TOKYO: The Japan Aerospace Exploration Agency, or JAXA, said Tuesday it has concluded that an explosion during a ground combustion test of an engine for the new Epsilon S solid-fuel rocket in July was caused by the melting and scattering of a metal part from the ignition device inside the engine.

JAXA reported the conclusion at a meeting of the science ministry’s experts panel on the day.

The explosion, which involved the second-stage engine of the 27-meter-long, three-stage rocket, occurred at JAXA’s rocket test site in Noshiro, Akita Prefecture, northeastern Japan.

JAXA suspected that damage to the propellant and the heat-insulating material that wrapped the propellant caused excessive heat, leading to the explosion.

Through experiments, it found that such damage is not caused even when the propellant and the insulating material are exposed several times to weight eight to nine times the acceleration at the time of transportation.

Meanwhile, it was confirmed that the metal part, if melted, could damage the insulating material, triggering extraordinary combustion.

JAXA has drawn up measures to prevent the metal part from melting, including covering it with insulating material. It will conduct another combustion test to find out the effectiveness of the measures.

JIJI Press