Super-launcher is back on the books
At the end of 2016 -- the beginning of 2017, RKK Energia formulated a new design for a super-heavy rocket for Russia's prospective lunar-exploration program. The new architecture, approaching NASA's Space Launch System, SLS, in size and payload, had two possible variations of the upper stage.
Energia-5VR and Energia-5V rockets as of 2016. Copyright © 2017 Anatoly Zak
By the middle of 2016, the Russian scenario for lunar expeditions based on four Angara-5V rockets was deemed too risky and unreliable. Instead, Russia's strategic plans for human exploration of deep space defaulted back to a much larger super-heavy rocket.
The path to the development of a super-heavy launcher was built into the 2016-2025 Federal Space Program, and it was apparently endorsed with a government document signed by the Russian Prime Minister Dmitry Medvedev. By the end of 2016, there were some rumors inside the industry that the Russian president Vladimir Putin would officially endorse the costly project as early as January 2017.
By that time, the architecture of the super-rocket favored by RKK Energia featured a five-booster first stage powered by RD-171MV engines. The boosters themselves would derive from the Feniks and Sunkar projects, which aim to build a medium-class rocket with a diameter of 4.1 meters. If the Sunkar-type rocket had ever been built, it would be only logical to re-tailor the path to a super-rocket utilizing the prospective new booster as a stepping stone.
The RD-171-based launcher built of standard modules with a diameter of 4.1 meters could carry between 80 and 100 tons of payload and after additional upgrades, it could lift up to 150 tons.
With the architecture of the first-stage boosters essentially determined by the Sunkar/Feniks project, engineers at RKK Energia tried to tackle the design of the upper stages. By the beginning of 2017, they formulated two different upper stage arrangements which could support a two-launch scenario of a lunar expedition.
The first configuration, known as Energia-5V, featured a two-stage space tug propelled by liquid hydrogen. The second configuration, designated Energia-5VR, had a larger single upper stage using the same propellant. Both rockets, would be topped with an upper composite consisting of the MOB-DM space tug responsible for deep-space maneuvers and the payload. In turn, the payload could include the PTK Federatsiya crew vehicle, a lunar lander, or a lunar cargo vehicle. In the two-launch lunar expedition scenario, the spacecraft would be represented by the PTK Federatsiya capsule carrying the crew, while the second rocket would have a lunar lander as its payload. The manned PTK vehicle would link up with the lunar lander in lunar orbit.
The Energia-5VR architecture offered obvious advantages over the Energia-5V: namely, it was shorter and lighter, while carrying practically the same cargo. Moreover, because it consisted of only three stages, rather than the four stages making up the 5V variant, the 5R version would likely be cheaper and more reliable. During a lunar mission, the third stage of Energia-5R would fire twice: first to accelerate the payload to nearly orbital velocity and then to deliver it into a highly elliptical orbit with an apogee of 35,000 kilometers. Once there, the crew of the PTK spacecraft could check all onboard systems and, if everything had gone according to plan, the spacecraft would fire its MOB-DM space tug to enter an Earth-escape trajectory toward the Moon.
In contrast, Energia-5V would use its third stage to enter an initial parking orbit and after its separation, the fourth stage would accelerate its payload on an Earth-escape trajectory.
Known specifications of the Energia-5V and Energia-5R rocket:
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RD-170 engine was to power five boosters of the Energia-5V and Energia-5R rockets. Click to enlarge Copyright © 2005 Anatoly Zak
External design of the Energia-5VR and Energia-5V rockets.