Japan has successfully launched the first of its next-generation cargo spacecraft, the HTV-X1, destined for the International Space Station (ISS). The launch occurred on an H3 rocket from the Tanegashima Space Center at 8 p.m. Eastern time on October 25, following weather-related postponements. This marked the inaugural flight of the H3-24W variant of the H3 rocket, equipped with twin first-stage engines, four solid-rocket boosters, and an expanded payload fairing.
Approximately 14 minutes after liftoff, the HTV-X1 detached from the rocket's upper stage, and its solar arrays were deployed within 10 minutes. The HTV-X represents an enhanced iteration of the HTV cargo vehicle, previously utilized by the Japan Aerospace Exploration Agency (JAXA) for ISS cargo transport between 2009 and 2020. Weighing 16 tons at full capacity, the new spacecraft can transport approximately six metric tons of cargo, a 50% increase compared to its predecessor. This includes four tons of pressurized cargo and two tons of unpressurized cargo.
The HTV-X incorporates several design advancements, featuring a pressurized module with a 60% larger volume than the original. It employs deployable solar arrays, providing 50% more power compared to the body-mounted panels of the previous HTV. The unpressurized cargo is now positioned atop the spacecraft, enhancing overall capacity. The HTV-X1 is carrying around 4.5 tons of cargo, including space station hardware, experiments, and supplies. This includes six cubesats slated for deployment from the Kibo module's airlock.
The planned arrival of HTV-X1 at the ISS is October 29, where it will be docked to the station's Harmony module using the Canadarm2 robotic arm. The spacecraft is designed to remain at the ISS for up to six months, although JAXA officials mentioned at an Oct. 19 briefing that the exact duration of its stay had not been determined. After departing the station, HTV-X1 will undergo technology demonstrations in low Earth orbit for roughly three months. These tests will include releasing a cubesat, evaluating a laser retroreflector on the spacecraft, and deploying a structure with a flat-panel antenna and solar cells to assess technologies for future space-based solar power systems.
Before its eventual reentry and burnup over the South Pacific Ocean, the HTV-X will be filled with waste material from the ISS. Currently, there are at least three planned HTV-X missions to the ISS. JAXA has also proposed a modification of the spacecraft to transport cargo to the lunar Gateway.