Japan's H3 rocket fails to put satellite into planned orbit

H3 Rocket Flight 8 (F8) Launch Failure Investigation Summary Failure Sequence Immediately following the fairing separation, the Payload Support Structure (PSS) suffered a total structural failure. As the PSS lost its load-bearing capacity, its upper section—along with the satellite—broke away under inertial forces and collided with the rocket's second stage. This impact damaged the liquid hydrogen (LH2) tank pressurization lines, leading to a drop in pressure, system anomalies, and the subsequent mission failure. Root Cause: PSS Manufacturing Defects The PSS utilizes a sandwich structure consisting of Carbon Fiber Reinforced Plastic (CFRP) skins bonded to an aluminum honeycomb core. The failure originated from quality control issues during the bonding process: Thermal Damage: During the bonding phase, localized heating temperatures exceeded design specifications, directly degrading the adhesive strength between the CFRP skin and the honeycomb core. Environmental Impact: Prior to bonding, the panels were stored in a high-temperature, high-humidity environment. Moisture absorption caused internal air and water vapor to expand during the heating process, exerting "peeling" force on the skins and creating initial delamination before the rocket even left the factory. Physical Failure Mechanism The shock loads generated by the fairing separation acted as the trigger. This shock caused the pre-existing internal delamination to expand rapidly, leading to localized buckling of the skin. Since the PSS is a primary load-bearing component, this local instability quickly escalated into a total structural collapse and fracture. Corrective Actions and Remediation Standard Rocket Models: The structural connection method for PSS panels will be transitioned from "adhesive bonding" to "mechanical fastening (bolting)" to physically eliminate risks associated with thermal damage during processing. Test Flight (F6): As the payload for this mission is relatively light (approx. 2 tons vs. the 8-ton design limit), a repair scheme will be implemented. This involves removing defective areas, injecting resin, and applying reinforcement patches, followed by rigorous strength verification. Cross-System Inspection: Other components using similar processes, such as the fairings, were inspected. While minor delamination was found, it remained within safety margins. Moving forward, JAXA will focus on overhaul and tightening its quality management systems.