Japan’s Space Program, Part 1: Professor Itokawa, the World’s Smallest Rocket, and the Satellite Boom

When Imperial Japan was defeated in 1945, its economic and technological development became heavily dependent on the United States, which now had the power to shape the future of its former adversary. The new generation of Japanese politicians was wise enough to play by American rules, gradually gaining access to licenses to establish and develop Japan’s aerospace sector.  

Japan’s space program is an excellent example of the peaceful use of space, with a strong emphasis on unmanned spacecraft and autonomous systems. Today, we will explore how the Land of the Rising Sun gradually achieved such progress.

Pencil: launch of the world’s smallest rocket

The Japanese decided to start small—quite literally. In mid-1954, the engineering department of the Institute of Industrial Science at the University of Tokyo began developing the so-called “Pencil” rocket. The name was no coincidence: the rocket stood only 23 cm tall, slightly longer than a regular pencil. Its fuselage was made of brass, steel, and duralumin, with just 13 grams of fuel. This allowed the rocket to generate approximately 30 kg of thrust, with a maximum speed ranging from 110 to 140 m/s, depending on the specific model.

The Pencil rocket’s chief developer was Professor Hideo Itokawa, who led the Avionics and Supersonic Aerodynamics (AVSA) research group. During World War II, Itokawa worked on the Ki-43 Hayabusa fighter aircraft project and was involved in aeronautical research.

Surprisingly, the scientist had no plans to launch his rocket into space until February 1955, when a colleague’s suggestion sparked his interest in developing a Japanese launch vehicle for participation in the International Geophysical Year (IGY). The Pencil rocket was intended as an experimental prototype to test essential technologies on Earth in preparation for a future launch that Japan aimed to achieve by 1958.

Since the Pencil was an experimental rocket, it was launched horizontally with a single goal—to pass through several paper screens stretched along its flight path. Starting on April 12, 1955, a total of 29 Pencil rockets were launched, and each was successful. The rockets took off from specialized launch platforms, traveling distances of 10 to 20 meters while piercing the paper screens. After the success of the first single-stage version of the Pencil, the AVSA group moved on to developing a two-stage variant measuring 46 cm in length, a version without tail fins, and an extended single-stage model with a 30 cm fuselage, which, in a vertical launch, reached an altitude of 600 meters.

Conducting vertical rocket launch experiments proved to be a real challenge for Itokawa’s team, as safety regulations required them to be carried out near the coastline to ensure that spent rockets or their debris would fall into the sea. But, by the mid-1950s, most remote coastal areas of Japan’s prefectures were occupied by the U.S. military. The only exceptions were the islands of Sado and Michikawa, as well as the Oga Peninsula. After visiting all three potential launch sites, Itokawa chose Michikawa Beach in Akita Prefecture, where a launch pad was set up. This site remained Japan’s primary rocket testing range until 1962.

Thus, the Pencil rocket became Japan’s first experimental rocket. The series of aeronautical studies conducted with it enabled Professor Itokawa and his research team to move on to developing the next generation of rockets, which had the potential to reach outer space.

Aiming for Orbit: the Kappa rocket

After the success of the Pencil’s horizontal launches, the AVSA research group reached a crossroads. Their engineers outlined two possible paths for further development: larger and more powerful ground-launched rockets (later named Kappa) and a type of air-launched rocket that would be deployed from a balloon lifted several kilometers above the Earth. Design work on both projects began almost simultaneously.  

The rocket intended for balloon launches was called “Rockoon.” However, the Rockoon was not an original development by Dr. Itokawa’s engineering team: the first concepts for such rockets had been developed by the Americans in the spring of 1949, when tests for the “Aerobee” project began aboard the USS Norton Sound. Six years later, similar rockets (Loki I and Deacon) were launched from balloons near Greenland. However, the Rockoon ultimately proved too complex to realize, and the project was scrapped a year after it was approved.  

This left ground-launched rockets as the only alternative. Pencil’s direct successor was the “Baby” rocket, which came close to reaching the speed of sound. The Baby rockets were 120 cm long and featured an innovative design element: an onboard telemetry system housed in the rocket’s nose. Three main versions were developed: S (a test version), T (equipped with telemetry), and R (fitted with a parachute for soft recovery). The parachute system enabled Japan’s first successful recovery of launched equipment. All three versions of the Baby rocket were tested in 1955, reaching a maximum altitude of 6 km.  

One day, during the testing process, a haiku appeared on the board where the Michikawa range personnel listed their daily tasks. The author was none other than “Dr. Rocket” himself: Hideo Itokawa, nicknamed after his early successes. The haiku read:  

The skies are high, yet
My imagination soars
Above autumn seas

And indeed, the entire AVSA team seemed to realize that their rockets would soon be capable of reaching orbit. Where the maximum altitude was once 6 km, it would soon rise to 60, and perhaps even beyond. The new generation of Kappa rockets was poised to turn these dreams into reality.  

The first concepts for these new rockets emerged in 1956, but the most active phase of development occurred between 1959 and 1960, when Itokawa’s engineering team designed a new type of composite solid rocket fuel. This breakthrough enabled the K420V booster and the Kappa 8’s K250 upper stage to cross the Kármán line, the conventional boundary of space at 100 km above sea level, and ultimately achieve an altitude of 200 km.  

By comparison, earlier generations of Kappa rockets (models 1, 2, 4, and 6) were merely precursors to fully capable space rockets, as their peak altitudes ranged from 40 km (for models 1 through 4) to 60–80 km (for model 6 and its 6N modification). Notably, the Kappa 6 rocket took part in the 1958 International Geophysical Year (IGY) launches, a milestone that had its roots in the development of the miniature Pencil rocket just four years earlier.  

It didn’t matter that the payload capacity of the Kappa 9L was only 15 kg: the rocket was already capable of placing small payloads into low Earth orbit (LEO). Its successor, the Kappa 9M, which debuted in 1962, increased this figure to 50 kg. This improvement was achieved by equipping the rocket with a more powerful engine, the K420H. The 9M modification became one of Japan’s most widely used and longest-serving rockets, with launches continuing until 1988, for a total of 81 flights. Only one launch failed, in 1971.  

By 1962, it also became clear that the Michikawa Beach launch site in Akita Prefecture was no longer sufficient for these new rockets. As a result, a larger coastal area in Uchinoura, Kagoshima Prefecture, was selected as the new launch site. This location would later become the Kagoshima Space Center (now renamed the Uchinoura Space Center). Today, the majority of JAXA’s space launches take place from its four launch pads.

The final modification of the rocket family was the Kappa 10, a direct successor to the Kappa 9M, which debuted in August 1965. The rocket’s booster remained unchanged, but the second stage was redesigned. It featured a slimmer fuselage and a new version of the main engine, the K420(1/3). The primary purpose of the Kappa 10 was scientific space missions carrying research payloads. On its third flight, it was equipped with a photon detector, while its fourth mission carried a telescope and an infrared radiation sensor.  

The Kappa 10 also underwent several modifications. During the 1960s, two variants were introduced: the Kappa 10S and the Kappa 10C. However, this rocket never reached the same level of mass deployment as the Kappa 9M. In total, 14 Kappa 10 launches were conducted, with three flights of the Kappa 10C and just one launch of the Kappa 10S. Nevertheless, this single Kappa 10S launch proved to be one of the most significant milestones in the development of Japanese launch vehicles. It achieved the highest apogee of any rocket in the series and, more importantly, successfully tested a new apogee motor technology. This innovation later enabled the Lambda 4S rocket family to place Japan’s first artificial satellite into orbit.

The Lambda rocket and constitutional obstacles

By the late 1960s, Japan conducted all its space research using sounding rockets like the Kappa. However, their flights were too brief for sustained activity in space. To achieve this, Japan needed to place an artificial satellite into orbit, equipped with experimental instruments and radio receivers for communication with the ground. But first, the country had to develop a launch vehicle capable of fulfilling this task.  

To conduct research in Antarctica, Japan developed two single-stage rockets: the smaller S-310 and the larger S-520 (with the numbers representing their diameters in millimeters). These rockets became the primary tools for Japan’s polar research throughout the 20th century.

The Kappa’s direct successor was the Lambda. The development of this new, larger rocket began during the Kappa launches. On August 24, 1963, the first Lambda 2 took to the skies. However, this mission ended in failure, as the rocket was lost at an altitude of 50 km. The next, more successful, attempt to launch a Lambda 2 occurred in December of the same year. During this mission, the rocket conducted its first ionospheric research experiment, reaching an altitude of 410 km. 

1964 proved to be the pivotal year for the rocket. That year, the Institute of Space and Aeronautical Science (ISAS) was founded, headed by Hideo Itokawa, eventually becoming Japan’s leading aerospace organization. Also that year, a new three-stage version of Lambda 3 was launched, reaching an altitude of 857 km. The success of this mission was due to the new third stage of the rocket, which completely replicated the final stage of the Kappa 8. During two subsequent launches in the next year, Lambda 3 reached over 1000 km, successfully completing X-ray and ionospheric research missions. 

Once Japanese rockets crossed the 1000 km threshold, Itokawa began assembling a new team of specialists, including scientists from the University of Tokyo’s Institute of Industrial Science, the newly founded ISAS, and engineers selected from Prince Motor Company, the automotive company that merged with Nissan in 1966. It’s worth noting that Prince Motor Company rebranded after World War II: before that, it was known as Tachikawa Aircraft Company and developed several Japanese fighter and attack aircraft. Itokawa specifically sought to involve their specialists in the development of new Lambda modifications. 

Interestingly, the success of Lambda rockets was unique insofar as they were not equipped with guidance system sensors, which were installed on almost all ballistic rockets of that era. The main reason for their absence was Article 9 of the postwar Japanese Constitution, which explicitly prohibited the development of offensive weapons, including rockets with guidance systems, since such systems were the easiest way to quickly convert research rockets into military ones. Thus, Japanese legislation hindered the country’s rocket developers in their quest to conquer Earth’s orbit.

Starting in 1963, Japanese fishermen also became an obstacle, filing a collective complaint against ISAS due to the danger posed by coastal rocket launches. Interagency litigation on this matter effectively prevented rocket launches from 1967 to 1968. Eventually, a compromise was reached. ISAS was allowed to launch its rockets from coastal spaceports only four months per year: in January and February and, later, in August and September. These new regulations significantly slowed the development of the Lambda rocket family and were likely a key reason for the numerous failures of Japan’s first satellite, OHSUMI.

The four failures of the OHSUMI satellite 

The concept for Japan’s first artificial satellite began to take shape in 1961-1962. However, its actual development only started in 1965. According to the plan, the country was supposed to launch the spacecraft within five years. The OHSUMI satellite consisted of two main sections: a propulsion unit made of titanium and an aluminum fuselage, inside which was a payload with three main sensors (a telemetry sensor, an accelerometer, and a temperature sensor). The total weight of the satellite was 23.8 kg, and power for its radio receiver/transmitter was supplied by ordinary household batteries.

The launch of OHSUMI on September 26, 1966, was entrusted to the new, four-stage modification of the Lambda 4S rocket (these rockets were equipped with two SB-310 side boosters). The first three stages successfully completed their tasks, but the fourth stage encountered a positioning control failure, causing the rocket’s payload to miss its intended orbit.

In December of the same year, a second attempt to launch OHSUMI was made, still using the Lambda 4S. Once again, problems occurred with the final stage of the rocket. This time, after separation from the third stage, the ignition of the main engine failed, causing the rocket to lose momentum and not reach the necessary altitude to deploy the satellite.

The third failure of OHSUMI’s launch occurred in April 1967. The reasons for the failure were the same: after reaching an altitude of 200 km, the fourth stage failed to ignite, leading to the loss of the payload.

This third consecutive failure was the end of Hideo Itokawa’s tenure at ISAS and he soon resigned. However, he did not leave the scientific community entirely: later that year, he founded a company that sold systems engineering technologies based on aerospace research. After his career at ISAS, “Dr. Rocket” also found free time to pursue a lifelong dream: he began taking ballet lessons. After five years of training, the eccentric professor even performed on the stage of the Imperial Theater in Tokyo, playing a role in the ballet “Romeo and Juliet.”

In any case, in 1969, Japan established the National Space Development Agency (NASDA). However, the creation of a new agency did not guarantee success for the fourth attempt to launch the OHSUMI satellite and the Japanese press openly mocked the failures of the country’s aerospace engineers. It seemed as though the OHSUMI fiasco would ultimately bury both the satellite project and the problematic Lambda 4S, which repeatedly failed to carry its payload into orbit.

Nevertheless, they kept trying and the fifth attempt to launch OHSUMI took place on February 11, 1970. After Lambda 4S disappeared from sight, high in the sky, ground stations were able to begin tracking the satellite. According to the mission plan, the mission would be considered a success when OHSUMI reached Earth orbit and completed one full revolution around the planet. NASA’s space observation stations assisted in tracking the Japanese satellite, one by one informing their colleagues that they were receiving a signal from the satellite. More than two hours later, the signal from OHSUMI was received at the Uchinoura Space Center. It was official: Japan had become the fourth country in the world to successfully launch a satellite into orbit.

The active phase of the OHSUMI’s mission, during which the satellite could transmit signals to Earth, lasted less than 15 hours before the transmitter’s batteries were completely drained. However, the probe continued to orbit the Earth until 2003.

Just one year after OHSUMI’s hard-won success, the first fully functional scientific satellite, SHINSEI, was launched, performing ionospheric observations and studying cosmic and solar rays. A few years later, the first satellite for X-ray observations, HAKUCHO, was launched. Japan’s “satellite era” had begun, and, starting in 1971, the Land of the Rising Sun launched approximately one scientific satellite per year.

1970 was a turning point, both in terms of the rocket industry and the development of Japan’s space program. The new generation of rockets, Mu (also known simply as M), replaced the rather unreliable Lambda rockets. The most successful modifications, M-3S and M-4S, launched dozens of Japanese satellites into orbit, and various versions of Mu were used by Japan for 40 years, from 1966 to 2006.

The 1970s also brought another significant innovation to Japan’s rocket industry. In the late 1960s, U.S. President Lyndon Johnson proposed to Japan’s leadership the return of control over the Okinawa Islands and the Ogasawara Archipelago, territories that had been occupied by American forces since 1945. One of the conditions for this return was that Japan would acquire an American license for the Thor-Delta launch vehicle.

Such unilateral pressure from the Americans to acquire such a license represented a more-or-less direct demand that Japan abandon the development and production of its own launch vehicles, which would ultimately lead to technological dependence on the American missile-industrial base. Nevertheless, the desire to regain control over the lost territories outweighed the goal of developing Japan’s rocket industry and the agreement was ratified in 1970.

Mitsubishi Heavy Industries began the development of the first rockets in the N-1 (Nippon 1) series, which, to the surprise of many, did not make Japan’s space program weaker. Read about this and other notable events in Japan’s space program in our next article.