An ultralight airship must weigh less than 254 pounds empty weight, except for floats and safety devices like a parachute. It also cannot exceed a maximum level flight speed of 55 knots, (which is unlikely to be a limiting factor in a hot air blimp). The stall speed limit of 24 knots should provide no problem as a lighter-than-air craft should be able to sustain flight at 0 knots.
The airship fuel source that provides propulsive power cannot exceed 5 U.S. gallons. If more than 5 gallons of fuel is carried then the fuel used to propel the vehicle in the horizontal direction should be separate from the fuel providing lift.
The ultralight airship may carry any amount of fuel to power the burner that creates lift. However? the empty fuel tanks must be included in the total empty vehicle weight of less than 254 pounds.
To be truely "Green" our craft will contain it's own hydrogen generator, which transforms Ethanol into Hydrogen and then releases it into the BalloonWing or converts it into Electricity to power the TurboFan, which provides horizontal and vertical forces for steering, direction and even emergency lift. Experimental craft will then be tested for more practical applications.