H-II Transfer Vehicle

The H-II Transfer Vehicle (HTV), designed and built in Japan, is JAXA’s uncrewed cargo transfer spacecraft that delivers supplies to the International Space Station (ISS). The HTV delivers more than 12,000 pounds of cargo, both pressurized and unpressurized, to the ISS. HTV performs a rendezvous with the space station and holds position several meters away. The crew uses the station’s robotic arm to capture HTV and install it on the bottom side of the station’s Harmony node.

HTV has two main parts. The Pressurized Logistics Carrier (PLC) carries cargo for onboard use (experiment racks, food, and clothes). Internal air pressure of the PLC is maintained at one atmospheric pressure (1 atm). The temperature inside the HTV is controlled during its solo flight phase and berthing phase.

The second part, the Unpressurized Logistic Carrier (ULC), accommodates an Exposed Pallet (EP) while the HTV flies to the ISS. The EP is a pallet used to carry external experiments and spare parts to be used outside of the ISS.

While the HTV is berthed to the ISS, ISS crew can enter HTV’s pressurized logistics carrier to transfer onboard supplies to the ISS. The ISS crew will also unload the unpressurized cargo using the station’s robotic arm and Kibo’s robotic arm. After the supplies are unloaded, the HTV will then be loaded with trash and other discarded items. Once HTV undocks and departs the ISS, it is sent intro a destructive reentry into Earth’s atmosphere.