In an engineering lab at Virginia Tech, a white jellyfish pulses gently up and down through a small tank of water.
In a similar setting at the University of Virginia, a manta ray "flies" on wing-shaped fins.
They look alive. They are not.
They are robots, tethered now to power supplies and computers but aiming, someday, for independent movement. Their development is funded in part by the Navy, which supports a number of researchers around the country building robots that look and move like live animals.
Their designers imagine the robots performing a number of tasks, from cleaning up oil spills to spying. The Navy says it is basic research on propulsion, with no specific applications.
Whether such work leads to swarms of artificial jellyfish riding the currents, or to ships that move like manta rays, the quest is the same: to improve on nature's design.
Building a better manta ray is not easy.
U.Va. is in its fifth year of working on the $6.5 million project, in conjunction with UCLA, Princeton and West Chester University in Pennsylvania. A full-size silicone version of Mantabot takes test swims in the U.Va. swimming pool, where the robot flaps and turns like the real thing, albeit with wires coming out the top.
Rays and skates are superb swimmers. They come naturally in two general styles: undulators, whose winglike fins ripple through the water, and oscillators such as cownose and manta rays, which flap more like birds.
Although the machine is called Mantabot, it is modeled more on cownose rays, which are abundant in the Chesapeake Bay. In fact, graduate student Trevor Kemp drove to Gloucester Point to pick up frozen cownose rays from the Virginia Institute of Marine Science for hands-on study.
"We're not totally mimicking nature and applying it in engineering," said Hilary Bart-Smith, an associate professor of mechanical and aerospace engineering. "It's a question of what's being done really well by nature. It's created systems that can swim really well or climb trees really well or fly in small spaces really well. How does Mother Nature achieve those things?"
Good question. Even the simplest of shapes -- a 6-inch-long solid silicone ray on a stick -- pulls itself forward when plunged up and down in the tank. Why it does so is of interest to the Navy, which is always looking for better ways to travel through the water.
Mantabots could carry environmental monitors or map the seafloor, Kemp said. Current mapping equipment is torpedo-shaped, which limits maneuverability, he said. With the appropriate sensors, Mantabots could inspect bridge pilings underwater, Bart-Smith said. Or they could conceivably track drug-smuggling submarines without being detected, she suggested.
"I've swum with sting rays, and they are so maneuverable," Bart-Smith said. "Our interests are in the science. How do they achieve that? Then we will see how to apply it."
Rays and jellies are not the only fish in the sea, so to speak, when it comes to artifacts mimicking life.
Around the world, in various stages of development, are robots based on cockroaches (they climb), bees (for artificial pollination), sea turtles (lots of room for sensors), ocean sunfish (solar-powered), bats (Army-funded), hummingbirds (surveillance in urban environments, funded by the Defense Advanced Research Projects Agency), butterflies (a breakthrough in aerodynamics), tuna (among the first bio-inspired robots), octopuses (for underwater rescue, perhaps) and more.
Nobody wants an artificial cockroach; there are too many real ones around. But maybe the best attributes of a cockroach -- the way it moves -- can be made better.
Virginia Tech chose to improve on jellyfish.
"Ships and submarines are based on a propeller structure. That's been our traditional design," said Shashank Priya, associate professor of mechanical engineering and materials science. "We realized there's some simplicity in nature."
Priya oversees the development of Robojelly, which can move sideways as well as vertically with the pulsing of its bell, just like the real thing.
The silicone Robojelly is small, but on a table near a bottle of "Goo Gone" is a version 6 feet in diameter. "It weighs about 200 pounds," said graduate student Kenneth Marut. "You wouldn't think it would swim. It swims really well."
The $5 million Robojelly project involves Providence College, which is studying jellyfish biology; UCLA, which is working on underwater communication; the University of Texas at Dallas, which is working on muscles and sensors; and Stanford University, which is examining chemical and pressure sensors.
"Everything comes back to Virginia Tech to be integrated into these prototypes," Priya said. "These are to demonstrate we understand what nature was trying to do."
Robotic jellyfish of the future could perform surveillance for the Navy, clean up oil spills and take environmental measurements, he suggested.
Another silicone jellyfish, with more complex tentacles, sat nearby. Someday, Robojellies might be able to trap natural food particles with such tentacles -- just like the real ones do -- and convert them into electricity, or capture solar power, Priya said.
"This is going to be the cool one," one of the students said. "If you could run a jellyfish off its normal food, it could run forever."