The Russian space agency is expected to unveil development plans for a next-generation manned spacecraft on Monday.
Roscosmos should name the ship's prime developer, which has competed to win government funds for the project.
The proposed new spacecraft should enter into service sometime towards the end of the next decade.
It will replace the venerable three-seat Soyuz capsule, which has carried Russian cosmonauts into orbit for more than four decades.
Although Roscosmos has remained tight-lipped about the upcoming presentation, the agency has quietly released its requirements for a future manned transport system to the Russian space industry.
In doing so, the agency has shed some light on the ship's likely design and its possible missions.
The spacecraft, currently known only by the Russian abbreviation PPTS, for Prospective Piloted Transport System, would be able to reach low-Earth orbit or to enter orbit around the Moon.
The Earth-orbiting version of the ship would have a mass of 12 tonnes, carry a crew of six, along with no less than 500kg of cargo; while its "lunar cousin" would weigh 16.5 tonnes, have four seats and be capable of delivering and bringing back 100kg of cargo.
The unmanned cargo version of the vehicle would be required to carry no less than 2,000kg to Earth orbit, and return at least 500kg back to the planet's surface.
Roscosmos has reserved the option of making the crew module of the spacecraft reusable, reckoning that a cone-shaped capsule could fly up to 10 missions during its 15-year lifespan.
Soyuz also acts as the "lifeboat" at the International Space Station
In providing the technical specifications for the new spacecraft, the agency has also given a glimpse of its vision for the future of the Russian space programme.
Although the most capable version of the ship is meant to support expeditions to the Moon, "intermediate" configurations are intended for a variety of other tasks.
For example, the agency wants the future developer to evaluate the possibility of sending the ship into high-inclination orbits extending towards Earth's poles, usually frequented by Earth-observation and spy satellites.
While in Earth's orbit, the new spacecraft would have to be able to fly 30-day-long autonomous missions; or stay no less than a year in space when it is docked to the International Space Station, or to a possible future Russian space station. (Currently, Soyuz spacecraft, which serve as "lifeboats" for the International Space Station, have to be replaced roughly every six months due to potential deterioration of some of their systems, such as batteries and propellant).
In addition to docking to the station, the spacecraft would have to be able to conduct servicing of unmanned vehicles in space and even remove pieces of space junk from their orbits, as well as conduct unspecified military tasks.
The lunar version of the ship would be capable of flying no less than 200 days in space when docked to a space station in orbit around the Moon.
A number of Russian reports have described recent studies looking at the possibility of a lunar orbital station, LOS. Such an outpost would also serve as a hub for lunar modules, which would deliver crews from lunar orbit to the surface of the Moon.
Europe will now pursue its own plans, but incorporate Russian technology
The 200-day mission requirement probably provides some hint about Russian plans to eventually build a permanently occupied lunar outpost, similar to Nasa's lunar base developed under its Constellation programme.
In a recent interview with the ITAR-TASS news agency, Aleksei Krasnov, the head of the manned space flight directorate at Roscosmos, said that the future spacecraft could serve as the "core" technology for a future Martian mission.
This apparently referred to the role that the vehicle might play as a delivery and return craft for the large complex that would be needed to raise a manned assault on the Red Planet.
By the time the new Russian spacecraft could enter service around 2018, the Soyuz family will have logged more than half a century in service.
In recent years, Russia and Europe did look at the possibility of developing the next-generation vehicle together, but the two parties could not agree on the work share. Europe will now separately pursue the possibility of upgrading its robotic ATV space freighter to a manned ship, but still using some Russian technology.
As reported by BBC News last month, Roscosmos has already completed a tender for the new rocket that would carry the future manned vehicles into space.
Although the agency has delayed the announcement of the winner until at least 6 April, many unofficial sources in Russia maintain that TsSKB Progress, based in Samara, will lead the development of the new rocket.
It is believed that the launch vehicle will feature a three-booster first-stage, each booster equipped with powerful RD-180 engines, burning a mix of liquid oxygen and kerosene.
Russia will also introduce a new fleet of launchers in the next few years
The engine was originally developed by Moscow-based NPO Energomash for the US Atlas 5 rocket and its performance to date has been impressive.
Ironically, Russian officials rejected a design of the yet-to-be flown Angara rocket that featured the RD-180. Now, the power plant, which has earned such a fine reputation across the Atlantic, could return vindicated to its native land
The second stage of the new manned rocket would probably sport a pair of RD-0124 engines, currently in use on the Soyuz-2 rocket. Thus, both stages of the future launcher would be equipped with the newest existing power plants, greatly reducing the cost and the risk to the overall project.