Marquardt Corporation was one of the few aeronautical engineering firms dedicated almost solely to the development of the ramjet. Its designs were developed through the 1940s into the 1960s, but the ramjet concept never became a major product, and Marquardt turned to other fields in the 1970s. It suffered a particularly bad financial crisis with the ending of the Cold War, and went bankrupt in the 1990s.
The C20-.85 was an athodyd-type ramjet, produced in 1946, using ram air for compression. It was designed for subsonic flight using thrust obtainable from combustion of fuel, and intended as an aircraft auxiliary power plant and expendable missile engine.
The C20-.85 powered the Martin Gorgon IV testbed, developed in 1946 as an air-to-surface missile, and later used as a target drone. The Gorgon IV was considered the U.S.'s first successful ramjet missile, although it never became operational.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.