Editing International Space Station (section)

===Power and thermal control===
{{Main|Electrical system of the International Space Station|External Active Thermal Control System}}
{{multiple image
| align             = right
| total_width       = 400
| image1            = ROSSA.jpg
| caption1          = Russian solar arrays, backlit by sunset
| image2            = P4 deployed.jpg
| caption2          = One of the eight truss mounted pairs of USOS solar arrays
| image3            = ISS new iROSA deployed.jpg
| caption3          = ISS new roll out solar array as seen from a zoom camera on the P6 Truss
}}

Double-sided [[solar panel|solar arrays]] provide [[Electric power|electrical power]] to the ISS. These bifacial cells collect direct sunlight on one side and light [[Albedo|reflected off]] from the Earth on the other, and are more efficient and operate at a lower temperature than single-sided cells commonly used on Earth.<ref name="andreas-2005">{{Cite conference|url=http://wenku.baidu.com/view/a815121ffc4ffe473368ab7a.html|title=The early history of bifacial solar cell|last=Cuevas|first=Andrés|date=January 2005|publisher=WIP Renewable Energies|access-date=14 August 2012|url-status=live|archive-url=https://web.archive.org/web/20230405131511/https://wenku.baidu.com/view/a815121ffc4ffe473368ab7a.html|archive-date=5 April 2023|conference=European Photovoltaic Solar Energy Conference|hdl=1885/84487|volume=20}}</ref> <!-- don't worry about the 'lower absobance' thingy, that's about heat not electricity--><!--http://spaceflight.nasa.gov/gallery/search.cgi?startrow=1391&maxrows=10&page=1&pages=1878&count=18775&navpage=139&images=images&searchwhat=all shows a sequence of photographs taken on 11 September 2000, from the sequence and orientation of the station, it's a sunset in the background of ROSSA.jpg-->

The Russian segment of the station, like most spacecraft, uses 28&nbsp;[[volt|V]]&nbsp;[[Extra-low voltage|low voltage]] [[direct current|DC]] from two rotating solar arrays mounted on ''Zvezda''. The USOS uses 130–180&nbsp;V&nbsp;DC from the USOS&nbsp;PV array. Power is stabilised and distributed at 160&nbsp;V&nbsp;DC and converted to the user-required 124&nbsp;V&nbsp;DC. The [[High voltage|higher distribution voltage]] allows smaller, lighter conductors, at the expense of crew safety. The two station segments share power with converters.

The USOS solar arrays are arranged as four wing pairs, for a total production of 75 to 90 kilowatts.<ref name="ISS_stats" /> These arrays normally track the Sun to maximise power generation. Each array is about {{convert|375|m2|sqft|0|abbr=on}} in area and {{convert|58|m|ft|0|abbr=on}} long. In the complete configuration, the solar arrays track the Sun by rotating the ''alpha [[gimbal]]'' once per orbit; the ''beta gimbal'' follows slower changes in the angle of the Sun to the orbital plane. The [[Night Glider mode]] aligns the solar arrays parallel to the ground at night to reduce the significant aerodynamic drag at the station's relatively low orbital altitude.<ref>{{Cite journal|author1=G. Landis|author2=C-Y. Lu|year=1991|title=Solar Array Orientation Options for a Space Station in Low Earth Orbit|journal=Journal of Propulsion and Power|volume=7|issue=1|pages=123–125|doi=10.2514/3.23302}}</ref>

The station originally used rechargeable [[nickel–hydrogen battery|nickel–hydrogen batteries]] ({{chem2|NiH2}}) for continuous power during the 45 minutes of every 90-minute orbit that it is eclipsed by the Earth. The batteries are recharged on the day side of the orbit. They had a 6.5-year lifetime (over 37,000 charge/discharge cycles) and were regularly replaced over the anticipated 20-year life of the station.<ref>{{cite web|first=Thomas B.|last=Miller|date=24 April 2000|title=Nickel-Hydrogen Battery Cell Life Test Program Update for the International Space Station|url=https://www.grc.nasa.gov/WWW/RT/RT1999/5000/5420miller.html|url-status=dead|archive-url=https://web.archive.org/web/20090825125740/https://www.grc.nasa.gov/WWW/RT/RT1999/5000/5420miller.html|archive-date=25 August 2009|access-date=27 November 2009|series=Research & Technology|publisher=NASA{{\}}Glenn Research Center|website=grc.nasa.gov}}</ref> Starting in 2016, the nickel–hydrogen batteries were replaced by [[lithium-ion battery|lithium-ion batteries]], which are expected to last until the end of the ISS program.<ref name="sfn-20161213">{{Cite news|url=https://spaceflightnow.com/2016/12/13/japanese-htv-makes-battery-delivery-to-international-space-station/|title=Japanese HTV makes battery delivery to International Space Station|last=Clark|first=Stephen|date=13 December 2016|access-date=29 January 2017|url-status=live|archive-url=https://web.archive.org/web/20230810132031/https://spaceflightnow.com/2016/12/13/japanese-htv-makes-battery-delivery-to-international-space-station/|archive-date=10 August 2023|work=Spaceflight Now}}</ref>

The station's large solar panels generate a high potential voltage difference between the station and the ionosphere. This could cause arcing through insulating surfaces and sputtering of conductive surfaces as ions are accelerated by the spacecraft plasma sheath. To mitigate this, [[plasma contactor]] units create current paths between the station and the ambient space plasma.<ref>{{cite web|last=Patterson|first=Michael J.|date=18 June 1999|title=Cathodes Delivered for Space Station Plasma Contactor System|url=https://www.grc.nasa.gov/WWW/RT/RT1998/5000/5430patterson.html|url-status=dead|archive-url=https://web.archive.org/web/20110705135954/https://www.grc.nasa.gov/WWW/RT/RT1998/5000/5430patterson.html|archive-date=5 July 2011|series=Research & Technology|publisher=NASA{{\}}Lewis Research Center|website=grc.nasa.gov}}</ref>

[[File:EATCS.png|thumb|upright=2.2|ISS External Active Thermal Control System (EATCS) diagram]]
The station's systems and experiments consume a large amount of electrical power, almost all of which is converted to heat. To keep the internal temperature within workable limits, a passive thermal control system (PTCS) is made of external surface materials, insulation such as MLI, and heat pipes. If the PTCS cannot keep up with the heat load, an External Active Thermal Control System (EATCS) maintains the temperature. The EATCS consists of an internal, non-toxic, water coolant loop used to cool and dehumidify the atmosphere, which transfers collected heat into an external liquid [[ammonia]] loop. From the heat exchangers, ammonia is pumped into external radiators that emit heat as infrared radiation, then the ammonia is cycled back to the station.<ref name="nasa-stayingcool">{{Cite web|url=https://science.nasa.gov/science-news/science-at-nasa/2001/ast21mar_1/|title=Staying Cool on the ISS|last1=Price|first1=Steve|last2=Phillips|first2=Tony|last3=Knier|first3=Gil|date=21 March 2001|publisher=[[NASA]]|access-date=22 July 2016|url-status=dead|archive-url=https://web.archive.org/web/20230203012526/https://science.nasa.gov/science-news/science-at-nasa/2001/ast21mar_1/|archive-date=3 February 2023}}</ref> The EATCS provides cooling for all the US pressurised modules, including ''Kibō'' and ''Columbus'', as well as the main power distribution electronics of the S0, S1 and P1 trusses. It can reject up to 70&nbsp;kW. This is much more than the 14&nbsp;kW of the Early External Active Thermal Control System (EEATCS) via the Early Ammonia Servicer (EAS), which was launched on [[STS-105]] and installed onto the P6 Truss.<ref name="acts-overview">{{Cite tech report|url=https://www.nasa.gov/wp-content/uploads/2021/02/473486main_iss_atcs_overview.pdf|title=Active Thermal Control System (ATCS) Overview|publisher=[[Boeing]]|access-date=8 October 2011|url-status=live|archive-url=https://web.archive.org/web/20231016111319/https://www.nasa.gov/wp-content/uploads/2021/02/473486main_iss_atcs_overview.pdf|archive-date=16 October 2023}}</ref>