls is
considerable. “A fly on a panel of the spacecraft would find it hard
to keep its footing. An acceleration many times that of gravity would
be pushing it off,” says McCoy.
The Mars Express spacecraft has now completed its phase of mechanical
testing at Intespace and has returned to Alenia in Torino, Italy, for
integration of the flight models of the instruments and the spacecraft
electrical equipment.
USEFUL LINKS FOR THIS STORY
* Listen to the ‘music’ of the Mars Express spacecraft
* More about Mars Express
http://sci.esa.int/marsexpress
IMAGE CAPTION:
[http://sci.esa.int/content/searchimage/searchresult.cfm?aid=9&cid=12&oid=28859&ooid=28861]
The Mars Express spacecraft during its vibration tests at Intespace,
Toulouse.
