| How long do you suppose it takes to drill from the
seabed to a depth of 5,000 meters? Weeks? No, several months to half a year. And during all that time, D/V
CHIKYU must stay in the same spot relative to the position of the drill hole regardless of wind,
wave or current at the ocean surface. In order to drill deep into the earth beneath the sea, a 50cm diameter
pipe must stretch from the ship 2,000m down to the seabed. The pipe walls are about 3cm thick; see Photo
1. But even iron pipe with 3cm walls will break if the ship moves out of position by more than a few
meters.
How does D/V CHIKYU manage to stay in one place relative to the drill hole?
D/V CHIKYU uses GPS positioning data from satellites plus an acoustic positioning system that
communicates with transponders on the ocean floor, to specify its position and measure the forces acting
on the ship (wind, wave, and current direction and speed). Those data are used to predict the direction
and speed at which the ship could deviate from its position. Based on those predictions, computer-controlled
thrusters (huge propellers that can rotate 360 degree, Photo 2) apply counter-thrust in opposition to
that deviation to hold D/V CHIKYU in position. This Dynamic Positioning System, or DPS, received
special enhancements in Japan for installation on D/V CHIKYU, and is much more powerful than earlier
versions.
It takes much longer to describe the process and theory of DPS than it takes for DPS to perform its function.
In fact, positioning adjustments are made almost instantaneously to suit the constantly changing conditions
at sea. This system can fix the position of D/V CHIKYU 's derrick to within a radius of
15 m. D/V CHIKYU can drill to a maximum depth of 2,500 m. That's 80% of the height of Mt. Fuji!
This is like hanging from the ceiling of your room and trying to put thread through the head of a needle
that is lying on the floor (Photo 3). Holding the ship in one spot with remarkable accuracy is critical
to our mission. In fact, it takes really sophisticated systems to drill in the seabed. | 
