Propulsion Module of the PTK spacecraft
Russia's PTK/Federatsiya new-generation transport spacecraft will consists of two main sections: the reentry module, VA, and the Propulsion Module, DO.
The propulsion module of the PTK Federatsiya (later Orel) spacecraft as of 2016.
Design of the Propulsion Module
The expendable propulsion module, known in Russian as Dvigatelny Otsek or DO, of the PTK spacecraft was designed to accommodate the ship's propulsion system, including a dual main engine and eight clusters of attitude control and orientation engines, DPOs, distributed around the module. Four clusters will be located in the front of the module, including a pair containing six engines each, and another two groups with five engines. Four more pairs of engines will be located on the aft bulkhead of the module.
The main propulsion system, KDU, is expected to include a dual s5.92 engine with a trust of two tons each developed at KB Khimmash design bureau in Korolev. The similar engine is used on the Fregat upper stage.
Propellant supplies in the low-pressure tanks of the PO module would be able to provide a total of around 1,300 meters per second in velocity change to the spacecraft, first of all for the departure from the lunar orbit toward Earth.
On its exterior, the DO module will carry a pair of deployable solar panels, the main communications antenna capable of maintaining link with ground control at lunar distances, the main rendezvous antenna of the Kurs-NA system, star trackers and other sensors of the flight control and navigation system.
Various avionics and power batteries will be located inside the DO module along with the tanks of the propulsion system. In July 2016, ZAO Orbita based in the city of Voronezh announced a contract with RKK Energia to develop equipment for power distribution and control aboard the PTK spacecraft, which had to be delivered in 2020.
A special detachable umbilical mast will connect key systems of the DO module and the Return Vehicle, VA, carrying the crew. During the launch and the ascent to orbit, the DO module will be protected by a payload fairing, which will split into four parts and fall away above the dense atmosphere.
The DO and VA modules will remain connected during the most of the flight separating only during the final reentry into the Earth's atmosphere at the end of the mission. The DO module will then burn up over a remote part of the ocean.
A photo released in December 2020, shows a prototype of the Propulsion Module during manufacturing.
At the origin of the PTK program as a joint effort with the European Space Agency, Europe's aerospace industry was to be responsible for the propulsion module. Following the breakdown of the Russian-European ties on the project in 2009, the development of the module shifted back to Russia.
Seemingly lagging behind the work on the Return Vehicle, the DO module underwent several incarnations while still on the drawing board in the 2010s. One early configuration studied around 2013 featured torus-shaped tanks. However in an apparent effort to provide more propulsion capability and to save weight, a new complex geometry of the propellant tanks emerged by the mid-2010s. The latest architecture relies on tried and proven spherical tanks to store hypergolic propellant. A pair of three-tank clusters, including a pair for fuel and oxidizer and one smaller tank carrying pressurization gas, were tightly integrated inside the cylindrical compartment. In 2016, a similar design of the propellant tanks was also adopted for the new-generation cargo ship, TGK PG.
In another major design change, the DO module's flat aft bulkhead became bulbous to accommodate more propellant during lunar missions...
The propulsion module of the PTK NP spacecraft circa 2011. Click to enlarge. Credit: RKK Energia
Depictions of the PTK NP spacecraft released in June 2013 at the Le Bourget Air and Space Show. Note flat aft bulkhead. Credit: RKK Energia
A propulsion module of the PTK NP spacecraft as of 2013. Credit: RKK Energia
The S5.92 engine serves as the main propulsion unit of the Fregat upper stage. Click to enlarge. Copyright © 2008 Anatoly Zak