The Laboratory Cabin Modules (LCM) (Chinese: 实验舱) are components of the Tiangong space station. Based on the Tiangong-2 experimental space module, the LCMs complete the third and final stage of Project 921, the CNSA's program to establish a permanent Chinese space station. While China's small uncrewed spacecraft can provide platforms for zero gravity and exposure to space for scientific research, the LCMs offer a long term environment combined with ready access by human researchers over periods that far exceed the capabilities of Shenzhou spacecraft. Operations are controlled from the Beijing Aerospace Command and Control Center in China.
Diagram of the Wentian moduleDiagram of the Mengtian module
The first laboratory module provides additional navigation avionics, propulsion and orientation control as backup functions for the Tianhe core module (TCM). Both LCMs provide a pressurized environment for researchers to conduct science experiments in freefall or zero gravity which could not be conducted on Earth for more than a few minutes. Experiments can also be placed on the outside of the modules, for exposure to the space environment, cosmic rays, vacuum, and solar winds.
The axial ports of the LCMs are fitted with rendezvous equipment, and each first docked to the axial port of the CCM. A mechanical arm dubbed the Indexing Robotic Arm, somewhat like the Lyappa arm used on the Mir space station, moved Wentian to a starboard-side port and Mengtian to a port-side port of the CCM.[3] It is different from Lyappa as it works on a different mechanism. Lyappa arm is needed to control the pitch of the spacecraft and redocking in a different plane. But the Indexing Robotic Arm is used when docking is needed in the same plane. In addition to this arm used for docking relocation, the Chinarm on Tianhe module can also be used as a backup in place of Indexing Robotic Arm.[4][5]
Indexing Robot Arm on Wentian
Wentian was successfully relocated to the starboard port on 30 September 2022 at 04:44 UTC[6] using the indexing robot arm.
In addition to this, Wentian houses a small 5 m (16 ft) long robotic arm like the Chinarm as a supplemental to that arm. It is used for manipulating extravehicular payloads and their positioning accuracy is 5 times better than the Chinarm. There are standard adapters (silver squares) on the modules to host the payloads.[7] There is also an adapter by which one of these arms can be grappled by the Chinarm it to work a single robotic arm like Orbiter Servicing Arm with Canadarms.[8]
Mengtian also carries a toolbox equipped with a dexterous robotic arm (similar to the Lyappa arm used on the Mir space station) installed to assist in cargo transfer and payload release, and can be used to deploy external payloads.[9][10]
Electrical power is provided by two steerable solar power arrays, which use photovoltaic cells to convert sunlight into electricity. Energy is stored to power the station when it passes into the Earth's shadow. Resupply ships will replenish fuel for LCM 1 for station-keeping, to counter the effects of atmospheric drag.
Dimensions
The length of each module is 17.9 m. They are cylindrical with a maximum diameter of 4.2 m and an on-orbit mass of approximately 20,000 kg (44,000 lb) apiece.[11][12]
^Graham, William; Gebhardt, Chris (April 28, 2021). "China readies launch of Tianhe module, start of ambitious two-year station construction effort". NASASpaceflight.com. This means the two future science modules, Wentian ("Quest for the heavens") and Mengtian ("Dreaming of the heavens"), cannot dock directly to their planned radial port locations. [...] To account for this, each module will carry a Russian Lyappa robotic arm — like the ones used on Mir for the same purpose — to move the module from the forward port to its respective permanent location on a radial port of Tianhe's docking hub.
^Hong Yang (2020). Manned Spacecraft Technologies. China: Springer. p. 355. ISBN978-9811548970.
