Speaker
Description
Destructive atmospheric re-entry has become a major focus of current research, as it serves as the primary disposal strategy for satellites after their end of operation. The fragmentation of the satellite remains a key area of investigation, since its underlying mechanisms are not well understood. Observation data from multiple airborne observation campaigns conducted over the past decade show, as one key finding, the occurrence of a distinct explosive event triggering the further fragmentation process. We have named this event the main break-up and the corresponding altitude the main break-up altitude. Interestingly, the observation data show that the break-up occurs almost always at an altitude range from 75 km to 80 km for controlled as well as semi-controlled re-entries. This holds true for re-entries with various entry conditions and ballistic coefficients.
In this work, we apply a dimensional analysis to investigate the impact of the driving parameters on the break-up altitude. Based on this and under the assumption of comparable structural materials, a simplified model equation is derived
$h_\mathrm{Bu} = a \cdot \ln\left(\frac{v_0^4}{\sin(\gamma)}\right) + b$
The break-up altitude $h_\mathrm{Bu}$ is a function of the entry velocity $v_0$ and of the entry angle $\gamma$ only. The dimensional analysis reveals that characteristic parameters, such as the ballistic coefficient, play a minor role, which is consistent with the observation data. The model parameters a and b are identified by fitting the equation to data obtained from airborne observations. Additionally, numerical data were used, generated with the destructive re-entry tool SCARAB. The numerical data are used to account for uncontrolled re-entries, because there are no observation data available yet. The fitted function is in good agreement with both the experimental and numerical data, which indicates that the simplifying assumptions are reasonable and the simplified model equation captures the essential physics of the system. During the talk, we will present more insight into this approach and provide further discussion of the underlying simplifications.