Tuesday, September 18, 2012
Flying Above Mars
You think we have it tough flying here on Earth? Consider the problems of aviating above Mars.
Not too surprisingly, NASA was way ahead of me. The idea is far from new. Nearly a half-century ago, the late Wernher von Braun envisioned landings utilizing hypersonic gliders. NASA-Langley has been investigating the possibilities for several years, concentrating on a concept called ARES (Aerial Regional-Scale Environmental Surveyor), a rocket-powered system that would maneuver a mile above the planet at 400 mph until it ran out of fuel. NASA isn't sure the concept is viable, but they're continuing to investigate the possibilities for a future mission. NASA scientists would love to come up with an aircraft that could explore all the impressive geologic features on the planet, especially Valles Marineris, the 2,500-mile-long, 30,000-foot-deep canyon that makes our Grand Canyon look like a road rut.
By any method, flying on Mars is an intriguing idea, especially to one who's been operating above Earth for the last 50 years. Mars is a much smaller planet, so gravity is only about 37% of the standard one G force here on Earth. Lifting the weight of a research aircraft would be far less of a problem on Mars than it is here.
Unfortunately, that's about the only positive factor of aviating above Mars. The typical Martian atmosphere is extremely thin, about six millibars, less than one percent of Earth's protective shield. At a typical ground level (there are no seas on Mars), it's roughly the equivalent density of the Earth's sky 100,000 feet above sea level.
That means any form of aircraft might need very large lifting surfaces, and stall speeds would be extremely high, just to remain aloft. Such realities would demand an imaginative takeoff and launch mechanism, and controlled landings on the surface of Mars would be nearly impossible because of the high stall speed.
Several concepts have been considered for a Mars-capable aircraft. One was a series of small, expendable gliders, launched from orbit. These could enter the atmosphere as capsules, descend to a reasonable altitude, leave their cocoons, deploy wings and a tail and reconnoiter and photograph specific areas of interest before landing and perhaps serving as miniature science platforms after touchdown, assuming they survived the crash. There's nothing even close to a runway on Mars, as the surface is strewn with boulders and craters.
Another option might be entomopters, small machines that fly like insects. To bypass the problem of large lifting surfaces, one proposal was to design aircraft that would generate lift similar to insects on Earth. Unlike aircraft or birds, insects develop lift by the continuous creation and shedding of vortices on their wings. Such vortex formation and shedding produces very high lift coefficients, roughly five times more efficient than conventional aircraft airfoils.
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