Future hybrid aircraft. Illustration of a design for a future hybrid aircraft. This design was produced by Lockheed Martin. The concept proposes a box wing design using lightweight composite materials. Its Rolls Royce Liberty Works Ultra Fan Engine pushes the limits of turbofan technology to maximize efficiency. This design is one of several designs produced by the aviation industry in 2011 in response to a NASA challenge to design future aircraft that were more fuel efficient, less polluting, and less noisy. The designs were assessed by NASA Aeronautics Research Mission Directorate's Environmentally Responsible Aviation Project.