A Belgian start-up company called Sagita caught much attention at the 2013 Paris Air Show with its ultra efficient helicopter design. The super lightweight aircraft, named Sherpa, is powered by a material that costs close to nothing -- hot air. It is estimated that the Sherpa is around 85% more efficient than the regular helicopter, while delivering similar performance.
The Sherpa's rotors are powered by an air compressor that takes in oxygen for two purposes: some of the air directly aids engine combustion, while the rest is mixed with the helicopter's engine exhaust fumes to heat the air to 100º C. Compressing the hot air can charge two turbines that directly run the Sherpa's two rotors. This is a brand new concept in helicopter technology and is expected to spark many new creative flying innovations.