NOAA Teacher at Sea
Aboard NOAA Ship Rainier
July 8 — 25, 2013
Mission: Hydrographic Survey
Geographical Area of Cruise: Shumagin Islands, Alaska
Date: July 30, 2013
Current Location: 54° 55.6’ N, 160° 10.2’ W
Weather on board: Broken skies with a visibility of 14 nautical miles, variable wind at 22 knots, Air temperature: 14.65°C, Sea temperature: 6.7°C, 2 foot swell, sea level pressure: 1022.72 mb
Science and Technology Log:
Sometimes in school you hear, “You’ll need this someday.” You have been skeptical, and (at times) rightfully so. But here on the Rainier, Avery and I encountered many areas in which what we learned in school has helped us to understand some of the ship operations.
How does a 234 ft. ship, like the Rainier, float?
If you take a large chunk of metal and drop it in the water, it will sink. And yet, here we are sailing on a large chunk of metal. How is that possible? This all has to do with the difference between density (the amount of mass or stuff contained within a chunk of a substance) and buoyancy (the tendency of an object to float). When you put an object in water, it pushes water out of the way. If the object pushes aside an amount of water with equal mass before it becomes fully submerged, it will float. Less dense objects typically float because it doesn’t take that much water to equal their mass, and so they can remain above the water line. The shape of a ship is designed to increase its buoyancy by displacing a greater quantity of water than it would as a solid substance. Because of all the empty space in the ship, by the time the ship has displaced a quantity of water with equal mass to the ship itself, the ship is still above water. As we add people, supplies, gasoline and so on to the ship, we ride lower. As evidenced by the sinking of numerous ships, when a ship springs a hole in the hull and water floods in, the buoyancy of the ship is severely compromised. To take precaution against this, the Rainier has several extra watertight doors that can be closed in case of an emergency. That way, the majority of the ship could be kept secure from the water and stay afloat.
How does a heavy ship like the Rainier stay balanced?
Another critical consideration is the balance of the ship. When the ship encounters the motion of the ocean, it tends to pitch and roll. Like a pendulum, the way in which it does this depends largely on the distance between the center of gravity of the ship (effectively the point at which the mass of the ship is centered) and the point about which it will roll. Ships are very carefully designed and loaded so that they maintain maximum stability.
Boat stability diagram
Ballast is often added to the hulls of ships for the following reasons:
- to help keep them balanced when there is not enough cargo weight
- to increase stability when sailing in rough seas
- to increase the draught of the ship allowing it to pass under bridges
- to counteract a heavy upper deck like that of the Rainier, which itself contains 64, 000 pounds of launches.
Ballast comes in many forms and historically rocks, sandbags and pieces of heavy metal were used to lower a ship’s center of gravity, thus stabilizing it. Cargo ships, when filling up at port, would unload this ballast in exchange for the cargo to be transported. For example, in the 1800s, the cobblestone streets of Savannah, Georgia were made with the abandoned ballast of ships. Today water is used as ballast, since it can be loaded and unloaded easier and faster. Most cargo ships contain several ballast tanks in the hull of the ship.
Cargo ship with several ballast tanks
It is thought that the capsizing of the Cougar Ace cargo ship bound for the west coast of the US in 2006, was caused by a ballast problem during an open-sea transfer. The ship was required to unload their ballast in international waters before entering US waters to prevent the transfer of invasive species carried by the stored water. The result of the Cougar Ace snafu: 4, 700 Mazdas scrapped and millions of dollars lost. Oops!
Cougar Ace capsized in open ocean
Because the Rainier is not loading and unloading tons of cargo, they use a permanent ballast of steel rebar, which sits in the center of the lower hull. Another source of ballast is the 102, 441 gallons of diesel which is divided between many gas tanks that span the width and length of the ship on the port and starboard sides. These tanks can be filled and emptied individually. For stability purposes the Rainier must maintain 30% of fuel onboard, and according to the CO, the diesel level is usually way above 30% capacity. The manipulation of the individual diesel tank levels is more for “trimming” of the boat which essentially ensures a smoother ride for passengers.
Where does all the freshwater come from for a crew of 50?
If only humans could drink saltwater, voyages at sea would be much easier and many lives would have been saved. Unfortunately, salt water is three times saltier than human blood and would severely dehydrate the body upon consumption leading to health problems such as kidney failure, brain damage, seizures and even death. So how can we utilize all this salt water that surrounds us for good use? Well, to avoid carrying tons of fresh potable water aboard, most large ships use some type of desalination process to remove the salt from the water. Desalination methods range from reverse osmosis to freeze thawing to distillation. The Rainier uses a distillation method which mimics the water cycle in nature: heated water evaporates into water vapor, leaving salts and impurities behind, condensing into liquid water as the temperature drops. This all is happening inside a closed system so the resulting freshwater can be kept. To speed up this process, the pressure is lowered inside the desalinator so the water boils at a lower temperature. Much of the energy needed to heat the water comes from the thermal energy or waste heat given off by nearby machines such as the boiler.
Desalinator in the Rainier engine room
Distillation purifies 99% percent of the salt water and the remaining 1% of impurities are removed by a bromine filter. The final step of the process is a bromine concentration and PH check to ensure the water is potable. The bromine should be about .5 ppm and the PH between 6.8-7.2.
Daily water quality log
Everyday the Rainer desalinates 2500 gallons of saltwater to be used for drinking, cleaning and showering. The toilets, however, use saltwater and if you are lucky like me, you can see flashes of light from bioluminescent plankton when flushing in darkness. It’s like a plankton discotec in the toilet!
How does the chicken cross the road when the road is moving?
The difference between a road map and a nautical chart is that a road map tells you which way to go and a nautical chart just tells you what’s out there and you design your course. Thus, navigating on the ocean is not as simple as “turn left at the stop sign,” or “continue on for 100 miles”, like directions for cars often state. Imagine that the road beneath you was moving as you drove your car. In order to keep following your desired course, you would need to keep adjusting to the changes in the road. That’s a lot like what happens in a ship. If you want to drive due west, you can’t simply aim the ship in that direction. As you go, the ship gets pushed around by the wind, the currents, and the tides, almost as if you drove your car west and the road slid up to the north. Without compensating for this, you would end up many miles north of your desired location. If you have a north-going current, you have to account for this by making southward adjustments. In a physics class, we might talk about adding vectors, or directional motion; in this case, we are considering velocity vectors. When you add up the speed you are going in each direction, you end up with your actual speed and direction. In the ship we make adjustments so that our actual speed and direction are correct.
Which way to the North Pole?
Did you know that when you look at a compass, it doesn’t always tell you the direction of true north? True north is directly towards the North Pole, the center of the Earth’s axis of rotation which passes directly to the true south pole. However, compasses rely on the location of the magnetic pole which is offset somewhat.
Compass showing true north and magnetic north
The combination of the solid iron core and the liquid iron mantle of the Earth create a magnetic field that surrounds the Earth (and protects us from some really damaging effects of the sun). If you visualize the Earth like a bar magnet, magnetic north is located at an approximate position of 82.7°N 114.4°W, roughly in the middle of northern Canada. If you stood directly south of this point, your compass would point true north because true north and magnetic north would be on the same line of longitude. However, as you get farther away from this west or east, the North indicated by your compass is more and more offset.
The magnetic poles of the earth
Earth showing true and magnetic poles
Our navigational charts are made using “true” directions. Because of our location in Alaska, if we were steering by compass, we would have to offset all of our measurements by roughly 14° to account for the difference in true and magnetic north. Fortunately, due to the advent of GPS, it is much simpler to tell our true direction.
Why so much daylight and fog?
Every hour, the crew of the Rainier measures the air temperature, sea water temperature, atmospheric pressure, and relative humidity. Aside from keeping a record of weather conditions, this also allows the National Weather Service to provide a more accurate weather forecast for this geographical region by providing local data to plug into the weather prediction models.
Hourly weather log
Weather in the Shumagin Islands could be very different from that of the nearest permanent weather station, so this can be valuable information for mariners. In our time out here, we have experienced a lot of fog and cool temperatures (although the spectacular sunshine and sunsets of the past few days make that seem like a distant memory). One reason for this is our simultaneous proximity to a large land mass (Siberia, in far-east Russia) and the ocean. Cool air from the land collides with warm waters coming up from Japan, which often leads to fog.
Currents around Alaska
However, because we are pretty far north, we also experience a lot of daylight (although not the 24-hour cycles so often associated with Alaska). At this time of the year, even though the Earth is farther away from the sun that it is in our winter season, the axis of the Earth is tilted toward the sun, leading to more direct sunlight and longer hours of illumination.
Earth’s orbit around the sun
One slightly bizarre fact is that all of Alaska is on the same time zone, even though it is really large enough to span several time zones. Out in the west, that means that sunset is in fact much later than it otherwise should be. Our last few spectacular sunsets have all happened around 11pm and true darkness descends just past midnight. I have on several occasions stayed up several hours past my bedtime fishing on the fantail or getting distracted wandering around the ship because it is still light out at 11pm!
Rosalind and Avery (with Van de Graaf generator hair) at sunset
After roughly a week back on land, I have already been inundated with questions about life on the Rainier, the research we were doing, the other people I met, and so on. It occurs to me that as challenging as it was to embark on this journey and try to learn as much as possible in three weeks, perhaps the greater challenge is to convey the experience to friends, family, and most importantly, my students. How will I convey the sense of nervousness with which I first stepped from the skiff to land, trying not to fall in the frigid north Pacific? What will I do in my classroom to get my students as excited about learning about the ocean and diving into new experiences as I was on this trip? How will I continue to expand on the knowledge and experiences I have had during my time on the Rainier? At the moment, I do not have excellent answers to these questions, but I know that thinking about them will be one of the primary benefits of this extraordinary opportunity.
For the moment, I can say that I have deepened my understanding of both the value and the challenge of working in collaboration with others; the importance of bringing my own voice to my work as well as listening to that of others; and the extent to which new experiences that push me out of my comfort zone are incredibly important for my development as an individual. I genuinely hope that I can develop a classroom environment that enables this same learning process for my students, so that, like the science I discussed above, they aren’t doing things that they will, “need some day,” but doing things that they need now.
Finally, I will say that I am finishing this trip even more intrigued by the ocean, and its physical and biological processes, than I was before. When one of the survey techs declared, “This is so exciting! We are the first people ever to see the bottom of this part of the ocean!” she wasn’t exaggerating. Even after my time on the Rainier, I feel like I am only beginning to scratch the surface of all of the things I might learn about the ocean, and I can’t wait to explore these with my students. I look forward as well to the inevitable research that I will do to try to further solidify my understanding and appreciation of the world’s oceans.
I leave with fond memories of a truly unique 18 day voyage aboard the most productive coastal hydrographic survey platform in the world: her majesty, the NOAA Ship Rainier. Thank you lovely lady and thank you Rainier crew for making this Teacher at Sea adventure so magical!
The most striking sunset of our voyage.