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RANKING & DESIGN

Despite the presence of liquid water, organic chemicals, and the possibility of life, only one spacecraft, the Huygens Probe, has ever been sent to Saturn’s largest moon, Titan. The largely untapped potential of this lunar body has recently gained significant recognition by the scientific community, meaning that on-site exploration of Titan using spacecraft is likely to take place in the near future.

Rocket engines and their parts are designed with expected environmental conditions in mind. Upon deciding a destination for a spacecraft, each part’s design must be altered to ensure both survival and efficiency, which go hand in hand. Rocket nozzle proportions, specifically, are adapted to the pressure of the target body’s atmosphere, known as ambient pressure. 

As such, an ideal nozzle for the moon’s dense lower-layer atmosphere must be designed to optimize thrust usage; high atmospheric pressure leads to the overexpansion of thrust if not accounted for, reducing efficiency. Minimizing thrust loss on Titan through a novel model for rocket nozzles is a crucial step in humanity’s understanding of the moon, and, with alterations to its dimensions, the design is applicable to an array of high-pressure atmospheres, including Earth's. Thus, the rocket nozzle design developed in this project will also be created with the atmospheric pressure of Earth, and Saturn in mind.

Now, what does this mean? Let us start with the basics. A rocket is mainly comprised of the fuel, which is combusted into a stream of controlled explosions down the bottom, which we call thrust. The nozzle is the bottom component of the rocket that directs and expels the flow of thrust. Why is this important? The thrust's pressure, volume, and exit velocity can be controlled, simply by the shape of the nozzle. This means that various nozzle shapes suited to various environments can significantly decrease fuel consumption, lighten the payload, maximize thrust and stability, and lower the costs of space missions.

What does the atmosphere have to do with this? When a rocket fires, and the thrust is expelled down the bottom, the pressure of that thrust is quiet large. This matters because if the pressure of the thrust does not match with the pressure of the atmosphere it is firing in, commonly referred to as "ambient pressure", the thrust will either expand outwards, or contract inwards, depending on the ambient pressure. This phenomena is named "over-expansion" and "under-expansion". Over-expansion occurs when the ambient pressure is greater than the pressure of the thrust, causing the atmosphere to squeeze in on the thrust and make the rocket highly unstable. Over-expansion typically occurs in high-density atmospheres. On the other hand, "under-expansion" occurs when the pressure of the thrust is greater than that of the ambient pressure, causing the thrust to spread out, and decrease efficiency, as well as consume large amounts of fuel. Under-expansion typically occurs in low-density atmospheres. The ideal scenario for a rocket is for its thrust pressure to match the ambient pressure. This maximizes thrust, saves fuel, and keeps the rocket stable. This is where the nozzle comes in. By changing the shape of the nozzle, the flow of thrust can be manipulated to match the ambient pressure, and work efficiently.

Hasn't NASA already done this? put simply, yes. but have they perfected it? No. There are infinite configurations and shapes of a nozzle that all produce different levels and types of thrust. Each atmosphere demands a different nozzle, and with the unlimited possibilities that exist, there exist countless of ways to optimize a nozzle.

Overall, the future of space exploration and rocket technology holds a myriad of potential. Each component of a rocket, such as the nozzle, hold equal importance in obtaining success. By continuously innovating, even when unnecessary, contributions are made in the future of space exploration, and the perseverance of human curiosity.

Design six efficient rocket nozzles that will maximize thrust and propulsion in high-pressure atmospheres, aiding in future research and exploration.

Determine whether a bell-shaped or conical rocket nozzle is most optimal to minimize thrust loss when faced with the ambient pressures of Titan, Earth, and Saturn.

The efficiency of currently used rocket nozzle designs will be tested and modeled using Computational Fluid Dynamics (CFD) software, along with analytical methods in the form of hand calculations.

Exit velocities of the studied designs will provide insight into the nozzles' efficiency rankings, and the highest-placing model will be used as the basis for a new design. Areas of thrust loss in the most efficient design will be pinpointed visually and analytically to aid in the novel model's development.

After modeling the new design, CFD software be used again to rank it against those studied before it.

Click here for more details on our methodology.