Can Jet Engines Work Underwater?

The idea of using jet engines for underwater propulsion might seem both fascinating and challenging. This article explores the feasibility of jet engines working underwater, delving into the physics of rocket engines and jet engines. We will also discuss the potential of using jet engines in underwater vehicles, such as submarines.

Understanding Jet Engines vs. Rocket Engines

Jet engines are designed to thrive in the air, harnessing the oxygen in the air for combustion and producing thrust. However, when considering their use underwater, the basic operating principles of jet engines need to be re-evaluated.

The air-breathing nature of jet engines makes them much less suitable for underwater use compared to rocket engines, which have their own oxidizers and can operate independently. In contrast, a rocket engine carries both fuel and oxidizer on board, allowing it to function even without external air. This inherent property makes rocket engines a viable option for underwater propulsion, as demonstrated in various applications.

Rocket Engines: An Underwater Proposition

Rocket engines can indeed work underwater, provided a few specific conditions are met. These engines need to maintain a chamber that is both clear and dry to ensure proper operation. One approach is to modify the engine's design, possibly altering the exhaust nozzle to optimize performance. For instance, the Sea Dragon project tested the use of rocket engines underwater as part of missile launches from submarines.

The Sealed Nature of Rocket Engines

Rocket engines do not rely on oxygen from the air, so they can operate in any environment, including underwater. This characteristic makes them ideal for applications where air supply is unavailable or impractical. The absence of an air intake in rocket engines allows for their use in water, contributing to their versatility in various marine environments.

Jet Engines: Challenges Underwater

Jet engines are intrinsically air-breathing, requiring a constant supply of oxygen-rich air to function efficiently. The presence of water would fundamentally disrupt the combustion process, as water molecules interfere with the oxygen/fuel mixture necessary for jet engines to operate.

Moreover, the physics of jet engines relies on compressing and heating air. This process creates the high-speed exhaust that propels the aircraft. When submerged, water would act as a physical barrier, preventing the necessary air compression and heating, making jet engines unsuitable for underwater use.

The Diesel Submarine Analogy

Interestingly, diesel submarines often utilize a snorkel system to draw in air from the surface when close to the water's surface. This system is designed to keep the engine running without sinking the submarine. The same principle could, theoretically, be adapted for underwater jet engines, albeit with significant challenges and no clear advantage over traditional propulsion methods.

Conclusion

While jet engines can theoretically work underwater with modifications, the practical limitations and inherent challenges make them less ideal for this purpose. On the other hand, rocket engines offer a more viable solution due to their self-contained nature and ability to operate independently of external air. Understanding the differences between these propulsion systems is crucial for selecting the most appropriate technology for various underwater applications.