KVTK (rocket stage)
The KVTK (, Oxygen/Hydrogen Heavy Class) is a liquid oxygen/hydrogen upper stage for high energy orbits that is currently under development. The KVTK contains an RD-0146D engine and is designed for use on Angara rockets. 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 Indian GSLV. 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.

History 
The KVTK was originally studied as an upper stage for the Energia family of rockets, but in 1987 was superseded by the RCS stage (Retro and Corrections Stage), based loosely on the American S-IVB. In 1996, consideration was briefly given to constructing a KVTK-derived Russian Propulsion Module for the International Space Station. Most likely, this module would have been transported to the ISS by a Space Shuttle.

On 10 December 2020, Roscosmos signed a 20.6 billion Russian ruble (US$279M as of December 2020) contract with Khrunichev to manufacture KVTK test models and flight test them by December 2025.

In August 2021, Khrunichev announced that the first flight test of the KVTK is expected to occur in 2027 on an Angara-A5M launch vehicle.

Variants 
The KVSK (RCAF) would be a smaller cryogenic stage carrying  of propellant for the proposed Angara A3, while the KVSK-A7 would be a larger stage loaded with  for the proposed Angara A7.

References 

Rocket stages
Space launch vehicles of Russia