H-II Transfer Vehicle (HTV)

HTV Components

The H-II Transfer Vehicle (HTV) consists of two logistic carriers, the Pressurized Logistics Carrier (PLC) and the Unpressurized Logistics Carrier (ULC), which also includes the Exposed Pallet (EP), as well as an Avionics Module and a Propulsion Module.

The Japanese Experiment Module (JEM), known as "Kibo," is equipped with antennas, reflectors and a Proximity Communication System (PROX) that will enable inter-orbit communication with the HTV as the HTV approaches the ISS.

Pressurized Logistic Carrier

The Pressurized Logistics Carrier (PLC) will carry cargo such as International Standard Payload Racks (ISPRs), drinking water and clothes that will be used aboard the ISS. The PLC's internal air pressure is controlled and maintained at one atmospheric pressure (1atm). While the HTV is berthed with the ISS, the ISS crew will be able to enter the PLC to unload the supplies. After the supplies are unloaded, waste material will be loaded. The ISS crew members enter and exit through the HTV's berthing port that's equipped with the Common Berthing Mechanism (CBM).

Unpressurized Logistic Carrier

The Unpressurized Logistics Carrier (ULC) will carry the Exposed Pallet (EP).

Exposed Pallet

The Exposed Pallets (EPs) will carry unpressurized payloads, as well as the ISS battery Orbital Replacement Units (ORUs). There are two types of Exposed Pallets, Type I and Type III.

Type I: This type of pallet carries payloads that will be used on Kibo's Exposed Facility (EF). Two or three Kibo Exposed Facility Payloads per flight can be delivered. This pallet will be attached to the EF.

Type III: This type of pallet carries the US unpressurized ORUs, such as the battery ORUs. This pallet will be attached to the station's Mobile Base System (MBS). Up to six battery ORUs can be delivered.

Avionics Module

The Avionics Module contains navigational and electrical systems used for navigation control, communication and supplying power. The Avionics Module will enable an HTV remote-controlled flight to navigate by receiving commands sent from the ground or to navigate by HTV autonomous flight systems. In addition, the Avionics Module distributes power to each component of the HTV.

Propulsion Module

The Propulsion Module has four propellant tanks. The HTV's thrusters generate propulsion for orbital adjustment or attitude control. The HTV has 32 thrusters installed.

Proximity Communication System (PROX)

The Proximity Communication System (PROX), which is installed in Kibo, consists of a PROX antenna, a PROX-GPS antenna, PROX communication equipment and a Hardware Command Panel (HCP). With the exception of the PROX antenna, the PROX-GPS antenna and the HCP, the PROX is installed in the JEM Pressurized Module.

When the HTV approaches close to the ISS, the PROX antenna will initiate communications with the HTV. This antenna contains GPS receivers. The ISS's orbital location and speed are immediately relayed to the HTV through the PROX. At the same time, data from the HTV are relayed to the ISS. In addition, the antenna relays commands sent from the ground to the HTV.

Reflector

The reflectors are installed on the nadir (bottom) side of Kibo. The reflectors reflect the lasers that are beamed from the HTV's Rendezvous Sensor (RVS) during the HTV close proximity operation.