The airplane was substantially damaged upon impact with terrain during an emergency landing. The pilot reported he was conducting high speed taxi-checks when the airplane inadvertently became airborne. The pilot stated he knew that the rotation speed of the airplane was 50 miles per hour (mph). The pilot reported the airplane lifted off at about 50 mph during the high speed taxi checks. The pilot stated he continued the takeoff to avoid going off the end of the runway. The pilot reported flying a normal traffic pattern. The pilot stated that on final approach he saw an airplane on the runway so he decided to perform a 'go-around.' During the 'go-around' the engine lost power. The pilot reported that he checked the fuel shutoff valve, mixture and ignition, but these did not remedy the situation. The airplane impacted a dirt mound near the runway surface. The airplane has a registration certificate but was never issued an airworthiness certificate. The pilot reported the airplane "was not finished."