Tsybin's OKB-256 built the rocket-propelled transonic research aircraft LL-1, LL-2, and LL-3 from 1945. On 23 May 1955 they were selected to build the RS air-launched ramjet-powered Mach 3 intercontinental reconnaissance/strike aircraft. In 1957, in response to the USAF Dynasoar project, OKB-256 was one of two aviation bureaus tasked with producing draft project designs for a manned spaceplane. Tsybin's draft project for the PKA gliding spacecraft, undertaken in co-operation with Korolev's OKB-1, was signed by Tsybin on 17 May 1959. Meanwhile a subsonic aerodynamic test vehicle for the RSR was built and first flown on 7 April 1959.
The Tsybin bureau was closed in October 1959. Tsybin and his staff transferred to the Myasishchev bureau in October 1959 (which had its own on-going VKA-23 winged spacecraft project). The Myasishchev bureau was then in turn closed and the staff transferred to Filial 1 of Chelomei's OKB-52 bureau in 1960. Construction of RSR prototypes was stopped in the spring of 1961, with three airframes nearly finished. Tsybin went to work for Korolev at OKB-1. OKB-256's work on the PKA was passed to the Mikoyan bureau and formed the starting point for the design of the Spiral spaceplane. At OKB-1 Tsybin worked on the Vostok, Soyuz, and Soyuz-T manned spacecraft; AMS planetary probes; and Molniya communications satellite. He was finally Deputy Designer of the Buran space shuttle from 1974 until his death in 1992.