Video courtesy of NASA Television
Two weeks after the metaphorical bird brought joy to the Duke and Duchess of Cambridge, a high-tech stork of a different kind is presently winging its way to the International Space Station, following a smooth liftoff from the Tanegashima Space Center. The Japan Aerospace Exploration Agency (JAXA) successfully lofted its fourth H-II Transfer Vehicle (HTV-4), nicknamed “Kounotori” (“White Stork” or “Oriental Stork”), from Launch Pad 2 at the Pacific spaceport at 4:48 a.m. Japan Standard Time Sunday (3:48 p.m. EDT Saturday). The giant cargo craft is laden with around 11,900 pounds of payloads and supplies for the Expedition 36 crew and is scheduled to berth at the space station on Friday, 9 August.
Preparations for today’s launch have been in high gear at the launch site—which sits on the Pacific coastline of southeastern Tanegashima, one of the Ōsumi Islands in southern Japan—for the past several weeks. The HTV-4 spacecraft was loaded with propellants for its maneuvering thrusters through late June and into early July, and on the 11th it was mated to its payload attach fitting, ahead of encapsulation within the fairing of its H-IIB launch vehicle. It was transferred from the Second Spacecraft and Fairing Assembly Building (SFA2) to the Vehicle Assembly Building (VAB) for integration with the rocket on 20 July, although final installation of time-critical, “late access” payloads was not completed until yesterday (Friday). The vehicle was then closed-out for flight, and the H-IIB rolled out to Launch Pad 2 early Saturday morning (JST).
A little under ten hours ahead of the scheduled liftoff, a “Go” was received to authorize the loading of cryogenic oxygen and hydrogen propellants into the first and second stages of the 185-foot-tall H-IIB. Four hours later, at approximately 11:20 p.m. JST (10:20 a.m. EDT) Saturday), this process was concluded. In addition to the two stages, the rocket—which marked its fourth launch today and has now delivered four HTVs into orbit since September 2009—was powered uphill by four solid-fueled (polybutadiene) boosters.
At 4:38 a.m. JST Sunday (3:38 p.m. EDT Saturday), about ten minutes before launch, a final “Go” to proceed was given and the countdown entered its “Terminal” phase. With two minutes to go, the giant rocket transitioned to internal power and all liquid propellants were verified at their correct flight pressures. Liftoff took place precisely on time, and the dazzling plumes of the first stage’s twin LE-7A engines and the four solids turned night into day across Tanegashima Island. At the instant of launch, the International Space Station—HTV-4’s target—was traveling high above Russia.
The solid-fueled boosters burned out and separated from the rapidly ascending vehicle at T+114 seconds, to be followed by the jettison of the payload fairing two minutes later, which exposed HTV-4 to the near-vacuum of space for the first time. Meanwhile, the LE-7A engines continued to burn fiercely and finally shut down at T+352 seconds, after establishing the proper conditions for separation of the first stage and ignition of the H-IIB’s single LE-5A second stage engine. By now, the rocket had attained an altitude of around 125 miles and the eight-minute-plus firing of the LE-5A served to inject HTV-4 into an initial elliptical orbit of about 124 x 186 miles, inclined 51.6 degrees.
Fifteen minutes after leaving the Tanegashima Space Center, at 5:04 a.m. JST Sunday (4:04 p.m. EDT Saturday), HTV-4 had separated from the second stage and was confirmed to be in independent flight. Its solar arrays and communications appendages were due to be deployed as this article was being prepared. According to JAXA’s English-language press kit, the first few hours will be consumed with “HTV subsystem activations, attitude-control and three-axis stabilization, self-check, communications establishment with the Tracking and Data Relay Satellite (TDRS), initiation of communication with the HTV Mission Control Room at Tsukuba, [and] initiation of orbit control for rendezvous maneuver.”
Over the next five days, HTV-4 will transfer itself toward a rendezvous with the International Space Station. It is due to approach autonomously to within about 33 feet of the orbital complex on 9 August, from where it will be grappled by Canadarm2 and steadily positioned into a “ready to latch” orientation over the active Common Berthing Mechanism (CBM) of the “nadir” (Earth-facing) port of the Harmony node. At the controls of the Canadian-built robotic arm will be Expedition 36 astronauts Chris Cassidy and Karen Nyberg, whilst Italian crewmate Luca Parmitano will monitor the final stages of the rendezvous. Four latches will engage to hold HTV-4 in place, after which 16 bolts will be driven to achieve a “hard mate.”
The astronauts’ next steps, as detailed in JAXA’s press kit, will entail “Vestibule outfitting (e.g. installation of lines and cables), activation of HTV power supply from the ISS, [and] switching of the communications lines from wireless to wired communications.” On 10 August, Cassidy, Nyberg, and Parmitano are expected to remove the Controller Panel Assemblies from the active CBM, open the hatch, and enter the pressurized compartment of HTV-4. One of their first internal tasks will be to activate the Inter-Module Ventilation system and transfer portable fire extinguishers and breathing apparatus.
This is the fourth mission by the H-IIB, which previously delivered HTV-1 into orbit in September 2009, followed by HTV-2 in January 2011 and HTV-3 in July 2012. The arrival of the gold-colored HTV-4 at the space station will begin a four-week period of operations, during which about 11,900 pounds—about 5.4 metric tons—of payloads and supplies will be transferred. This includes about 3.9 metric tons of pressurized cargo and 1.5 metric tons aboard HTV-4’s unpressurized segment.
Key payloads include the newly-developed Freezer-Refrigerator of Stirling Cycle (FROST) for the pressurized Kibo module, which will cool experimental samples to below -70 degrees Celsius, even in the case of power outages. The ISS Cryogenic Experiment Storage Box (ICEBox) will keep a container cool without electrical power, whilst a Re-entry Data Recorder (known as the “i-Ball”) will measure velocities, accelerations, temperatures, and imaging data during HTV-4’s fiery re-entry. The spacecraft’s unpressurized segment will house a replacement Main Bus Switching Unit (MBSU), a Utility Transfer Assembly (UTA), and NASA’s Space Test Program-Houston4 (STP-H4). Four small CubeSats—the PicoDragon, TechEdSat-3, ArduSat-1, and ArduSat-X—are also aboard, as is the “super-sensitive” 4K camera to observe Comet ISON and Japan’s unique “Kirobo” talking robot.
On a more basic level of necessity, clothes, dried food, snacks, and beverages for the ISS crew, including 480 liters of water, will be aboard. Additionally, the Advanced Technology On-Orbit Test Instrument for Space Environment-mini (ATOTIE-mini) will fly for the first time to evaluate changes in surface potential of HTV-4 before and after berthing at the space station and if this potentially affects spacewalkers. The spacecraft will be loaded with trash at the end of its mission and will be unberthed on 5 September and deorbited two days later.
First flown in September 2009, the HTV measures over 30 feet long and 14 feet in diameter, weighs about 21,000 pounds, and can carry 13,000 pounds of payload to the space station. Its pressurized segment can house up to eight refrigerator-sized International Standard Payload Racks (ISPRs), which are transferred in a shirt-sleeve environment by the ISS crew, whilst an unpressurized segment enables external payloads to be robotically removed and installed onto the porch-like Exposed Facility of Japan’s Kibo laboratory. Like SpaceX’s Dragon, the HTV approaches the ISS and is captured and berthed to the Harmony node by means of the Canadarm2 robotic arm.
Unlike Dragon, the Japanese craft burns up in the atmosphere at the end of each mission, although JAXA has advanced plans for a HTV-R variant, with a “return” capsule to transport around 3,200 pounds of payload back to Earth. The first flight of the HTV-R is tentatively scheduled for 2018. Since its maiden voyage, a HTV mission has flown approximately every 12-18 months, delivering a wide range of payloads and experiments to the ISS, including the Hyperspectral Imager for the Coastal Ocean (HICO) instrument, a high-tech aquarium capable of supporting several generations of fish for up to three months, a Gradient Heating Furnace, and a number of small CubeSats.
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