Space Shuttle Reentry
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.
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.
Orbiting
Deep Space Network
The Deep Space Network (DSN) is NASA’s international array of powerful antennas that enables communication with spacecraft exploring our solar system and beyond. The DSN consists of several complexes located in different places in the world. This global positioning ensures a stable contact with spacecrafts in the condition of the Earth’s weather and rotation. The DSN supports the transmission of data and control for serving spacecrafts such as Voyager 1 & 2, Hubble Space Telescope (STS-31), Chandra X-ray Observatory (STS-93), and James Webb Space Telescope on the Sun–Earth L2. It is the foundation of deep space exploration that allows scientists and engineers to receive scientific data not only in the Solar system but also from a distance of light year away.
In telecommunications, it is essential to understand the communication protocols used whether they are simplex, half-duplex, or full-duplex and to ensure the security of data in transit, in use, or at rest if needed. These are also common concepts used in software development for network and security programming.
Additional Resources
- KSP Visual Calculator
- Reentry Blackout
- kOS Shuttle OPS1
- kOS Shuttle OPS3
- kOS Shuttle Entry Sim
- Reentry Explained – Video
- Principia
- Real Solar System
- Oreilly - The Kerbal Player’s Guide
Fifty Fifty
Feb 25th 2025
Gravity (live + choreography + rock)
The rock version of this song is really great and reminds me of the conflicting emotions in the philosophy of Korean music, which are often explored in traditional one. They are Puri, Han, and Heung. Han and Heung are contrasting artistic emotions that are not separated but fluidly connected. Han represents negative emotions and tends to condense while Heung is filled with positive emotions that are excited and heightened. It is said that there is an appropriate way to resolve the conflict and create a work of art. That is where Puri, which can be translated as Purification or Sanctification, comes in. Puri resolves the conflict by enhancing the aesthetic value associated with the combination of Han and Heung.
There are poetic patterns found in sentences, and the easiest to recognize may be “gravity, insanity.” I always have a thought in mind that escaping reality might be helpful sometimes for an artist working on creative artwork, similar to how an ancient scientist experimentally thinks about escape velocity that is fast enough to constantly miss the chance of touching the surface and overcome the Earth’s gravity in orbital mechanics. This has become the Puri that enables me to experience both science and art simultaneously.
Basically, everything is falling even the Moon due to the same gravitational force that keeps us on the ground. However, the Moon remains in its nearly perfect circular elliptical orbit because it has enough velocity to move forward along the Earth’s horizon while falling toward the Earth itself for every fragment of second. Following the Kepler’s second law about the motion of moons around planets, a line from the Earth to the Moon sweeps out equal areas of the ellipse in equal times. As the two exert gravitational pull on each other, the Moon has caused water on the Earth to be redistributed, leading to the phenomenon known as tide and resulting in high tides on two opposite sides of the Earth.
A spacecraft on a typical return mission can make use of gravity assist from another celestial body, such as the Moon, to adjust its path toward the Earth. The spacecraft achieves this by approaching and entering the Moon gravitational influence unstoppably at a precise angle and distance to refine its velocity and trajectory. This has been proven to be fuel-efficient and effective in shortening the journey.
Astronauts have different roles in a space mission, and while a driver’s license might be helpful, it is not as relevant as a pilot’s license is. Pilots on a spacecraft, of course, have extensive flight training, but many astronauts in other roles do not need piloting experience rather than specific training in spacecraft and mission operations. In practice, the push for automation in blank space is motivated by many factors to increase the reliability of space travel.
Starry Night (live + choreography)
Hangul characters are made up of 3 main symbols: a vertical stroke, a horizontal stroke, and a circle. These symbols represent different things: the vertical stroke stands for human (neutral), the horizontal stroke symbolizes the Earth (Yin), and the circle represents the Sun (Yang). As the idealism suggests the importance of the 3 components, the Earth’s rotation and its revolution around the Sun have formed the cycle of days, nights, and seasons and have a profound effect on human cultures and activities.
If I were to fit the entire solar system at scale on a piece of paper, I would probably come up with something so small that I would not be able to see anything. To give an idea of the vast distances, if light could travel 7.5 times around the Earth in just 1 second, it would take about 8 minutes and 20 seconds, approximately 1 Astronomical Unit, for light to travel from the Sun to Earth. Given the size that large, the solar system is still tiny when compared to the size of the observable universe. When it comes to observing distant astronomical objects, light is one of the most important measurements. As light takes an incredible amount of time to travel from a distant observable, what a telescope captures and an astronomer interprets are events that already happened in the past. To study astronomy is to study the properties and formation of ancient stars, planets, moons, galaxies, and other astronomical objects through light and other massful particles.
It is a good practice to iterate on old work even if it was completed years ago. As one of Leonardo da Vinci’s design principles states that “Art is never finished, only abandoned.” In other words, there is no such thing as a final work in term of perfection but a work in progress at an acceptable state. Painting is interesting. And it is surprising to see its presence in the music, a type of art naturally structured around patterns. As I remember there are 7 basic musical notes (C, D, E, F, G, A, B) in combination with 5 accidentals (sharp, flat, double sharp, double flat, and natural) and they become the fundamental components for creating scales and chords in music theory. It is important to address the arrangement of time in music by first understanding time signatures in the form of x/y, where x indicates the number of beats in each measure and y represents the type of beat. This can be practiced by counting using cardinal numbers. For example, in the case of type of 4, 4/4 means 4 beats per measure and 1/4 equals 1 beat. Some common time signatures include 2/4, 3/4, 5/8, 6/8, 7/8, 8/8. While it is possible for x to be greater than y, I do not know if such time signatures are also common, such as 5/4 and 7/4.