Karen's Daily Blog

What does this jar of white stuff have to do with this picture of Alvin? The answer has to do with buoyancy.

I have, in my life, been a fool for buoyancy. One of my favorite things David Letterman does is a game called “Will It Float?”  Letterman has thrown all manner of objects into a giant tank of water, after giving his audience, band, and stage crew a chance to guess how it will behave in the water. Will a bag of kitty litter float? How about a football? I got into the act when I was a marine educator at the Maritime Aquarium back home in Connecticut.  Which will float? A lemon or a lime? Which will float? A can of Coke or a can of Diet Coke?  I could throw things in the water all day!

 

Letterman says the idea was adapted from a British program called “Is It Buoyant?” The buoyancy isn’t anything fancy; it’s something we’ve all explored in our bathtubs and swimming pools.  Playing in water is something humans just naturally do.

But applying the phenomenon of buoyancy -- a show of relative density, in which the less dense object rises to the top -- to a material we can use to build a sub that can float quickly and power-free through two miles of water? Well, that’s high-tech stuff indeed. 

It should come as no surprise to anyone that Alvin itself is made of some pretty high-tech stuff. There aren’t many objects in the world that need to become buoyant as fast as Alvin. Alvin has to go so far down in the sea that if it needed power either to descend or to ascend, it wouldn’t have enough power to stay on the bottom for long.

The solution is a substance called syntactic foam. Think about foam you know:  shaving foam, whipping cream, the foam on top of a soda pop, soap foam you can make by rubbing your hands together. Then there’s styrofoam.  In another day or two, we aboard Atlantis will be happy to show you how styrofoam coffee cups shrink at the bottom of the ocean. Here’s why:  because pressure pushes the air out from between the spaces in the foam, resulting in a miniature coffee cup. The definition of foam is a matrix material -- a solid or liquid -- into which bubbles are mixed.

Syntactic foams are made of matrix materials that are filled with bubbles whose walls may be made of metal, ceramic, polymers (plastics), or something else manmade. The material forming Alvin’s outer white shell is made of  hollow microscopic spheres of glass embedded in a hard epoxy resin. The resulting material is lighter than water, but strong enough not to crust under the cruel pressure of the deep ocean. (An even higher-tech syntactic foam is being developed for the new submersible being constructed now.) Oh, by the way: that jar of white stuff?  It’s a jar of the microscopic spheres of glass.

 

So why does Alvin sink to the bottom in the first place? With the help of four 250-pound stacks of iron weights that are fitted into its sides. After Alvin is released from the stern of Atlantis, the weights make it negatively buoyant and pull it swiftly to the bottom. There, the pilot turns on the engines and drops two stacks of weights.  This allows Alvin to achieve neutral buoyancy, during which it can hover along the bottom as the scientists and pilot do their work.  Once they are done and it’s time to return to the ship, the pilot drops the remaining weights, and the submersible rises gently up. 

In the course of our safety briefing inside Alvin’s sphere, Dave Walters instructs Dr. Eric Wommack of the University of Delaware and me in what would happen if Alvin were trapped by fallen rocks or something else at the bottom. We learn how to drop the weights, the cargo basket, the manipulator arms, and finally the bottom of the sub itself, so that the sphere could eject and float free. It hasn’t ever happened, and it probably never will.

I don’t have any idea if I’ll get to dive in Alvin. There are many aboard who hope to make the dive, and a limited number of spaces. Pilots-in-training must be trained on some of the dives, which limits observer spaces, and weather or technical difficulties could cause dives to be scrubbed. Doesn’t matter! Just climbing down into Alvin’s funnel and sitting for a while inside the sphere is a thrill, as you can see from the loony smile on my face as I climb back out again. (Eric took the picture!)

Today's Extreme Blogger:
Katrina Twing

I am a second-year master’s student at the University of Delaware, and this is my first hydrothermal vent cruise. I’ve been on a research vessel a couple of times before, but it was for two-day cruises in the Delaware Bay, where you can see Delaware on one side and New Jersey on the other.  It is a much different experience to be out to sea for three weeks with no land in sight.  I thought it would take longer to get used to being on a ship, but after only two and a half days, I already feel comfortable here and with the other scientists.  It has been a great experience getting to meet people from different places and hear all about their research and interests. 

While an undergraduate at Clark University, I took a course called Topics in Marine Biology, which focused on bacteria in the oceans. During that class, I was assigned to read a scientific paper on hydrothermal vent bacteria and have been intrigued ever since. There was a certain excitement surrounding a diverse world at the bottom of the ocean waiting to be explored.  While most life on the planet gets energy from the sun, the animals living at hydrothermal vents are in complete darkness.  They instead rely on the chemicals from the vent for food.  Much like we need plants to convert light energy from the sun into an energy source we can eat, the animals at the vent need bacteria to convert toxic chemicals into a food source. 

Shortly after reading my first paper on hydrothermal vents and the bacteria that live at them, I traveled to Boston specifically to see an IMAX movie on vents and then went to an exhibit at Mystic Aquarium in Connecticut where I could see live video feed from a vent dive taking place.  Everywhere I turned, there were hydrothermal vents and I started getting really excited about them.  I decided my sophomore year of college that I wanted to go to graduate school and I wanted it to be at an institution that does research on hydrothermal vents; which is why I am currently studying at the University of Delaware.  It’s been a great journey over the past couple of years from reading a paper about vent bacteria to getting to be on a cruise trying to grow them!  It’s funny to think that all it took was a school assignment and participating in an outreach program similar to Extreme to start a dream that eventually would come true!

Today was the first Alvin launch of the cruise.  Everybody got up to see off the first divers on the trip, Chief Scientist, Dr. Craig Cary and Principal Investigator, Dr. Eric Wommack.  Alvin can hold three people; one pilot and two scientists.  There are about 25 scientists on board and 14 dives (13 left, if you don’t count today’s).  The chief scientist decides each day which scientists get to dive the following day, so you have to wait and see whether you get a chance.  I am really excited (and nervous) at the prospect of getting to dive, but I am also just really thankful just to have the chance to be here at all. I have dreamed about going to the ocean bottom in Alvin and getting to see a vent in person for years and would love the opportunity to dive.  However, I recognize the reality that I may not get to dive and am really excited just to be on the ship and be a part of Extreme 2008.

Photo Gallery

The Sipper. 

Video Gallery