The development and key technologies of 2.0 m high energy shock tunnel

The Φ2.0 m high energy pulsed tunnel （FD–21） of CAAA is a free piston shock tunnel, which expands the test capability of CAAA. This paper mainly introduces the develop-ment process and key technologies of the FD–21 tunnel. Many key aerodynamic problems are settled independently. And the aerodynamic design is completed by the reverse design method. Based on these efforts, the engineering technical difficulties such as piston launch, piston stop, full floating support have been gradually overcome during the construction of the FD–21 tunnel. The successful development of the FD–21 tunnel marks the mastery of the free piston driving techno-logy, reduces the gap between China and some foreign countries, and improves the hypersonic research level in China greatly.