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[[File:Wentian Module.png|thumb|right|Diagram of the ''Wentian'' module]]
[[File:Mengtian module.png|thumb|right|Diagram of the ''Mengtian'' module]]
The first laboratory module provides additional navigation avionics, propulsion and [[Yaw, pitch and roll#Aircraft attitudes|orientation]] control as backup functions for the [[Tianhe Corecore Modulemodule |''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 wind]]s.
The axial portports of the LCMs isare fitted with rendezvous equipment, and willeach first dockdocked to the axial port of the CCM. A mechanical arm dubbed as the Indexing Robotic Arm, lookingsomewhat alike sort ofthe [[Lyappa arm]] used on the Mir space station, movesmoved ''Wentian'' to Starboarda starboard-side port and ''Mengtian module'' to a portsideport-side port of the CCM.<ref>{{cite news |url=https://www.nasaspaceflight.com/2021/04/china-station-construction-begins/ |title=China readies launch of Tianhe module, start of ambitious two-year station construction effort |first1=William |last1=Graham |first2=Chris |last2=Gebhardt |date=April 28, 2021 |website=NASASpaceflight.com |quote=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.}}</ref> 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 indexingIndexing robotRobotic armArm 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 robotRobotic armArm.<ref>{{Cite book |last=Hong Yang |title=Manned Spacecraft Technologies |publisher=Springer |year=2020 |isbn=978-9811548970 |___location=China |pages=355}}</ref><ref>{{cite news |url=https://www.nasaspaceflight.com/2021/04/china-station-construction-begins/ |title=China readies launch of Tianhe module, start of ambitious two-year station construction effort |first1=William |last1=Graham |first2=Chris |last2=Gebhardt |date=April 28, 2021 |website=NASASpaceflight.com}}</ref>
[[File:Rotation Arm on Wentian.jpg|thumb|Indexing Robot Arm on Wentian]]
''Wentian'' was successfully relocated to the starboard port on 30 September 2022 at 04:44 UTC<ref>{{cite web|title=我国成功实施问天实验舱转位|url=https://news.sciencenet.cn/htmlnews/2022/9/487156.shtm#:~:text=%E5%8C%97%E4%BA%AC%E6%97%B6%E9%97%B42022%E5%B9%B49,%E8%88%B1%E6%AE%B5%E8%BD%AC%E4%BD%8D%E6%93%8D%E4%BD%9C%E3%80%82|publisher=科学新闻网|access-date=30 September 2022}}</ref> using the indexing robot arm.
In addition to this, ''Wentian'' houses a small {{cvt|5|m}} 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 adaptorsadapters (silver squares) on the modules to host the payloads.<ref>{{Cite tweet |title=Wentian is 17.7m long and its dry mass is ~21500kg. With additional 1550kg propellant, the launch mass will be more than 23 tonnes.|url=https://twitter.com/cnspaceflight/status/1550846854123778049 |number=1550846854123778049|user=CNSpaceflight|access-date=2022-07-23 |website=Twitter |language=en}}</ref> 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 [[Canadarm]]s.<ref>{{Cite tweet |title=An illustration of the China Space Station core module robotic arm with the laboratory module arm connected at the end.|url=https://twitter.com/cnspaceflight/status/1543492387950931969 |number=1543492387950931969|user=CNSpaceflight|access-date=2022-07-23 |website=Twitter |language=en}}</ref>
''Mengtian'' also carries a toolbox equipped with a dexterous robotic arm (Similarsimilar to the [[Lyappa arm]] used on the ''[[Mir|Mir]]'' Spacespace Station]]station) installed to assist in cargo transfer and payload release, and can be used to deploy external payloads.<ref name="nsf_mengtian">{{cite web |last=Beil |first=Adrian |date=30 October 2022 |title=China launches Mengtian science module to Tiangong space station |url=https://www.nasaspaceflight.com/2022/10/china-launch-mengtian/ |access-date=31 October 2022 |work=[[NASASpaceFlight]]}}</ref><ref name="cbs_mengtian">{{cite web|url=http://www.china.org.cn/china/2022-10/31/content_78494902.htm |title=China launches lab module Mengtian as space station approaches completion |website=China News Service |author=Xinhua |date=31 October 2022 }}</ref>
[[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.
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