Japan’s venerable HTV spacecraft made its fourth launch to the ISS tonight, blasting off atop a H-IIB booster from the Tanegashima space center in Southern Japan at 7:48:46 PM GMT. HTV-4 is carrying a cargo of food, hygiene items, internal and external spare parts, and scientific experiments for the ISS and its crew.
The HTV, named “Kounotori” (White Stork), is funded by the Japan Aerospace eXploration Agency (JAXA) as part of its contributions to the ISS program, with three HTVs having flown to the ISS to date – HTV-1 from September-October 2009, HTV-2 from January-March 2011, and HTV-3 from July-September 2012.
The unmanned resupply freighters feature four main components – a Pressurized Logistics Carrier (PLC) capable of holding eight rack-bays worth of internal cargo, and also capable of delivering racks to the ISS, the only resupply vehicle to possess such a capability now that the Space Shuttle fleet is retired.
Attached below the PLC is the Unpressurized Logistics Carrier (ULC), inside which resides an Exposed Pallet (EP) onto which external cargo can be mounted – making the HTV one of only two vehicles capable of delivering external cargo to the ISS (with the other vehicle being SpaceX’s Dragon).
The EP is removed from the ULC once the HTV has arrived at the ISS by the space station’s robotic arm, and the external cargo is then removed from the EP and installed onto the ISS.
Below the ULC resides the avionics module, which contains all the vehicle’s power and command & control systems. Finally, the propulsion module houses all the vehicle’s propellant tanks and main orbital adjustment engines.
Following liftoff atop its Japanese H-IIB booster – which is used specifically for the HTVs – at 7:48:46 PM GMT from Launch Pad-2 (LP-2) at the Tanegashima space center in Southern Japan, HTV-4 was placed into an initial orbit of 200x300km, inclined at 51.6 degrees to the equator, after a roughly 14 minute insertion.
Over the next six days of free flight, HTV-4 will conduct a series of rendezvous burns in order to raise its altitude to around 410km, the height of the ISS, in order to put itself in the correct position to rendezvous with the ISS on Friday August 9.
In a now well proven procedure, HTV-4 will then fly itself to a point 30 feet below the ISS, whereupon the station’s robotic arm will reach out and “capture” the vehicle.
HTV-4 will then be maneuvered below the Node 2 Nadir Common Berthing Mechanism (CBM) port on the ISS, whereupon it will be berthed to the station, with hatch opening following within the next day. Internal and external cargo operations will then begin, and will continue over the next month as HTV-4 is emptied of its cargo and re-filled with trash for disposal.
On September 5, HTV-4 will be un-berthed and released from the ISS, with a de-orbit coming two days later on September 7, for a destructive re-entry over the South Pacific ocean in order to dispose of both internal trash and, for the first time on the HTVs, an external ISS experiment that is no longer needed.
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Capture volume anomaly:
In preparation for the arrival of HTV-4, over the past week the ISS crew have been conducting what is known as a “capture volume checkout” ahead of the HTV-4 rendezvous.
The capture volume is a computer-generated overlay for the video monitors of the Robotic Work Station (RWS) aboard the ISS, which tracks where the HTV is in relation to the ISS via the station’s external video cameras, and then, in real time, overlays this information around the HTV that is visible on the video monitors, in order to aid the ISS crew in tracking the vehicle.
This same method is employed for the HTV, Dragon and, in future, Cygnus rendezvous with the ISS.
A checkout of the capture volume, which per L2 info involves “maneuvering the Space Station Remote Manipulator System (SSRMS) to various positions within the capture volume to confirm the capture volume overlay is drawn accurately”, is conducted prior to the launch of every spacecraft that requires it.
In the case of the HTV, via L2 info, “per HTV flight rule F2-1, the Capture Volume checkout is a Launch Commit Criteria (LCC)” – meaning that the HTV cannot launch until a capture volume checkout has been successfully conducted.
Earlier this week however, the HTV capture volume checkout failed, as, per L2 notes “the capture volume overlay position and shape was not as expected”. The cause of the problem was subsequently identified: “The capture volume function is dependent on having an active HTV telemetry stream. Without active vehicle telemetry, the Rendezvous Navigation Flag is set to zero. This in turn zeroes out the origin of the HTV coordinate frame”.
“This feature was implemented in Mobile Servicing System (MSS) 7.2 software update in Feb 2013, and is only applicable to HTV. SpaceX and Orbital do not use that same flag. This explains why the anomaly was not observed during SpX-2 check out and capture.”
As it was a simple software error, a workaround was simple: “The workaround used previous HTV Proximity Operations checkout data located in the Command and Control Software. The existing HTV data has the Rendezvous Navigation Flag set to a non-zero value”. This workaround was successful, thus meeting HTV-4’s LCC in time for launch.
HTV-4 cargo – internal:
HTV-4 is carrying a large amount of internal cargo to the ISS, via its eight rack bays, all of which are filled with HTV Resupply Racks (HRRs) that will remain inside the HTV for the duration of its mission. The HRRs are packed with food, water, hygiene items, clothing, spare parts, personal items, and scientific experiments for the ISS crew.
Among the notable internal items aboard HTV-4 is a small humanoid robot, known as Kirobo (Kibo Robot Project), which, while much smaller than its bigger cousin Robonaut, has the ability to interact with humans via speech. Kirobo will stay aboard the ISS until December 2014 to test human-robot voice interaction in space, prior to being returned to Earth.
Also notable is a new task board for the Robotic Refuelling Mission (RRM) payload outside the ISS. The new task board, known as Task Board 3 (TB3), features hardware for Phase II of the RRM mission, with Phase I having being completed earlier this year. While Phase I focused on access to and performing satellite refuelling, Phase II will focus on replenishing cryogens in the instruments of legacy satellites.
TB3 features new hardware to test cryogen replenishment, which includes five brand new adapters for the RRM Multi Function Tool (MFT). TB3 will be transferred outside the ISS via a new piece of hardware also launching on HTV-4, called the RRM On-orbit Transfer Cage (ROTC).
The ROTC, with TB3 attached, will be transferred outside the ISS via the Japanese scientific airlock, whereupon the Dextre robot will remove TB3 from the ROTC and install it onto the RRM payload. Used TBs from RRM will also be brought back inside the ISS via the ROTC.
Another interesting payload aboard HTV-4 is the “Ham TV” package, which will give the ISS the capability to downlink video via the station’s amateur Ham radio link. The Ham TV electronics box will reside in the European Columbus module and plug into an existing ISS camcorder.
This will enable organizations who conduct amateur radio sessions with astronauts aboard the ISS, typically schools, to both see and hear the astronauts aboard.
Four Cubesats also launched on HTV-4, which will be deployed via the station’s Japanese airlock using the JEM-Small Satellite Orbital Deployer (J-SSOD) hardware in a repeat of a similar deployment last October. The four Cubesats are “Pico Dragon”, a 1U Cubesat built by Japan and Vietnam, which will test Earth imaging technologies.
In addition, Ardusat-1 and Ardusat-X, which are 1U, crowd-funded Cubesats built by US companies Nanoracks and Nanosatisfi, will test open re-programmable platforms on-orbit. Finally, TechEdSat-3, built by NASA’s Ames research center, is a 3U Cubesat which will test a new aerobraking de-orbit method called Exo-brake.
Several new Japanese-developed hardware items for the ISS also launched aboard HTV-4, including a super-HD “4K camera” that will be used to shoot Comet ISON in December. The 4K camera possesses a resolution 4 times higher than current HD cameras on the ISS, and has been specially altered to shoot ISON with more than 8 times the ultra-high sensitivity than the existing cameras.
A new -70 degree centigrade Japanese freezer for ISS, called the Freezer-Refrigerator of Stirling Cycle (FROST), and a new Japanese cool box to keep experiment samples cold without the need for electrical power, called the ISS Cryogenic Experiment storage Box (ICE Box), also launched on HTV-4. In addition, parts to repair the Japanese Inter-orbit Communication System (ICS), which failed in August 2011 and was since returned to Earth for repair, were launched.
HTV-4 cargo – external:
In addition to its internal cargo located in the PLC, HTV-4 launched some external cargo, attached to the EP in its ULC. The external cargo consists of two spare parts – or “Orbital Replacement Units (ORUs)” – and one new experiment for the outside of the station.
One of the ORUs launched on HTV-4 was a Main Bus Switching Unit (MBSU), which is a component of the Electrical Power System (EPS) of the ISS. Four operational MBSUs on the ISS each take inputs from two of the eight power channels on the station, which generate power via the eight large solar arrays, and distribute those two inputs to user loads.
There is already one spare MBSUs on the ISS, however, since they are such critical components, a third is desired – especially since an MBSU on the ISS has already failed, and was Removed & Replaced (R&Rd) last year during two difficult spacewalks.
The spare MBSU on HTV-4 is attached to a Flight Releasable Attachment Mechanism (FRAM) adapter plate, in order to allow it to be attached to an external platform outside the ISS, which also uses the FRAM interface. A slight difference however in the MBSU ORU launched on HTV-4 is that it did not have a thermal cover installed.
All other spare MBSUs on the ISS have thermal covers over them to protect them from the space environment, however, while MBSUs feature interfaces to allow them to be R&Rd robotically by the Dextre “robotic hand”, the thermal covers preclude this from occurring since Dextre is not able to remove the thermal cover to access the interfaces to unbolt the MBSU from its FRAM adapter plate.
Due to the ISS program’s desire to increase the use of robotics in the future, analysis was conducted that showed that the thermal covers can be removed with no adverse effects, which will allow Dextre to access the MBSU in a future R&R scenario.
The second ORU launched on HTV-4 was the Utility Transfer Assembly (UTA), again a component of the EPS. UTAs facilitate the transfer of electrical power from the solar arrays, across the rotating Solar Alpha Rotary Joint (SARJ), to the rest of the station, as simple cables cannot be used as they would become twisted.
There are two operational UTAs on the ISS, one on the Port SARJ and one on the Starboard SARJ. There is one spare currently aboard, but since they are such critical components (if one ever failed, 50 per cent of the station’s power would be lost), HTV-4 carried an additional spare.
Rounding out the external cargo on HTV-4 was the Space Test Program-Houston 4 (STP-H4) payload, a collaboration between the Naval Research Laboratory (NRL) and the Department of Defence Space Test Program (DoD STP), which features eight different experiments to test atmospheric observation, thermal control, radiation measurement, data processing, and phenomenon caused by lightning.
After HTV-4 has been berthed with the ISS, the EP (with MBSU, UTA and STP-H4 attached) will be extracted from the ULC using the SSRMS, and then maneuvered and handed off to the JEM RMS, whereupon the EP will be temporarily attached to the Japanese Exposed Facility (JEF).
The Dextre robot will then one-by-one remove the cargo from the EP and robotically install them onto their respective locations outside the ISS, all controlled entirely from the ground.
The MBSU will be installed onto an empty FRAM on the ExPrESS Logistics Carrier-2 (ELC-2), while the UTA will be installed onto an empty FRAM on ELC-4. STP-H4 will be installed onto an empty FRAM on ELC-1, following which Dextre will remove the old STP-H3 experiment from ELC-3, and place it on the EP, with the EP then being removed from the JEF and inserted back into the HTV ULC.
STP-H3 was launched to the ISS on STS-134 in May 2011, however since the experiment is now completed, it will be disposed of on HTV-4 to make room for future experiments, in the process marking the first time that a HTV has been used to dispose of external cargo.
(Images via L2, JAXA and NASA).
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