April 21, 2005

Funded by the National Science Foundation Office of Polar Programs

Location: 59 40.034 S, 63 41.883W

Temperature: 0 C
Wind Chill: N/A
Port Wind: 10-15 knots

SHALDRIL, The Season Final

The Palmer is sailing north. We are well into the infamous Drake Passage and the crossing is smooth so far. The wise and experienced tell us that we are lucky to have calm seas. I personally have mixed feelings. The kid in me did not get the promised rollercoaster ride.

The last specimens are being labeled and readied for shipment. The equipment is being disassembled and packed. The success of the cruise is being analyzed and debated and the final reports are being typed. There is more talk of home.

From the labs I went up to my cabin, then to the lounge, and the conference room to end up on the bridge and the ice tower. I have done my little inspection of the Palmer. Like the true lady that she is, she was being spiffed up and polished for the port call. I realized how fond I have become of this ship. Freshly baked chocolate chip cookies were waiting for me in the galley. They were just what the doctor ordered for the end of the cruise melancholy.

The ship's inspection was not over yet. Rob and JP had a very special surprise for all of us. We had a tour of the engine room, the underworld, where the Palmer's heart, intestines, and bladder are hidden. Those mere mortals that travel on the Marco Polo, or other fancy cruise ships, are not privy to the secrets of the engine room. I was expected to be blindfolded before being taken below. Instead we were ordered to plug our ears. I suppose each sacred place has its own rituals. I was more puzzled by the expectation that I would be able to hear explanations and warnings our guides were giving with earplugs in my ears. I decided that the prudent thing would be to follow along and politely smile and nod. The four big engines are huge and powerful despite of a somewhat delicate cantaloupe yellow color. The tour continued and we were shown the water purification plant and some other pipes, pistons, and rotating things whose names and functions I did not hear, but are surely very important and impressive and make our life aboard the ship possible. The deafening "hard metal concert" was over and we gratefully returned to the familiar world.

Inspired by the engine room tour and several e-mails from our web-page readers, I asked Captain Mike to shed some light on the mystery of the dynamic positioning system, which kept the ship within a three-meter radius while the drilling was going on. He was kind to reply:

"DP is an abbreviation of Dynamic Positioning, a process that's easy to describe but fairly complicated in how it's actually performed. At the most basic descriptive level, DP is the process of taking a position reference for a ship and applying a combination of engine and thrusters to counter any forces trying to move the ship off a preferred location, i.e., wind, weather, seas, pack ice(!) and just plain old random drifting of a ship at sea. On the Palmer this system has several components to do all that. We have multiple GPS navigation references (for redundancy in the event that a single system fails) that feed into the Electronic Chart Display on the Bridge. This compares the ship's current position with the desired position and sends the information to the Robertson SDP600 controller in the center console. This black box does the actual math of calculating the amount of thrust needed in what direction to push the ship back to its desired position. To do this it also has to decide what combination of propulsors to use. On the Palmer we have a 1500 hp azimuthing bow thruster that can thrust in any direction, an 800 hp stern tunnel thruster that thrusts to either port or starboard, and last but not least we have our main engines putting power into the water via two 13 ft controllable-pitch propellers. By controllable pitch, I mean that the engines turn at a constant speed and the angle of the blades is changed to give very precise control from full ahead to full astern. The ship's rudders are also a part of the control system as they determine the direction of the propeller wash from the main engines. With all of these variables available, the DP system has to be run through a specific set-up procedure where you tell the SDP600 how much effect each component can apply to a virtual model of the ship taking into account the power and directional capabilities of each propulsor as well as its location on the ship fore and aft of the center of rotation of the ship. The point of rotation can also be modeled so that you can tell the system to rotate around a specific point on the ship. In the case of SHALDRIL, the ship rotates around the location of the moon pool. This lets us turn the ship to keep it facing into the wind or seas or ice without putting sideways stress on the drill string during drilling ops."

Thank you Captain.

This is my last journal entry for this cruise. In addition to our wonderful Captain, there is a long list of people I owe my endless gratitude. To begin with I thank John Anderson, our chief scientist, and Julia Smith Wellner, who have invited me to come aboard as a ship doctor and journal writer. Julia has earned sainthood for editing this journal and putting up with my unorthodox spelling and some wacky grammar. This journal would not have been possible without April Metz and Suzanne O'Hara who have designed SHALDRIL's Rice University and NPB web pages. I thank all of the scientists I have met on this cruise for the their dedication and hard work that has inspired me to write these pages. I am very grateful to Ashley Lowe, our marine project coordinator, and the Raytheon staff for all the organizational and technical help they have provided and to the ship's crew for the safe and comfortable travel. Last but not least, I thank Alejandra for all the freshly baked cookies.

I thank all of you who have followed this journal. SHALDRIL II is coming out in February 2006. I hear that it is even better than the first and definitely better than the book.

Alexander Injac, NBP0502's ship doctor and the first Antarctic pediatrician, a certified marine mammal observer, and an amateur mud aficionado

Alex Injac

Ice petrel

pancake ice

Gerlache Strait

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