When You and I Were Fishes Still
Insects were the first creatures to take to the air in powered flight - 350 million years or so ago, back when our ancestral line were all still fishes - and they still seem to have a few aerodynamic tricks to teach us. The number one problem of heavier than air flight is how to support oneself against gravity, and the universal answer for powered flight is the wing. Flight is accomplished by dragging a wing (fixed, rotating, or flapping) through the air at an angle and thereby causing air to be accelerated downward. The details are in Newton’s second and third laws. Law three says that if a wing exerts a downward force is exerted on air, and equal opposite upward force will be exerted on the wing by the air. The second law says that keeping an object of mass m aloft against gravitational force mg requires transferring downward momentum to air at a rate of dP/dt = d(Mv)/dt = mg where M is the mass of the air and is its speed. For example, if dM/dt is the rate at which air is recruited...
