HTV-X1

HTV-X1

Mission type	ISS resupply
Operator	JAXA
COSPAR ID	2025-241A
SATCAT no.	66174
Website	Official website (in Japanese)
Mission duration	5 days, 1 hour and 14 minutes (in progress) ~9 months (planned) [1]
Spacecraft properties
Spacecraft type	HTV-X
Manufacturer	Mitsubishi Heavy Industries
Launch mass	~14,500 kg (32,000 lb) [a]
Dimensions	8.0 × 4.4 m (26.2 × 14.4 ft)
Start of mission
Launch date	26 October 2025, 00:00:15  UTC (09:00:15  JST) [2]
Rocket	H3-24W, Flight 7 [b] [2] [3]
Launch site	Tanegashima, LA-Y2
Contractor	Mitsubishi Heavy Industries
Orbital parameters
Reference system	Geocentric orbit
Regime	Low Earth orbit
Inclination	51.6°
Berthing at ISS
Berthing port	Harmony nadir
RMS capture	29 October 2025, 15:58 UTC
Berthing date	30 October 2025, 11:10 UTC
Unberthing date	January 2026 (planned)
RMS release	January 2026 (planned)
Time berthed	14 hours and 4 minutes
Cargo
Mass	~4,250 kg (9,370 lb)
Pressurised	~4,000 kg (8,800 lb) [1] [4]
Unpressurised	~250 kg (550 lb) [1] [4] [a]
Mission insignia HTV (Kotonotori) ←  Kounotori 9 HTV-X2  → HTV-X HTV-X2  →

HTV-X1 is 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. ^[2]

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

Launch

Initially, HTV-X1 was scheduled to be launched on 21 October 2025. ^[7] Due to the unfavorable weather forecast, the launch was postponed. ^[8]

HTV-X1 was launched successfully on 26 October 2025, 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 the Tanegashima Space Center. ^[9] This was the first flight of an H3 rocket with four solid rocket boosters and the first with a wide payload faring. ^[10]

Cruising, Rendezvous with ISS

On 29 October, JAXA astronaut Kimiya Yui, with help from Zena Cardman, captured the spacecraft using Canadarm2 at 15:58 UTC. JAXA astronaut Akihiko Hoshide served as CAPCOM during the docking from the Mission Control Center at NASA's Johnson Space Center in Houston, Texas. ^[11] Ground teams at NASA's Johnson Space Center and JAXA's Tsukuba Space Center completed the berthing to the nadir (Earth facing) port of the Harmony module at 11:10 UTC on 30 October. ^[12] During the approach for docking the HTV-X1 performed a demonstration of retreat, commanded by the ISS crew. ^[13]

Notes

1. Pre-launch press briefing ^[5] (41:30–44:30) "初号機ということで、14.5弱ぐらいの質量でHTV-X1号機は打ち上げさせていただいてます。[…]これが出来るようになると、フルの16トンが打ち上がるというような使い方になります。[…]暴露カーゴの付きましては、大きく搭載しないという前提で開発しておりましたので、その分1.5トンは減らした打ち上げとなっている。"
2. Although designated F7 (Flight 7), it was the rocket's sixth flight.
3. Pre-launch press briefing ^[5] (40:52–41:20) "HTV-XやGTOのミッションでより大きな打ち上げ能力が必要になった場合にオプションとして使う[…]"
4. Pre-launch press briefing ^[5] (39:20–40:28)

References

1. HTV-X1号機ミッションプレスキット (PDF) (in Japanese). JAXA. Retrieved 10 October 2025.
2. "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.
3. ２０２５年度ロケット打上げ計画書 新型宇宙ステーション補給機１号機（HTV-X1）／H3 ロケット 7 号機（Ｈ３・Ｆ７) (PDF) (in Japanese). JAXA. August 2025. Retrieved 9 September 2025.
4. G. D. Krebs. "HTV-X1, 2, 3 (Kotonotori 1, 2, 3)". Gunter's Space Page. Retrieved 25 August 2025.
5. "新型宇宙ステーション補給機1号機（HTV-X1）／H3ロケット7号機 打上げ前ブリーフィング" [HTV-X1 / H3 flight 7 pre-launch press briefing](video). youtube.com (in Japanese). JAXA.
6. "H3 Flight No.7 Press Kit" (PDF) (in Japanese). JAXA. 16 October 2025. p. 138. Retrieved 26 October 2025.
7. "Launch Schedule of New unmanned cargo transfer spacecraft1（HTV-X1） aboard the 7th H3 Launch Vehicle (H3 F7)". JAXA. 22 August 2025. Retrieved 30 October 2025.
8. Foust, Jeff (25 October 2025). "H3 launches first HTV-X cargo spacecraft". Space News. Retrieved 30 October 2025.
9. "Launch Result of New unmanned cargo transfer spacecraft1(HTV-X1) aboard the 7th H3 Launch Vehicle (H3 F7)". JAXA. 26 October 2025. Retrieved 30 October 2025.
10. Yamaguchi, Mari (26 October 2025). "Japan successfully launches new cargo spacecraft to deliver supplies to International Space Station". AP News. Retrieved 30 October 2025.
11. "Japan's new resupply spacecraft docks at International Space Station". The Japan Times. 30 October 2025. Retrieved 30 October 2025.
12. "Successful berthing of the HTV-X1 to the International Space Station (ISS)". JAXA. 30 October 2025. Retrieved 31 October 2025.
13. Wall, Mike (29 October 2025). "Japan's 1st HTV-X cargo craft arrives at the International Space Station". Space.com. Retrieved 30 October 2025.