H-II Transfer Vehicle

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H-II Transfer Vehicle
H-II Transfer Vehicle (HTV-1) approaching the ISS
Role: Automated cargo spacecraft to resupply the International Space Station
Crew: None
Height: ~9.8 m (including thrusters)[1]
Diameter: 4.4 m[1]
Spacecraft Mass: 10,500 kg[1]
Total Launch Payload: 6,000 kg[2]
Pressurized Payload: 5,200 kg[2]
Unpressurized Payload: 1,500 kg[2]
Return Payload: None[3]
Mass at launch: 16.5 ton[2]
Pressurized Volume: 14 m3[4]
Endurance: Solo flight about 100 hours, stand-by more than a week, docked with the ISS about 30 days[1]
Apogee: 460 km[1]
Perigee: 350 km[1]
Inclination: 51.6 degrees[1]

The H-II Transfer Vehicle (HTV), also called Kounotori (こうのとり Kōnotori?, "Oriental Stork" or "White Stork"), is an automated cargo spacecraft used to resupply the Kibō Japanese Experiment Module (JEM) and the International Space Station (ISS). The Japan Aerospace Exploration Agency (JAXA) has been working on the design since the early 1990s. The first mission, HTV-1, was originally intended to be launched in 2001. It launched at 17:01 UTC on 10 September 2009 on an H-IIB launch vehicle.[5] The name Kounotori was chosen for the HTV by JAXA 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".[6]


Inside view of the Pressurised Logistics Carrier section of HTV-1.
Canadarm2 removing unpressurised payload from HTV-2.

The HTV is about 9.8 m long (including maneuvering thrusters at one end) and 4.4 m in diameter. Total mass is 10.5 tonnes, with a 6,000 kilograms (13,000 lb) payload.[1] The HTV are comparable in function to the Russian Progress, European ATV, commercial Dragon, and commercial Cygnus spacecraft, all of which bring or are planned to 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 capsules and ATVs, which dock automatically, HTVs and American commercial crafts approach the ISS in stages, and are signaled by ISS crew or ground control to continue from one holding point to the next. 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.[7]

The HTV has an external payload bay which is accessed by 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 Orbital Sciences Cygnus can carry resupply cargo bags but not ISPRs.)

The four main thrusters. Smaller attitude control thrusters can be seen at the right side of this view of HTV-1.

The baseline configuration, known as the "Mixed Logistics Carrier", uses one pressurized and one unpressurized segment and can carry 7,600 kg of cargo in total and is 9.2 m long. When two pressurized units are used together the cargo decreases slightly to about 7,000 kg, and the overall length is reduced to 7.4 m.[8]

To control the HTV's attitude and to perform the orbital maneuvers such as rendezvous and re-entry, 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.[9] HTV-1, -2, and -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.[9] Later HTVs use 500 N class HBT-5 thrusters and 120 N class HBT-1 thrusters made by Japanese manufacturer IHI Aerospace Co., Ltd.[10] The HTV carries about 2400 kg of propellant in four tanks.[9]

After the unloading process is completed, the HTV will be loaded with waste and undocked. The vehicle will then deorbit and be destroyed during reentry, the debris falling into the Pacific Ocean.[3]


HTV-2 departing Tanegashima spaceport bound for the International space station

The first vehicle was launched on an H-IIB rocket, a more powerful version of the earlier H-IIA, at 17:01 GMT on 10 September 2009, from Launch Pad 2 of the Yoshinobu Launch Complex at the Tanegashima Space Center.[11]

As of March 2015, five subsequent missions are planned—one each year for 2015–2019[12] —one fewer total mission than had been planned in August 2013 at the time the fourth HTV mission was underway.[13]

HTV Launch date/time (UTC) Berth date/time (UTC)[14] Carrier rocket Re-entry date/time
HTV-1 10 September 2009, 17:01:56 17 September 2009, 22:12 H-IIB F1 1 November 2009, 21:26[15]
HTV-2 22 January 2011, 05:37:57 27 January 2011, 14:51 H-IIB F2 30 March 2011, 03:09[16]
HTV-3 21 July 2012, 02:06:18 27 July 2012, 14:34 H-IIB F3 14 September 2012, 05:27
HTV-4 3 August 2013, 19:48:46 9 August 2013, 15:38 H-IIB F4[17] 7 September 2013, 06:37[18]
HTV-5 17 August 2015[12] H-IIB
HTV-6 2016[12] H-IIB
HTV-7 2017[12] H-IIB
HTV-8 2018[12] H-IIB
HTV-9 2019[12] H-IIB

Evolution prospects[edit]


As of 2010, JAXA is planning to add a return capsule option. HTV's Pressurized Cargo is replaced by a reentry module capable of returning 1.6 tonne cargo from ISS to Earth.[19][20] It is expected to be launched by 2018.[21][not in citation given]

Further, it is expected to be followed on by 2022 by capsules which accommodate a crew of three and carry up to 880 pounds (400 kilograms) of cargo.[22]

Lagrange outpost resupply[edit]

As of 2014, both JAXA and Mitsubishi have conducted studies of a next generation HTV as a possible Japanese contribution to the proposed international manned outpost at Earth-Moon L2.[23][24] This variant of HTV is to be launched by H-X Heavy and can carry 1.8 tons of supplies to EML2.[23] Modifications from the current HTV includes the addition of solar electric paddles and extension of the propellant tank.[23]

See also[edit]


  1. ^ a b c d e f g h "H-II Transfer Vehicle "KOUNOTORI" (HTV)". Japan Aerospace Exploration Agency. 2007. Retrieved 2010-11-11. 
  2. ^ a b c d Overview of the "KOUNOTORI". Japan Aerospace Exploration Agency. Retrieved 2011-01-18.
  3. ^ a b JAXA (2007). "HTV Operations". Retrieved 2011-01-02. 
  4. ^ "JAXA H-II Transfer Vehicle (HTV)" (PDF). NASA. Retrieved 8 December 2013. 
  5. ^ "NASA Sets Briefing, TV Coverage of Japan's First Cargo Spacecraft". NASA. Retrieved 2009-09-03. 
  6. ^ ""KOUNOTORI" Chosen as Nickname of the H-II Transfer Vehicle (HTV)". JAXA. 11 November 2010. Retrieved 11 November 2010. 
  7. ^ http://www.aprsaf.org/data/aprsaf17_data/DAY1-seu_0950-Kibo_Utilization_Status.pdf[dead link]
  8. ^ http://www.abo.fi/~mlindroo/Station/Slides/sld098a.htm[dead link] - NASDA H-II Transfer Vehicle
  9. ^ a b c IAC paper IAC-05-C4.1.03 - Shinobu Matsuo and al. "The design characteristics of the HTV propulsion module"
  10. ^ "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" (PDF) (in Japanese). June 20, 2012. Retrieved June 24, 2012. 
  11. ^ Launch of the H-IIB Launch Vehicle Test Flight, JAXA Press release, 8 July 2009 (JST)
  12. ^ a b c d e f "International Space Station Flight Schedule". SEDS. 2015-03-13. Retrieved 15 March 2015. 
  13. ^ "International Space Station Flight Schedule". SEDS. 15 May 2013. Retrieved 9 August 2013. 
  14. ^ "H-II Transfer Vehicle "KOUNOTORI" (HTV) Topics". Japan Aerospace Exploration Agency. 
  15. ^ Stephen Clark (1 November 2009). "History-making Japanese space mission ends in flames". Spaceflight Now. Retrieved 13 November 2010. 
  16. ^ Stephen Clark (29 March 2011). "Japan's HTV cargo freighter proves useful to the end". Spaceflight Now. Retrieved 21 April 2011. 
  17. ^ Stephen Clark (3 August 2013). "Japan launches resupply mission to space station". Spaceflight Now. Retrieved 3 August 2013. 
  18. ^ Stephen Clark (9 August 2013). "JJapan's cargo craft makes in-orbit delivery to space station". Spaceflight Now. Retrieved 9 August 2013. 
  19. ^ "回収機能付加型宇宙ステーション補給機(HTV-R)検討状況" (in Japanese). JAXA. August 11, 2011. Retrieved September 7, 2011. 
  20. ^ "回収機能付加型HTV(HTV-R)" (in Japanese). JAXA. Retrieved September 7, 2011. 
  21. ^ "JAXAでは宇宙ステーション補給機「こうのとり」(HTV)への回収機能の付加について研究を行っています。" (in Japanese). JAXA. September 7, 2011. Retrieved 9 August 2013. 
  22. ^ Rob Coppinger. "Japan Wants Space Plane or Capsule by 2022". Space.com. Retrieved October 25, 2012. 
  23. ^ a b c "International Human Lunar Mission Architecture / System and its Technologies" (PDF). JAXA. 2014-04-10. Retrieved 22 January 2015. 
  24. ^ "An International Industry Perspective on Extended Duration Missions Near the Moon" (PDF). Lockheed Martin Corporation. 2014-04-10. Retrieved 22 January 2015. 

External links[edit]