Ann, watch some of those fish in the big aquarium at your local zoo. There are a few of them that are huge when viewed from the side, and they really do become hard to see when they turn and swim away. My guess is that it is that way to confuse predators.
Rob, sometimes efficiency and streamlining are not the only consideration. Watch some of those fish at the aquarium, some very big fish disappear when they are viewed from the front or the rear. And you don't see very many fish with missile launching abilities.
William is right about shape mattering even more in water than it does in air as far as a fish--or a robot's--speed, maneuverability, and efficiency and therefore power consumption. Just think how much harder it is to swim through water than to walk through air, and the muscles swimming gives your arms as a result.
Rob, shape matters a whole lot in the water and under it, much more than it matters in air. Not only that the greater density takes a lot more power to move it out of the way, but also that the friction of moving through water is greater. One large difference though is that water is generally not compressible,at least not like air.
Festo's BionicKangaroo combines pneumatic and electrical drive technology, plus very precise controls and condition monitoring. Like a real kangaroo, the BionicKangaroo robot harvests the kinetic energy of each takeoff and immediately uses it to power the next jump.
Design News and Digi-Key presents: Creating & Testing Your First RTOS Application Using MQX, a crash course that will look at defining a project, selecting a target processor, blocking code, defining tasks, completing code, and debugging.
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