Reentry trajectory and survivability analysis codes for reentry space debris, such as the Object Reentry Survival Analysis Tool (ORSAT) from NASA and Spacecraft Atmospheric Reentry and Aerothermal Breakup (SCARAB) from HTG, have been developed by various research centers and space agencies over the years. The reentering space debris experiences various type of ablation, non-equilibrium surface heat transfer, and natural breakup. The existing codes, however, seems to not have the capability to predict these phenomena, make the trajectory and the survivability difficult to predict. High temperature generated during reentry at high Mach number hypersonic speeds, where the flow behind the shock wave in the stagnation region becomes subsonic, triggers an onset of thermochemical non-equilibrium.
The existing codes compute the stagnation-point heat transfer rates using the popular Lees’ and Fay and Riddell’s formulae which assumes an equilibrium boundary layer flow with a super-catalytic wall, where the surface recombination efficiency is regarded infinity. However, in the case of small space debris having sizes of 2.5–10 cm, the flow residence time behind a shock wave is far too short, so that the super-catalytic assumption leads to over-estimation of surface heat transfer rates.
Seong-Hyeon Park and Gisu Park (corresponding) at the Korea Advanced Institute of Science and Technology proposed a study on the reentry trajectory and survivability estimation of space debris based on simple shapes. They aimed at developing a reentry trajectory and survivability estimation code by placing major emphasis on the small size debris with catalytic recombination at the surface. They hoped to implement the non-equilibrium heat transfer approach to the reentry trajectory estimation and survivability study of miniature-sized space debris. Their research work is now published in Advances in Space Research.
They developed a code to analyze reentry trajectories and survivability of the space debris focusing mainly on the small size debris. They then adopted simple shapes such as a sphere, a box and a cylinder with sizes 12.5cm – 50cm to compute reentry trajectories. The researchers considered the space debris to be mainly made up of the materials graphite epoxy, titanium and aluminum. In total, they examined 120 different cases. Eventually, they compared and validated the results with various existing codes.
The authors also observed that in the heat transfer calculation, the existing codes used the popular Lees’ and Fay and Riddell’s formulae that assume an equilibrium boundary layer flow with a super-catalytic wall. However, it was noted that for the small space debris, the flow residence time behind a shock wave was far too short, in that the super-catalytic assumption led to over-estimation of surface heat transfer rates. They also observed that as the catalytic efficiency increased, the heat transfer also increased leading to the low space debris survivability.
Herein, a reentry trajectory and survivability estimation code has been developed by Seong-Hyeon Park and Gisu Park with particular emphasis on small size debris with catalytic recombination at the surface. The results obtained here suggest that as the catalytic efficiency increases the heat transfer rate increases, leading to the low space debris survivability. Therefore, the catalytic effect is crucial for the debris survivability, thereby implying the importance of the implementation of the non-equilibrium heat transfer approach to the reentry trajectory estimation and survivability study of the small sized debris problem.
Seong-Hyeon Park, Gisu Park. Reentry trajectory and survivability estimation of small space debris with catalytic recombination. Advances in Space Research, volume 60 (2017) pages 893–906.Go To Advances in Space Research