With the launch of the NEM module, the first element of the Russian national space station ROS, expected around 2026, it is necessary to have a transport system for goods and fuel that can guarantee the maintenance of the first modules to be assembled in orbit.
Pending the entry into operation of the new PTK-Orel/ROS transport systems, whose use is conditional on the preparation of the dedicated ground structures located at the Vostochny cosmodrome. The decision was made to adapt the Progress MS for docking and refueling of the station, which required heavy structural modifications.
A continually evolving program
One of the first proposals developed for the ROS station envisaged that the NEM module (from the Russian: energy and research module) would initially be assembled by hooking it to the ISS and following the decommissioning of the latter, taken to its destination orbit, which will incline 97°.
In this way, Progress could have been launched from both Baikonur and Vostochny using the Soyuz 2.1a launcher while maintaining its load capacity intact both in terms of fuel and in terms of material to be delivered to the station.
In 2023, Roscosmos changed the assembly plans of the national space station, deciding to carry out all launches directly into the destination high-inclination orbit from the new cosmodrome in the Amur region.
However, while waiting for the new PTK-Orel/ROS transport spacecraft with crew and cargo to come into operation, this involves the duplication of the ground structures intended for the Progress ships already located in Baikonur. Above all, the change of launcher from Soyuz 2.1a to 2.1b, is capable of reaching the final orbit inclination without penalizing the load capacity of the transport spacecraft.
Changes to Progress spacecraft
The main change to be implemented on the Progress to be launched towards the ROS will be the one regarding the docking system.
The national space station will be equipped with a hybrid docking mechanism called ASA which replaces the long-lived SSVP so far mounted on Soyuz, Progress, and on the modules of the Russian section of the ISS except for the Prichal node where the ASA system made its debut.
ASA guarantees a much wider passageway (920 mm versus 800) and greater stability during the docking phase, preventing the oscillations that the docked vehicles experience during the docking consolidation phases, in the face of greater weight than 45 kg.
Furthermore, the ASA system can be easily changed from the active to the passive phase simply by applying an adapter ring.
The installation of this mechanism, specifically designed for the PTK-Orel, requires that the KURS-NA approach system also be replaced with the new IPS system specifically designed for the ROS. This will result in the loss of approximately 50 kg of load capacity.
Changes to the NEM module
To accommodate the Progress, the NEM module will also be modified to allow, in the event of failure to dock with the automatic IPS system, the use of the on-board remote control device that we know by the name of TORU and which has made its debut already at the time of the MIR.
Since its use was not foreseen in the original design phase, the NEM will be reorganized in its internal structure and also in the external configuration with the addition of the characteristic target lines for use by the operator at the TORU.
Overall, this is a demanding engineering challenge, but it allows the ROS station to be able to respect the timetable of its assembly. This is already currently conditioned by the delay of the Orjol program and the full operation of the Vostochny cosmodrome as well as by the economic repercussions caused by the Russian-Ukrainian war and the resulting economic sanctions against Russia.