Japan launches HTV cargo vehicle on debut ISS mission

by Chris Bergin

Japan space agency JAXA has successfully launched the HTV (H-II Transfer Vehicle) on its debut flight to the International Space Station (ISS). The HTV launched on schedule from Tanegashima Space Center on an H-IIB vehicle – into an initial 200 km x 300 km orbit – at 02:01 local time on Friday (13:01 on Thursday Eastern time).


Established in 1969, the Tanegashima Space Center (TNSC) is the largest rocket-launch complex in Japan with an area of 9.7 million square meters. It is located in the south of Kagoshima Prefecture, along the southeast coast of Tanegashima Island.

The center is in charge of launch activities for Japanese rockets with various payloads, including the assembly of a launch vehicle, final inspections of payloads, and the loading of payloads onto the launch vehicle.

The H-IIB launch vehicle is a two-stage rocket using liquid oxygen and liquid hydrogen as propellant and has four strap-on solid rocket boosters (SRB-A) powered by Polybutadiene.

The H-IIB has two liquid rocket engines (LE-7A) in the first-stage, instead of one for the H-IIA. It has four SRB-As attached to the body, while the standard version of H-IIA had two SRB-As. In addition, the H-IIB’s first-stage body has expanded to 5.2m in diameter from 4m of H-IIA.

The vehicle is extended by the total length of the first stage by 1m from that of H-IIA. At the result of such enhancement, the H-IIB requires 1.7 times more propellant than the former.

HTV Flight:

The 10 ton JAXA cargo vehicle is capable of supplying a total of six tons of pressurized and unpressurized cargo to the ISS at an altitude of 407 km. Pressurized cargo can be received at the rack level (an International Standard Payload Rack (ISPR)) or sub-rack level; such as Cargo Transfer Bags (CTBs).

A2Sub-rack level cargo is integrated into HTV resupply racks (HRRs). All HRRs and ISPR equivalents are integrated into the HTV Pressurized Logistics Carrier (PLC). Unpressurized cargo is integrated onto an exposed pallet and, subsequently, into the HTV Unpressurized Logistics Carrier (UPLC).

After the HTV has delivered cargo to the ISS, waste cargo from the ISS is loaded into the HTV; and is destroyed upon reentry into the Earth’s atmosphere.

A successful debut flight of the HTV is vital for the resupply line of the ISS from a logistical standpoint, taking up some – albeit only a small fraction – of the upmass requirements that will be lost once the Space Shuttle is retired.

However, the HTV adds an extra dimension to resupplies, when compared to the Russian Progress and European ATV vehicles.

“The Space Shuttle and the HTV have the same distinctive features in that both can carry inter-vehicular supplies (daily supplies and experiment equipment) and extra-vehicular supplies (the orbital replacement unit for the ISS and exposed experiment equipment – exposed pallet),” noted HTV project manager Yoshihiko Torano.

“After the retirement of the Space Shuttle, the HTV will be the only logistic carrier for the extra-vehicular supplies and large inter-vehicular experimental equipment. Expectations for the HTV have been increasing day by day.”

This debut flight will involve numerous tests and meetings to approve the mission to proceed to an eventual arrival with the Station. Safety of the ISS is paramount for any vehicle arrival, especially when it is making its first even approach.

A total of 12 demonstrations of HTV capability are planned for this mission, with reviews on its performance taking place at key stages of the flight – including an Integrated Mission Management Team (MMT) meeting on Flight Day 6, which will result in approval for the HTV to continue on to rendezvous with the Station two to four days later.

“Free flight demonstrations are planned for all of safety critical functions before the flight phase where these functions are needed,” noted one of 16 MOD FRR presentations acquired by L2.

See here for a full preview article based on the FRR materials: http://www.nasaspaceflight.com/2009/08/nasa-ready-for-japans-htv-via-flight-readiness-review/

A3A safe termination of the approach, in the event of a problem – such as LOS (Loss Of Signal) – is one of the main priorities for the safety of the ISS, with Station crewmembers utilizing the HTV Crew Monitoring (HCM) system to check the vehicle’s status and approach, allowing for an abort if required.

“HCM is also used to monitor approach corridor. Dynamic abort corridor. Inside 300m, if LOS with MCC-H (Mission Control Center, Houston) and HTV exceeds abort corridor, crew prime to initiate HTV abort,” added one of the FRR presentations.

“Rendezvous can be terminated via an Abort or a No-Go command (i.e. no burn). Flight rules define burn Go/No-Go criteria based on system functionality and trajectory limits.

“HTV will automatically abort for numerous system failures. Ground initiated abort is required for violation of trajectory limits or certain ISS failure (e.g. loss of attitude control). No-Go (upload of 0 delta V) is only allowed for a few burns that have a 24 hour safe coast trajectory without an abort. All HTV aborts are designed to ensure a minimum X-axis delta V of 1.2 m/sec.

“Abort ensures that the HTV drift trajectory will not enter the approach ellipsoid within 24 hours of burn completion. Abort prior to 300 meters is retrograde. Abort during 300 meter yaw around is passive (i.e. no burn). Abort after 300 meter yaw around is posigrade.”

A4Once at Station, the SSRMS (Space Station Remote Manipulator) will play a key role as the vehicle arrives at the ISS, given it will not dock like previous cargo ships. Instead, the SSRMS – or Canadarm2 – will grapple the HTV, before robotic operations will gently translate the new arrival on to the Harmony module.

Further robotics will be involved when the HTV’s Exposed Pallet (EP) is handed over to the Japanese arm (JEM-RMS), which will then locate the EP on to the Exposed Facility (JEM-EF). The handoff operations between the SSRMS and JEM RMS will also be another first for the ISS.

This will be followed by Flight Day 12’s: “JEM RMS removal of EP. JEM RMS to SSRMS handoff of EP. SSRMS installation of EP into HTV.”

The bulk of the HTV work on Station relates to the transfer of the vehicle’s internal cargo – involving 70 hours of soft stowage transfer and trash (from the ISS) being stowed back on the HTV – taking place between Flight Day 12 and 28, providing there are no issues with the vehicle during these procedures.

On Flight Day 29, the SSRMS will be translated back to the HTV for grappling, before the maneuver to release position. Flight Day 30 will see the SSRMS release, ahead of the HTV’s departure burns to gain distance from the ISS.

Around two days later, the HTV will end its mission with a destructive re-entry, hopefully marking a successful conclusion to its debut mission.

L2 members: Documentation – from which the above article has quoted snippets – is available in full in the related L2 sections, now over 4000 gbs in size.

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