Expedition 13 Mail Buoy: December 14

Hi, I'm Pranav from Ms. Sheild's class in Clarke Middle School. I was wondering about the outer white layer of the Alvin sub. What is it made of and how thick is it?

Pranav Gandham

The outer layer is mostly fiberglass about 3/8" thick and in a few places it's the syntactic foam, which provides the sub with its buoyancy. The fiberglass cover doesn't do much other than protect the mechanical and electrical systems on the sub and give it a more hydrodynamic shape.

—Bruce Strickrott, Alvin Expedition Leader

What if a shark or other animal hits the Sentry? Can the animal damage the propellers?

William, from Ms. Dunbar's class

The propellers are made of carbon fiber and are very strong, so it would probably do more damage to the shark than sentry. A broken or lost propeller is no problem because Sentry is programmed to adjust its thrust if that happens, as well. If an animal bumped into the vehicle body, Sentry would just recover and resume its course. In fact, currents knock it around all the time.

—Dana Yoerger, Sentry team