HTV-X by JAXA: status and timeline · The Techno Optimist

HTV-X

Resupply the ISS at about half the cost of Japan's earlier HTV ship while carrying more, and turn each ship into a free-flying lab for testing new space hardware after it leaves the station.

PilotStage 3 of 5

HTV-X1 flew in 2025-26; HTV-X2 launches no earlier than fall 2026 on an H3.

Updated 11 Mar 2026Checked 11 Oct0 updates this week

Milestones

Next · HTV-X2 launch to the ISS

HTV-X1 launches on an H3 from Tanegashima26 Oct 2025Complete.
HTV-X1 captured and berthed at the ISSOct 2025Complete.
HTV-X1 leaves the ISS after about four months6 Mar 2026Complete.
Deploys Nihon University's Ten-Koh2 satellite in free flight11 Mar 2026Complete.
HTV-X1 reenters after three months of tests26 May 2026Complete.
HTV-X2 launch to the ISSTarget Q4 2026+3 mo~~originally Q3 2026~~Current milestone.
HTV-X3 launchTarget 2027Not yet reached.

Most important updates

Upcoming

Q4 2026HTV-X2 launch to the ISS+3 mo~~originally Q3 2026~~ (next)
2027HTV-X3 launch

Current obstacles

Tied to the H3 rocketHTV-X can only fly on Japan's H3, so its schedule follows the rocket's; HTV-X2 has already slipped from summer to fall 2026 or later.
Automated docking demo may moveHTV-X2 was meant to test docking on its own instead of being caught by the arm; JAXA said in 2025 the demo may move to a later flight.

Physics limits

Single-use by designCargo ships are built to burn up with the station's rubbish. Bringing anything back needs a heat shield and recovery system, which cost mass that would otherwise be cargo.
Berthing needs a robot arm and a crewA berthed ship must hover close enough for the arm to grab it, which needs a crewed station and its arm. Docking on its own needs extra sensors and a docking port.

How it works

4 parts

Two-part ship

A cargo can on an engine room

A pressurized module reused from the old HTV holds crew supplies; a new service module carries the thrusters, solar panels, batteries and radios.

Outside cargo

Big items ride on top

Unpressurized cargo sits on top of the service module, so its size is set by the rocket's fairing rather than an internal rack.

Berthing

Caught by the station's arm

HTV-X flies to a point just below the ISS and holds still; astronauts grab it with the Canadarm2 robot arm and bolt it to a port.

Test platform

A lab after the delivery

After leaving, it can fly for up to 18 months; HTV-X1 deployed a satellite and tested a laser reflector, a light antenna and solar cells.

Spec sheet

vs HTV (Kounotori)

Spec	HTV-X	HTV (Kounotori)	Change
Launch mass	16,000 kg^R (reported)	—	—no comparable change
Pressurized cargo	4,070 kg^R (reported)	—	—no comparable change
Unpressurized cargo	1,750 kg^R (reported)	—	—no comparable change
Pressurized volume	39.6 m³^R (reported)	—	—no comparable change
Length × diameter	8 m × 4.4 m^R (reported)	—	—no comparable change
Solar power	1 kW^R (reported)	200 W (HTV)	—no comparable change
Time berthed at ISS	Up to 6 months^R (reported)	—	—no comparable change
Free flight after departure	Up to 1.5 years^R (reported)	—	—no comparable change

^R reported by the company

Update log

2 updates

Wed 11 Mar

Minor: HTV-X1 deploys Nihon University's Ten-Koh2 satellite, its first free-flight demonstrationPressTest

Fri 6 Mar

Major: HTV-X1 leaves the ISS after four months and begins three months of free-flying testsPressTest

About JAXA

The team behind HTV-X

JAXA

Martian Moons eXploration, H3 rocket

Japan's national space agency, responsible for launch vehicles, exploration spacecraft and ISS experiments. Leads Japan's space science and deep-space missions.

JAXA operates Japan's H3 heavy-lift launch vehicle and leads scientific deep-space missions.
The Martian Moons eXploration (MMX) spacecraft launches on H3 F10 on October 20, 2026, to return samples from Phobos.
MMX is a collaborative mission with NASA, ESA, CNES and DLR.

global.jaxa.jp (opens global.jaxa.jp)Company profile →

Founded: 200323 yrs
Headquarters: Japan
Status: Government
Valuation: government
Works in: SpaceflightPlanetary missions
Coverage: 2 programs · 3 updateslatest 20 Aug 2026checked 11 Oct
Partners: NASA (opens nasa.gov)European Space Agency (opens esa.int)French Space Agency (opens cnes.fr)German Aerospace Center (opens dlr.de)
People: Hiroshi Yamakawa (opens global.jaxa.jp)President

Spec

HTV-X

HTV (Kounotori)

Change

Launch mass

16,000 kg^R (reported)

—

—no comparable change

Pressurized cargo

4,070 kg^R (reported)

—

—no comparable change

Unpressurized cargo

1,750 kg^R (reported)

—

—no comparable change

Pressurized volume

39.6 m³^R (reported)

—

—no comparable change

Length × diameter

8 m × 4.4 m^R (reported)

—

—no comparable change

Solar power

1 kW^R (reported)

200 W (HTV)

—no comparable change

Time berthed at ISS

Up to 6 months^R (reported)

—

—no comparable change

Free flight after departure

Up to 1.5 years^R (reported)

—

—no comparable change