Planning and Preparation for all Eventualities

　The OSI’s duties don’t end when he steps off the ship. “Discussing and planning all the tasks that need to be carried out during a research expedition in an important part of my job. Then we need to identify the right tools for the task, and get the necessary equipment ready.” A safe and successful expedition relies on precise pre-expedition planning. The CHIKYU drills in a wide variety of environments, from the strong Kuroshio current to the seabed hydrothermal ore deposits hot enough to melt plastic equipment. Challenging circumstances like these can call for custom-developed technical solutions or highly specialized equipment. “By working out new tools and methods to deal with novel drilling circumstances, we are helping to broaden the possibilities of future scientific drilling as well. It’s definitely a job worth doing.”

　The CHIKYU is scheduled to begin drilling this April at the seismic hypocenter of the Great East Japan Earthquake. The ship will drill 1,000m into the ocean floor, at a point 7,000m beneath the surface—an unprecedented depth for scientific drilling. This poses a new set of challenges for scientific drilling that need to be resolved before the work can begin. “Making sure that the drill pipe is up to the job is our first concern,” says Saruhashi. The steel drill pipe will need to extend to the ocean floor 7,000m below the CHIKYU before any drilling can take place. From there, the drill will plunge another kilometer into the ocean floor. At such great depths, multiple challenges arise. For example, small surface movements caused by waves and tidal changes are greatly magnified below. And of course, 7,000m of drill pipe is very heavy. A total of 400t of steel will be perched atop the lowest segment of pipe where it contacts the ocean floor. These conditions approach the functional limits of drill pipes, and could cause material failure. The CHIKYU team performed stress tests to identify the strongest pipes best suited to the task. The project also faces a great unknown in the ocean floor itself. The target area has never been drilled before, and the team does not know whether to expect hard or soft soils. “We have to be ready for anything at all. The best we can do is work out a plan for every contingency.” Under normal circumstances, the CHIKYU would send out an unmanned probe to visually monitor drilling operations. But the probe can only withstand depths up to 3,000m, and can’t be used for this deep-water operation. Instead, the drilling pipes will be fitted with an attached camera relay. Unlike the unmanned probe, which allows near total flexibility, this underwater camera arrangement is constrained to a single vertical axis of motion. Just lowering the camera 7,000m to the drill site will take a great deal of time. The OSI gets involved in improving the capabilities of the camera equipment, and to develop better, more efficient means to deliver the equipment to the sea floor. “The single most important thing is that the project is carried out safely,” Saruhashi stressed. Preparations for the vital April expedition continue.