'Pocket Airports' Would Link Neighborhoods By Air

cylonlover writes "NASA's light-aircraft partner, CAFE (Comparative Aircraft Flight Efficiency), is running a competition to design a low-cost, quiet, short take-off personal aircraft, that requires little, if any, fossil fuel. It envisions the resulting Suburban Air Vehicles taking off and landing at small neighborhood 'pocket airports.' At last week's Future of Electric Vehicles conference, CAFE president Dr. Brien Seeley outlined just how those airports would work."

Comments

You lost me at "that requires little fossil fuel"

[goodmanj]

There is a fundamental difference between internal combustion engines and other technologies: they have *phenomenal* power-to-weight and energy-to-weight ratios.

There is a fundamental difference between aircraft and other vehicles: if their power-to-weight ratio is too low, they do not fly. An underpowered car is an underpowered car, but an underpowered plane is not a plane.

There is a reason why nobody invented a workable aircraft until 1905, and it's not because everybody who tried before the Wright brothers was an idiot.

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Example:

A set of lithium-ion batteries plus a modern electric motor of the type used in hybrid cars has a power-to-weight ratio of about 250 W/kg, and an endurance of 20-30 minutes at that power level. A small aircraft engine, including fuel tank, has a power-to-weight ratio of about 1000 W/kg, and an endurance of several hours.

For most small passenger aircraft, if you increase the weight of the power system by a factor of four, they will be too heavy to get off the ground. (Example: Cessna Skycatcher, engine weight 100 pounds, "spare" weight limit with only the pilot aboard: 150 pounds)

http://en.wikipedia.org/wiki/Cessna_162
http://en.wikipedia.org/wiki/Lithium-ion_battery
http://en.wikipedia.org/wiki/Power-to-weight_ratio#Electric_Motors.2FElectromotive_Generators