BI-1 (Bereznyak-Isayev 1)
The Bereznyak-Isayev 1 (BI-1) was the Soviet Union's first high-speed rocket plane. Developed during World War II, it used a liquid-fueled engine built by Aleksei Isayev (1908–1971) with a thrust of 1.5 tons.
The maiden flight of the BI-1, following accidents in ground runs of the rocket engine, came on May 15, 1942, lasted three minutes, and reached a speed of 400 kilometers per hour. Problems with corrosion, caused by the acid fuels, slowed testing. On its seventh flight, on March 27,1943, the aircraft reached 800 kilometers per hour (unofficially breaking the world speed record) but then experienced a previously unencountered tendency to pitch down and crashed, killing the pilot. Plans to put the plane into production were abandoned, and rocket plane development in the Soviet Union only resumed with the testing of German designs after the war.