Submitted by Manohar Samal, Research Intern on Application of Artificial Intelligence on Space Activities.
Space debris is often a result of explosions of rocket upper stages and satellites. The role of artificial intelligence has been significant in improving operational activities by the assessment of risks emanating from space debris and deeper knowledge of creation and residence of debris in orbit.
The European Space Agency in collaboration with Lawrence Livermore National Laboratories studied the collision of Cosmos 2251 and Iridium 33 with the aim of obtaining information on debris characteristics such as area-to-mass-ratio, number, size distribution, momentum transfer, orbit parameter, relative orientation, mass, geometry and relative velocity. The main objectives of this study were to establish a numerical methodology which would characterise hypervelocity collisions of satellites. Furthermore, simulations would be performed utilising this established numerical methodology and various collision scenarios. The transition between the effects of local damage and catastrophic disruption would then be analysed in context to the traditional 40 J/g electromagnetic radiation (EMR) definition.
The methodology selected for this study was sophisticated numerical simulation with hydrocodes by a software tool referred to as PHILOS- SOPHIA which uses graphical user interface (GUI) aiding in analysing fragmentation, defining collision scenarios and visualising simulation results. Hydrocodes are advanced physics and time explicit dynamic analysis tools for numeric simulation which covers aspects like explosion, penetration, crash and impact by virtual and simulated experiments using loading conditions and models that are close to reality.
The three stages of the hydrocode simulation were to configure, simulate and evaluate. The capabilities of the PHILOS- SOPHIA software tool in numerically simulating complex spacecraft collisions was demonstrated through this study. The main benefit of using numerical simulations was that it is more effective than ground testing because ground testing requires tremendous effort, but is unfortunately only capable of covering a small range of parameter space.
While studying impact analysis, empirical models that predict impact damage, semi-empirical models and sophisticated numeric simulations that solve fundamental conservation equations for energy, momentum and mass were employed. Such applications enable the researchers to model complex scenarios and space objects similar to reality, increase the fidelity, range and flexibility of the applicability and reduce computational time and effort. A detailed fragmentation analysis of collision using six complex collision scenarios was performed to shed light on the transition between local damage effects and catastrophic disruption on impact.
One of the significant outcomes of this study indicates that the PHILOS-SOPHIA software tool is powerful for the purposes of studying collisional fragmentation as it can provide precise data in a wide parameter range provided that it is thoroughly backed with experimental data. Other results and outcomes of this study include successful particle tracking of space debris, collection of more data from hypervelocity impact experiments, identification and tracking of individual fragments of space debris, an extension of the hydrocode numerical simulation method in 3D and increased quantitative investigations of complex geometries. These results of the study have paved the path for the systematic study of spacecraft breakup behaviour which is significant in assessing the risks of space debris.
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