09/15/2006. Remarks by Bernhard Klein: "This single-seat experimental aircraft was the world's first liquid-fuel rocket jet fighter aircraft designed by A. Y. Bereznyak, A. M. Isayev and V. F. Bolkhovitinov in 1941. Eight prototypes were built, the first unpowered flight with a Petleyakov Pe-2 as tug was made on September 10, 1941, with the first powered flight made by Bakhchivandzhi on May 15, 1942; the second prototype crashed in 1943.

Photos above depict the fifth prototype with a 'belly pack' possibly with gun enclosed.

Replica (Sergey Riabsev Collection)

A replica is kept at the Air Force Museum at Monino, Moscow."