Japan’s Kounotori 6 leaves ISS, readies tether experiment
After six weeks attached to the International Space Station (ISS), Japan’s Kounotori 6 spacecraft was unberthed and commanded to leave the vicinity of the outpost. It will now spend a week conducting a few stand-alone experiments for the Japan Aerospace Exploration Agency (JAXA).
A few hours after ground teams commanded the 57.7-foot (17.5-meter) long robotic Canadarm2 to move the spacecraft, also called the H-II Transfer Vehicle (HTV) 6, from the Earth-facing port of the Harmony module to about 33 feet (10 meters) below the Destiny laboratory, Expedition 50 flight engineer Thomas Pesquet of the European Space Agency (ESA) and Commander Shane Kimbrough of NASA commanded the arm to release the vehicle. The official release time was 10:46 a.m. EST (15:46 GMT) on Jan. 27, 2017, while flying 261 miles (420 kilometers) above the south Atlantic Ocean.
A few minutes after being released, the Kounotori was commanded slowly thrust away from the orbiting laboratory. Some eight minutes later, a second burn pushed the spacecraft away faster. Once the cargo ship was outside the station’s “Keep-Out Sphere” – a virtual bubble of about 656 feet (200 meters) around the complex – a third burn was performed to push the spacecraft to a position where it will remain for the next week to conduct experiments.
Holding about 12 miles below the outpost and 23 miles ahead, the spacecraft will release a 2,300-foot (700-meter) tether with a 44-pound (20-kilogram) end-mass. The KITE experiment, which stands for Kounotori Integrated Tether Experiments, is an electrodynamic tether designed to test advanced high-efficiency propulsion. This technology could potentially be used to help deorbit space debris.
Kounotori 6 will stay in this position testing KITE for about a week before the whole spacecraft will be commanded to deorbit and destructively re-enter Earth’s atmosphere over the south Pacific Ocean. This is currently scheduled for Feb. 5, 2017.
JAXA launched the cargo ship atop an H-IIB rocket back on Dec. 9, 2016, from the Tanegashima Space Center in Japan and was berthed with the outpost a week later on Dec. 13. It carried with it 3.9 metric tons of pressurized cargo and 1.9 metric tons of unpressurized cargo.
The pressurized cargo included 30 bags of potable water, food, experiments, and crew commodities. Among them were a 4K camera, a small satellite deployer, and a number of CubeSats. During the course of six weeks, the Expedition 50 crew emptied the pressurized section of its cargo and reloaded with unneeded equipment and trash.
The unpressurized cargo was the main focus, however. It included six new lithium-ion batteries that replaced 12 nickel-hydrogen batteries on the station’s starboard truss. The new batteries were lighter and more efficient than the old units, so, in addition to the batteries, adapter plates were included for the six slots on the truss that were no longer needed. This completed the electrical circuit for each two-battery string.
The batteries were brought up on an external pallet inside the unpressurized section of the spacecraft. During the course of two spacewalks and a number of days’ worth of ground-controlled robotics work, the pallet was emptied of its lithium-ion batteries and adapter plates and then filled with nine of 12 replaced nickel-hydrogen units. They will be destroyed with the Kounotori 6 next week when the spacecraft re-enters the atmosphere. The three remaining aboard the outpost are in permanent storage.
JAXA is expected to launch the seventh Kounotori spacecraft in February 2018. Only three more of the current model are planned before they are expected to be replaced by the HTV-X, which will be an improved, cost-reduced version which is expected to include a recoverable pressurized section. Additionally, the unpressurized cargo would be loaded on top of the spacecraft.
The first HTV-X mission is expected to occur sometime after 2020.
Video courtesy of NASA
Derek Richardson has a degree in mass media, with an emphasis in contemporary journalism, from Washburn University in Topeka, Kansas. While at Washburn, he was the managing editor of the student run newspaper, the Washburn Review. He also has a website about human spaceflight called Orbital Velocity.