H-II Transfer Vehicle

The HTV (H-2 Transfer Vehicle) is a system developed by the Japan Aerospace Exploration Agency JAXA unmanned supply ship, the first launch took place on 10 September 2009.

It is currently planned to 2016Vorlage: / start Future In two years, an annual HTV.


The 10.5 ton HTV consists of a cylindrical body of 9.80 meters and 4.40 meters in diameter. The HTV is divided into two cargo sections, an avionics module and a power module ( Propulsion Module). In addition to the pressurized part of the cargo compartment (PLC - Pressurized Logistics adapter) that can be accessed after the docking of the crew of the International Space Station ( ISS), the HTV has a non-pressurized part ( UPLC - Unpressurized Logistics adapter) in the payload can be transported. To this end, an opening located on the side with a size of 2.7 x 2.5 meters. Advantage of this method is that bulky items that can not be transported through the locks of the station, may be carried as an external load. Main task of the HTV will be the supply, equipment, and supply of the Japanese Kibo laboratory to the ISS. The HTV can carry up to six tons of cargo to the ISS, the standing of about 4,500 kg and 1,500 kg in the pressurized non-pressurized area of ​​the HTV can be accommodated. In the non- pressurized part can be accommodated up to three standard experimental containers for the Japanese Kibo ISS module, among other things a support platform of the type I ( Exposed pallet ) which is then fed out from the Canadarm2 the ISS. Alternatively, a support platform (type III ) can be transported up to six U.S. ORU containers (for example ORU batteries). Due to the passive coupling adapter with U.S. standard sizes ( Passive Common Berthing Mechanism - PCBM ), the HTV is also able to transport standard built for the Columbus module or Destiny that do not fit through the Russian docking port.

The HTV has on the bottom four main engines from Aerojet, which are operated in pairs and deliver a thrust of 490N. They are mainly used for the increase to a transfer orbit to the ISS and for braking the HTV towards the end of the mission. The HTV is designed so that it can reach up to an altitude of 460 km, the ISS. In addition, 28 thrusters ( Attitude Control Thruster ), each with 110 N thrust available (normally 14 jets are used, due to the redundancy are another 14 available). All engines are using monomethyl hydrazine (MMH ) and nitrogen tetroxide ( MON3 ) operated as oxidizer. In the drive module four fuel tanks with a maximum of 2400 kg capacity are installed for it as well as four smaller helium tank to the pressure supply.

The power supply of the freighter is ensured by 47 solar panels on the outside. The avionics module provides for two redundant power grid (50 VDC) for the further portions of the HTV available. After docking, the power supply externally of the ISS effected (120 V DC vehicle power supply ). The energy storage is performed by seven battery modules (Primary Batteries P -BAT ) with 200 Ah, which are housed in the avionics module. To hedge is another battery (Secondary Battery S -BAT )

Mission Steps

The HTV is started with an H -2B rocket from Tanegashima space center in southern Japan from. After a flight time of 15 minutes, the HTV is separated at an altitude of about 287 km from the second stage of the rocket and takes a transfer orbit to the ISS. Navigation takes place mainly via GPS, communication with the earth via the TDRS ( Tracking and Data Relay Satellite ) satellite of NASA. From a distance of 23 km and the HTV is in the " Proximity Communication Zone" and can thus communicate directly with Kibo. From a distance of 500 meters to the ISS Rendezvous sensor is activated, the navigated with optical cameras and laser sensors, the HTV up to a distance of 10 meters to the station. The HTV independently maneuvered into a parking position in front of the International Space Station and is then captured by the Canadarm2 robotic arm of the space station and led to a coupling point with U.S. standard sizes. The coupling is normally carried out after approximately 5 days and 16 hours.

The HTV can usually stay docked up to 30 days ( at HTV -1 around 45 days) and at the end, as the Russian Progress cargo, and ATV, with up to 6000 kg of waste and no longer needed equipment loaded and controlled in the brought Earth's atmosphere to burn-out.

Distinguishing features to the ATV and the Progress cargo

During the design phase in the late 1980s it was clear from the beginning that the HTV should be made fast to the American part of the space station. It had to be dispensed with a docking system, such as in Progress cargo or ATV, as the American coupling sites were not designed for autonomous couplings. Therefore, it was decided to capture of the van with the help of a robot arm. The ATV uses, among others, the acquired license in Russian COURSE docking the company RCS Energia, the approach system of HTV was developed in Japan. Served this purpose the experimental satellite launched in 1997 Kiku -7, which consisted of two sub-satellites that could be approximated independently and dock. The ATV uses the Russian SSVP - G4000 - coupling system, the HTV American Common Berthing Mechanism ( CBM).

By default, the HTV is docked at the American Harmony module, but it can also dock to each other free American coupling port ( HTV -1 nadir port of Harmony). However, the American coupling sites have in contrast to Russian coupling sites no fuel transfer lines. Therefore, the HTV, in contrast to the ATV are not carrying any fuel supplies, oxygen or water to the ISS (the latter can be carried in water bags though). But contrast, bulky items such as Laboratory modules ( science racks) are carried by the pressurized part of the HTV to the station, since the coupling cross-section of the American modules with approximately 1.27 x 1.27 meters is approximately square, this to the round Russian couplings with 0.8 meters in diameter.

The ATV docked to the Russian section of the ISS. This means that the ATV is but unlike the HTV not in grasp of the Canadarm2, since in this part of the station, no matching connectors - the so-called Power Data Grapple Fixture (PDGF ) - are located. Both the ATV as with progression of transporting bulky loads is not possible. The HTV is thus the only supply ship able to carry larger items as external cargo to the ISS or to remove unneeded items from the station.

In contrast to the ATV, the HTV is not designed to lift the orbital path of the ISS. This would require the thrust vector of the HTV own engines passing through the common center of gravity of the ISS. Since the HTV for it is at the "wrong" position (nadir or zenith ), an ignition of the engines would only lead to a rotation of the station by its centroid.

So far, six HTV units were ordered, including a demonstration copy.


The first demonstration flight of HTV -1 " Kounotori "

With the launch of HTV - demonstrator on September 10, 2009 at 17:01 UTC the first HTV was sent on their way to the ISS. HTV -1 is cataloged as Satellite Catalog Number 35817 or with the COSPAR designation 2009- 048A. After several proximity and demolition demonstrations, the module then took on 17th September a stable waiting position under the module Unity one. There it was taken by the astronauts of the ISS Expedition 20 at 19:47 UTC clock with the Canadarm2 and docked after 22 clock to the Harmony module.

In contrast to the following series - TRV the unladen mass of HTV -1 was 11.5 thousand kilograms, as the mission profile of the first flight of the others departed ( demonstration test for roll and abort maneuvers, etc.). For disposal HTV - 1 via four extra batteries ( a total of 11 battery modules, each 175 Ah) as well as other fuel supplies ( 918 kg MMH and 1514 kg MON3 ). For this reason, the payload mass was only 4500 kg on the first demonstration flight. The HTV -1 included the following payloads:

For the outer platform (Japanese Exposed Facility, JEF ) of the Kibo module (900 kg):

  • SMILES (Superconducting Submillimeter -Wave Limb- Emission Sounder ), 329 kg
  • The two-piece HREP measuring complex 312 kg, consisting of HICO & RAIDS; HICO ( Hyperspectral Imager for the Coastal Ocean ) used to test Hyperspektralabbildung the example of coastal regions, RAIDS (Remote Atmospheric and Ionospheric Detection System) research into Earth's atmosphere and ionosphere.
  • SFA (Small Fine Arm ) extension of the robot arm for filigree work

In pressurized cargo area (3600 kg):

  • Express Rack 8, U.S. Rack for Destiny
  • HTV Resupply Packs for seven cargo racks
  • Supplies, consumables and experimental supplies

The mission was originally due to end in the earth's atmosphere after about 37 days and 10 hours with the burn-out of HTV. On the first day after docking mission was extended. Undocking and exposing using the Canadarm2 robotic arm took place on 30 October 2009. On board about 700 kg of waste and unneeded devices were previously housed. Two of the four interior lights were broken as spare parts and stowed in the ISS. The brake ignition took place on 1 November 2009. The main engines of the HTV lit in three maneuvers. The first two firings brought the HTV into an elliptical orbit with an apogee of 335 km and a perigee of 143 km. The last 400 seconds long ignition at 21:01 UTC slowed the HTV from 89 m / s, then was shot with the help of the HTV thrusters so that its long side looked to the flight direction. After disabling the drive system the occurrence took place in the Earth's atmosphere at an altitude of 120 km over New Zealand. The last telemetry data were received from 116 km altitude. The mission ended successfully after 52 days.

After the successful mission, JAXA led in the summer of 2010 by a campaign to give the HTV a name. As part of this campaign, the name " Kounotori " was ( Japanese:こうのとり) is selected, which means " White Stork " means. This name applies to the entire series and not just for HTV -1.

The flight HTV -2 " Kounotori 2 "

The HTV -2 is the first production model flying to the ISS. Based on the experience gained from the first HTV flight some modifications were made. In addition to a modified flight software (Rendezvous Flight software, RVFS ), a revised navigation software of the GPS and the second (redundant ) communication system was changed to a Japanese development ( Proximity Link System String B). The four light modules of the interior lights were moved from the side wall and are now located at the front wall next to the door. This allowed valuable storage space are obtained. Two of the four light modules are new Japanese developments based on LEDs (Permanent Solid-state Lightning, PSL). They use less energy (along 29 W) and also produce less heat than the previous lamps (General Luminaire Assembly, GLA). Since this flight does not include further demonstrations, could be dispensed with some of the built-up batteries and fuel that could be used to increase the cargo capacity.

The HTV -2 hit, broken down into its individual modules, 23 or July 29, 2010 at the spaceport Tanegashima one. The freighter was in accordance with the chosen name of the transporter HTV name Kounotori 2 and transported following payloads to the ISS:

In pressurized cargo area (4000 kg):

  • Kobairo Rack ( 723 kg ) with the Gradient Heating Furnace ( GHF ) for the JPM module from Kibo
  • Two MPS racks (580 kg) were placed in the Kibo JPM module
  • HTV Resupply Packs for eight cargo racks
  • Four bags (CWC -I Bags) with iodine-containing water ( drinking water)
  • REBR Reentry Breakup Recorder (8 kg Aerospace Corporation)
  • More supplies, consumables and experimental supplies

In non-pressurized cargo area ( 1300 kg ):

  • Two ORU freight container
  • FHRC (Flex Hose Rotary Coupler ), was removed with the help of the robot Dextre from the Exposed Pallet, brought to ELC -4 and stored there.
  • CTC -4 ( Cargo Transportation Container 4), has also been linked with the help of the robot arm to ELC -4 and stored there.

HTV -2 was originally supposed to start on 20 January 2011. After two days of delay due to bad weather Kountori finally launched on January 22, 2011 at 14:37:57 Japanese time from Launch Complex 2 at Tanegashima. The Space Shuttle was disconnected after a flight time of 15 minutes and 13 seconds from the upper stage of the launch vehicle H2B. The capture by the Canadarm2 robotic arm of the ISS on 27 January and was conducted by NASA astronaut Catherine Coleman and ESA astronaut Paolo Nespoli. HTV -2 was initially as well as HTV -1 coupled to the ( pointing down to the ground ) nadir docking of Harmony. On February 19, this was converted to the ( upward-pointing ) Zenit - port because the nadir port had to be cleared for mission STS -133 Discovery, otherwise the installation of the PMM Leonardo at the nadir docking port of Unity not possible would have been. After the mission HTV -2 was on Nadir reset on March 10, 2011. Opening the hatch to the pressurized part was delayed by four days due to the severe earthquake of 11 March, in which the Tsukuba Space Center had to be evacuated. Minor damage, overturned server cabinets as well as a break in a submarine cable meant that control of the HTV to Houston had to be passed. These flew staff of JAXA on the same day to Houston to conduct there a makeshift opening the hatch. The return of the control Tsukuba took place on March 22. Among the waste, transported the HTV -2 from the station, there were also parts, cover and flight hardware from the PMM Leonardo, which are no longer needed, since the module remains on the ISS.

Two days before disconnecting a 4 -kg Re-Entry Breakup Recorder ( REBR ) was placed in the interior. This recorded data from inside the pressure hull, as well as the stresses to which the HTV was exposed during entry into the Earth's atmosphere. The recorder was released upon rupture of the transporter and was built so that it can survive the re-entry. As REBR in the atmosphere about 18 km altitude reached subsonic speed, this transferred the data via the Iridium satellite phone network.

Uncoupling and exposure was a day late on 28 March 2011 and was led by Cady Coleman and Paolo Nespoli. After two thruster firings Kounotori entered a 280 x 120 km elliptical orbit. The third final ignition took place on 30 March 2011 at 11:44 clock ( JST) and led to the controlled entry into the Earth's atmosphere over the South Pacific. The mission was successfully completed after 67 days. HTV -2 is as Satellite Catalog Number 37351 or cataloged with the COSPAR designation 2011- 003A.

Multi-purpose Small Payload Rack ( MPS)

CTC -4 Cargo Transport Container

HTV -3 " Kounotori 3"

The third HTV was fitted over its predecessor with further modifications. Thus originated both the four main engines, as well as the 28 thrusters ( Attitude Control Thruster ) made ​​in Japan. Furthermore, were replaced by new developments in the field of avionics transponder and the diplexer and extending the software. For the non-pressurized external payload a new support platform ( Exposed Pallet Multi- Purpose) was developed. This was not only easier, but also made it possible to include other payloads that do not meet the standard dimensions of the Kibo EFUS or ORUs.

Thanks to the experience gained from the previous two Kounotori missions it was also the first time possible to invite a portion of the payload until shortly before the start ( Late Loading Capability ). This is used typically for perishable or time-sensitive goods, thereby expanding the range of possible types of cargo. These special loading platforms were developed and optimized the timing of loading.

Kounotori 3 adopted the following payloads:

In pressurized cargo area:

  • Aquatic Habitat ( AQH ) to be installed in Kibo (75 kg)
  • Four bags (CWC -I Bags) with iodine-containing water ( drinking water)
  • I -Ball (24 kg), recording of re-entry, similar to the REBR
  • Five CubeSats ( RAIKO, FITSAT -1, WE WISH, F -1 and TechEdSat 1) suspended for the airlock of the Kibo module via an adapter
  • More supplies, consumables and experimental supplies

For the outer platform (Japanese Exposed Facility, JEF ) of the Kibo module:

  • SCAN Testbed (NASA), experimental unit for new data communication, 450 kg
  • Multi-mission Consolidated Equipment (MCE should be installed prospectively at EFU 8 of Kibo ) 450 kg for

HTV -3 was launched from the spaceport Tanegashima from 21 July 2012. The H -IIB rocket lifted off at 11:06 clock from ( Japanese time) from the starting complex 2 and put the HTV after a flight time of 14 minutes and 53 seconds successfully on a 200 × 300 km transfer orbit to the ISS from. After a self- test, the HTV stabilized his attitude and built a connection to the TDRS communications system on NASA, which forwards the data to the ground station Tsukuba.

Since the ISS was at the time of the launch at an altitude of 403 km, the flight to the ISS took a day longer than that of Kounotori 2 The capture by the robotic arm of the ISS was performed by Joseph Acaba on July 27. The Japanese astronaut Akihiko Hoshide then docked at the HTV to the American Harmony module. In contrast to the previous two flights, the planned duration of the entire mission was only 37 days. HTV -3 was released again on 12 September 2012, fired its main engines and burned up on September 14.

HTV -3 is as Satellite Catalog Number 38706 or cataloged with the COSPAR designation 2012 - 038A.

HTV -4 " Kounotori 4"

HTV -4 was launched on August 3, 2013 19:48 UTC from the spaceport Tanegashima with an H- IIB rocket from Launch Complex 2. The transport spacecraft has docked with the ISS on August 9. The uncoupling took place on September 4, 2013 September 7, is " Kounotori 4" burns up over the Pacific.

On board were, inter alia,

  • Four CubeSats ( Ardusat X, Ardusat 1, 3 and TechEdSat Pico Dragon) were exposed from the airlock of the Kibo module via an adapter.

Possible use by NASA

In July 2008 it was reported that NASA and the Japanese Space Agency JAXA leads unofficial negotiations to buy some HTV. According to reports, the NASA fears that she will no longer be in a position after the closure of the shuttle fleet to supply the ISS. These reports were denied by officials but since the NASA has been working together with SpaceX and Orbital Sciences Corporation on the future supply of the station.

Bill Gerstenmaier, NASA Program Director for Human Spaceflight, announced end of March 2012, that NASA plans to give more HTV flights in order. So far, it is provided that the last of seven flights a year 2016Vorlage: Future / takes place in two years. Thus could be two to three more flights will be commissioned to ensure the supply of the station until 2020.

Cygnus receives HTV approach control

The of the private American company Orbital Sciences Corporation ( OSC) commercially developed space shuttle Cygnus will be equipped with the used in HTV Proximity Link System (PLS ). For this purpose, a contract between OCS and Mitsubishi Electric Corporation in the amount of 6 billion yen was signed ( about 66 million U.S. dollars ) on 22 October 2009. The approaching, catching and docking using the Canadarm2 robotic arm is analogous to HTV. The first components of the PLS to be delivered from the Mitsubishi factory in Kamakura from 2010 (engineering test modules ).

HTV Return

The HTV -return program ( HTV -R) was launched even before the first flight of the HTV. The aim was to investigate to what extent the HTV could be converted to transport samples and experiments back to Earth can. Since the retirement of the U.S. Space Shuttle, Space Shuttle in 2011 and laboratory experiments can be returned to the private American spaceship Dragon with the Russian Soyuz spacecraft or since May 2012. The four to five Soyuz spacecraft per year can but only 100 kg payload per flight back carry. Therefore, the following modifications have been proposed:

  • In the 0 option designated planning a small return capsule in the coupling adapter of HTV is integrated. This approximately 50 cm in diameter capsule has an ablative heat shield and, in contrast to other HTV -R resist the return to Earth. Inside only small laboratory samples could be accommodated. Shortly after ignition, the capsule of the brake from the HTV -R is emitted. You should then land on parachutes hanging softly on the ground. This plan would be relatively quick and inexpensive to implement, since Japan has already gained a lot of experience in re-entry technologies ( re-entry modules: OREX, AFLEX, HYFLEX, DASH, USERS, the return capsule of the Hayabusa spacecraft, etc.). A disadvantage is the increased security measures for the hatch would be through the capsule would be ejected, as this is by no means fail or may leak during the HTV -R connected to the ISS. The loading capacity of the HTV -R would hardly differ from the current HTV.
  • Another plan is referred to as Option 1. Here, a greater return capsule is in the unpressurized cargo hold of the HTV and replaces the previous cargo pallets ( Exposed Pallet ). Access to the interior of the capsule will take place over a further hatch located on the rear wall of the interior. The return capsule would be empty about two tons, 2.6 meters in diameter and about 1.5 meters high. After loading cargo zurückzuführender the capsule is sealed before the HTV -R leaves the ISS. Shortly after the successful brake ignition this is laterally ejected from the cargo hold of the HTV. She gets slowed by parachutes back to Earth. In contrast to option 0 but a landing in the sea is scheduled to take on mainland. A equipped with this measure HTV could carry 3200 kg cargo to the ISS and take about 300 kg back to Earth. This measure also requires some modifications to the current HTV. It would need another access hatch to be installed, constructed an ejection mechanism for re-entry and be made ​​on the basis of the altered center of gravity further small modifications. The disadvantage is that no other external payloads can be transported. This solution would be relatively easy to implement.
  • In the planning stage, referred to as Option 2 of all the pressurized area of ​​the HTV with a single, truncated return capsule is replaced. It would have a diameter of about four meters, a height of 3.80 meters and a weight of about six tons. This is during takeoff around 3,200 kg of cargo. In non-pressurized cargo area further 1600 kg can be transported on cargo pallets, as is possible with the HTV today. In the capsule around 1,600 kg of cargo could be transported back to Earth. Before the HTV enters the Earth's atmosphere, the return capsule is separated from the rest of the HTV -R. As with Option 1, is this capsule can be soft landing with parachutes hanging in the sea. The first launch could take place in 2016. This plan offers the great advantage that Japan 's mission to develop a manned space capsule, comes a step closer.

Currently alternatives being researched and developed at all three. End of 2010, a decision can be made, as the successor of the TRV will look like.