National / Science & Health

From Tottori dunes to the moon, Japan's Xprize team hopes to win lunar rover race


A private-sector group of some 100 engineers and other experts is finalizing preparations to launch a lunar probe, hoping to achieve the first feat in Japan’s history of space exploration.

The 58-cm rover will be launched aboard an Indian rocket in December for the Google Lunar Xprize, a $20 million inducement prize contest organized by X Prize Foundation, an American nonprofit organization encouraging technological development through public competitions, and sponsored by Google Inc.

In addition to the Japanese team called Hakuto, Indian, Israeli, U.S. and multinational groups will all launch lunar probes by the end of this year as well.

The five probes will be required to move more than 500 meters on the surface of the moon and send high-definition moving and static images to Earth. The prize money will go to the first team to transmit the images.

The United States, the former Soviet Union and China are the only countries that have successfully sent moon probes as national projects. The Xprize competition is aimed at promoting private-sector space exploration.

Team Hakuto was formed in 2010 under the leadership of Takeshi Hakamada, founder and chief executive officer of ispace Inc., a space exploration startup in Tokyo.

Hakuto’s technology is based on many years of research and development by Kazuya Yoshida, professor of aerospace engineering at Tohoku University.

“We want to demonstrate that a private-sector project on the stage of space is possible,” Hakamada said.

The surface environment of the moon is severe. Covered with regolith, or a layer of dust, soil and other superficial material, the temperature difference between day and night is more than 250 degrees.

The moon is effectively surrounded by a vacuum and directly exposed to heat from the sun and cosmic radiation. The temperature rises to more than 100 degrees in the daytime and drops to more than 150 degrees below zero at night.

The team revised the design of the rover seven times to overcome challenges including the severe environment and costs.

To protect equipment in the rover, the vehicle is coated with fluorine resin that keeps the internal temperature between 60 and minus 25. Team Hakuto has also developed an adhesive that can resist the gap in temperatures.

The rover itself is made of carbon fiber-reinforced plastic, the same extremely strong and light composite material used in modern aircraft. The plastic, in combination with design changes, reduced the rover’s weight to 4 kg from about 10 kg for a steep cost cut. A launch costs around ¥120 million (about $1 million) per kg of payload.

The probe’s wheels have teeth made of a flexible plastic also used in eyeglass frames designed to prevent slippage while the rover traverses the lunar surface.

Hakuto means white rabbit in Japanese and refers to a Japanese folktale in which the shape of a rabbit can be made out from darker parts of the moon’s surface. In February, the team picked Sorato (space rabbit) as the name of the rover after soliciting some 37,000 suggestions from the public.

Following final tests on the Tottori Sand Dunes in Tottori Prefecture to determine the feasibility and durability of Sorato under extreme conditions, the rover will be sent to India in August to be launched together with the Indian team’s probe on Dec. 28. The probes are expected to reach the moon in about a month.

“We will steadily advance preparations to win the competition,” Hakamada said.

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