Узловой модуль The editorial board of the Korolev's Planet website continues reviewing the possibilities for using Lagrange points in space activities. We offer to you the answers of specialists of the RSC Energia Scientific and Technical Center for the Design of Manned Space Systems and Transportation Systems to the questions on this subject.

The questions are asked by Oleg Volkov, deputy head of the Great Start project.

Question No.1. What design configuration is envisaged for a man-tended space station in the Lagrange point near the Moon (the one behind it)? What would be the purpose of that station? What is its place within the circumlunar-based space infrastructure?

In our opinion, the lunar infrastructure, just as the entire space infrastructure, will consist of the following elements:

- Elements which require servicing (bases on the surface and in orbit, man-tended platforms, research vehicles and systems);

- A transportation system (launch vehicles, upper stages, orbital transfer vehicles, manned transportation and unmanned cargo orbital spacecraft, takeoff-and-landing and landing systems, vehicles for transportation on the surface);

- Supporting elements (spacecraft for communications, navigation, control, weather forecasts).

Initially, the lunar infrastructure will most likely consist of a lunar base (at first man-tended, and then permanently manned) and a transportation system consisting of a launch vehicle, upper stages, a reusable orbital transfer vehicle, takeoff-and-landing systems, moon rovers;

Subsequently, after the production of propellant components on the Moon begins, there will appear a circumlunar station, a platform in a libration point of the Earth-Moon system, reusable manned and unmanned cargo spacecraft, takeoff-and-landing systems.

The use of libration points in the Earth-Moon system may be of interest from the standpoint of setting up a manned space infrastructure and transportation system as a staging base for missions to the Earth or to the Moon, as a depot for temporary storage of elements and supplies for interplanetary programs, as a place for storing and accumulating the results of the industrial development of the Moon.

In our opinion, Lagrange points are well suited for placing into them various research instruments, equipment to watch asteroids and comets, depots for propellant components and materials produced in space or on the lunar surface. Human presence is needed there only occasionally and for the sole purpose of fixing something or to transfer from one transportation spacecraft to another. The configuration of the platform (man-tended station) in Lagrange points will be driven by its payload (optical or radio telescope, depot for propellant and gases, equipment need to detect and intercept Earth-threatening asteroids, etc.). Such a platform is expected to operate in automatic mode, but the platform may include a habitable module with an airlock and maintenance and repair equipment to be used whenever a servicing crew visits it. However, if the frequency of such servicing is less than once in several years, the habitable module may be delivered together with the servicing spacecraft during each visiting mission.

Question No.2. What is the amount of cargo traffic from Earth that would be required to deploy and operate a station at that point (upmass to a parking near-Earth orbit, masses delivered and retrieved from the station, the frequency of manned missions to the station, crew safety issues, etc.)?

If the decision to establish such a station is made (for example, to try out new technologies and hardware for further manned space exploration beyond low-Earth orbits and within the framework of the interplanetary vehicle development effort), then its configuration could be tentatively defined.

For a crew of three, without payload equipment and hardware, the mass of the platform (station) in the libration point L1 or L2 in the Earth-Moon system may be about 30-40 metric tons in man-tended mode and 60-80 tons in permanently manned mode. The increase in the mass has to do with the need to install a life support system which is self-contained to a very high degree and a strong radiation shield. 

To deliver a 40-ton man-tended platform from a low-Earth orbit to libration points, upper stages with liquid propulsion will be needed, bringing the launch mass of the stages with the platform up to 150 tons. For an 80-ton platform (for a permanently manned mission), the launch mass of the upper stages with the platform can be as high as 300 tons. 

If a reusable orbital transfer vehicle with electric propulsion is used, this mass can be reduced by a factor of 2 to 3.

The duration of the crew stay onboard the platform depends on the availability of the equipment for countering the effects of zero gravity on the crew (treadmill, stationary bike, other hardware). Without such equipment the total duration of the mission can be 10 -14 days. If there is such equipment onboard, The crew may have their mission extended up to 6 -12 months. 

If the platform is permanently manned with a crew of three, up to 10 tons of cargo (water, food, systems and science equipment) will need to be delivered every year.

The frequency of the visiting missions depends on the frequency of the required repairs or maintenance of the payload equipment (which can be tentatively set at once in several years).

In permanently manned mode the crew is supposed to be rotated every 6 months (as is the case now onboard the ISS) with this period subsequently extended up to 9 or 12 months taking into account the optimization of the delivery costs.

New modules that are currently under development for the Russian Segment of the ISS (node module, science-and-power module and transformable module) can be used as prototypes for developing such man-tended platform in the libration point.  

These same modules (Fig.1, Fig.2, Fig.3) in the future will become the basis for an interplanetary orbital vehicle for the interplanetary exploration complex.

Узловой модуль
Fig.1 Node module

Научно-энергетический модуль
Fig.2 Science and Power Module 

 

 

 

Трансформируемый модуль
Fig.3. Transformable module 

The new-generation manned transportation spacecraft (Fig.4) will also be widely used in these programs.

 

l-4
Fig. 4. New-generation manned transportation spacecraft 

 

Question No.3. What would be a possible configuration of a space segment based on stations placed at three Lagrange points to search for dangerous asteroids and track them?

There are five libration points in the Earth-Moon system and five libration points in the Sun-Earth system. The question of which of these points would be best suited for placing into them spacecraft (platforms) for observation, tracking, and, eventually, interception of space objects threatening Earth needs further study. 

Considering the fact that manned intervention in the operation of such platforms (stations) will most likely consist in periodic maintenance and repairs, such platforms in the libration points are expected to be automated and adapted to maintenance and repairs performed by both robots and humans.

The configuration of the platform depends on the payload that it will carry. Such a platform is most likely to consist of three modules:  

- A support systems module providing communications, navigation, control, power supply, thermal control;

- A payload module containing, for example, an optical or radio telescope with a system with a search and tracking system, equipment and instruments for studying asteroids;

- A module to support dockings with repair equipment and supplies.

At present, an international team with participation from RSC Energia, Boeing and Lockheed Martin conducts technical consultations to define a configuration for such a platform. One of the options is presented in Fig.5.  

Maintenance and repairs of platforms in libration points of the Earth-Moon system could be carried out using remotely controlled robotic equipment or a servicing spacecraft built on the basis of the new-generation manned transportation spacecraft which is currently under development and will have free-flight duration of up to 14 days.

But servicing and repair of the platforms stationed in the libration points of the Sun-Earth system would require developing a vehicle of a heavier class, an interplanetary exploration complex, since a round trip to that destination would take about half a year.

It is most likely that at the first phase of deployment of the Earth’s counter-asteroid system the space platforms will be placed in libration points L2, L4, L5 of the Earth-Moon system. During subsequent phases such platforms could be placed in libration points of the Sun-Earth system and in the vicinity of Mars.

 

Посещаемая платформа в точке либрации системы Земля-Луна
Fig.5. A man-tended platform in a libration point of the Earth-Moon system  

 

 

 

 

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