H-II Transfer Vehicle

The H-II Transfer Vehicle, or HTV, is a robotic spacecraft intended to resupply the "Kibō" Japanese Experiment Module (JEM) on the International Space Station (ISS), and the rest of the station, if need be. The Japan Aerospace Exploration Agency, JAXA, has been working on the design, on and off, since the early 1990s. Originally intended to be launched in 2001, it is currently planned to enter operation in 2009.

HTV is about 9.2 m long (including maneuvering thrusters at one end) and 4.4 m in diameter. Empty, it weighs 10.5 tons. HTV is a larger and simpler vehicle than the Progress spacecraft currently used by Russia to bring supplies to the station, since it does not have a complex docking and approach system. Instead, it will be flown just close enough to the station to allow capture by Canadarm2, which will pull it to a berthing port on the ISS "Harmony" module.

HTV can carry supplies in a combination of two different "segments" that can be attached together. One is a pressurized hold with a capacity of 6,000 kg, which includes an optional docking adapter at one end to allow it to be unloaded in a shirt-sleeves environment. It is designed specifically to carry eight International Standard Payload Racks in total. It will also have a tank to deliver up to 300 kg of water to the station. The other is a lighter and slightly longer unpressurized segment, which includes a hatch on the side to allow it to be unloaded remotely.

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 [ [http://www.abo.fi/~mlindroo/Station/Slides/sld098a.htm NASDA H-II Transfer Vehicle] ] . These numbers are somewhat vague in the various sources, some suggesting that the pressurized/unpressurized combination carries only 6,000 kg in total, less than the pressurized/pressurized combination, which should be heavier. No sources suggest an unpressurized/unpressurized combination is planned, perhaps due to the overall length.

The HTV will be launched from the Tanegashima Space Center in Japan by the Japanese H-IIB launch system, an uprated version of the existing H-IIA. The first test launch is expected in 2009.fact |date=July 2008

In July 2008, it was reported that the United States space agency NASA had begun unofficial negotiations with JAXA on the purchase of HTV spacecraft as the successor to the space shuttle fleet due to NASA's concerns about refueling and servicing the ISS after it retires the shuttle fleet in 2010. [cite web |url=http://news.yahoo.com/s/nm/20080720/sc_nm/nasa_japan_dc
title=NASA eyes buying Japan's cargo spacecraft: report |date=2008-07-20 |accessdate=2008-07-20
publisher=Reuters] A day later, NASA released a press statement declaring that "NASA has not officially or unofficially been discussing the purchase of H-II Transfer Vehicles." The space agency remains committed to "domestic commercial cargo resupply to the space station." [cite web |url=http://www.nasa.gov/home/hqnews/2008/jul/HQ_08181_HTV_statement.html
title=Statement on Inaccurate Reports About Japanese Cargo Services |date=2008-07-21
accessdate=2008-07-21 |publisher=NASA] NASA has been working with private launch firms such as SpaceX and Orbital Sciences Corporation.

References

ee also

* Automated Transfer Vehicle - a similar cargo vehicle developed by ESA

External links

*http://www.jaxa.jp/missions/projects/rockets/htv/index_e.html -- Project overview of H-II Transfer Vehicle.