Over the past decade, the undersea robots known as autonomous underwater vehicles (AUVs) have become increasingly important in oceanographic research. Today’s AUVs fall into two groups:
1) propeller-driven vehicles that can travel fast and carry lots of instruments, but are limited to expeditions of only a few days; and 2) “gliders,” which can stay at sea for weeks or even months at a time, but cannot travel very quickly. MBARI engineers recently demonstrated a new super-efficient AUV that combines the best of these two approaches. This new long-range AUV (LRAUV) can travel rapidly for hundreds of kilometers, “hover” in the water for weeks at a time, and carry a wide variety of instruments. The new robot, called Tethys, spent most of October crisscrossing Monterey Bay as part of MBARI’s CANON experiment. Oceanographers used Tethys to track patches of microscopic algae that were carried around the bay by currents. During this experiment, the robot showed that it could travel fast enough to buck the currents, but could also go into “hover mode” to drift with the currents when needed.
In “high-speed mode” the LRAUV can travel up to one meter per second (2.25 miles an hour) – about four times faster than most underwater gliders. However, it can also travel long distances at around half this speed.
After spending four years designing, building, and testing Tethys, MBARI engineers were happy to see it working out in the real ocean. In fact, the AUV performed even better than expected. The AUV completed a four-day science run with plenty of battery power remaining, using relatively low-power rechargeable batteries. Based on these promising initial results, the researchers hope that the little robot will eventually be able to travel from California to Hawaii using high-power disposable batteries.