HTV (Kounotori)

HTV 1 [NASA]

The HTV (H-2 Transfer Vehicle) or Kounotori is an unmanned, non-reusable cargo spacecraft for delivering pressurized and unpressurized cargo to the International Space Station. Launched by an H-2B-304 rocket, it maneuvers to the vicinity of the ISS, where the Canadarm-2 grapples the HTV and berths it to Node-2.

The HTV consists of four main components:

• A propulsion module installed at the rear and composed of main engines for orbit change, Reaction Control System (RCS) thrusters for position control, fuel and oxidizing reagent tanks, and high-pressure air tanks; The first HTV used 4 R-4D engines, all other use 4 IHI BT-4 engines for propulsion.
• An avionics module installed in the center part, with electronic equipment for guidance control, power supply, and telecommunications data processing.
• A unpressurized logistics carrier to carry material on exposed pallets to the ISS. This section is open on one side to allow the Canadarm-2 to grapple the exposed pallet.
• A pressurized logistics carrier to carry materials to be used on board of the ISS. This section is fitted with a CBM (Common berthing mechanism) to allow the spacecraft to be docked with the ISS and the crew to enter the pressurized section of HTV.

Electrical power is provided by body mounted solar cells.

HTV has a cargo capacity for supplies and equipment of max. 6,000 kg in total. The pressurized cargo can be max. 5,200 kg and the unpressurized cargo max. 1,500 kg. It can deorbit 6,000 kg of waste.

The maximum duration of a mission solo flight is approx. 100 hours. It can stay on sand-by on orbit for more than a week. The berthed time with the ISS is up to 30 days.

At the end of the mission, the HTV is unberthed from the ISS by the Canadarm-2 and it is deorbited to a destructive reentry.