Paul, it was not a VTOL project, just a STOL design. Its roots date back to 1936, when M. Sukhanov was a student. The 'Koltseplan' was the topic of his dissertation. The ring wing has a diameter of 3 m, estimated maximum speed had to be 600 km/h, enabled by a 800 hp Hispano-Suiza engine. Beginning in 1940 the VVS supported the research work. B. N. Yuryev (at this time at the TsAGI), N. N. Polikarpov and other engineers helped him during different stages of development. At the end (1943?) the following characteristics were given:
Take-off weight : 2,500 kg
One engine M-82A with 1,600 hp
Diameter of the ring wing : 3 m
(lifting) wing area : 10,5 m²
Chord of the wing pylons : 1,1 m
Coaxial airscrews of 3 m diameter
Maximum speed (estimated) : 740 km/h
Speed at 3,000 m : 640 km/h
There is a little bit more described in Makarov's book "Letatyelnyye apparaty MAI" (Moscow, 1994, ISBN 5-7035-0161-X). Sorry Paul, but I have not enough spare time at the moment to translate the paragraphs. Check your mailbox (you too, Matej).