pencil locket


August 8, 2022

The pencil rocket is a series of small rockets that was developed in Japan under the leadership of Hideo Itokawa, a professor at the University of Tokyo. The first launch was carried out horizontally at a remodeled semi-underground gun launch site in Kokubunji, Tokyo. The development name is "Tiny Lance". After Japan lost the Pacific War, aircraft research was prohibited by the Allied Forces Supreme Commander General Headquarters (GHQ). Itokawa, who had turned his focus from wartime military aircraft development to acoustic engineering research, learned of the United States' space rocket program when he traveled to the United States in 1952. The AVSA (Avionics and Supersonic Aerodynamics) group at the Institute of Industrial Science, the University of Tokyo worked on the development and launch experiment of a pencil rocket.


It is the first experimental rocket in post-war Japan. Development began in 1954 with an annual budget of 5.6 million yen. Due to budget constraints, it used an ultra-compact gunpowder-powered rocket as an experimental device, and this nickname was born from the fact that it looks like a pencil. A total of over 150 aircraft were launched. Although it was extremely small as a rocket, and it was not capable of carrying a payload, it was established as a rocket system by itself, and aerodynamic characteristics due to changes in the material, shape, and center of gravity of the nose cone and tail. The effect of variance due to changes in It is said that these data were effectively used in the later analysis of the flutter phenomenon during the development of the Kappa and Lambda rockets. At first, we considered ultra-high-speed flight in the upper stratosphere (atmospheric interface) as an aerospace research subject to which rockets should be applied. According to the website of the Institute of Space and Astronautical Science (ISAS), "Space Lab Monogatari", the upper layer has a thin atmosphere, so the problem of temperature rise is suppressed, and the influence of weather (a phenomenon of the troposphere) is also suppressed. It is said that ``Itokawa's high-speed projectile concept'' was such that it would be possible to fly safely between Tokyo and San Francisco in about four hours. This is what Itokawa said in response to a newspaper interview, and the article that appeared in the world featured headlines such as "rocket passenger plane" and "crossing the Pacific Ocean in 20 minutes." A rocket made of paper” was introduced with the caption “Prototype domestic rocket No. 1”. For this reason, the impression that it was aiming for a space plane (like NASP later) is spreading. However, as it became so popular, it caught the attention of officials from the Ministry of Education and others, and became an opportunity for collaboration with space science for the International Earth Observation Year, which led to a major advance in Japan's solid-fuel rocket development. .

Kokubunji Experiment

In March 1955, a horizontal launch test of a pencil rocket was conducted in Kokubunji, Tokyo. This experiment was conducted using a pencil standard type with a total length of 230 mm, and a rocket launched from a horizontal launch pad with a length of 1.5 m flew through the screen. The first test took place on March 11, and by March 23, 29 Pencil rockets had been launched. There are variations in the mounting angle of the tail and the weight of the warhead, and basic data was collected under various rocket-side conditions.

Chiba Experiment

In June 1955, Chiba City, Chiba Prefecture