Japan sends cargo to the International Space Station
The H-II Transfer Vehicle, also called Kounotori, is how Japan sends cargo to the International Space Station. It is the only cargo ship that can carry large International Standard Payload Racks—the standard rack size on the outpost.
The Japan Aerospace Exploration Agency started working on the design of the spacecraft in the early 1990s before finally flying the first vehicle in 2009. JAXA launches an HTV about once a year atop the country's H-IIB rocket from the Tanegashima Space Center in Japan.
It carries more than twice the cargo that the Russian Progress, however, it launches less than twice as often.
When Kounotori gets close to the station, it is grabbed by the space station's robotic arm and is berthed to an Earth-facing port on the outpost.
Upon completion of its mission, it is loaded with trash and sent into a destructive reentry over the Pacific Ocean.
— Specifications —
Max. cargo: 6,000 kg
Return payload: None
Launch site: Tanegashima Space Center, Japan
Launch vehicle: H-IIB
Design life: About 2 months
First flight: HTV-1, Sept. 10, 2009
Number flown: 5 as of Nov. 2016
Stations serviced: The International Space Station
Name meaning: White stork
HTV-X: NET 2021
— Sections —
Pressurized Logistics Module
Width: 4.4 m
Height: 3.3 m
Max. Cargo: 5,200 kg
Pres. volume: 14 m³
While visually one big spacecraft, the Kounotori is actually composed of four parts. The forward-most piece is called the Pressurized Logistics Module. Like its name sounds, it contains pressurized cargo. At the front of this section is a Common Berthing Mechanism to allow for attachment to the space station and crew access.
Inside, there are eight International Standard Payload Rack bays that can be unloaded by crews in a shirt-sleeve environment. The racks are arranged in two groups of four and each group has a rack on each of the four walls. The forward four are located near the hatch the PLM while the other four are located in the rear.
The four in the front are able to hold either an ISPR or fixed HTV Resupply Rack while the rear four only contain fixed HRRs.
The ISPRs are able to be detached and moved onto the ISS if needed while the HRRs must stay inside the cargo ship.
Unpressurized Logistics Module
Width: 4.4 m
Height: 3.5 m
Max. Cargo: 1,500 kg
The Unpressurized Logistics Module primarily holds the Exposed Pallet, which carries external experiments and orbital replacement units for the space station.
The EP is secured to the spacecraft during launch by four tie-down separation mechanisms. Additionally, once the robotic Canadarm2 grabs onto the power and data grapple fixture attached to the EP, three rails help guide the pallet in and out of the ULM.
The robotic arm, after removing the EP, moves it to the Exposed Facility on the Kibo module complex.
In addition to some solar panels on the PLM, the ULM also has solar panels; between the two, there are 57. This section also has a power and data grapple fixture to allow for Canadarm2 to "grab" on to it and attach the cargo ship to the space station.
Width: 4.4 m
Height: 1.2 m
This section contains the computers, batteries, guidance and electrical power subsystems of the cargo ship. Kounotori uses GPS, rendezvous sensors and Earth sensors to detect where it is relative to the space station.
There are a couple different types of batteries in this section. There are 11 non-rechargeable primary batteries as well as a single secondary battery that can be recharged.
This secondary battery powers the spacecraft during orbital night and charged during orbital day by the cargo ship's many solar panels.
The non-rechargeable are uses when the secondary doesn't have sufficient power. Additionally, while the spacecraft is berthed to the space station, a power control unit routes power from the outposts solar arrays.
Propellant Mass: ~2,400 kg
Width: 4.4 m
Height: 2.0 m
Sporting four main thrusters, the Propulsion Module is used for major orbital maneuvers like orbit changes.
The four engines consume monomethylhyrazine as a fuel mixed with oxides of nitrogen as an oxidizer. These are located in four helium-pressurized tanks holding up 2,400 kilograms of propellant.
When these fuels combine in the engines, each produce 490 newtons of thrust.
Additionally, there are a total of 28 attitude control thrusters situated around the four sections. Each provides 110 newtons of thrust.