Rocket Reentry Path Explained: How To Avoid Uncontrolled Fall of Human Spacecraft?

Witnessing the launch of a man-made spacecraft is a breathtaking and rare experience. Similarly, the reentry of these objects through the atmosphere of the Earth is equally stunning, although they come with some challenges that need to be addressed with advanced technologies.

What Does Rocket Reentry Look Like?

Atmospheric reentry refers to the movement of an object from outer space into and through the atmosphere of a dwarf, planet, or natural satellite. The space objects that undergo this process include spacecraft from orbit and suborbital reentry vehicles.

The reentry of a human-made space object usually resembles shooting stars, often leading to confusion. The distinctions are described by aerospace experts at the Center for Orbital and Reentry Debris Studies (CORDS).

Space debris comes from man-made objects launched into Earth's orbit and usually move parallel to the ground at a 7 km/sec speed. The re-entry, which can occur at any time of the day, is characterized by a glowing central body followed by a long, dazzling tail and can break into smaller parts. On the other hand, meteors come from natural debris which can hit the Earth at all angles and from all directions. Meteors are often seen near dusk and occasionally appear to be traveling parallel to the ground.

Dealing With Problems in Rocket Reentry Path

As an object reenters the Earth, it can experience several challenges. Problems involved in rocket reentry paths are complex and include a lot of uncertainties. Some of these problems include atmospheric drag, where an object experiences mechanical stress and aerodynamic heating caused by compression of the air in front of the spacecraft. Such forces can lead to ablation (loss of mass) or the complete collapse of smaller objects.

On November 4, 2022, a rocket booster from China fell from space and crashed uncontrolled back to Earth. This rocket booster was used on a mission on October 31, carrying the parts of China's Tiangong space station to orbit. The space rocket reentered the atmosphere over the south-central region of the Pacific Ocean. This event marks the fourth uncontrolled reentry for a Long March 5B vehicle since the China National Space Administration started operating it two years ago.

In a 2022 study, a group of researchers discussed the proposed search space reduction (SSR) technique to solve the problem encountered in the rocket reentry path. To get the optimized spacecraft reentry trajectories, control variables such as angle of attack and bank angle are considered while the rocket reentry is unpowered.

The study includes using the SSR technique to find the control profiles for maximized spacecraft capability. Next, this technique is used to minimize the total heat experienced by the rocket. The result of the study reveals that SSR is effective in achieving optimal control profiles where the ideal terminal conditions of the spacecraft are accurately achieved.

Aside from the SSR technique, reentry analysis tools were developed for predicting the rocket reentry path and survival. These representative tools include ORSAT, DEBRISK, SCARAB, and DRAMA/SESAM.