HTV-X1 was the first flight of the HTV-X series, serving as a technical demonstration mission of the new uncrewed expendable cargo spacecraft. It launched on 26 October 2025.
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 (3,300lb) deducted mainly from unpressurised cargo. Attaining the full design capacity of the HTV-X, 4,069kg (8,971lb) pressurised and 1,750kg (3,860lb) unpressurised, requires use of the H3 rocket's optional 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.
HTV-X1 remained berthed to the ISS for four months, during which cargo was transferred to the ISS and waste loaded onto the HTV-X.
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Unpressurised cargo
i-SEEP3B (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:
H-SSOD, a small satellite deployer that will release the CubeSatTen-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, which 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:
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, originally intending to launch the first flight in JFY2021, though eventually it was delayed to 2025 due to the delay of H3 launch vehicle development. Manufacturing of a proto-flight model began in 2018. 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. The Service Module (SM) was assembled by Mitsubishi Electric in Kanagawa Prefecture and delivered to TNSC in January 2025.
At TNSC, the PM and SM were integrated, and a full system checkout was completed in May 2025. The modules were then separated for cargo and propellant loading beginning in August 2025. 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. Late-access cargo, including perishable food, was loaded on 19 October.
Launch
HTV-X1 was initially scheduled for launch on 21 October 2025. The launch was postponed due to unfavorable weather conditions.
HTV-X1 was successfully launched on 26 October 2025 at 00:00:15UTC (09:00:15JST) aboard Flight7 of the H3 launch vehicle from Launch Area2 of the Yoshinobu Launch Complex at TNSC. This mission marked the first H3 flight to use four solid rocket boosters and the first with a wide payload fairing.
Cruise and rendezvous with the ISS
On 29 October 2025, JAXA astronaut Kimiya Yui, assisted by Zena Cardman, captured the spacecraft using the robotic Canadarm2 at 15:58UTC. Akihiko Hoshide served as CAPCOM from NASA’s Mission Control Center at the Johnson Space Center in Houston, Texas. Ground teams at NASA and JAXA's Tsukuba Space Center completed berthing to the nadir (Earth-facing) port of the Harmony module at 19:43UTC. Power transfer from the ISS to HTV-X1 was confirmed at 11:10UTC on 30 October. During the approach, the spacecraft conducted a commanded retreat maneuver as part of a proximity operations demonstration.
Operations while berthed to the ISS
The hatch of the Pressurized Module was opened at approximately 12:37UTC on 30 October.
On 4 November, the Canadarm2 removed the i-SEEP3B payload from the unpressurized cargo deck and transferred it to the robotic JEMRMS arm for installation inside the Kibō module’s airlock.
Departure from the ISS and post-berthing operations
HTV-X1 was grasped by Canadarm2 and detached from Harmony nadir port at 19:26, 5 March 2026. While held by Canadarm2, HTV-X1 performed the demonstration of the laser ranging device for automated docking.
HTV-X1 left the ISS on 6 March 2026 at approximately 17:00 UTC.
Following its departure from the ISS, HTV-X1 conducted a series of technology demonstration missions lasting approximately three months. HTV-X1 transferred to a higher orbit around 500 km height, and Ten-Koh2 was deployed into orbit from HTV-X1 on 11 March 2026. Technology demonstration of Mt.FUJI was performed since 15 March. Demonstration of DELIGHT was performed since 13 April.
HTV-X1 was disposed by destructive reentry to the Earth atmosphere around 14:09 UTC on 26 May 2026.
123"H3ロケット7号機による新型宇宙ステーション補給機1号機（HTV-X1）の 打上げ結果"[Launch result of new unmanned cargo transfer spacecraft HTV-X1 aboard H3 rocket flight 7] (Press release) (in Japanese). JAXA. 26 October 2025.
↑Sasaki, Hiroshi; Ito, Norimasa (9 February 2021). 新型宇宙ステーション補給機（HTV‐X）の開発状況について(PDF) (in Japanese). Ministry of Education, Culture, Sports, Science and Technology. Retrieved 7 November 2025.
Launches are separated by dots ( • ), payloads by commas ( , ), multiple names for the same satellite by slashes ( / ). Crewed flights are underlined. Launch failures are marked with the † sign. Payloads deployed from other spacecraft are (enclosed in parentheses).
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