Cooler Than UAVs? I Think So

This week, I'll be continuing upon last week's post, which focused on my experiences at the SPIE Defense Security & Sensing symposium in Orlando, FL. Hopefully, though, this post will be a bit more interesting to those who are not conducting research in sensor development. On the first day of the conference, after I had finished my presentation, an event called 'student lunch with the experts' was held. The event took place in one of the resort's ballrooms, and the dining tables were set up in such a way that every other seat at a table was occupied by an 'expert' - mostly high-level researchers at top laboratories, companies, and universities - and the seats in between were open, to be filled by the students attending the lunch.

At the 'student lunch with the experts,' I ended up sitting with two gentlemen from the Naval Research Laboratory. One of the NRL researchers discussed his research on analyzing and modeling light propagation in turbulent media, which was definitely pretty cool, but was more interested in having his colleague explain his work. Once coaxed into speaking about his work, the second NRL researcher explained that he was involved with 'gliders.'

"Are you familiar with gliders?" he asked us. We shook our heads no.

Gliders, it turns out, are unmanned vehicles. Similar in some ways to the UAVs - unmanned aerial vehicles - that the US armed forces have been implementing over the past few years, but these vehicles are quite different. The gliders are also known as AUVs - autonomous underwater vehicles. Unlike their airborne brethren, the underwater gliders are not piloted by a technician at a console in another location. Instead, the technician gives the glider a set of GPS coordinates. Once given its destination, off it goes, completely on its own at a nice leisurely pace of 1-2 knots. Upon reaching its destination, the AUV pops up to the surface of the water and establishes a satellite communication link with its home base. At this point, the glider can either stay put at its current location or can be given a new set of coordinates, in which case it will submerge and continue along to the new destination.

Another difference between the underwater gliders and the UAVs are that the glider has no visible means of propulsion; no jets, no propellers. Rather than relying on power-gobbling propellers, the glider makes use of ballasts, combined with fins and the ocean's thermal gradient, to transfer vertical motion into horizontal thrust. In practice, this would mean that the glider would receive its coordinates and then dive. As it dives, internal ballasts push the nose of the glider downward, pushing the glider forward. Once a certain depth is reached, thermal gradients buoy the glider back toward the surface. As it ascends, the nose points upwards, propelling the glider forward in a fashion similar to its descent. The resulting trajectory takes on a saw-tooth profile: up-and-down over and over again, but always moving forward. And because the AUV has no motor to speak of, its power consumption is minimal. So efficient are they that the duration of their submerged journeys can last for months, limited only by the life of the battery. That is unless they are attacked by sharks first, which has proven to be a bit of a problem.

Current research on these vehicles is focused on how to utilize them to solve practical problems. One area of interest, which we discussed during the lunch, is the ability to mount sensors onto the AUVs, allowing them to autonomously collect data and monitor ocean water for analytes, such as environmental pollutants. Given the fact that it would be totally awesome to see a glider in action, not to mention the fact that my research emphasis is on environmental sensors, I'm sensing a possible collaboration here.