Japanese Launch Options: H3, KAIROS and ZERO Compared

Japan's main launch option for satellite operators is JAXA's H3, joined by two private small launchers working towards orbit: Space One's KAIROS and Interstellar Technologies' ZERO. H3 carries at least 4 t to a 500 km sun-synchronous orbit and returned to successful flights in 2026 after a failure in December 2025. KAIROS has flown three times without reaching orbit, and ZERO is waiting for its new launch pad in Hokkaido, which is expected to be finished in the first quarter of 2027.

This guide summarises payload, flight record, launch sites and booking for all three, based on what JAXA and the two companies publish.

H3: Japan's mainstay launch vehicle

H3 was developed by the Japan Aerospace Exploration Agency (JAXA) together with Japanese industry as the successor to H-IIA. JAXA's stated goals are high flexibility, high reliability and lower cost than H-IIA. On Carrier Space the rocket is listed under Mitsubishi Heavy Industries.

Configurations: two or three LE-9 first stage engines, zero, two or four SRB-3 solid boosters and a short or long fairing. The standard H3-24L is 63 m tall with the long fairing.
Payload: at least 4 t to a 500 km SSO and at least 6.5 t to GTO (ΔV 1,500 m/s), according to JAXA.
Price target: JAXA gives a target price of about 5 billion yen for the light configuration without solid boosters, which is mainly intended for low Earth orbit.
Preparation time: JAXA says H3 cuts the launch preparation time for vehicle assembly and satellite encapsulation by more than half compared with H-IIA.
Launch site: Yoshinobu Launch Complex at the Tanegashima Space Center.

Recent H3 flights

22 December 2025, flight No. 8: the second stage engine failed to start normally on its second ignition, and the QZS-5 navigation satellite could not be placed in its planned orbit. JAXA set up a special task force.
12 June 2026, flight No. 6: the test flight of the H3 30 configuration. The second stage reached its planned orbit and released several small satellites, among them PETREL and STARS-X.
11 August 2026, flight No. 9: QZS-7 was separated about 29 minutes after lift-off and injected into its planned orbit.
Next: flight No. 10 with JAXA's Martian Moons eXploration (MMX) spacecraft is scheduled for 20 October 2026, with a reserve period until 7 November 2026.

The June 2026 flight shows that H3 can also carry small satellites alongside a test vehicle. For a commercial slot, ask early about available flights.

Space One: KAIROS

Space One is a private company that builds the solid-fuel KAIROS rocket and operates its own launch site, Spaceport Kii, in Kushimoto, Wakayama Prefecture, on the southern tip of Honshu.

Payload: 150 kg to SSO (97° inclination, 500 km) and 250 kg to LEO (33° inclination, 500 km).
Schedule: within 12 months from contract to launch for a primary payload, with satellite delivery four days before launch.
Why solid: Space One argues that a solid rocket can be stored fuelled and launched at short notice, with a simple structure and few components.

KAIROS flight record

13 March 2024, first flight: flight terminated during the climb, before reaching orbit.
18 December 2024, second flight: flight terminated at a later phase of the ascent, again without reaching orbit.
5 March 2026, third flight: flight terminated during the ascent; Space One said it was analysing the flight data.

Space One continues to sign customers. In August 2026 it announced a memorandum of understanding with Sarmony that targets a KAIROS launch opportunity in 2028. Until KAIROS has reached orbit, plan it as an option with schedule risk and keep an alternative. Profile: KAIROS.

Interstellar Technologies: ZERO

Interstellar Technologies flew the suborbital MOMO rocket to space three times and is now building ZERO, a two-stage orbital rocket for dedicated and rideshare missions.

Payload: up to 1,000 kg to LEO, with available inclinations from 42.2° to SSO.
Vehicle: 32 m long, 71 t, a 5.0 m tall fairing, nine sea-level Cosmos engines and one vacuum Cosmos engine burning liquid biomethane and liquid oxygen.
Launch site: Launch Complex 1 at Hokkaido Spaceport in Taiki. As of July 2026, pad, flame trench and propellant plant were in their final construction stages, with completion expected in the first quarter of 2027.
First flight customers: Interstellar has announced seven payloads for the maiden flight, most of them CubeSats from universities and startups.
Integration partner: in July 2025 Interstellar and Exolaunch signed a strategic partnership that makes Exolaunch the preferred provider of separation systems for ZERO.

Interstellar publishes a Payload User's Guide for ZERO that anyone can download. Profile: ZERO.

Payload capacity at a glance

KAIROS: 150 kg to 500 km SSO, 250 kg to 500 km LEO at 33°.
ZERO: up to 1,000 kg to LEO (not yet flown).
H3: at least 4,000 kg to 500 km SSO, at least 6,500 kg to GTO.

Our overview of launch vehicles by payload capacity compares these figures with rockets from other countries, and our small launcher comparison covers alternatives to KAIROS and ZERO.

How to book a launch in Japan

H3: ask about secondary payload opportunities on upcoming flights or a dedicated launch for a large satellite.
KAIROS: contact Space One directly; it quotes 12 months from contract to launch for a primary payload.
ZERO: use the booking page and the Payload User's Guide on the Interstellar website, or go through Exolaunch.
Compare first: use our launch provider checklist and send one request to several providers through the Carrier Space request form.

FAQ

What is Japan's main launch vehicle?

H3, developed by JAXA with Japanese industry as the successor to H-IIA. It launches from the Tanegashima Space Center.

How much does an H3 launch cost?

JAXA names a target price of about 5 billion yen for the light configuration without solid boosters. Actual contract prices are not published.

Have KAIROS or ZERO reached orbit?

Not as of October 2026. Space One's KAIROS flew in March 2024, December 2024 and March 2026 and terminated each flight before orbit. Interstellar's ZERO has not flown yet.

Can foreign satellites launch on Japanese rockets?

Yes. Interstellar describes the payloads on ZERO's first flight as coming from institutions and startups around the world. Check export and licensing requirements for your satellite early.

Which Japanese rocket suits a CubeSat?

ZERO is designed for small satellites and CubeSats and offers sample configurations with up to five CubeSats. KAIROS carries up to 150 kg to SSO.

Sources

Cover image: Mount Fuji, north of Suruga Bay and west of Tokyo, photographed from the International Space Station on 19 April 2021 (iss065e001158). Credit: NASA.