Payload
As the maiden flight, HTV-X1 is flown as a technical demonstration and was thus not loaded to maximum capacity, with a deficit of approximately 1,500 kilograms (3,300 lb) deducted mainly from unpressurised cargo. [a] Attaining the full design capacity of the HTV-X, 4,069 kg (8,971 lb) pressurised and 1,750 kg (3,860 lb) unpressurised, [4] requires use of the H3 rocket's optional [c] Autonomous Flight Safety System, which enables the flight to be aborted autonomously if anomalies are detected while the rocket is out of range of ground control centers. This system was first tested, but not fully operational during HTV-X1's launch on H3 Flight 7. [b] [6] [d]
HTV-X1 is scheduled to remain berthed to the ISS for up to six months, during which cargo will be transferred to the ISS and waste loaded onto the HTV-X. [1]
Pressurised cargo
HTV-X1 will deliver the following pressurised cargo to the International Space Station (ISS): [1]
- Crew supplies
- Kibō system components:
- LED light unit for JEMRMS
- AEP2 (Airlock Electronics Package 2), a replacement of the airlock control unit
- DRCS (Demonstration of Removing Carbon Dioxide System)
- NORS (Nitrogen/Oxygen Recharge System) tank
- RST (Water Resupply Tank)
- Science and technology experiments:
- TUSK (Test facility for lab-automation system in Kibo)
- Asian Try Zero-G 2025: experiments proposed by students from Asia-Pacific region
- CubeSats to be deployed into orbit from the ISS: CORAL, Gxiba-1, HMU-SAT2, KNACKSAT-2, LEOPARD, UiTMSAT-2
- Private-sector payloads under JAXA's fee-based Kibō commercial utilization program: [1]
- Sake brewery Dassai [ ja] will attempt sake fermentation in space using equipment co-developed with Mitsubishi Heavy Industries
- The Japanese licensee for outdoor apparel brand CHUMS [ ja] will film advertising and educational videos involving its mascot character in stuffed toy form
- Rice seeds from Kazo, Saitama are being sent to the ISS and will be subsequently recovered for cultivation on Earth in a local agriculture and education initiative by DigitalBlast
- Japan Airlines is sending "passports" of customers to be stamped and photographed on board the ISS before being returned to their owners
- Plant seeds sent to the ISS will be returned to Earth to be cultivated and flowered for display at the World Horticultural Exhibition 2027
- Stuffed toys of four VTubers and acrylic prints of 43 VTubers are being delivered to Kibō for live streaming and commemorative photo shoot
- A technology demonstration will showcase the deployment and operation of small, automatic, distributed sensors intended for monitoring environmental quality on board future commercial space stations
Unpressurised cargo
- i-SEEP (IVA-replaceable Small Exposed Experiment Platform)
Technology demonstration payloads
Apart from its primary cargo mission, the HTV-X is also capable of serving as an orbital platform for conducting experiments and technology demonstrations for up to one and a half years following departure from the ISS. The technology demonstration mission phase for HTV-X1 is planned to last three months, and involves the following payloads: [1]
- H-SSOD, a small satellite deployer that will release the CubeSat Ten-Koh 2 at an altitude of approximately 500 km. This will demonstrate HTV-X's capability to deploy microsatellites from a higher orbit than the ISS, wich offers a longer operational lifetime (with respect to orbital decay) and opens up new potential applications for deployed satellites.
- Mt.FUJI, a technology demonstration for satellite laser ranging (SLR). Apart from measuring distance from the ground to the HTV-X, this will be the time that the accuracy of spacecraft attitude determination using SLR is evaluated against actual spacecraft telemetry.
- Technologies related to construction of large space structures for future space solar power generation systems and other applications:
- testing of a deployable lightweight panel mechanism and measurement of its structural characteristics
- DELIGHT, a lightweight flat antenna mounted to the deployable structure
- SDX, a next-generation solar cell technology demonstration
Operation
Development
The HTV-X project was formally initiated in 2017, and manufacturing of a proto-flight model began in 2018. [7] The Pressurized Module (PM) for HTV-X1 was assembled by Mitsubishi Heavy Industries in Aichi Prefecture and shipped to the Tanegashima Space Center (TNSC) in August 2022. [1] [8] The Service Module (SM) was assembled by Mitsubishi Electric in Kanagawa Prefecture and delivered to TNSC in January 2025. [1] [8]
At TNSC, the PM and SM were integrated, and a full system checkout was completed in May 2025. [1] The modules were then separated for cargo and propellant loading beginning in August 2025. [1] The PM and SM were reintegrated and encapsulated within the payload fairing on 9 October, and mated to the H3 launch vehicle on 14 October. [5] Late-access cargo, including perishable food, was loaded on 19 October. [9]
Launch
HTV-X1 was initially scheduled for launch on 21 October 2025. [10] The launch was postponed due to unfavorable weather conditions. [11]
HTV-X1 was successfully launched on 26 October 2025 at 00:00:15 UTC (09:00:15 JST) aboard Flight 7 [b] of the H3 launch vehicle from Launch Area 2 of the Yoshinobu Launch Complex at TNSC. [12] This mission marked the first H3 flight to use four solid rocket boosters and the first with a wide payload fairing. [13]
Operations while berthed to the ISS
The hatch of the Pressurized Module was opened at approximately 12:37 UTC on 30 October. [18]
On 6 November, the Canadarm2 removed the i-SEEP payload from the unpressurized cargo deck and transferred it to the robotic JEMRMS arm for installation inside the Kibō module’s airlock. [19]
Departure from the ISS and post-berthing operations
Following its departure from the ISS, HTV-X1 is scheduled to conduct a series of technology demonstration missions lasting approximately three months. [1]
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