H-II Transfer Vehicle

Template:Short description Template:Use British English Template:Use dmy dates Template:Infobox spacecraft class

The H-II Transfer Vehicle (HTV), also called Template:Nihongo, is an expendable Japanese automated cargo spacecraft designed for International Space Station (ISS) resupply missions, particularly the 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 10Template:NbspSeptember 2009 on an H-IIB launch vehicle.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }} Template: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>{{#invoke:citation/CS1|citation |CitationClass=web }}</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 Racks (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 its maiden flight in early 2025.

DesignEdit

File:H-II Transfer Vehicle diagram.jpg

Structure

File:HTV from inside 02 - cropped and rotated.jpg

The inside view of the Pressurised Logistics Carrier section of HTV-1.

File:ISS-26 HTV-2 Exposed Pallet grappled by Canadarm2.jpg

The Canadarm2 removing unpressurised payload from HTV-2.

File:HTV-1 close-up view.jpg

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 Template:Convert long (including maneuvering thrusters at one end) and Template:Convert in diameter. Total mass when empty is Template:Convert, with a maximum total payload of Template:Convert, for a maximum launch weight of Template:Convert.<ref name=jaxa2007>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

The HTV is comparable in function to the Russian Progress, the ESA ATV, the SpaceX Cargo Dragons, and the 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 docking ports automatically, HTVs and American Dragon 1 approach the ISS in stages, and once they reach their closest parking orbit to the ISS, crew grapple them using the robotic arm Canadarm2 and berth them to an open berthing port on the Harmony module.<ref>Template:Cite conference</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's exposed facility. Internally, it has eight International Standard Payload Racks (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 Cygnus can carry resupply cargo bags but not ISPRs.Template:Citation needed

The intent behind the HTV's modularized design was to use different module configurations to match different mission requirements.<ref name="miki2010">Template:Cite journal</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">Template:Cite conference</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 HBT-5 thrusters and 120 N class HBT-1 thrusters made by Japanese manufacturer IHI Aerospace Co., Ltd.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The HTV's four spherical propellant tanks usually carry about 2 tonnes of propellant (the maximum capacity is 2432 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>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

FlightsEdit

File:H-IIB F2 launching HTV2.jpg

The HTV-2 departing 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">{{#invoke:citation/CS1|citation |CitationClass=web }}</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>Template:Cite press release</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>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Template:Sticky header

HTV	Launch date/time (UTC)	citation	CitationClass=web }}</ref>	Carrier rocket	Reentry date/time (UTC)	Outcome
HTV-1	10 September 2009, 17:01:56	17 September 2009, 22:12	H-IIB F1	citation	CitationClass=web }}</ref>	Template:Success
HTV-2	22 January 2011, 05:37:57	27 January 2011, 14:51	H-IIB F2	citation	CitationClass=web }}</ref>	Template:Success
HTV-3	21 July 2012, 02:06:18	27 July 2012, 14:34	H-IIB F3	14 September 2012, 05:27	Template:Success
HTV-4	3 August 2013, 19:48:46	9 August 2013, 15:38	H-IIB F4<ref>{{#invoke:citation/CS1\|citation	CitationClass=web }}</ref>	citation	CitationClass=web }}</ref>	Template:Success
HTV-5	19 August 2015, 11:50:49	citation	CitationClass=web }}</ref>	H-IIB F5	citation	CitationClass=web }}</ref>	Template:Success
HTV-6	9 December 2016, 13:26:47	13 December 2016, 18:24	H-IIB F6	citation	CitationClass=web }}</ref>	Template:Success
HTV-7	22 September 2018, 17:52:27	27 September 2018, 18:08	H-IIB F7	citation	CitationClass=web }}</ref>	Template:Success
HTV-8	24 September 2019, 16:05:05	28 September 2019, 14:09	H-IIB F8	3 November 2019, 02:09	Template:Success
HTV-9	20 May 2020, 17:31:00	25 May 2020, 12:13	H-IIB F9 (last)	20 August 2020, 07:07	Template:Success

SuccessorEdit

HTV-XEdit

{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}} Template:Cleanup split 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>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

In December 2015, the plan to develop HTV-X was approved by the Strategic Headquarters for Space Policy of the Cabinet Office, targeting launch in fiscal year 2021 for the flight of HTV-X1 (Technical Demonstration Vehicle) by the H3 rocket.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="jaxa20160714">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Template:Asof, 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>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> In 2022 the debut of the HTV-X spacecraft has been furtherly delayed to January 2024.<ref name="berger-20221026">Template:Cite tweet</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"/>

Template:As of, 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>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Former evolutionary proposalsEdit

HTV-REdit

Template:As of, 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 Template:Convert cargo from ISS to Earth.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</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 Template:Convert of cargo.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Lagrange outpost resupplyEdit

Template:As of, both JAXA and Mitsubishi conducted studies of a next generation HTV as a possible Japanese contribution to the proposed international crewed outpost at Earth-Moon L2.<ref name=jaxalunaraccess>{{#invoke:citation/CS1|citation |CitationClass=web }} Template:PD-notice</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> This variant of HTV was to be launched by H-X Heavy and can carry 1800 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 variantEdit

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-rated capsule for four people.<ref name="ISTS_2008-g-14">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Japanese space stationEdit

A Japanese space station has been proposed to be built up from HTV modules.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> This method is similar to how the modules in Mir, as well as many modules of the Russian Orbital Segment of the ISS are based on the TKS cargo vehicle design.Template:Citation needed

GalleryEdit

ISS-32 HTV-3 berthing 1.jpg

HTV-3 near ISS
ISS-44 Purple Aurora australis.jpg

Kounotori 5 (HTV-5) with Aurora australis
HTV-6 grappled by the International Space Station's robotic arm (2).jpg

HTV-6 grappled to a robotic arm of ISS