| Initial tests with simplified models the EAP actuators move the rudder.|
| The motion of the trout was simulated on the computer at the ETH Zurich providing the Empa researchers with aerodynamics data.|
A blimp would glide through the air by bending its body in one direction, while at the same time moving its tail in the opposite direction - just like a trout swimming in a brook. This would not only gives blimp a sleek look, but would also make it more aerodynamically efficient.
The key breakthrough in the design is electroactive polymers (EAPs) that convert electrical energy directly into mechanical work. They are made of elastic polymer films that, when subjected to an electrical charge, become thinner and expand in area, and they do it noiselessly and without wasting energy.
EPAs reach efficiencies of up to 70% because they work without electric motors and gears. Traditional internal combustion engines generally reach efficiencies of only 25 to 30%. "EPAs will be part of the hull, so the motor gearbox will blend into the body of the craft, allowing for greater maneuverability," says one researcher.
Experiments thus far show that EPAs can achieve the deformation levels and stresses required by the propulsion system. They can already expand and contract the 15% needed for the opposite movements of the blimp's hull. The next task is to construct EPAs that meet aerostatic, aerodynamic, and structural requirements, as well as reliability and durability goals.
The upper side of the large hull offers enough surface area for flexible solar cells to ensure enough energy is available to power the craft. However, this affects its aerodynamic efficiency.
Once all of the kinks are worked out, the team hopes their swimming blimps will eventually replace satellites and helicopters. They could also be used to observe animals in their natural habitats or, as television relay stations at sporting events.
Swiss Federal Institute for Materials Testing and Research (Empa)
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