The KVTK (Russian: Кислородно-водородный тяжёлого класса, Oxygen/Hydrogen Heavy Class) is a liquid Oxygen/Hydrogen upper stage booster for heavy-lift launch vehicle. The KVTK contains an RD-0146D engine and is designed for use on the Angara Rocket. KVTK would be the first hydrogen-powered upper stage for use on a Russian launch vehicle, although Khrunichev has previously produced a hydrogen-powered upper stage KVD-1 for the IndianGSLV. KVTK is designed to provide up to five ignitions, allowing for complex orbital maneuvering, and have an on-orbit lifespan of up to nine hours. KVTK would allow an increase in payload to GTO of 20-50% compared to the Angara A5's standard Briz-M upper stage, powered by UDMH and N2O4.
The RCAF would be a smaller cryogenic stage carrying 10,760 kilograms (23,720 lb) of propellant for the proposed Angara A3, while the KVSK-A7 would be a larger stage loaded with 26,500 kilograms (58,400 lb) for the proposed Angara A7.