The Japan Aerospace Exploration Agency (JAXA) conducted the scientific balloon flight B25-04, as part of the 2025 scientific balloon campaign, at the Taiki Aerospace Research Field. The balloon was launched on 31 August 2025, at 4:37 JST for the purpose of testing the performance of a model for a super-pressure balloon with a diamond-shaped net. The balloon had a fully inflated volume of 2,000 m3 (diameter 18 m) and ascended at a rate of approximately 340 m per minute.

27 minutes after launch, the balloon reached its highest altitude of approximately 9 km over the Pacific Ocean, approximately 30 km east-southeast from the Taiki Aerospace Research Field, and the balloon and the onboard equipment were separated by tele-command and slowly descended onto the sea, landing approximately 35 km east-southeast from the Taiki Aerospace Research Field, where they were recovered by recovery boats at 5:32 JST.

Regarding the flight test of a super-pressure balloon with a diamond-shaped net, further research will now be conducted through the thorough analysis of the data obtained in this flight.

At the time of launch, the ground weather conditions were: weather: cloudy, wind speed: 2 m/s, and temperature: 17 degrees Celsius.

※ Research overview
A super-pressure balloon with a diamond-shaped net has been developed to achieve a novel balloon that enables a high pressure resistance capability in a lightweight design, and enables long flight duration while carrying heavy onboard equipment. In the B20-03 experiment conducted in 2020, it was found that the conventional launch method could cause interference between the net and the balloon film and damage the balloon. Therefore, a quasi-static launch method using a winch has been newly developed. In this experiment, a super-pressure balloon with a volume of 2,000 m3 will be launched using this new method to verify the effectiveness of the launch method and the validity of operations throughout the flight from launch to recovery. The envelope deployment and pressure resistance of the balloon will be also evaluated during the flight. These achievements will establish an important milestone for the development of larger super-pressure balloons for practical use in scientific research.

A balloon being inflated in a large hangar for its scientific flight B25-04. (credit: JAXA)

The balloon just after the launch of B25-04. (credit: JAXA)