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"/>
| volume = '''Pressurized''': {{cvt|14|m3}}
| length = ~{{cvt|9.8|m}} (including thrusters)
| diameter = {{cvt|4.4|m}}<ref name="jaxa2007"/>
| capacities = {{Infobox rocket/payload
  |location        = [[International Space Station|ISS]]
  |kilos           = {{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>
 }}
| status = Retired
| built = 9
| orders = 
| launched = 9
| operational = 
| retired = 
| first = 10 September 2009 ([[HTV-1]])
| last = 20 May 2020 ([[Kounotori 9]])
| lastretired = 
| derivatives = [[HTV-X]]
| previous = 
}}


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

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 name ''Kounotori'' was chosen because "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>

The HTV is crucial for ISS resupply, especially after the [[retirement of the Space Shuttle]], as it's 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. JAXA is currently developing its successor, the [[HTV-X]], which is expected to make [[HTV-X1|its maiden flight]] in early 2025.

== Design ==
[[File:H-II Transfer Vehicle diagram.jpg|left|thumb|Structure]]
[[File:HTV from inside 02 - cropped and rotated.jpg|thumb|left|The inside view of the Pressurised Logistics Carrier section of HTV-1.]]
[[File:ISS-26 HTV-2 Exposed Pallet grappled by Canadarm2.jpg|thumb|left|The Canadarm2 removing unpressurised payload from HTV-2.]]
[[File:HTV-1 close-up view.jpg|left|thumb|The four main thrusters. Smaller attitude control thrusters can be seen at the right side of this view of HTV-1.]]

The HTV is about {{convert|9.8|m}} long (including maneuvering thrusters at one end) and {{convert|4.4|m}} in diameter. Total mass when empty is {{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>

The HTV is 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 bring supplies to the ISS. Like the ATV, the HTV carries more than twice the payload of the Progress, but is launched less than half as often. Unlike Progress spacecraft, Cargo Dragon 2's and ATV's which use the [[Androgynous Peripheral Attach System|docking ports]] automatically, HTVs and American Dragon 1 approach the [[International Space Station|ISS]] in stages, and once they reach their closest parking orbit to the ISS, crew [[Grapple fixture|grapple]] them using the robotic arm [[Mobile Servicing System|Canadarm2]] and berth them to an open [[Common Berthing Mechanism|berthing port]] on the [[Harmony (ISS module)|''Harmony'']] module.<ref>{{cite conference|last=Fujimoto|first=Nobuyoshi |url=http://www.aprsaf.org/data/aprsaf17_data/DAY1-seu_0950-Kibo_Utilization_Status.pdf|title=Kibo Utilization Status Update|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|date=23–26 November 2010|access-date=20 June 2019}}</ref>

The HTV has an external payload bay which is accessed by the robotic arm after it has been berthed to the ISS. New payloads can be moved directly from the HTV to ''[[Kibō (ISS module)|Kibō]]'''s exposed facility. Internally, it has eight [[International Standard Payload Rack]]s (ISPRs) in total which can 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]] can carry resupply cargo bags but not ISPRs.{{citation needed|date=December 2016}}

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 has four 500-N-class main thrusters and twenty-eight 110-N-class attitude control thrusters. Both use 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 use [[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 use 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 carry about 2 tonnes of propellant (the maximum capacity is 2432&nbsp;kg<ref name="IAC"/>).

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

== Flights ==
[[File:H-IIB F2 launching HTV2.jpg|thumb|right|The HTV-2 departing [[Tanegashima Space Center|Tanegashima spaceport]] bound for the [[International Space Station]].]]

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>
! Carrier rocket
! Reentry date/time (UTC)
!Outcome
|- 
| [[HTV-1]]
| 10 September 2009, 17:01:56
| 17 September 2009, 22:12
| [[H-IIB]] F1
| 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}}
|- 
| [[Kounotori 2|HTV-2]]
| 22 January 2011, 05:37:57
| 27 January 2011, 14:51
| [[H-IIB]] F2
| 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}}
|- 
| [[HTV-3]]
| 21 July 2012, 02:06:18
| 27 July 2012, 14:34
| [[H-IIB]] F3
| 14 September 2012, 05:27
| {{Success}}
|- 
| [[HTV-4]]
| 3 August 2013, 19:48:46
| 9 August 2013, 15:38
| [[H-IIB]] F4<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>
| 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}}
|- 
| [[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}}
|- 
| [[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}}
|- 
| [[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}}
|-
| [[HTV-8]]
| 24 September 2019, 16:05:05
| 28 September 2019, 14:09
| [[H-IIB]] F8
| 3 November 2019, 02:09
| {{Success}}
|-
| [[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}}
{{Cleanup split|HTV-X|date=August 2022}}
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>

In December 2015, the plan to develop HTV-X was approved by the Strategic Headquarters for Space Policy of the [[Cabinet Office (Japan)|Cabinet Office]], targeting launch in fiscal year 2021 for the flight of HTV-X1 (Technical Demonstration Vehicle) by the [[H3 (rocket)|H3 rocket]].<ref>{{cite web|url=http://www8.cao.go.jp/space/plan/plan2/kaitei_fy27/kaitei_fy27.pdf|script-title=ja:宇宙基本計画工程表（平成27年度改訂） |language=ja|date=8 December 2015|publisher=Strategic Headquarters for Space Policy|access-date=18 July 2016|url-status=live |archive-url=https://web.archive.org/web/20161020172008/http://www8.cao.go.jp/space/plan/plan2/kaitei_fy27/kaitei_fy27.pdf|archive-date=20 October 2016}}</ref><ref name="jaxa20160714">{{cite web|url=http://www.jaxa.jp/press/2016/07/files/20160714_htv-x_01_j.pdf|script-title=ja:ＨＴＶ‐Ｘの開発状況について|language=ja|date=14 July 2016|author=JAXA|access-date=18 July 2016|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}}</ref> {{asof|2019|06}}, new ISS plans from NASA's Flight Planning Integration Panel have set the launch of HTV-X1 for February 2022, which is on schedule.<ref>{{cite web|last=Gebhardt|first=Chris |url=https://www.nasaspaceflight.com/2019/06/station-planning-new-crew-launch-dates/|title=Station mission planning reveals new target Commercial Crew launch dates|website=[[NASASpaceFlight.com]]|date=20 June 2019|access-date=20 June 2019|quote=The new HTV is known as HTV-X and is now planned to make its inaugural trip to the Station in February 2022.}}</ref> In 2022 the debut of the HTV-X spacecraft has been furtherly delayed to January 2024.<ref name="berger-20221026">{{cite tweet|number=1585365132116635648|user=SciGuySpace|title=The debut of Japan’s new ISS cargo supply ship, HTV-X, has been delayed from January 2023 to January 2024. It will launch on Japan’s H3 rocket, which also has yet to make its debut.|author=Eric Berger|author-link=Eric Berger (meteorologist)|date=26 October 2022}}</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 to allow the pressurized cargo module to be swapped out for alternate modules, to add increased structural strength, and to accommodate the side hatch.<ref name="jaxa20160714"/>

{{As of|2021}}, an evolutionary 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>

== 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 includes 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 has been 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 is similar to how the modules in ''[[Mir]]'', as well as many modules of the [[Russian Orbital Segment]] of the [[International Space Station|ISS]] are 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:Cargo spacecraft]]
[[Category:Supply vehicles for the International Space Station]]
[[Category:Vehicles introduced in 2009]]
[[Category:JAXA]]