The Naval Research Laboratory, which created radar and the GPS navigational system among other well-known technologies, is applying its talents to designing and testing unmanned undersea vehicles that also fly.

Aerospace engineers Dan Edwards (left) and Trent Young (right), who both work for NRL’s Vehicle Research Section, prepare Flimmer prior to a test flight along the Potomac River. Credit: Jamie Hartman, U.S. Naval Research Center

Flimmer is the latest in a veritable zoo of odd creatures that the U.S. Naval Research Laboratory (NRL) has created over the years to map and monitor everything from oil spills to algal blooms.

The flying-swimmer, known as Flimmer, is an unmanned undersea vehicle (UUV) that NRL aerospace engineer Dr. Dan Edwards and his team designed and tested primarily to determine whether an unmanned aerial vehicle (UAV) could also double as a submarine, capable of fast and long-range travel from above the water to underwater locations.

After a three-year research effort that involved multiple test flights, the answer is an emphatic yes, said Edwards, who plans to continue his research with a different concept starting next year.

Overcoming Drag

What motivated Edwards was his desire to overcome a physical obstacle. Underwater vehicles are limited in how quickly they can travel because of the drag produced in water. Air, on the other hand, is about 1,000 times less dense.

By flying over the water’s surface rather than swimming long distances, a combination vehicle could arrive at its destination much faster — an especially important capability under time-sensitive conditions — despite adverse sea conditions.

To test the theory, Edwards and his team merged two separate research areas — UUVs and UAVs — and borrowed heavily from another NRL-developed undersea vehicle called WANDA, short for Wrasse-inspired Agile Near-shore Deformable Automaton. This craft is equipped with four actively controlled robotic fins based on the pectoral fin of a coral reef fish called the bird wrasse (Gomphosus varius). It maneuvers and controls itself by flapping its fins.

After equipping a repurposed WANDA with a set of wings, measuring 7 feet in wing span and, of course, the four moveable fin assemblies, the team flew Flimmer seven times, launching it from a peneumatic launcher in restricted airspace along the Potomac River. Additional water tests took place inside NRL’s Littoral High Bay pool at the Laboratory for Autonomous Systems Research. This water tank is equipped with wave generators and other technology that simulate the water environment. ‰ÛÏWe wanted to make sure the wings wouldn’t impede swimming,‰Û Edwards explained.

This image shows the launch, flight, and splashdown of the NRL-developed Flimmer, an unmanned vehicle that tested both flying and swimming capabilities all in one vehicle. Credit: Dr. Dan Edwards, U.S. Naval Research Center

The effort proved the concept, but it’s unlikely that Flimmer will find a position on the military’s fleet of unmanned vehicles. ‰ÛÏFlimmer is just the latest in NRL’s growing zoo of odd creatures,‰Û Edwards said. ‰ÛÏIt was purposively built to test this concept and is unlikely to be the final design.‰Û

But that doesn’t mean he and his team have given up on the flying submarine.

New Concept Planned

Under continuing research to begin in 2016, Edwards will take lessons learned from Flimmer to create a next-generation autonomously operated vehicle now called the Flying Sea Glider. Instead of flapping its fins to maneuver, the glider will propel itself using a saw-tooth gliding motion enabled by a variable-buoyancy system. Now just a back-of-the-envelope concept, the Flying Sea Glider will be less mechanically complex.

‰ÛÏThe Flying Sea Glider still emphasizes flying for fast, long-distance travel,‰Û Edwards said, but testing showed that while WANDA’s fins operated well under some surface conditions, making the mechanism sufficiently robust to survive splashdown added too much weight.

This image shows Flimmer’s wings and fins that enable it to fly and swim. Credit: Dr. Dan Edwards, U.S. Naval Research Center

He is convinced a flying swimmer has a role to play in ocean monitoring. In 2010, for example, BP’s Deepwater Horizon oil rig exploded, releasing some 4.9 million barrels of into the Gulf of Mexico. ‰ÛÏAircraft may see the surface in search of oil slicks, but they can’t go beneath the sea surface to see their extent,‰Û Edwards said. The deployment of a flying swimmer, like Flimmer or its next-of-kin, the Flying Sea Glider, could have shortened the months-long clean-up effort.

‰ÛÏWe could have equipped the vehicle with a camera and launched it from the shore to look for oil slicks on the surface and then splash down and search beneath the surface to measure the extent of that blob of oil,‰Û he said. Such a craft also could be useful looking for ocean trash, algal blooms, and other biological hazards.

‰ÛÏWe develop technologies and think of ways they could be used by the Navy,‰Û said Edwards. ‰ÛÏThe concept makes perfect sense for specific missions. And we showed that it works.‰Û

Lori J. Keesey is a freelance writer, who specializes in new technology development. She can be reached at Lori.J.Keesey@nasa.gov