Japan’s HTV-2 departs from the ISS after two month visit

by Pete Harding

The Japan Aerospace Exploration Agency’s (JAXA’s) H-II Transfer Vehicle-2 (HTV-2) “Kounotori” (White Stork) is departing from the International Space Station (ISS) on Monday, after a 60 day visit to the orbital outpost. Launched to the ISS on 22nd January, HTV-2 arrived at the space station on 27th January after a five day free flight, whereupon it was grappled by the Space Station Remote Manipulator System (SSRMS) and berthed to the Node 2 Nadir port.

HTV-2’s Successful Visit:

HTV-2 delivered approximately 6,000kg of supplies to the ISS via its Pressurised Logistics Carrier (PLC), including two brand new science racks – the Multipurpose Small Payload Rack (MSPR) and Kobairo, which contains the Gradient Heating Furnace (GHF). Both new racks were transferred to the ISS’s Japanese Pressurised Module (JPM) “Kibo” in the days following HTV-2’s arrival at the station. Aside from the new racks, many Cargo Transfer Bags (CTBs) of dry cargo, including food, spare parts, and scientific materials were also delivered.

HTV-2 also delivered two Orbital Replacement Units (ORUs) for the station’s exterior via its Exposed Pallet (EP), mounted inside its Unpressurised Logistics Carrier (ULC). The two ORUs were the Flex Hose Rotary Coupler (FHRC) and Cargo Transportation Container-4 (CTC-4).

In early February, the EP was extracted from HTV-2’s ULC via the SSRMS, and installed onto the Japanese Exposed Facility (JEF) via the JEM RMS (Japanese Experiment Module Remote Manipulator System). Once the EP was installed onto the JEF, the Special Purpose Dextrous Manipulator (SPDM) “Dextre” removed the FHRC and CTC-4 from the EP. The empty EP was then removed from the JEF and re-inserted into HTV’s ULC.

The SPDM still remains the temporary home of the FHRC and CTC-4, nearly two months after it took ownership of them from the EP. Now that the ExPrESS Logistics Carrier-4 (ELC-4) is attached to the ISS following the highly successful STS-133 mission, the SPDM will install the FHRC onto its final home (ELC-4) sometime next week, according to an ISS Specialist Status presentation available to download on L2.

Click here for all HTV news articles: http://www.nasaspaceflight.com/tag/htv/

The SPDM will keep hold of CTC-4 for a while longer yet, as CTC-4 contains some new Remote Power Control Modules (RPCMs). The SPDM was due to Remove & Replace (R&R) a faulty RPCM on the P1 Truss last year, until its operations were cut short due to the infamous Pump Module failure/R&R. As the SPDM already has a hold of CTC-4, an “R&R of opportunity” will be performed on the RPCM in question in the coming months.

HTV-2 was shuffled around on the ISS twice during its two month stay – once prior to the arrival of Space Shuttle Discovery/STS-133, when it was relocated to the Node 2 Zenith port to clear the way for Discovery, and once after the STS-133 mission when it was relocated back to its original home on Node 2 Nadir. The fact that HTV-2 was present on Node 2 Zenith during STS-133 provided for some unique views of HTV-2 during Discovery’s flyaround of the ISS.

Once HTV-2’s new cargo was completely unloaded, it began to take on its new role as a glorified trash can, as the ISS crew slowly filled HTV-2 with discarded items that have been cluttering up the station for the past few months. In December 2010, NASA managers decided to extend the HTV-2 mission by an additional month, so that HTV-2 could dispose of some unneeded cargo from the Permanent Multipurpose Module (PMM), which was recently delivered to the station on STS-133.

During the STS-133 mission, the decision was taken to grant Discovery an extra two days docked to the ISS in order to allow the STS-133 crew to make a significant dent into the PMM reconfiguration work planned for the Expedition 26 and 27 crews. 

STS-133 News Articles (over 110 articles): http://www.nasaspaceflight.com/tag/sts-133/

In total, the mission extension gave the STS-133 crew an extra 65 hours to reconfigure the PMM, which had to be complete prior to HTV-2’s departure in order to allow HTV-2 to dispose of the unneeded PMM hardware. 30 hours of reconfiguration and trash loading work still remained upon Discovery’s departure, including 12 hours for the Expedition 26 crew, and 22 hours for the Expedition 27 crew.

A total of 55 percent of HTV-2’s trash items have come from the PMM, which included two unneeded Resupply Stowage Platforms (RSPs) and two Integrated Stowage Platforms (ISPs). The ISPs were installed in HTV-2 during the STS-133 mission, and the RSPs were transferred from the PMM to HTV-2 by the Expedition 27 crew last week.

The two RSPs occupy the rack spaces that were previously occupied by the MSPR and Kobairo racks (Forward 1 and Aft 1), and the two ISPs are strapped to the front of two HTV Resupply Racks (HRRs) at the Starboard 1 and Port 2 locations.

A massive 85 percent of HTV-2 trash consists of discarded packing foam, the majority of which comes from the PMM. Most of the hardware launched in the PMM was large spare parts for ISS which needed to be protected inside large foam “clamshell” boxes.

These foam boxes are not needed on-orbit and take up valuable volume. The cargo was removed from the foam boxes during the STS-133 mission, and the Expedition 27 crew spent last week transferring and stowing the foam boxes in HTV-2.

Click here for ISS news articles: http://www.nasaspaceflight.com/tag/iss/

The large foam “clamshells” to be trashed on HTV-2 come from PMM-delivered hardware including the Pump Package Assembly, Inlet ORU, V-Guides, Water Tank, Waste Water Tank, and Robonaut 2’s (R2’s) Structural Launch Enclosure to Effectively Protect Robonaut (SLEEPR), which consists of a large metal box and surrounding packing foam.

According to NASA, other cargo to be trashed on HTV-2 includes: “6 large foam boxes inside the RSP locations, 4 M-01 bags worth of RFTA foam, 6 CTBEs of ISP launch foam, RSP filler foam, 2 large JAXA foam boxes, 3 CTBEs of common trash, 6 CTBEs of KTOs, HTV2 M-bags of launch foam, foam box from the cylinder flywheels, filler foam pulled from inside NASA CTBs, HTV-2 rack filler foam, 6 CTBEs of CWC-I foam, 1 CWC-I metal box, RSP fences from the racks remaining on ISS and 17 CTBEs of ballast”.

HTV-2 is filled to its volumetric limit for its departure, with cargo quite literally packed right up to the hatch. This will not cause a Center of Gravity (CG) issue for HTV-2 however, since most of the cargo is low-mass foam. JAXA have performed precise CG calculations to ensure that HTV-2’s thrusters will be able to handle the mass, and have also performed analysis to verify that none of the cargo will pose a threat during its burn-up in the atmosphere and splashdown into the Ocean.

Also installed in HTV-2 is the Re-Entry Breakup Recorder (REBR). REBR is the spacecraft equivalent of a black box typically found in most aircraft, and will be used to transmit breakup and re-entry data back to Earth using its GPS, temperature sensors, accelerometers, data recorder and Iridium modem.

HTV-2’s operations were affected by the devastating earthquake in Japan, which caused damage to the Space Station Integration & Promotion Center (SSPIC) in Tskuba, Japan. The earthquake severed an undersea communications line between Japan and the US mainland, which was utilised by the SSPIC. The prime communication line was recovered between the 16th and 17th March, and a back-up line was also established. Full command, telemetry and voice capabilities were fully restored, meaning that the SSPIC is able to support the HTV-2 unberthing and re-entry.

As a sign of support for the victims of the tragedy in Japan, the ISS crew conducted a voluntary activity called “Cranes for Japan”, which involved making paper cranes (Orizuru) using the traditional Japanese activity of Origami (paper folding). Paper cranes are a symbol of hope and good luck in Japan, and they will ride inside HTV-2 during its “falling star” descent through the atmosphere as a message of support to all the victim of the disaster. Cranes can also been see in the ISS Flight Control Room (FCR).

In preparation for the unberthing, HTV-2 was closed out yesterday, with close-out steps including scavenging items from HTV-2 that could be used on ISS, such as Restraint & Mobility Aids (R&MAs), a Portable Fire Extinguisher (PFE), a Portable Breathing Apparatus (PBA), and a Smoke Detector (SD). HTV’s General Luminaire Assembly (GLA) “lights” were previously removed.

Following close-out activities, the hatch into HTV-2 was closed and HTV’s vestibule connections were unplugged from the ISS yesterday. Final vestibule activities, Multi Layer Insulation (MLI) installation, Center Disc Cover (CDC) installation, and Node 2 Nadir hatch closure was completed this morning. Grappling of HTV-2 by the SSRMS was also completed Monday morning.

Once all sixteen Common Berthing Mechanism (CBM) bolts have been released, the SSRMS manoeuvred HTV-2 to a point below the ISS, whereupon HTV’s thrusters were activated and the SSRMS ungrappled HTV. SSRMS release of HTV-2 was at 3:46 PM GMT.

During HTV-2’s approach to the station on 27th January, an overlay on the Robotics Workstation (RWS) video monitors aboard the station did not match the vehicle location in the Mobile Base System (MBS) camera view.

A camera calibration was executed on 7th February, which resulted in pointing offsets that matched the offsets seen during approach. The camera has since been re-calibrated, which should correct the overlay offset issue for HTV-2’s departure.

Following release, HTV-2 will conduct two engine burns to set up for the de-orbit burn on Wednesday (30th March). Re-entry will occur at 3:10 AM GMT on Wednesday, following which the remains of HTV-2 will safely splash down in the Southern Pacific Ocean, bringing to end a flawless mission by the HTV-2 team.

HTV-3 is set to arrive at the ISS in January 2012 – only ten months away from now.

(Images via NASA.gov, L2 documentation and @carbon_flight (Ed Van Cise – ISS FD)

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