Angara-5/KVTK launch vehicle
In one of the major steps to upgrade the Angara-A5 rocket, its original Briz-M upper stage would be replaced with a KVTK space tug also known as Article 371KK82 or 372RB01. For the first time since the mighty Energia rocket flew its final mission in 1988, a new Russian booster propelled by hydrogen will take to the sky onboard the Angara-5 rocket.
A cutaway view of the Angara-5 rocket with the KVTK upper stage and the 14S735 payload fairing. Copyright © 2015 Anatoly Zak / RussianSpaceWeb.com
From the outset of the Angara project in mid-1990s, it was assumed that the rocket would be equipped with a hydrogen-propelled upper stage. In addition to delivering much heavier payloads, it would be loaded with environmentally safe liquid hydrogen and liquid oxygen, unlike the previous Briz-M stage, burning toxic propellants.
The latest design of the hydrogen upper stage for the Angara-5 became known as KVTK, a Russian abbreviation for the "Heavy-Class Hydrogen Oxygen stage." The introduction of the Angara-5/KVTK variant was expected to enable the rocket to carry most commercial and military payloads, first of all communications satellites, to the geostationary orbit.
When equipped with the KVTK upper stage, Angara-5 was also expected to feature a unique payload fairing with a diameter of 5.1 meters and designated 14S735. It was designed to accommodate single and dual payloads installed one above another with the help of a special adapter.
At the beginning of the development in the second half of 2000s, the first launch of the Angara-5/KVTK variant was expected as early as 2014. As of 2012, the Angara-5/KVTK was promised to fly as early as 2017 from its original launch pad in Plesetsk. However by 2015, the rocket variant was not expected to launch before 2021 from its future launch pad in Vostochny and by 2017, the first launch slipped to 2024 and by 2019 to 2027, with development funding apparently still on hold.
Known specifications of the Angara-5/KVTK variant:
An Angara-5/KVRB concept circa 1998 with an original version of the hydrogen-powered upper stage (known as KVRB). Credit: GKNPTs Khrunichev
Evolution of the Angara-5/KVRB design at the end of the 1990s -- beginning of 2000s. Note the differences in payload fairing and the use of a movable nozzle extension on one of the versions of the KVRB stage. Credit: GKNPTs Khrunichev
A scale model of the Angara-5 rocket unveiled around 2001. Copyright © 2010 Anatoly Zak
A circa 2014 artist rendering of the Angara-5/KVTK variant with a 14S735 payload fairing at liftoff. Credit: Roskosmos