Micro-UAVs Possible in Near Future
By Dale Kuska
Special to American Forces Press Service
MONTEREY, Calif., Jan. 7, 1998 A Navy SEAL creeps silently through dense bushes, and approaches a structure with American citizens held captive inside. He needs to see inside the building to find how many hostages there are and exactly where they're located, but he cannot simply walk up to the building.
He reaches into his belt and opens a small canister to release a micro-unmanned aerial vehicle -- a two-inch rotary aircraft that can fly quickly into the building to collect data and assess the situation.
Sounds futuristic, but vehicles like this are approaching reality, and at the Naval Postgraduate School, here, a two-man team is working to bring such vehicles to life.
"Our particular vehicle is remotely-piloted, meaning there will be someone on the ground providing the control, like a remote-controlled car. There would be a camera inside to provide real-time video information, which gives the operator the ability to see where he's flying," said electrical and computer engineering Professor David Jenn, who's been working on the project with doctorate student Bob Vitale. Surveillance during hostage situations is just one use for a micro-unmanned aerial vehicle. It could also inspect hazardous areas, such as an area contaminated by a chemical attack, or other instances when sending humans would be too risky. Plus, its small size gives other advantages. "It would be portable, so it can be carried on a SEAL's belt, for example, and, when he needs it, he can simply open the canister and flies it off," Jenn said. "These things are very small, they're covert, they are very difficult to see, and even if you do see them, they're very difficult to shoot down."
The primary focus of Jenn's research is to find an innovative power source for such a small aircraft.
"If you use a battery, it's too heavy," he said. "Besides, batteries will not provide a lot of power for a long duration of time. (In our research) we're using an off board source of energy. An antennae would track the vehicle and provide a microwave beam to provide energy to the vehicle. The vehicle receives it, rectifies it, then uses that energy to power the motor.
"One of the biggest advantages of using microwave power is that you can make these UAVs smaller and smaller. With a battery, if you continue making it smaller, you lose power," Jenn explained.
Jenn and Vitale's approach for obtaining power is ground-breaking.
"We've never seen anyone transfer power in this way before. In the past, people have used a microwave dish antennae with a large, flat panel suspended over it to gather energy. With a micro-UAV flying, this panel wouldn't work, because once the UAV flew off to the side, it wouldn't be able to receive energy and therefore would fall to the ground. The antennae we're working on is multi-directional, so it can continue to send energy no matter where the micro-UAV is," said Vitale. "We've also been able to use the body of the aircraft as an antennae."
Jenn and Vitale's goal is to fit required sensors into a small, graphite canister weighing no more than a piece of paper, so these micro-unmanned aerial vehicles must do more than maximize use of space.
"The types of sensors DoD would like to see in here are a video camera, radiation sensors, chemical sensors, and maybe even [Global Positioning System]," Jenn said. "There's also talk of using these as communication relays. All this equipment can be packaged together, but it's the weight that creates a problem."
Even with weight as an issue, these tiny vehicles are making progress.
"We've already demonstrated we can transfer power with microwaves. We've performed tests on the safety issues of microwaves, and we've shown that having multiple ground stations [sending microwaves] is the best possible method, said Jenn. "Now we plan to show how we can power these UAVs using radar systems -- systems the Navy already has."
(Kuska is a writer at the Naval Postgraduate School.)