A solar-powered aircraft uses solar energy to electrolyze on-board water
to produce hydrogen. The hydrogen fills various on-board tanks, causing
the aircraft to become lighter than air. The hydrogen is also used to
operate a fuel cell which provides power for electrical equipment,
including a motor for turning a propeller. Water produced as waste by the
fuel cell is recycled for use in the production of hydrogen. When
hydrogen is removed from the tanks, either because it is consumed by the
fuel cell or because it is compressed and pumped out of the tanks, air
returns to the tanks, and the aircraft becomes heavier than air. The
aircraft can thus be made to climb and descend by making it lighter than
air, or heavier than air. The aircraft emits no harmful substances into
the environment. The aircraft can remain aloft indefinitely, limited only
by an insignificant amount of leakage of hydrogen and water.