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Nature's Flight System Could Be Key To Exploring Mars
Atlanta - Dec 3, 2001 One of the oldest forms of flight -- the flapping wings of insects -- may support a revolutionary new class of robotic flying machine uniquely suited for exploring a brave new world: the planet Mars. The thin Mars atmosphere, composed mostly of carbon dioxide and lacking oxygen for combustion, provides an inhospitable environment for conventional aircraft and helicopters. Compounding the challenge are size constraints imposed by the spacecraft delivering air vehicles to Mars. But the flapping wing "Entomopter," a patented mechanical insect capable of both flying and crawling, may be ideal for meeting the demanding requirements of Mars aerial exploration. With support from NASA's Institute for Advanced Concepts, a team of researchers that includes Georgia Institute of Technology engineers is conducting a comprehensive feasibility study designed to show whether a fleet of scaled-up Entomopters could one day help explore the Red Planet. "Mars is a nasty place to fly a conventional air vehicle because almost everything there is working against you," says Anthony Colozza, who coordinates the Entomopter study as the principal investigator for the Ohio Aerospace Institute (OAI), the project facilitator. "The Entomopter concept is really a breath of fresh air because it makes the environment of Mars our friend." He envisions exploration by a fleet of Entomopters landing and taking off, perhaps from a rover able to refuel and support them as it crawls across the Mars surface gathering scientific information. In that scenario, the Entomopters could study the surface from an altitude of less than 100 feet, sample the atmosphere, look for minerals and collect surface samples, while guiding the rover to the most interesting locations for study. Though limited in range to one or two kilometers on either side of the rover, the Entomopters could nevertheless cross canyons, large rocks and other features that would stop the rover. "The trouble with the rovers is that they land in one spot and are very limited in the extent to which they can explore," says Robert Michelson, principal research engineer at the Georgia Tech Research Institute (GTRI) and lead developer of the Entomopter design. "It's frustrating to be looking through the camera of a rover and wonder what might be on the other side of the next ridge. If we could get a vehicle that could fly over that ridge, we could do surveys much more efficiently." The Entomopter concept originated at GTRI with U.S. military interest in palm-sized "micro air vehicles" that could surreptitiously explore underground bunkers and other structures. For that mission, a 50-gram Entomopter with a 15-centimeter wingspan could fly through ventilation ducts and using insect-like legs, crawl through narrow passageways or half-open doors. Development of that version continues in parallel with the Mars version.
Another World, Another Environment
Flapping wings also give insects the unique ability to land and take off, quickly change directions and hover. Unlike aircraft, which must move the entire vehicle rapidly to generate lift, insects can move only their wings rapidly -- while the body flies slowly. That could be as useful for exploring Mars as it is for spotting nectar in flowers. One scientist who has contributed to the understanding of insect flight is Charles Ellington, a professor at the University of Cambridge in England. Ellington met Michelson four years ago during a conference on micro air vehicles, and he has since become part of the team developing the terrestrial version of the Entomopter. To control their direction, insects use a complex system to vary the beating of each wing and alter how they encounter the air. Rather than replicate that system, Michelson and GTRI collaborator Robert Englar are adapting an active flow-control technique originally developed for fixed-wing aircraft. On aircraft, the system uses compressed air released by valves to control direction and augment lift over the wings. On the Entomopter, waste gases produced by its power source -- a reciprocating chemical muscle -- would substitute for the compressed air in multiplying lift and providing control. "This allows us to have a much simpler wing-beating mechanism," Michelson explains. "It makes the Entomopter manufacturable and helps keep the costs down." The term Entomopter combines the concept of an insect (ento) with segmented wings (mopter). The multi-modal design concept -- combining wings for flight, legs for ground locomotion and a chemical muscle for power -- received patent protection in July 2000. "They are intelligent, autonomous aerial robots that do more than just fly," he adds.
An Artificial Chemical Muscle "It's a simple device that can generate the fairly high levels of power that are essential to flight," he says. "Our liquid fuel has a higher energy density than a battery. We can extract enough of that energy to be able to create the force necessary to flap the wings, fly and still have some energy left over for other applications."
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