HTV-X

HTV-X, also known as the New Space Station Resupply Vehicle, is a Japanese cargo spacecraft of JAXA. Designed as the successor to the H-II Transfer Vehicle for International Space Station resupply missions, it was first launched on 26 October 2025.

Background

The HTV-X is manufactured by Mitsubishi Heavy Industries with contributions from Mitsubishi Electric. IHI Aerospace provides the propulsion system and American company Sierra Nevada Corporation provides the Common Berthing Mechanism and hatch kit.

Design

HTV-X consists of three main modules, arranged from top to bottom on the launch pad:

Unpressurized Cargo Support System : Unpressurized cargo is mounted externally on top of Service Module, rather than inside the spacecraft, allowing larger items limited only by the launch vehicle fairing and increasing capacity compared to the original HTV.
Service Module : A unit capable of independent operation. It includes two deployable solar arrays generating 1 kW of power, batteries with a 3 kW peak output, and upgraded communications with a 1 Mbit/s link alongside the previous 8 kbit/s channel. HTV-X omits a main engine, using a ring of reaction control system thrusters for propulsion, and mounts some components externally for easier astronaut access.
Pressurised Module : A section with an internal volume of and a payload capacity of. Identical in design to the original HTV, it is positioned at the bottom of the stack to improve mass distribution.

The HTV-X measures in length. It is launched by the H3 rocket with a payload fairing widened to , and Payload Adapter Fitting widened to to allow increased structural strength and accommodate the side hatch.
Reusing the pressurised logistics module design from previous HTV reduces development cost and risk. Concentrating RCS thrusters and solar arrays on the service module simplifies wiring and piping, lowering weight and manufacturing cost. External loading of unpressurised cargo enables larger payloads, limited only by the fairing. The goal is to halve costs while maintaining or extending HTV capabilities. Simplification was expected to reduce launch mass to from HTV’s, while increasing maximum cargo mass to from.
Other proposed payloads for replacing the unpressurised cargo module during ISS resupply missions include external sensor packages, an IDSS connector for automated docking, satellite rendezvous trials, piggyback small satellites, station return capsules, assembly of lunar mission modules, and acting as a space tug to store resources such as recyclable materials, excess propellant, and spare parts in orbit for future use.

History

In May 2015, Japan's Ministry of Education, Culture, Sports, Science and Technology announced a proposal to replace the HTV with an improved, cost-reduced version preliminarily called HTV-X. The proposal of HTV-X in 2015 was as follows:

To re-use the design of HTV's Pressurised Logistics Carrier as much as possible, except for adding a side hatch for late cargo access after the spacecraft-launch vehicle integration.
To replace the Unpressurised Logistics Carrier, Avionics Module, and Propulsion Module with a new Service Module.
To load the unpressurised cargo on top of the Service Module rather than inside the spacecraft.

In December 2015, the plan to develop HTV-X was approved by the Strategic Headquarters for Space Policy of the Cabinet Office, targeting launch in fiscal year 2021 for the flight of HTV-X1 by the H3 Launch Vehicle., NASA's Flight Planning Integration Panel had set the launch of HTV-X1 for February 2022.
With the Japan-US Open Platform Partnership Program agreement in December 2015 to extend cooperation on ISS operations through 2024, Japan will provide its share of ISS operation costs with the form of transportation by HTV-X, and also possible use of a small return capsule.
An early concept included a side hatch of Pressurised Module for late cargo loading, but the final 2021 design removed it; late access now uses the ISS docking hatch, requiring a Payload Adapter Fitting with access opening on the H3 rocket’s upper stage.
Due to the delay of H3 development, the launch of the first HTV-X slid to 2025. HTV-X1 was launched successfully on 26 October 2025.
, an evolved version of HTV-X called HTV-XG is being considered for transporting cargo to the Lunar Gateway as part of the Artemis program.

Flights

, three flights are planned to resupply the ISS.

HTV	Launch date/time	Berth date/time	Carrier rocket	Reentry date/time	Outcome
HTV-X1	26October 2025, 00:00:15	30October 2025, 11:10	H3-24W	January 2026
HTV-X2	JFY2026		H3-24W
HTV-X3	JFY2026		H3-24W

, HTV-X4 and HTV-X5 are tentatively planned for launch in JFY2027–JFY2029.