Japan’s HTV-7 arrives at ISS – will test new recoverable capsule

by Chris Gebhardt

HTV-7 has been captured by the International Space Station (ISS) on Thursday, delivering a new set of batteries for the external portion of the Station’s power generating and storage systems as well as new full-sized experiment racks and glove boxes for the inside of the orbital outpost.  The vehicle headed to space on the second attempt, launching at 02:52:27 JST on Sunday, 23 September at the Tanegashima launch site – which was 1752:27 UTC/13:52:27 EDT on Saturday, 22 September – ahead of a five day trip to the Station. 

HTV-7’s launch:

HTV-7, or Kounotori 7, had been scheduled to launch in mid-August before schedule slips moved the launch to NET (No Earlier Than) 11 September local time at Tanegashima.

From a technical, engineering, payload, and Space Station readiness standpoint, all was on track for the targeted 11 September liftoff.  However, mother nature interfered with those plans as Typhoon Mangkhut churned through the Eastern Pacific passing very close to Guam.

*See the detailed rendezvous timeline and HTV-7 cargo manifest in NSF’s L2 section here.*

The island of Guam, an unincorporated and organized territory of the United States, houses the main ground station through which communications with NASA’s TDRS-275 (Tracking and Data Relay Satellite) comm sat – the primary communications link between HTV and the H-IIB rocket and their ground controllers during launch – are handled.

Typhoon Mangkhut passed Guam in the hours immediately prior to the scheduled 11 September launch, forcing JAXA to delay liftoff until the hurricane passed and ground teams could assess damage to the communications network on Guam.

Ultimately, little to no damage was found and controllers rescheduled the launch for Friday, 14 September local time from the Tanegashima Space Center.

However, mother nature would once again run afoul of the launch team’s plans, with inclement weather predictions for the 14th forcing the team to once again postpone the launch to Saturday, 15 September JST (14 September UTC).

The countdown for Saturday morning local time, Friday afternoon and evening UTC and EDT, had been timed to ensure that HTV-7 was inserted into the orbital corridor of the International Space Station to permit a 3-day phasing profile with the outpost for capture and berthing.

The count – to all observations and reports – tracked nominally through fueling of the H-IIB rocket’s liquid fueled first and second stages.  However, the launch attempt was scrubbed around the 1hr 50min mark prior to liftoff.

The H-IIB rocket. (Credit: JAXA)

An official statement soon confirmed the scrub, with JAXA officials noting an off nominal pressure in a LOX valve as the cause of the delay and that it would take a week or more to fix the issue and get back into launch readiness posture.

The issue was quickly fixed, with JAXA setting Saturday, 22 September (local time)/Friday, 23 September (UTC/EDT) for launch; however, adverse weather forecasts for that day again forced a 24hr slip to the launch.

With the extra day, HTV-7 atop the H-IIB rocket launched at 02:52:27 JST on Sunday, 23 September from the Tanegashima Space Center in southern Japan – which was 1752:27 UTC/13:52:27 EDT on Saturday, 22 September.

When the countdown reached culmination, the first stage’s two LE-7A engines ignited on the pad at T-5.2 seconds and ramped up to full thrust, after which health checks were performed prior to ignition of the four SRB-A3 strap-on solid rocket motors at T0.

Location of the International Space Station at the scheduled 02:52:27 JST launch time of HTV-7. (Credit: GoISSWatch app & GoSoftWorks)

After rising from the pad, the H-IIB rocket pitched downrange, traveling southeast from Tanegashima to begin HTV-7’s 5-day chase of the International Space Station.

The four solid rocket boosters burned for 114 seconds (1 minute 54 seconds) before separating from the core stage at T+2 minutes 7 seconds.

After SRB burnout, the H-IIB was under the singular power of its first stage engines, which burned Liquid Oxygen (LOX) and Liquid Hydrogen (LH2) for a total of 352 seconds (5 minutes 52 seconds).

Payload fairing separation followed at T+3 minutes 40 seconds followed by first stage engine shutdown at T+5 minutes 47 seconds.

After first stage separation at T+5 minutes 54 seconds, the second stage, consisting of a single LE-5B engine burning LH2 and LOX, ignited at T+6 minutes 1 second for a 499 second (8 minutes 19 seconds) burn.

Second stage engine cutoff occurred at T+14 minutes 20 seconds and ended the launch phase of the mission.  HTV-7 separated from the second stage at T+15 minutes 11 seconds at a planned distance of just over 2,310 miles (3,720 km) from its launch site.

The orbital altitude at separation was planned to be roughly 287 km with an overall orbit aligned with the International Space Station to permit three days of phasing and orbit raising maneuvers to set up for rendezvous and capture on 27 September.

Overall, this was the 7th flight of the H-IIB rocket (a variant of the H-IIA) that was designed solely for launches of HTV crafts to the Space Station.  H-IIB and HTV both flew for the first time just over nine years ago on 10 September 2009.

HTV design changes – testing a new reentry capsule for ISS experiments:

Notably for HTV-7 is the inclusion of three major design changes from previous HTV/Kounotori vehicles.

A diagram of the four constituent parts of the HTV resupply vehicle. (Credit: JAXA/NASA)

HTV-7 will use only five primary battery units, a reduction of one battery unit from the previous HTV-6 flight and the seven battery units used for the HTV-2 through HTV-5 missions.

Moreso, the Hardware Control Panel has been replaced by Portable Computer Systems (laptops).  Previous versions of HTV crafts used the Hardware Control Panel as a dedicated control command box to permit Station crewmembers to send control commands to HTV crafts.

But most excitingly for HTV-7 is the inclusion of the HTV Small Re-entry Capsule (HSRC).

The HSRC, similar to the VBK-Raduga reentry capsule carried aboard Russian Progress flights to the Mir space station, will serve as a pressurized reentry vehicle capable of safely and quickly returning experiments from the International Space Station for retrieval and dissemination to scientists.

The HSRC was launched inside the pressurized section of HTV-7 and will be brought aboard the Station, where ISS-manufactured samples, including protein crystals, will be placed aboard the reentry craft.

The HRSC that will be the first Japan craft to return Space Station experiments to Earth for recovery. (Credit: JAXA)

At the end of HTV-7’s mission, the ISS crew will reinstall the craft’s forward hatch (as is standard procedure) and then mount the HSRC to that external hatch via a special port that’s connected with data and communication lines to HTV-7.

HTV-7 will then be unberthed from the Station and begin preparations for its destructive reentry.  After the deorbit burn and before entry interface (the point at which the discernable atmosphere begins to affect a spacecraft), ground controllers will remotely command HTV-7 to release the HSRC capsule at an altitude of 300 km (190 miles).

HSRC will then use its 3D printed nozzles to autonomously control its attitude during atmospheric reentry.  Once through reentry heating, a parachute will guide HSRC to a safe splashdown in the Pacific Ocean off the coast of the Ogasawara Islands.

Overall, the goal of the HSRC is to demonstrate its reentry and scientific sample return capability (max 20 kg, or 41 lb) – which will presently make it only the second craft capable of returning experiments from the International Space Station, the other being SpaceX’s Dragon.

Because HSRC needs to splashdown in an area where recovery will be easy to accomplish, HTV-7 will have the distinction of being the first JAXA Station resupply vehicle to perform a destructive reentry over the Northwestern Pacific Ocean instead of over the Southern Pacific Ocean spacecraft graveyard that has been used on all six previous HTV missions.

Payload – external batteries and internal science racks for ISS:

HTV-7’s liftoff mass was 36,400 lb (16,500 kg) with 13,700 lb (6,200 kg) of that being internal and external payload/cargo elements.

Overall, HTV-7 is carrying two new U.S. science racks, a new U.S. Life Sciences Glovebox (LSG), a new Life Support Rack from ESA (European Space Agency), the HSRC, a Loop Heat Pipe Radiator technology demonstrator, the JEM Small Satellite Orbital Deployer and CubeSat, three CubeSats, as well as cargo, food, clothes, and other provisions for the Station crew.

Among the food that will be delivered by HTV-7 includes a host of fresh fruit.  The fruit, as with the previous two HTV flights, was chosen earlier this week by the Fresh Fruit Selection Committee at JAXA and stored within HTV-7 during late load payload operations to ensure the fruits’ freshness by the time it reaches the Station on Tuesday morning.

But far more importantly for the International Space Station are the four full-sized experiment racks and science gloveboxes being delivered by HTV-7.

The Space Station was designed from inception to have its experiment racks routinely switched out via Space Shuttle Utilization and Logistics missions.  But with the cancellation of the Shuttle Program, the HTV resupply vehicle from JAXA became the only ISS vehicle capable of transporting full-sized racks and gloveboxes up to the outpost beginning in 2011.

The two new EXPRESS Racks, 9B and 10B (first two from left) hitching a ride to the Space Station on HTV-7. (Credit: JAXA)

As such, HTV-7 will deliver two U.S. experiment racks, EXPRESS (EXpedite the PRocessing of Experiments for Space Station) Rack 9B and 10 B – both of which have been modified for more simpler interfaces with ISS systems.

Likewise, a full-sized U.S. Life Sciences Glovebox, only the second large-scale glovebox for scientific experimentation aboard the Station, will be delivered by HTV-7 with eventual installation in JAXA’s Kibo laboratory (attached to the Station in June 2008 during the STS-124 flight of Space Shuttle Discovery).

Also hitching a ride and adding to the international nature of the delivery of supplies via HTV-7 is a full-sized Life Support Rack (LSR) developed by the European Space Agency.

The LSR houses new equipment that will demonstrate effective life support systems through the production of oxygen and water via electrolysis.

The LSR will also demonstrate a capability to take hydrogen, left over from the electrolysis process, and carbon dioxide, removed from the Station’s ambient air, and convert those two items into methane and water, which is then recycled for electrolysis.

The Life Science Rack from ESA. (Credit: Airbus Company)

Likewise, the Loop Heat Pipe Radiator is also a technology demonstration for high-efficiency heat rejection that will be used on future spacecraft.

Specifically, the Loop Heat Pipe Radiator will demonstrate the use of an expansion radiator equipped with a loop heat pipe to validate risk reduction in satellite development for the next generation of geostationary communication satellites.  The experiment will use JAXA’s Kibo laboratory as its test bed.

Scaling substantially down in size are two CubeSats that will be brought inside ISS and deployed from the JEM (Japan Experiment Module).

The CubeSats to include SPATIUM-1 (Space Precision Atomic-clock TIming Utility Mission) from the Kyushu Institute of Technology / Nananyang Technological University, which will demonstrate a new technique for ionosphere mapping using a constellation of CubeSats equipped with Chip Scale Atomic Clock to provide real-time three-dimensional mapping of ionosphere plasma density at the altitudes of electron density peak (200 to 400 km above the Earth).

Joining SPATIUM-1 is the STARS-Me (Space Tethered Autonomous Robotic Satellite – Miniature Elevator) dual CubeSat from Shizuoka University, which will perform a small-scale test of space elevator technology.

Artist’s concept of a future space elevator (Credit: Obayashi Corporation)

The CubeSat consists of two CubeSats linked with a tether – across which a “crawler” will move.  The “crawler” will communicate wirelessly with the two mother CubeSats and transmit its data to them – and the CubeSats themselves will then transmit that data to the ground.

If successful, this will be the first time an object traverses – or crawls across – a tether between two satellites in space.

Shifting to the external payload, HTV-7 will continue the four HTV mission plan of delivering new lithium-ion batteries to the ISS.

A total of six Orbital Replacement Units (ORUs) of the new batteries will be hauled to the Station on HTV-7 for installation over a duo of spacewalks (EVAs) scheduled for 23 and 29 September.

HTV-6 previously delivered the first set of six lithium-ion battery ORUs in December 2016/January 2017.  HTV-7 is the second in the four flight sequence of HTV missions that will each deliver six battery ORUs to completely change out the Station’s nickel-hydrogen batteries on the Integrated Truss Structure that was built over a series of successive Space Shuttle missions.

The original nickel-hydrogen batteries of the ISS that are being replaced by new Lithium-ION batteries. (Credit: NASA)

Overall, HTV-7 is a jam-packed mission requiring a great amount of crew time to complete all of the objectives, including movement and installation of new equipment and repacking HTV-7 full of trash and some of the old nickel-hydrogen batteries for disposal in Earth’s atmosphere.

Before the launch slipped from 11 September to 15 September, HTV-7 was scheduled to remain berthed to the ISS for 59 days, resulting in a departure on 11 November.

Assuming the plan does not change and HTV-7 remains berthed for 59 days despite the launch delay, the craft will be unberthed from the ISS on 15 November.

NASASpaceflight reached out to NASA and asked whether the berthed timeline would change (i.e. if the unberth date would remain on 11 November despite the launch slip) due to the Station’s busy Visiting Vehicle and crew rotation and crew reduction period in the final three months of the year.

That request for comment was not returned.

Related Articles