HTV-2 Cargo Ship On Way To Dock With ISS

TOKYO — Japan’s second unmanned H-II Transfer Vehicle (HTV-2), launched from the Tanegashima Space Center on Jan. 22., is due to dock with the International Space Station on Jan. 28 at 4 a.m., Japan time, to deliver supplies and instruments.

Liftoff for the HTV-2 came at 2:38 p.m. on a Mitsubishi H-IIB rocket. Separation was confirmed about 15 min. later at an altitude of 287 km. (178 mi.). The same type of rocket was used for the test launch of the first HTV in September 2009. For the second mission there were some changes to the fairing separation mechanism.

The cargo craft will approach the International Space Station (ISS), which is orbiting about 350 km. above Earth, and at 23 km. distance the HTV-2 will communicate to the Proximity Communication System mounted on Japan’s Kibo laboratory module. Navigating with GPS, it will approach to 5 km. behind the station, then maneuver to 500 meters underneath, at which point it will begin to use its Rendezvous Sensor, shining a laser on the side of the Kibo to measure distance. Stopping at 250 meters (820 ft.) and 30 meters, it eventually will arrive 10 meters below the station. Both spacecraft will be orbiting at 28,000 kph. (17,398 mph.).

Before the launch, HTV Project Manager Yoshihiko Torano looked back on the first HTV docking. “At the time, it seems no one, especially people at NASA, believed in our technology, to stop 10 meters below the ISS,” he said. “Actually, HTV [was so stable relative to the station] that it did not even budge a millimeter a second.” Once stationary, the HTV-2 will be grappled and attached by the station’s robotic arm head-first into the underside of the U.S. Harmony node.

The HTV-2 is shaped like a cylinder measuring 9.8 meters X 4.4 meters and includes an upper pressurized compartment and middle unpressurized compartment. Avionics and propulsion are installed in the bottom section. The slight difference from its predecessor is increased load capacity, achieved by rearranging some air conditioning systems and lights and by leaving out spare fuel tanks and four sets of batteries installed as a precaution in the first unit. Other changes have been made to transmitting equipment.

The HTV was nicknamed Kounotori, meaning “white stork” in Japanese. The nickname will be used for all HTV missions, the present mission being Kounotori 2.

Cargo load

The spacecraft is carrying 4 tons of pressurized cargo: two science experiment racks for the Kibo laboratory and six racks of food and supplies, including 80 liters of drinking water. The 1.3 tons of unpressurized cargo are secured on a pallet drawer and include two pieces of NASA equipment— a flex hose rotary coupler (a spare part for the thermal radiator rotary joint) and a cargo transport container, which contains spares for the remote power controller.

The HTV-2 will stay connected with the ISS for about 43 days, depending on the ISS schedule. When the shuttle Discovery docks with the ISS, the HTV-2 will need to be robotically grappled and moved to the upper part of Harmony, then put back in place again after the shuttle leaves.

Development cost for the HTV-2 was around 14 billion yen ($168 million), 6 billion yen cheaper than the previous model. At least five more HTVs are scheduled to be launched every fiscal year until 2015. The success of these HTV missions is crucial because of their large unpressurized cargo capability, which will make up for some capacity lost when the space shuttle is retired.