In their mad rush from the ion emitter to the main grid, the ions bump into neutral air molecules-air particles without electric charge.  The terrific wallop in these collisions hurls a mass of neutral air downward along with th e ions.  When they reach the main grid, the ions, being negative, are trapped by the positive charge on the grid.  But the grid has no attraction for the neutral air particles that got bumped along.  So the air flows right through the open grid mesh, making a downdraft beneath the Ionocraft.  The contraption rides on this shaft of air, getting it's lift just like a helicopter-by sucking air down from the top.
"Aerodynamically, it works just like a chopper," Yorysh summed it up.  "But instead of using a rotor and blades, we create the downward airflow electrically by means of an ionic discharge.  The ions act on the air like a man tread ing water.  They just push down."
The engineers working on the Ionocraft are the first to admit that their present rig is still a long way from any kind of practical aircraft.  The model we saw measures only 1296 square inches and consists of about $5 worth of balsa wood and aluminum wire.  But the principle holds an important promise for the future of aviation.
The problem now is improving efficiency-getting enough lift from a given grid area and a given amount of energy.  Present models cannot yet lift their own electric generators.  The get power through a feeder cable, dangling down like an umbilica l cord.  Ionocraft engineers tend to be close-mouthed on performance figures, but they will tell you that at present it takes 90 watts (30,000 volts at 3 milliamperes) to fly a two-ounce model.  Translated into ordinary power-to-weight ratios, t his works out to roughly .96 hp per pound, as compared with a typical .1 hp per pound of helicopter or .065 hp. For a pound of Piper Cub.
But Ionocraft designers are hard at work upping efficiency.  One possible power boosting technique is to pulse the power in short high-energy bursts rather than to apply steady voltage.  They are also trying out various grid patterns and ion emi tter layouts to minimize energy loss through turbulence in the downdraft.
Despite such unresolved problems, the development crew almost bristles with optimism, and the most optimistic of all is the Ionocraft's inventor, Major Alexander P. De Seversky.  No crackpot, Major de Seversky is a practical visionary who in many areas has been far in front of his field.
"We hope to fly a model with self contained power, perhaps by the end of the year," he told me, confidently. "Ultimately, the ionic drive will prove more efficient than either propeller or jet as a method of aircraft propulsion..
"It will achieve lift at less expenditure of energy and fuel than any other existing form of aircraft.  In fact, it will prove the most efficient method of converting electricity into motion."
Coming from a man of de Seversky's background, such a statement has an almost prophetic ring.  A leading aircraft designer and ace flyer for the past 50 years, de Seversky's ideas have often been ahead of their time - sometimes to the embarra ssment of other aviation experts.  Losing his right leg during his first flying mission in World War I didn't deter him from downing 13 enemy aircraft in later flights.  After coming to the United States from his native Russia, de Seversky d eveloped bombsights and course computers during the 1920's that were the forerunners of today's inertial guidance systems.