Fixed Piston Gravity Corer
The Calypso and Kullenberg corers are tools used for taking samples of sediment located on the sea floor.
They can retrieve large quantities of sediment without disrupting the historical record.
The piston corer comprises a weight of up to 10 tonnes fitted to an assembly of steel tubes which is tipped with a cutter bit to ensure penetration into the sediment.
The trigger mechanism comprises a lever from which hangs a counterweight. The cable between the lever and the counterweight is as long as the corer plus the desired length of the fall.
In order to collect the sediment, inside the tubes is a plastic liner of approximately 100 mm in diameter which contains a sliding piston of a similar diameter.
The piston’s starting position is just behind the cutter bit. A cable connects it to the lever. The piston cable runs up the inside of the tubes and exits at the top of the weight, where it forms a loop whose length is equal to the distance the corer drops. The piston cable may be given additional slack to compensate for the elastic quality of the cable connecting the trigger mechanism to the ship.
The piston helps the sediment enter the sleeve by creating a depression between the bottom of the piston and the sediment during penetration.
If the ship is unable to withdraw the corer, then the tube can be jettisoned using an acoustic release in order to recover the other parts of the corer. The acoustic release also serves as a beacon to mark the position of the corer on the sea floor.
The Cinema application is used to calculate the optimal configuration of the corer (drop height, weight, counterweight, length of piston cable, etc.).
It can also be used to generate kinematic curves from measurements taken during coring operations, to model coring operations, and to calculate the real position of sedimentary layers in the cores.