By Anatoly Zak
Russia could eventually convert its modules into the core of a new station
After a hiatus of almost a decade, Russia is resuming construction of its share in the International Space Station (ISS) with the launch of a new module this week.
A Poisk ("Quest") Mini-Research Module-2 (MIM-2 in the Russian abbreviation) launched from Baikonur Cosmodrome in Kazakhstan on Tuesday at 1422 GMT.
The spacecraft is essentially a twin of another Russian module - the Pirs Docking Compartment - added to the outpost in September 2001.
In the intervening years, economic problems kept further Russian pieces of the station on the ground and forced a significant scaling down of the Russian segment in comparison to its originally conceived architecture.
The MIM-2 module is only the first of three long-term components which Russia plans to add to the station over the next three years.
Another module, Mini-Research Module-1 or MIM-1, is currently undergoing final check-ups at RKK Energia, Russia's prime contractor for manned spacecraft. Energia is based in Korolev, near Moscow.
Next month, MIM-1 is due to be shipped to Cape Canaveral, Florida. From here, it is to be launched to the station in the cargo bay of Nasa's space shuttle in May.
The MIM-1 spacecraft was recycled from the habitation section of the aborted science and power-supply platform (NEP). This platform was never completed due to lack of cash.
Despite their identification as research modules, the primary function of both craft is to provide four docking ports for the Russian segment of the station, which are needed to receive Soyuz and Progress transport ships.
After this year's increase of the outpost's crew from three to six people, the number of Soyuz spacecraft heading to the station is set to double from two to four annually.
The lifetime of the ISS (shown in this model) is currently uncertain
At least two three-seat Soyuz spacecraft have to be docked to the station at all times to serve as a lifeboat for all crew members.
With the anticipated retirement of the shuttle within a year, and until the introduction of the Nasa's Orion spacecraft in the middle of the decade at the earliest, Russian Soyuz spacecraft would be the only way to transport people in and out of the station.
In addition to their function as "hallways" for the outpost, MIM-2 and MIM-1 sport interfaces for the installation of scientific instruments.
At the beginning of 2012, Russia plans to launch yet another long-delayed multi-purpose module, MLM, aboard a heavy-lift Proton rocket.
As one of its key elements, MLM would carry a European-built remote manipulator arm, known as ERA.
An 11m-long robot is expected to be deployed to shift up to eight tonnes of hardware, as well as astronauts, during assembly operations outside the Russian segment.
In order to add the MLM to the ISS, the Pirs docking compartment would have to be detached from its current position on the station and directed to a destructive re-entry into the Earth atmosphere.
Since Pirs currently serves as a "door" for all Russian spacewalks, all future work on the exterior of the Russian segment would be staged from the MIM-2 Poisk module.
With the improvement of Russia's economic situation, the nation's federal space agency, Roscosmos, started planning the development of two new modules, that would take on the responsibilities of the cancelled NEP science and power-supply platform.
Both spacecraft would feature specialised research labs and their own solar power systems. Provided sufficient funding were available, they would be launched to the station by Proton rockets in 2014 and 2015.
However, with the financial situation around the ISS looking clouded, Russia reserved the possibility of converting these new modules into the core of a new station, which could serve as a base for deep-space exploration in the following decades.
In June 2009, Simonetta Di Pippo, the European Space Agency's (Esa) director of human space flight, said she shared Russia's vision of the future space station as a platform for deep space missions.
"I have continuous consultations with officials in Russia. We meet every month to month-and-a-half, and now we are going to start joint work on the study for how to proceed beyond 2025," Ms Di Pippo said.
"We have a common idea that we would like to preserve a presence in [low-Earth orbit]. We are studying different scenarios, whether we need permanent presence or, maybe, a human-tended capability, and we can end up with a totally different solution in the end. But I don't believe we can leave Earth orbit."
Ms Di Pippo also said that although current Nasa plans for a return to the Moon left no major role for the station, that could change in the future.
"Even on the Nasa side, they have too many different developments (associated with Earth orbit) - including commercial involvement - which they cannot immediately give up," Ms Di Pippo said.
By the end of 2010, all partners in the ISS project expect to agree on an extension of the station's lifespan from 2015 to 2020 or even 2025.
Once a date for ending the life of the ISS had been decided, active planning for post-ISS manned spaceflight could begin in Russia, Europe and possibly the US.