In recent years, Japanese space policy has been shaped by the US-Japan alliance and intensifying great power competition.

[1] After World War II, many aeronautical engineers lost their jobs as aircraft development was banned under the US Occupation of Japan.

However, following Japan's participation in the International Geophysical Year, the focus of the rocket project shifted towards space engineering.

[6] Iterations of the Pencil Rocket eventually increased in size to such a degree that experimentation within Kokubunji was deemed too dangerous.

In 1958, the Kappa 6 rocket reached an altitude of 40 km (25 mi) and the collected data allowed Japan to participate in the International Geophysical Year.

The Science and Technology Agency subsequently focused its studies of Kappa launches on gathering technical information that would allow the new rockets to achieve higher altitudes.

[9] Although development on the Lambda rockets proceeded slowly, there were incremental improvements over the next couple of years; such as the new capability to reach an altitude of 2,000 kilometres (1,200 mi), getting closer to that required for the launch of a satellite.

[2] The failure was reportedly caused by a shock (from the sudden combustion of residual fuel) resulting in parts colliding.

All stages were able to work with the M-3S rockets, and this technology resulted in a string of successful satellite launches into orbit, reaching higher altitudes each time.

However, because of the pressing need for practical and commercial rockets, the Japan-U.S. space agreement was signed and technology from the United States was introduced.

However, the liquid rocket's orbital payload capacity was low, and the ability to manufacture satellites was not as strong as the United States's.

Imported components from the United States were black box systems, which Japanese engineers were not allowed to inspect.

[14] The LE-5 was characterized by its use of high-efficiency liquid hydrogen and oxygen propellant and the ability to re-ignite, which made it more capable than the N-II upper stage.

After successfully developing the LE-5 rocket engine, and taking into account the technological progress made in Japan up to that point, NASDA decided to develop a new rocket model, which would exclusively make use of liquid fuel made in Japan in order to foster the new space technologies being researched in the country.

Some of the problems brought about because of this propulsion system were, among others, parts damaging due to vibrations, concerns about the durability of the materials used, and explosions resulting from hydrogen leaks, all of which took quite some time to resolve.

From this point onward a period of inactivity for rocket research started to manifest, causing the launch of Nozomi, a mission intended to study Mars, to be postponed for two years.

These failures along with recent administrative reforms prompted the government to propose a motion to integrate the several space agencies of the time into a single organization.

In the process, a plan was set forward to strengthen cooperation between these organizations, emphasize functionality above all, and improve the efficacy of the organizational structure.

During this time the Institute of Space and Astronautical Science issued an apology for the unsuccessful H-II launches, then proceeded to start the development of the rocket all over again, with a special focus on the simplicity of the new design.

In 1997, the HOPE project was downscoped to be simply an uncrewed cargo vehicle for launches to the International Space Station, about the same time as the H-II launcher was downscaled to the smaller H-IIA.

The H-IIA is a derivative of the earlier H-II rocket, substantially redesigned to improve reliability and minimize costs.

In 2009 the H-IIB rocket, which was developed to have a higher payload capacity than H-IIA, was successfully launched to send equipment and supplies to the International Space Station.

[19] In order to launch small satellites more easily and more cheaply than the M-V solid fuel rocket, a successor known as Epsilon was also developed.

Japanese space law was amended in 2008 to allow the deployment of military satellites for reconnaissance and missile defense only.

Hayabusa was launched in 2003 from Uchinoura Space Center aboard an M-V rocket, returning to Earth in 2010 with samples from 25143 Itokawa.

[26] In June 2014, the Ministry of Education, Culture, Sports, Science and Technology said it was considering a space mission to Mars.

In a ministry paper, it indicated uncrewed exploration, crewed missions to Mars, and long-term lunar settlement as objectives for which international cooperation and support were going to be sought.

[27] In December 2021, Prime Minister Fumio Kishida said during a government meeting on space development strategy "We are aiming to realize a lunar landing by a Japanese astronaut in the latter half of the 2020s".

The momentum carried by governmental reforms and administrative changes during the 1990s and early 2000s, aggravated as well by the multiple failed launches of Japanese rockets, made it necessary to strengthen cooperation between the different space organizations, prompting the unification of these institutions under the Japan Aerospace Exploration Agency (JAXA).

[17][30] Currently, JAXA operates as part of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), and is the main entity responsible for Japan's space development.