Speaker
Description
Deorbiting & Passivation Technologies
Impact-Safe Tank Pressure Level
Fragmentation remains the dominant contributor to the space debris environment, with explosions of pressurized vessels and propellant tanks playing a particular role as the main cause for catastrophic breakup events. Passivation of satellite tanks and upper stages after mission completion is recognized as the most effective mitigation strategy to prevent on-orbit fragmentations. Passivation requires depleting or venting onboard stored-energy sources to levels that cannot cause explosion or deflagration leading to system breakup and debris release. However, no universal threshold exists; critical values are defined by mission-specific analyses and are often underpinned by limited empirical data.
We present the ESA study “Impact-Safe Tank Pressure Level,” which aims to build an engineering database to assess critical pressure thresholds that could trigger tank explosions from hypervelocity impacts by space debris. The database targets unshielded, large titanium tanks subjected to spherical debris impacts. While this exhaustive in terms of potential failure conditions on orbit, the study advances the understanding of failure initiation and demonstrates a robust evaluation approach based on both numerical and experimental simulations. Given the high cost of spacecraft tanks and hypervelocity impact testing, the study relies largely on numerical simulations, validated by impact tests on pressurized, sub-scale tank samples.
The reference tank design Features 600 mm Diameter titanium tank with 1 mm wall thickness, a configuration that challenges the numerical stability of full-scale simulations when using commercial hydrocode solver. The tank failure process depends on complex interactions between high strain-rate loading by the impactor in the tank wall, shock waves induced by the impact generated fragments within the fluid contained in it, and their interactions with the inner tank wall after passaging through it. To address these challenges, we developed a novel coupling approach that integrates two Fraunhofer EMI in-house codes—a structural-dynamic module and a fluid-dynamic module—to model solid–fluid interactions and evaluate critical failure conditions.
A simplified model was derived to quantify the explosion initiation pressure as a function of impact parameters (impactor size and velocity) for the investigated failure scenario. This study's final presentation introduces the challenges for impact experiments and numerical simulations, details the study approach and its implementation, presents the study results, and delivers the derived failure model.