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Moon Race rocket to launch next-generation spacecraft

The veteran Proton rocket might get a role in flight testing of Russia's new-generation manned spacecraft after all, Russian officials said.

First developed in the 1960s, during the Moon Race, the UR-500 rocket, later named Proton, became the workhorse of Russia's commercial launch business after the collapse of the USSR. However, the developers of the nation's next-generation manned spacecraft, PTK NP, shunned Proton, because its entire launch infrastructure was left in the former Soviet republic of Kazakhstan and the Russian government pledged to replace it with a new-generation Angara rocket based in Plesetsk and Vostochny on the Russian territory.

However, as the PTK NP spacecraft is about to go from the drawing board to metal at the end of 2013, the Angara rocket is yet to fly its first mission from Plesetsk and its future launch site dedicated to manned missions in Vostochny was barely cleared from trees in the midest of Siberian taiga. At the same time, the payload capabilities of the existing Zenit rocket put sever limitations on the evolving flight test program, after a liftoff mass of the PTK NP spacecraft had increased in 2011 and 2012.

As a result, the spacecraft developers at RKK Energia decided to take a second look at Proton, RKK Energia engineers told the editor of this web site at MAKS-2013 air and space show last month. Their studies showed that a pair of such rockets, capable of delivering up to 20 tons of payload to the low Earth orbit each, could be used to carry an unmanned version of the PTK NP spacecraft on a test mission around the Moon as early as 2018.

According to a flight scenario evaluated in 2013, the first Proton would launch a Block DM space tug into the low Earth orbit. The second vehicle would launch an unmanned test version of the PTK NP spacecraft. The two vehicles would then rendezvous and dock in orbit. The Block DM upper stage would then fire its engine sending the spacecraft toward the Moon. During the mission, Russian flight controllers would test all the communications and flight control modes necessary for guiding future manned expeditions to the lunar orbit.

After a swing behind the Moon, PTK NP would head back to Earth and reenter the atmosphere with a speed of around 11 kilometers per second, testing the riskiest phase of the lunar mission. The successful completion of the flight would validate the thermal protection shield of the crew capsule for the return from lunar missions.

Mission analysis

Unofficial estimates indicate that a Block DM-03 upper stage could send a test version of the PTK NP spacecraft from the Earth orbit toward the Moon, only if the the spacecraft could be lightended somewhat from its nearly 20-ton liftoff mass. It could be easily achieved by reducing the propellant load in the propulsion module, DO, of the PTK NP vehicle. The spacecraft would still have enough fuel to fly behind the Moon, but it would not be able to enter the lunar orbit.

Given some mass reserve on the first Proton rocket carrying Block DM-03, the stage could carry some extra propellant for its lunar mission. Also the rendezvous between the Block DM-03 and the PTK NP spacecraft could be conducted at somewhat higher orbit than the lowest parking orbit achievable with maximum payload on the two Protons. As a result, a stack combining Block DM and the PTK NP spacecraft would require less energy to escape the Earth orbit on its way to the Moon.

Previous scenarios of unmanned trials

The idea of using Proton came to the forefront of the emerging PTK NP's test flight program after around two years of studies.

During 2011, engineers also looked at launching unmanned test versions of PTK from a soon-to-be-completed Angara pad at Russia's northern cosmodrome in Plesetsk. By October of that year, engineers also completed the calculation of four different trajectories that could be followed by an Angara-5.2 rocket carrying PTK NP from Vostochny. (575)

In the meantime, during the summer of 2012, Roskosmos announced a formal tender for the development of the new "lunar" version of the launch vehicle for the manned space program, which would be based at Russia's future launch site in Vostochny, in the nation's Far East. Specifications for the future vehicle closely matched those of the Angara-5 rocket, even though it had never been mentioned in the tender documentation. Not surprisingly, GKNPTs Khrunichev, the Angara developer, turned out to be the only bidder in the "tender" and the company was ultimately awarded the contract.

By 2013, various sources enabled to compile an emerging picture of the flight test program aimed to validate the PTK NP spacecraft for manned missions. According to official statements, up to three launches of the Zenit rocket beginning as early as the middle of 2018, would carry unmanned prototypes of the spacecraft into low Earth orbit, possibly, culminating with a docking at the International Space Station.

At least one launch, possibly on a Proton rocket or on the Zenit rocket was thought to be considered in order to accelerate PTK NP's crew capsule to match the velocity of a mission returning from the Moon. The flight would test the capability of PTK NP's heatshield to withstand the atmospheric reentry.

All these initial test flights were expected to originate in Baikonur. It is logical to assume that the switch of the PTK NP spacecraft to the Angara-5-derived launch vehicle based in Vostochny would require additional unmanned launches into low Earth orbit. Finally, with the appearance of a heavy-lifting launch vehicle, two unmanned versions of the PTK NP spacecraft were expected to fly test missions into lunar orbit, paving the way to a manned circumlunar flight by 2030. (642) At the time, Russian space officials predicted the first launch of the Yenisei-5 heavy-lifting launch vehicle from Vostochny Cosmodrome around 2028.

Next chapter: STK super-heavy rocket

The article and graphics by Anatoly Zak; Last update: September 10, 2013

Research and technical estimates by Igor Rozenberg