The HTV-X is an uncrewed cargo spacecraft under development by the Japan Aerospace Exploration Agency (JAXA) as the successor to the H-II Transfer Vehicle (HTV), also known as “Kounotori.” Designed to enhance Japan’s capabilities in resupplying the International Space Station (ISS), the HTV-X introduces significant improvements in payload capacity, operational flexibility, and cost efficiency.
Initiated in 2015, the HTV-X project aims to provide a more capable and cost-effective solution for ISS resupply missions. The spacecraft is being developed by Mitsubishi Heavy Industries, with contributions from Mitsubishi Electric and IHI Aerospace. The first flight, designated HTV-X1, is scheduled for launch on October 21, 2025, aboard the H3-24W launch vehicle from the Tanegashima Space Center .
Design and Specifications
The HTV-X features a modular design comprising three main sections:
- Pressurized Logistics Module (PLM): Located at the bottom of the stack, this module is similar in design to the HTV’s PLM but extended by 0.2 meters. It can carry up to 4,070 kg of pressurized cargo .
- Service Module (SM): Positioned centrally, the SM houses avionics, power systems, and propulsion. It features two solar panel arrays generating 1 kW of power and batteries with a peak output of 3 kW. The SM uses a ring of reaction control system (RCS) thrusters for propulsion, eliminating the need for a main engine .
- Unpressurized Cargo Module (UCM): At the top, the UCM is a hollow cylinder with internal shelving, significantly increasing the volume available for unpressurized cargo. It can carry up to 1,750 kg of unpressurized payload .
The spacecraft measures 8.0 meters in height and 4.4 meters in diameter, with a launch mass of approximately 16,000 kg .
Operational Enhancements
The HTV-X introduces several operational improvements over its predecessor:
- Late Cargo Loading: Cargo can be loaded up to 24 hours before launch, compared to the 80-hour requirement for the HTV. This allows for the transportation of time-sensitive items such as fresh food and experiment samples .
- Power Supply for Cargo: The HTV-X can provide power to cargo during transit, enabling the transportation of items requiring temperature control, such as refrigerated experiment samples .
- Extended Mission Duration: After completing its primary mission, the HTV-X can serve as an on-orbit experiment platform for up to 18 months, supporting various technology demonstrations .
Future Applications
Beyond ISS resupply missions, the HTV-X is being considered for roles in future space exploration initiatives. JAXA plans to utilize the HTV-X for missions such as transporting supplies to the Lunar Gateway, a planned lunar-orbiting space station under the Artemis program .
The HTV-X represents a significant advancement in Japan’s space logistics capabilities, offering enhanced payload capacity, operational flexibility, and support for future exploration missions. Its development underscores JAXA’s commitment to contributing to international space endeavors and advancing human presence in space.
