View source for H-II Transfer Vehicle

{{short description|Uncrewed cargo spacecraft developed by JAXA}}
{{Use British English|date=August 2020}}
{{Use dmy dates|date=August 2020}}
{{Infobox spacecraft class
| name = H-II Transfer Vehicle<br>Kounotori
| image = Iss020e0413802 - cropped.jpg
| image_caption = H-II Transfer Vehicle (HTV-1) approaching the ISS
| country = Japan
| operator = [[JAXA]]
| applications = [[Uncrewed spaceflights to the International Space Station|ISS resupply]]
| spacecraft_type = [[Uncrewed spacecraft|Uncrewed cargo vehicle]]
| launch_mass = {{cvt|16500|kg}}<ref name="KOUNOTORI2"/>
| dry_mass = {{cvt|10500|kg}}<ref name="jaxa2007"/>
| payload_capacity = {{cvt|6000|-|6200|kg}}<ref name="KOUNOTORI2">{{cite web|url=http://www.jaxa.jp/countdown/h2bf2/overview/htv_e.html|title=Overview of the "KOUNOTORI" |archive-url=https://web.archive.org/web/20101115022444/http://www.jaxa.jp/countdown/h2bf2/overview/htv_e.html|archive-date=15 November 2010|work=[[JAXA]]|access-date=18 January 2011}}</ref><ref name="jaxa20150731">{{cite web|url=http://www.mext.go.jp/b_menu/shingi/gijyutu/gijyutu2/060/shiryo/__icsFiles/afieldfile/2015/11/02/1359727_6.pdf|script-title=ja:「こうのとり」（HTV）5号機の搭載物変更について |date=31 July 2015|access-date=17 December 2015|url-status=live |archive-url=https://web.archive.org/web/20151222104032/http://www.mext.go.jp/b_menu/shingi/gijyutu/gijyutu2/060/shiryo/__icsFiles/afieldfile/2015/11/02/1359727_6.pdf|archive-date=22 December 2015}}</ref>
| volume = {{Unbulleted indent list
  | Pressurised: {{cvt|14|m3}}
  | Unpressurised: {{cvt|35|m3}}
  }}
| length = ~{{cvt|9.8|m}} (including thrusters)
| diameter = {{cvt|4.4|m}}<ref name="jaxa2007"/>
| status = Retired
| built = 9
| launched = 9
| first = 10 September 2009 ([[HTV-1]])
| last = 20 May 2020 ([[Kounotori 9]])
| derivatives = [[HTV-X]]
| launch_vehicle = [[H-IIB]]
}}

The '''H-II Transfer Vehicle''' ('''HTV'''), also called {{nihongo|'''Kounotori'''|こうのとり||{{lit| [[oriental stork|white stork]]}}|lead=yes}}, was an [[Expendable launch system|expendable]] Japanese [[Cargo spacecraft|automated cargo spacecraft]] designed for [[International Space Station]] (ISS) resupply missions, particularly [[Kibo (ISS module)|''Kibō'']], the Japanese laboratory module. 

Development of the spacecraft began in the early 1990s and the HTV's first mission, [[HTV-1]], was launched on 10{{Nbsp}}September 2009 on an [[H-IIB]] launch vehicle.<ref>{{cite web |title=NASA Sets Briefing, TV Coverage of Japan's First Cargo Spacecraft |url=http://www.nasa.gov/home/hqnews/2009/aug/HQ_M09-164_HTV_Briefing.html |url-status=live |archive-url=https://web.archive.org/web/20110417014822/http://www.nasa.gov/home/hqnews/2009/aug/HQ_M09-164_HTV_Briefing.html |archive-date=2011-04-17 |access-date=2009-09-03 |publisher=NASA}} {{PD-notice}}</ref> The HTV was crucial for ISS resupply, especially after the [[retirement of the Space Shuttle]], as it was the only vehicle capable of transporting large [[International Standard Payload Rack]]s (ISPR) and disposing of old ones within the ISS's [[US Orbital Segment]]. The final HTV mission, [[Kounotori 9]], was launched on 20 May 2020. HTV's successor, the [[HTV-X]], made [[HTV-X1|its maiden flight]] in October 2025.<ref name=":0">{{Cite news |date=2025-08-22 |title=Japan to launch new spacecraft to resupply International Space Station in October |url=https://www.reuters.com/science/japan-launch-new-spacecraft-resupply-international-space-station-october-2025-08-22/ |access-date=2025-08-22 |work=Reuters |language=en}}</ref>

== Name ==
The name ''Kounotori'' was chosen because: <blockquote>"a white stork carries an image of conveying an important thing (a baby, happiness, and other joyful things), therefore, it precisely expresses the HTV's mission to transport essential materials to the ISS".<ref>{{cite web |date=11 November 2010 |title="KOUNOTORI" Chosen as Nickname of the H-II Transfer Vehicle (HTV) |url=http://www.jaxa.jp/press/2010/11/20101111_kounotori_e.html |url-status=dead |archive-url=https://web.archive.org/web/20101222201702/http://www.jaxa.jp/press/2010/11/20101111_kounotori_e.html |archive-date=22 December 2010 |access-date=11 November 2010 |publisher=JAXA}}</ref></blockquote>

== Design ==
[[File:H-II Transfer Vehicle diagram.jpg|thumb|Structure of HTV]]
[[File:HTV from inside 02 - cropped and rotated.jpg|thumb|Inside view of the Pressurised Logistics Carrier section of HTV-1]]
[[File:ISS-26 HTV-2 Exposed Pallet grappled by Canadarm2.jpg|thumb|[[Canadarm2]] removing unpressurised payload from HTV-2]]
[[File:HTV-1 close-up view.jpg|thumb|The four main thrusters. Smaller attitude control thrusters can be seen at the right side of this view of HTV-1.]][[File:H-IIB F2 launching HTV2.jpg|thumb|right|HTV-2 departing [[Tanegashima Space Center|Tanegashima spaceport]] bound for the [[International Space Station]]]]

The HTV was about {{convert|9.8|m}} long (including maneuvering thrusters at one end) and {{convert|4.4|m}} in diameter. Total mass when empty was {{convert|10500|kg}}, with a maximum total payload of {{convert|6000|kg}}, for a maximum launch weight of {{convert|16500|kg}}.<ref name=jaxa2007>{{cite web|title=H-II Transfer Vehicle "KOUNOTORI" (HTV)|url=http://www.jaxa.jp/projects/rockets/htv/design_e.html |publisher=Japan Aerospace Exploration Agency|year=2007|access-date=2010-11-11|url-status=dead|archive-url=https://web.archive.org/web/20101116044853/http://www.jaxa.jp/projects/rockets/htv/design_e.html
|archive-date=2010-11-16}}</ref>  It consists of Pressurised Logistics Carrier (PLC), Unpressurised Logistics Carrier (ULC), and Main Body which contains [[avionics]] and propulsion system. The intent behind the HTV's modularized design was to use different module configurations to match different mission requirements.<ref name="miki2010">{{cite journal
|url=https://www.mhi.co.jp/technology/review/pdf/e471/e471058.pdf|title=Development of the H-II Transfer Vehicle (HTV)|journal=Mitsubishi Heavy Industries Technical Review|volume=47|issue=1|first1=Yoichiro |last1=Miki|first2=Naohiko|last2=Abe|first3=Koichi|last3=Matsuyama|first4=Kazumi|last4=Masuda|first5=Nobuhiko|last5=Fukuda|first6=Hiroshi|last6=Sasaki|date=March 2010|publisher=Mitsubishi Heavy Industries |url-status=live|archive-url=https://web.archive.org/web/20150720201230/https://www.mhi.co.jp/technology/review/pdf/e471/e471058.pdf|archive-date=2015-07-20}}</ref> However, to reduce the development cost it was decided to fly the mixed PLC/ULC configuration only.<ref name="miki2010" />

To control the HTV's attitude and perform the orbital maneuvers such as rendezvous and reentry, the craft had four 500-N-class main thrusters and twenty-eight 110-N-class attitude control thrusters. Both used bipropellant, namely [[monomethylhydrazine]] (MMH) as fuel and [[mixed oxides of nitrogen]] (MON3) as oxidizer.<ref name="IAC">{{cite conference|last1=Matsuo|first1=Shinobu|last2=Miki|first2=Yoichiro |last3=Imada|first3=Takane|last4=Nakai|first4=Shunichiro|url=https://arc.aiaa.org/doi/10.2514/6.IAC-05-C4.1.03|title=The Design Characteristics of the HTV Propulsion Module|location=[[Fukuoka]], Japan |conference=56th [[International Astronautical Congress]]|date=17–21 October 2005|access-date=20 June 2019|doi=10.2514/6.IAC-05-C4.1.03|url-access=subscription}}</ref> HTV-1, HTV-2, and HTV-4 used [[Aerojet]]'s 110 N R-1E, [[Space Shuttle]]'s [[vernier engine]], and the 500 N based on the [[Apollo spacecraft]]'s [[R-4D]].<ref name="IAC"/> Later HTVs used 500 N class [[BT-4 (rocket engine)|HBT-5]] thrusters and 120 N class HBT-1 thrusters made by Japanese manufacturer [[IHI Corporation|IHI Aerospace Co., Ltd]].<ref>{{cite web|url=http://iss.jaxa.jp/htv/mission/htv-3/library/presskit/htv3_presskit.pdf|title=宇宙ステーション補給機「こうのとり」3号機（HTV3）ミッションプレスキット|language=ja|date=June 20, 2012|access-date=2012-06-24|url-status=live|archive-url=https://web.archive.org/web/20121031141116/http://iss.jaxa.jp/htv/mission/htv-3/library/presskit/htv3_presskit.pdf|archive-date=October 31, 2012}}</ref> The HTV's four spherical propellant tanks usually carried about 2 tonnes of propellant (the maximum capacity was 2432&nbsp;kg<ref name="IAC"/>).

== Mission profile ==
The HTV was comparable in function to the [[Roscosmos|Russian]] [[Progress (spacecraft)|Progress]], the [[European Space Agency|ESA]] [[Automated Transfer Vehicle|ATV]], the [[SpaceX]] [[SpaceX Dragon 2|Cargo Dragons]], and the [[Cygnus (spacecraft)|Cygnus spacecraft]], all of which brought supplies to the ISS. Like the ATV, the HTV carried more than twice the payload of the Progress, but was launched less than half as often. Unlike Progress spacecraft, Cargo Dragon 2's and ATV's which used the [[Androgynous Peripheral Attach System|docking ports]] automatically, HTVs and American [[SpaceX Dragon 1|Dragon 1]] approached the [[International Space Station|ISS]] in stages, and once they reached their closest parking orbit to the ISS, crew [[Grapple fixture|grappled]] them using the robotic arm [[Mobile Servicing System|Canadarm2]] and berthed them to an open [[Common Berthing Mechanism|berthing port]] on the [[Harmony (ISS module)|''Harmony'']] module.<ref>{{cite conference |last=Fujimoto |first=Nobuyoshi |date=23–26 November 2010 |title=Kibo Utilization Status Update |url=http://www.aprsaf.org/data/aprsaf17_data/DAY1-seu_0950-Kibo_Utilization_Status.pdf |conference=17th Session of the Asia Pacific Regional Space Agency Forum |archive-url=https://web.archive.org/web/20120317080738/http://www.aprsaf.org/data/aprsaf17_data/DAY1-seu_0950-Kibo_Utilization_Status.pdf |archive-date=17 March 2012 |access-date=20 June 2019}}</ref>

The HTV had an external payload bay which was accessed by the robotic arm after it had been berthed to the ISS. New payloads could be moved directly from the HTV to ''[[Kibō (ISS module)|Kibō]]'''s exposed facility. Internally, it had eight [[International Standard Payload Rack]]s (ISPRs) in total which could be unloaded by the crew in a [[shirt-sleeve environment]]. After the retirement of [[NASA]]'s [[Space Shuttle]] in 2011, HTVs became the only spacecraft capable of transporting ISPRs to the ISS. The [[SpaceX Dragon]] and [[Northrop Grumman Innovation Systems|Northrop Grumman]] [[Cygnus (spacecraft)|Cygnus]] could carry resupply cargo bags but not ISPRs.{{citation needed|date=December 2016}}

After the unloading process was completed, the HTV was loaded with waste and unberthed. The vehicle then deorbited and was destroyed during reentry, the debris felling into the [[Pacific Ocean]].<ref name="jaxa2007op">{{cite web |author=JAXA |year=2007 |title=HTV Operations |url=http://iss.jaxa.jp/en/htv/operation/ |url-status=live |archive-url=https://web.archive.org/web/20110126091208/http://iss.jaxa.jp/en/htv/operation/ |archive-date=2011-01-26 |access-date=2011-01-02}}</ref>

== Flights ==
Initially seven missions were planned between 2008–2015. With the extension of the ISS project through 2028, three more missions were added, with the tenth flight planned to debut an improved, cost-reduced version called the [[HTV-X]].<ref name="mext20150520">{{cite web|url=http://www.mext.go.jp/b_menu/shingi/gijyutu/gijyutu2/071/shiryo/__icsFiles/afieldfile/2015/05/28/1358152_1.pdf|script-title=ja:2016年～2020年のISS共通システム運用経費（次期CSOC）の我が国の負担方法の在り方について|publisher=Research and Development Division, Ministry of Education, Culture, Sports, Science and Technology|date=May 20, 2015|access-date=June 4, 2015|url-status=live|archive-url=https://web.archive.org/web/20150605155155/http://www.mext.go.jp/b_menu/shingi/gijyutu/gijyutu2/071/shiryo/__icsFiles/afieldfile/2015/05/28/1358152_1.pdf|archive-date=June 5, 2015}}</ref>

The first vehicle was launched on an [[H-IIB]] rocket, a more powerful version of the earlier [[H-IIA]], at 17:01 UTC on 10 September 2009, from Launch Pad 2 of the [[Yoshinobu Launch Complex]] at the [[Tanegashima Space Center]].<ref>{{cite press release|url=http://www.jaxa.jp/press/2009/07/20090708_h2b_e.html|title=Launch of the H-IIB Launch Vehicle Test Flight |archive-url=https://web.archive.org/web/20090711101704/http://www.jaxa.jp/press/2009/07/20090708_h2b_e.html|archive-date=11 July 2009|work=[[JAXA]]|date=8 July 2009|access-date=20 June 2019}}</ref>

By May 2020, all nine missions planned for HTV had been successfully launched, and the spacecraft was retired. The improved HTV-X is planned to be first used for the tenth flight and will perform scheduled ISS resupply duties starting in 2025.<ref>{{Cite web|url=https://spacenews.com/jaxa-astronaut-charts-future/|title=Koichi Wakata, JAXA vice president and astronaut, helps chart future of ISS and human space exploration|date=27 July 2018|website=SpaceNews}}</ref>{{sticky header}}
{| class="wikitable sticky-header"
|-
! HTV
! Launch date/time ([[UTC]])
! Berth date/time (UTC)<ref>{{cite web|title=H-II Transfer Vehicle "KOUNOTORI" (HTV) Topics|publisher=Japan Aerospace Exploration Agency|url=http://www.jaxa.jp/projects/rockets/htv/topics_e.html|url-status=live |archive-url=https://web.archive.org/web/20130822155343/http://www.jaxa.jp/projects/rockets/htv/topics_e.html|archive-date=2013-08-22}}</ref>
! Rocket, flight
! Reentry date/time (UTC)
! Outcome
|- 
| {{nowrap|[[HTV-1]]}}
| 10 September 2009, 17:01:56
| 17 September 2009, 22:12
| [[H-IIB]], {{Abbr|TF1|Test Flight 1}}
| 1 November 2009, 21:26<ref>{{cite web|url=http://spaceflightnow.com/h2b/htv1/091101reentry|title=History-making Japanese space mission ends in flames|author=Stephen Clark|date=1 November 2009|access-date=13 November 2010|publisher=Spaceflight Now|url-status=live|archive-url=https://web.archive.org/web/20110607103049/http://spaceflightnow.com/h2b/htv1/091101reentry/|archive-date=7 June 2011}}</ref>
| {{Success}}
|- 
| {{nowrap|[[Kounotori 2|HTV-2]]}}
| 22 January 2011, 05:37:57
| 27 January 2011, 14:51
| [[H-IIB]], {{Abbr|F2|Flight 2}}
| 30 March 2011, 03:09<ref>{{cite web|url=http://spaceflightnow.com/h2b/htv2/110329entry/|title=Japan's HTV cargo freighter proves useful to the end|author=Stephen Clark|date=29 March 2011|access-date=21 April 2011|publisher=Spaceflight Now|url-status=live|archive-url=https://web.archive.org/web/20110419195421/http://spaceflightnow.com/h2b/htv2/110329entry/|archive-date=19 April 2011}}</ref>
| {{Success}}
|- 
| {{nowrap|[[HTV-3]]}}
| 21 July 2012, 02:06:18
| 27 July 2012, 14:34
| [[H-IIB]], F3
| 14 September 2012, 05:27
| {{Success}}
|- 
| {{nowrap|[[HTV-4]]}}
| 3 August 2013, 19:48:46
| 9 August 2013, 15:38<ref>{{cite web|url=http://spaceflightnow.com/h2b/htv2/110329entry/|title=Japan launches resupply mission to space station|author=Stephen Clark|date=3 August 2013|access-date=3 August 2013 |publisher=Spaceflight Now|url-status=live|archive-url=https://web.archive.org/web/20130925172736/http://spaceflightnow.com/h2b/htv2/110329entry/|archive-date=25 September 2013}}</ref>
| [[H-IIB]], F4
| 7 September 2013, 06:37<ref>{{cite web|url=http://spaceflightnow.com/h2b/htv4/130809arrival/#.UgVTo8u9KK0|title=Japan's cargo craft makes in-orbit delivery to space station|author=Stephen Clark|date=9 August 2013|access-date=9 August 2013|publisher=Spaceflight Now|url-status=live|archive-url=https://web.archive.org/web/20130814111151/http://www.spaceflightnow.com/h2b/htv4/130809arrival/#.UgVTo8u9KK0|archive-date=14 August 2013}}</ref>
| {{Success}}
|- 
| {{nowrap|[[HTV-5]]}}
| 19 August 2015, 11:50:49
| 24 August 2015, 17:28<ref name="global.jaxa.jp">{{cite web|url=http://global.jaxa.jp/press/2015/08/20150825_kounotori5.html|title=Successful berthing of the H-II Transfer Vehicle KOUNOTORI5 (HTV5) to the International Space Station (ISS)|url-status=live|archive-url=https://web.archive.org/web/20161104014317/http://global.jaxa.jp/press/2015/08/20150825_kounotori5.html|archive-date=2016-11-04}}</ref>
| [[H-IIB]], F5
| 29 September 2015, 20:33<ref>{{cite web|url=http://global.jaxa.jp/press/2015/09/20150930_kounotori5.html|title=Successful re-entry of H-II Transfer Vehicle "KOUNOTORI5" (HTV5)|publisher=JAXA|date=September 30, 2015|access-date=September 30, 2015|url-status=live|archive-url=https://web.archive.org/web/20151001175036/http://global.jaxa.jp/press/2015/09/20150930_kounotori5.html|archive-date=October 1, 2015}}</ref>
| {{Success}}
|- 
| {{nowrap|[[HTV-6]]}}
| 9 December 2016, 13:26:47
| 13 December 2016, 18:24
| [[H-IIB]], F6
| 5 February 2017, 15:06<ref>{{cite web|url=http://iss.jaxa.jp/en/htv/mission/htv-6/|title=HTV6:H-II Transfer Vehicle KOUNOTORI (HTV) - International Space Station - JAXA|last=JAXA|website=iss.jaxa.jp|access-date=2018-11-26}}</ref>
| {{Success}}
|- 
| {{nowrap|[[HTV-7]]}}
| 22 September 2018, 17:52:27
| 27 September 2018, 18:08
| [[H-IIB]], F7
| 10 November 2018, 21:38<ref>{{cite web|url=http://iss.jaxa.jp/en/htv/mission/htv-7/|title=HTV7:H-II Transfer Vehicle KOUNOTORI (HTV) - International Space Station - JAXA|last=JAXA|website=iss.jaxa.jp|access-date=2018-11-26}}</ref>
| {{Success}}
|-
| {{nowrap|[[HTV-8]]}}
| 24 September 2019, 16:05:05
| 28 September 2019, 14:09
| [[H-IIB]], F8
| 3 November 2019, 02:09
| {{Success}}
|-
| {{nowrap|[[HTV-9]]}}
| 20 May 2020, 17:31:00
| 25 May 2020, 12:13
| [[H-IIB]], F9 (last)
| 20 August 2020, 07:07
| {{Success}}
|}

== Successor: HTV-X ==
{{Main|HTV-X}}
In May 2015, Japan's [[Ministry of Education, Culture, Sports, Science and Technology]] announced a proposal to replace the HTV with an improved, cost-reduced version preliminary called [[HTV-X]].<ref name="mext20150520"/><ref>{{cite web|url=http://www8.cao.go.jp/space/comittee/27-kiban/kiban-dai5/siryou2.pdf|title=国際宇宙ステーション計画を含む有人計画について|language=ja|date=June 3, 2015|access-date=July 13, 2015|url-status=live|archive-url=https://web.archive.org/web/20150713084731/http://www8.cao.go.jp/space/comittee/27-kiban/kiban-dai5/siryou2.pdf|archive-date=July 13, 2015}}</ref> The HTV-X has a length of 6.2 m, or 10 m with the unpressurised cargo module fitted. The payload fairing adaptor and payload dispenser have been widened from 1.7 m to 4.4 m.<ref name="jaxa20160714">{{cite web |author=JAXA |date=14 July 2016 |script-title=ja:ＨＴＶ‐Ｘの開発状況について |url=http://www.jaxa.jp/press/2016/07/files/20160714_htv-x_01_j.pdf |url-status=live |archive-url=https://web.archive.org/web/20160715121556/http://www.jaxa.jp/press/2016/07/files/20160714_htv-x_01_j.pdf |archive-date=15 July 2016 |access-date=18 July 2016 |language=ja}}</ref> An evolved version of HTV-X called HTV-XG is being considered for transferring cargo to the [[Lunar Gateway]] as part of the [[Artemis program]].<ref>{{cite web |url=https://www.mext.go.jp/kaigisiryo/content/0210630-mxt_uchukai01-000016486_5.pdf |language=Japanese |script-title=ja:アルテミス計画に関する各国の開発状況について |author=JAXA |publisher=Ministry of Education, Cultura, Sports and Technology |date=30 June 2021 |access-date=9 July 2021}}</ref> The first flight of HTV-X took place on 26 October 2025.<ref name=":0" />

== Former evolutionary proposals ==
=== HTV-R ===
{{As of|2010}}, JAXA was planning to add a return capsule option. In this concept, HTV's pressurized cargo would be replaced by a reentry module capable of returning {{convert|1600|kg}} [[downmass|cargo]] from ISS to Earth.<ref>{{cite web|url=http://www.jaxa.jp/press/2010/08/20100811_sac_htv-r_j.html|title=回収機能付加型宇宙ステーション補給機（HTV-R）検討状況|publisher=JAXA|language=ja|date=August 11, 2010 |access-date=September 7, 2011|url-status=live|archive-url=https://web.archive.org/web/20100914081746/http://www.jaxa.jp/press/2010/08/20100811_sac_htv-r_j.html|archive-date=September 14, 2010}}</ref><ref>{{cite web |url=http://iss.jaxa.jp/htv-r/|title=回収機能付加型HTV(HTV-R)|language=ja|publisher=JAXA|access-date=September 7, 2011|url-status=dead |archive-url=https://web.archive.org/web/20110826205442/http://iss.jaxa.jp/htv-r/|archive-date=August 26, 2011 }}</ref> Further, conceptual plans in 2012 included a follow-on spacecraft design by 2022 which would accommodate a crew of three and carry up to {{convert|400|kg}} of cargo.<ref>{{cite web |url=http://www.space.com/18198-japan-plans-manned-capsule-space-plane.html|title=Japan Wants Space Plane or Capsule by 2022|author=Rob Coppinger|publisher=Space.com|access-date=October 25, 2012|url-status=live |archive-url=https://web.archive.org/web/20151224020505/http://www.space.com/18198-japan-plans-manned-capsule-space-plane.html|archive-date=December 24, 2015}}</ref>

=== Lagrange outpost resupply ===
{{As of|2014}}, both JAXA and [[Mitsubishi Heavy Industries|Mitsubishi]] conducted studies of a next generation HTV as a possible Japanese contribution to the proposed [[Exploration Gateway Platform|international crewed outpost]] at [[Lagrangian point|Earth-Moon L2]].<ref name=jaxalunaraccess>{{cite web|url=http://www.nasa.gov/sites/default/files/files/04-Ueno_Lunar_Access_Architecture.pdf |title=International Human Lunar Mission Architecture / System and its Technologies|format=PDF|publisher=JAXA|date=2014-04-10|access-date=22 January 2015|url-status=live |archive-url=https://web.archive.org/web/20150415015209/http://www.nasa.gov/sites/default/files/files/04-Ueno_Lunar_Access_Architecture.pdf|archive-date=15 April 2015}} {{PD-notice}}</ref><ref>{{cite web |url=http://www.nasa.gov/sites/default/files/files/02-Hopkins-Intl-Industry-Perspective.pdf#page=13 |title=An International Industry Perspective on Extended Duration Missions Near the Moon |format=PDF |publisher=Lockheed Martin Corporation|date=2014-04-10|access-date=22 January 2015|url-status=live|archive-url=https://web.archive.org/web/20150415020947/http://www.nasa.gov/sites/default/files/files/02-Hopkins-Intl-Industry-Perspective.pdf#page=13|archive-date=15 April 2015}}</ref> This variant of HTV was to be launched by [[H3 (rocket)|H-X]] Heavy and can carry 1800&nbsp;kg of supplies to EML2.<ref name=jaxalunaraccess /> Modifications from the current HTV included the addition of solar electric paddles and extension of the propellant tank.<ref name=jaxalunaraccess/>

=== Human-rated variant ===
A proposal announced in June 2008, "Preliminary Study for Manned Spacecraft with Escape System and H-IIB Rocket" suggested combining HTV's propulsion module with a [[Human-rating certification|human-rated]] capsule for four people.<ref name="ISTS_2008-g-14">{{cite web|author1=Takane Imada|author2=Michio Ito|author3=Shinichi Takata|date=June 2008|url=https://archive.ists.ne.jp/upload_pdf/2008-g-14.pdf |title=Preliminary Study for Manned Spacecraft with Escape System and H-IIB Rocket|format=PDF|publisher=26th ISTS|access-date=2010-12-25}}</ref>

=== Japanese space station ===
A Japanese space station was proposed to be built up from HTV modules.<ref>{{cite web|url=https://archive.ists.or.jp/upload_pdf/2008-k-64.pdf|title=Development Plan for Future Mission from HTV System |last1=Sasaki|first1=Hiroshi|last2=Imada|first2=Takane|last3=Takata|first3=Shinichi|publisher=JAXA|date=2008|access-date=2016-07-19}}</ref> This method was similar to how the modules in ''[[Mir]]'', as well as many modules of the [[Russian Orbital Segment]] of the [[International Space Station|ISS]] were based on the [[TKS (spacecraft)|TKS]] cargo vehicle design.{{citation needed|date=December 2016}}

== Gallery ==
<gallery>
File:ISS-32 HTV-3 berthing 1.jpg|HTV-3 near ISS
File:ISS-44 Purple Aurora australis.jpg|[[Kounotori 5]] (HTV-5) with Aurora australis
File:HTV-6 grappled by the International Space Station's robotic arm (2).jpg|HTV-6 grappled to a robotic arm of ISS
</gallery>

== See also ==
{{Portal|Spaceflight}}
* [[Cargo spacecraft]]
* [[Comparison of space station cargo vehicles]]
* [[Cygnus (spacecraft)|Cygnus]] – an American commercial cargo spacecraft that used the communication system developed for HTV
* [[Fuji (spacecraft)|Fuji]] – cancelled Japanese crewed spacecraft proposal
* [[HOPE-X]] – cancelled cargo spaceplane proposal

== References ==
{{reflist|colwidth=30em}}

== External links ==
{{Commons category|H-II Transfer Vehicle}}
* [http://www.jaxa.jp/projects/rockets/htv/index_e.html Project overview of H-II Transfer Vehicle.] {{Webarchive|url=https://web.archive.org/web/20131014013807/http://www.jaxa.jp/projects/rockets/htv/index_e.html |date=14 October 2013 }}, JAXA
* [http://www.jaxa.jp/countdown/h2bf1/index_e.html HTV/H-IIB launch Special site], JAXA
* {{youTube|ShGS4_UkdzY|For Future Space Transportation Mission -HTV/H-IIB Promotional Movie}}. JAXA
* [https://www.youtube.com/watch?v=H9fhz_HhZSc H-II Transfer Vehicle -Road to the HTV's launch-], JAXA
* {{youTube|Nj8jgKmTs8Y|HTV1/H-IIB TF Quick Review}}. JAXA
* [http://www.asahi.com/special/rocket/h2b-3d/ H-2B rocket and Kounotori 3D model], Asahi Shinbun
* [http://news.bbc.co.uk/2/hi/science/nature/8249357.stm Japan's space freighter in orbit], BBC News

{{H-II Transfer Vehicles}}
{{Cargo spacecraft}}
{{International Space Station}}
{{Japanese space program}}

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[[Category:H-II Transfer Vehicles| ]]
[[Category:Cargo spacecraft]]
[[Category:Supply vehicles for the International Space Station]]
[[Category:Vehicles introduced in 2009]]
[[Category:JAXA]]