Complex sentence: The polywell was developed by the late Dr Robert Bussard, with funding from the Defense Threat Reduction Agency, DARPA, and the U.S. Navy as an improvement on another inertial electrostatic confinement fusion reactor, the fusor.
Split into simpler sentences: The polywell was developed by the late Dr Robert Bussard, with funding from the U.S. Navy. Dr Bussard developed the polywell as an improvement of another inertial electrostatic confinement fusion reactor, the fusor.