MOB-1-KVTK space tug
Designed to launch on the Angara-5V rocket, the MOB-1 space tug (a.k.a. MOB KVTK) will be a beefed up version of the standard KVTK stage, but customized to boost the manned PTK spacecraft and the lunar module from the Earth orbit toward the Moon in the second half of the 2020s.
General architecture of the MOB-1 KVTK space tug
The MOB-KVTK concept emerged in 2015, when engineers at GKNPTs Khrunichev evaluated the possibility of using the newly proposed Angara-5V rocket for missions around the Moon and for lunar expeditions. The proposed scenarios required a space tug which would be capable of sending the PTK NP spacecraft and the lunar module from the Earth's orbit toward the Moon.
Since the basic one-engine KVTK stage, which was under development for the Angara-5 series, would be too small for the task, a heavier and more powerful version was proposed to take maximum advantage of the capabilities of the Angara-5V variant.
Key upgrades to the KVTK stage included enlarged propellant tanks and the installation of two RD-0146D engines instead of one. Similar upgrades were previously considered for various configurations of the even more powerful Angara-7 rocket, which was never funded.
The beefed-up KVTK stage for the Angara-5V would also be equipped with rendezvous equipment, communications antennas and a passive docking port to receive the PTK spacecraft or the lunar module, depending on the task of a particular space tug. The docking port could be simplified, since it would not require a crew transfer or refueling. However, at the same time, the port would have to withstand dynamic loads onto the structure during all planned maneuvers.
During a typical lunar mission, the MOB KVTK stage would fire its engines to reach an initial parking orbit and then restart them again after docking with either the PTK or with the lunar module. The space tug would release its payload in a highly elliptical orbit, leaving it to the ship's MOB-2 stages to complete the insertion into the lunar trajectory.
The MOB KVTK stage could also be used for the delivery of heavy payloads, such as large communications satellites, into the geostationary transfer orbit and into the proper geostationary orbit.
Ground support and launch infrastructure for the Angara-5V rocket featuring the MOB KVTK stage would be built at Pad No. 2 of the Angara launch facility in Vostochny, according to plans formulated during 2015.
Known specifications of the Angara-5V rocket with an enlarged KVTK variant as of 2015:
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Angara-5V rocket configured to carry the MOB-1 KVTK space tug. Copyright © 2015 Anatoly Zak
A MOB KVTK space tug performs trans-lunar injection maneuver, TLI, after its docking with the PTK NP spacecraft in the Earth's orbit. Click to enlarge. Copyright © 2016 Anatoly Zak