H-II Transfer Vehicle KOUNOTORI (HTV)

The HTV2 Mission’s primary objectives include launch of the second H-IIB launch vehicle, cargo delivery to the ISS, and support of the station’s trash disposal.

After the HTV1 Mission, some modifications were made to HTV’s original configuration and operational procedures based on the HTV1 mission results. During the HTV2 Mission, performances of the modified parts will be monitored. Major modifications are as follows.

HTV Pressurized Logistics Module (PLC)

• Cargo loading capacity of the HTV Re-supply Rack (HRR) was increased by modifying its cargo layout
• Cargo capacity of the PLC was increased by creating additional cargo spaces inside the PLC
• Of four lights inside the PLC, two lights were replaced to domestic (Japanese) LED lights.

Avionics Module

• The total number of onboard batteries was reduced. In addition, the onboard batteries were upgraded
• Onboard rendezvous flight software was modified
• Space Integrated GPS/Inertial Navigation System (SIGI) software was modified
• Proximity Link System String B transponder was replaced to a domestic (Japanese) transponder

Propulsion Module

• Some of the injection temperature sensors on the HTV’s Reaction Control System (RCS) thrusters were modified to increase the upper measurement range

KOBAIRO Rack (left), MSPR (right)

The HTV2 delivers approximately 5,300 kg of cargo to the ISS.

For pressurized cargo, the HTV2 delivers JAXA’s two science racks, KOBAIRO Rack and the Multi-purpose Small Payload Rack (MSPR). This is the first time that the HTV delivers JAXA’s science experiment rack to the ISS. In addition, the HTV2 Mission delivers potable water to the ISS.

For unpressurized cargo, the HTV2 delivers NASA’s two Orbital Replacement Units (ORUs), the Cargo Transport Container (CTC) and the Flex Hose Rotary Coupler (FHRC), to the ISS. These unpressurized ORUs will be stored outside of the ISS for later use.