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Space Shuttle Reentry

Posted at — Feb 1, 2023

My first Space Shuttle

Last year, I was trying to create my own space program to deploy a satellite into Earth’s orbit and later bring it back to Earth safely. Below is an attempt of the space shuttle starting its reentry—the most dangerous phase of any space mission. The other critical phase is liftoff, which occurs just a few seconds after ignition.

When the vehicle sinks into the Earth’s atmosphere, its bottom faces and compresses the air ahead of it. As high pressure comes with frictional force, the bottom generates a lot of heat. This is why a heat shield, made of panels of superheated carbon-carbon composite sandwiching a lightweight, thick carbon foam core, is attached to cover the vehicle. It protects the vehicle from burning up.

Similarly, when Earth’s gravity attracts an object from space, causing it to fall through the atmosphere, the object burns and breaks into small parts before reaching and potentially damaging the Earth’s surface. This falling object is called a shooting star or meteor, and people often make wishes upon seeing one. As there is no scientific proof behind, it is simply considered a belief.

The atmosphere acts as a shield, protecting the Earth’s surface. Any object or debris falling from space is not only decelerated but also burned up and broken into pieces. This dramatically helps reduce the damage of objects striking the surface.

On my first attempt, my space shuttle just spun or stood upright like this as it was hard to keep the vehicle balanced. After several attempts and gaining more experience, I finally mastered the skill to pilot it effectively. For advanced and precise maneuvers, the community provides scripting support, which allows me to write autopilot code.

February 1, 2023, marked the 20th anniversary of the space shuttle Columbia disaster. The disaster was caused by a small piece of foam falling from the external fuel tank during ascent, which damaged the protective carbon tiles on the left wing. When the vehicle was re-entering the atmosphere at a speed 18 times the speed of sound, the heat was increased inside and led to the explosion. This event reminds me of my own experience while playing in the simulation.

Reentry Simulation

This video demonstrates a very accurate reentry flight in the simulation from deorbit burn to atmospheric descent and landing. The flight was made based on the real guidance and configuration in the official documents.

N-body Physics

By default, a spacecraft in the simulation is only influenced by the gravitational pull of the celestial body it is currently orbiting. This simplifies orbital calculations, making the simulation easier for players to perform the most fundamental maneuvers. However, no n-body physics means no accurate modeling of lagrange points, flight path and body motion are more predictable. I think this is one of the most shortcomings of the stock mechanics that makes the simulation less realistic. Fortunately, Principia is developed as a solution to this limitation.

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