http://www.scientificamerican.com/artic ... wered-subs
June 19, 2009
Human-Powered Subs Start Your 'Engines'
Student submariners gather at the Naval Surface Warfare Center in Maryland to compete in a race that tests their engineering skills—and ability to pedal under water
By Larry Greenemeier
A group of budding engineers will be diving, splashing and swimming in the pool next week for the first time this summer. The difference between them and a lot of other high school and college students is the pool: an in-ground, freshwater basin that is about 3,000 feet (914.4 meters) long, 51 feet (15.5 meters) wide, and 22 feet (6.7 meters) deep at the Naval Surface Warfare Center in Bethesda, Md. The occasion is this year's International Human-Powered Submarine Race.
Twenty-one teams from around the world compete to see whose submarine can cut through the water fastest using a hull and propulsion system designed and built by the students. Each sub will have one or two pilots onboard who use pedals or some other propulsion system to guide their vessel across the 328-foot (100-meter) submerged racecourse the fastest. (Only one sub races the course at a time.)
"I'll have 300 kids there," says Claude Brancart, the competition's head judge and chairman of the Foundation for Underwater Research and Education (FURE), the Brunswick, Maine-based not-for-profit that organizes the competition and promotes marine science education. "I want to give an award for someone who breaks the 10-knot [11.5 miles per hour] barrier."
The fastest speed so far in the competition's 20-year history came during the 2007 competition, when a University of Quebec team reached 8.035 knots with its Omer 5 sub.
More than accolades, the competition teaches students about the challenges and rewards of engineering. One of the most important lessons the students can learn is the importance of the design, says Chris Land, engineering technology teacher at Sussex County Technical School, a high school in Sparta, N.J. He says he will give students "two extra months to design something if it means [they will] get it right the first time."
Land is also the project mentor for the Sussex Technical team, which has competed in each race since 2003 (the races are held every other year). Land's students use the preparation for the race as their senior-year project, and he has been impressed with their commitment to designing a sub that one or more of the students will pilot in an actual competition against college-age students. Sussex Technical is one of the few high schools that competes. Student pilots and support divers must become scuba certified in order to compete. Land himself is a certified diver and former submariner with the U.S. Navy.
Although the school won first place in the 2007 competition's innovation category for a linear drive propulsion system that converted back and forth motion of the pilot's arms and legs into continuous rotary motion to propel the sub, it was not a very efficient system and the vessel topped out at less than 1.7 knots.
"The only thing that's not new this year is the shape of the hull," Land says. "Last year, we had a lot of mechanical difficulties and couldn't get the hull up to speed."
This time around, the propulsion system relies on tried-and-true bicycle-style pedals. They power a blade in the water that the pilot can adjust to reduce drag. "It's a variable-pitch propeller, which is like having gears on a bike," Land says. In addition, all of the controls (including the rudder) are enabled by electronically controlled servos—much like a remote control car that can be controlled by a joystick.
Many of Land's students have gone on to study engineering, and one of the things he is most proud of is that most of those students do not change majors during their college careers. "If college is averaging $35,000 per year," he says, "what's it worth for a student to know what they want to do and not change their mind in the middle of it?"
As usual, Land's kids will face a tough field that includes entries from major U.S. universities from and international teams from Canada, England, Mexico and Venezuela.