The ESTEC Test Centre’s Hydra – short for Hydraulic Multi-axis Shaker – serves to simulate the extreme vibration experienced during the first few minutes of a rocket launch, to ensure that satellites and their component parts will not be shaken to pieces during their actual flight to orbit.
The facility can shake test items weighing up to 23 tonnes, generating accelerations of 0.02 – 5 Earth gravity. Overall, Hydra is capable of generating vibrations equivalent to upwards of a Magnitude 7 earthquake. It is the most powerful yet precise shaker the Test Centre possesses.
From above Hydra appears quite modest. Its visible part is just a 5.5 x 5.5 m octagonal aluminium plate lying flush with the floor. But this plate is only the top surface of an 18-tonne table that is moved by eight hydraulic actuators and braced by shock absorbers to prevent vibrations disturbing the rest of the ESTEC Centre.
Hydra was installed in 1996 and underwent extensive refurbishment in 2011, having been originally designed to serve the testing needs of ESA’s eight tonne Envisat satellite. Its largest load was the ATV space truck, which weighed 22 tonnes with its tanks full. On a smaller scale, its precision made it suitable for ‘slosh’ testing, simulating conditions inside a rocket’s fuel tank during launch.