Mikoyan-Gurevich I-250

The Mikoyan-Gurevich I-250 (a.k.a. Samolet N) was a Soviet fighter aircraft developed as part of a crash program in 1944 to develop a high-performance fighter to counter German turbojet-powered aircraft such as the Messerschmitt Me-262. The Mikoyan-Gurevich design bureau decided to focus on a design that used something more mature than the jet engine, which was still at an experimental stage in the Soviet Union, and chose a mixed-power solution with the VRDK motorjet powered by the Klimov VK-107 V12 engine. While quite successful when it worked, with a maximum speed of 820 km/h (510 mph) being reached during trials, production problems with the VRDK fatally delayed the program and it was canceled in 1948 as obsolete.

Read more about Mikoyan-Gurevich I-250:  Design and Development, Specifications (first Prototype)