The scientific name of the "bulge" in the intake duct is the "non boundary layer separated supersonic intake duct" (DSI), whose primary function is to reduce weight and improve efficiency. Traditional fighter jets often install heavy and complex adjustable baffle systems at intake ports and other locations to adapt to high-speed airflow during supersonic flight. This not only increases the weight of the aircraft, but also increases the radar reflection area on the front of the aircraft. The DSI intake duct, with its unique "bulge" design, can actively pre compress the incoming airflow and cleverly strip off the boundary layer airflow on the surface of the aircraft, achieving "slimming" for the fighter jet. Taking the F-35 Lightning II as an example, after adopting DSI intake technology, the aircraft not only saved hundreds of moving parts and successfully reduced weight, but also improved structural reliability. The second function of the "bulge" in the intake duct is related to the stability of the aircraft's power. When a fighter jet enters supersonic flight, a strong shock wave is generated in front of the aircraft. If the traditional intake duct is not handled properly, the severe oscillation of shock waves may lead to engine surge or even shutdown. The magic of the DSI intake lies in its ability to generate a stable pre compression shock wave, like an invisible "stabilizing shield" for the engine, allowing supersonic airflow to flow into the engine combustion chamber in a smooth subsonic state after multiple deceleration and pressurization processes. The third function of the "bulge" in the air intake is to coat the fighter jet with "stealth armor". The internal channel of a traditional intake duct is straight and deep, like a resonant cavity for radar waves, which is prone to strong reflection of radar waves. The "bulge" and lip of the DSI intake adopt an integrated design, combined with an internal S-shaped curved channel, forming a radar barrier. The 'bulge' itself shields the strong reflection source of the engine fan, while the curved channel forces the incident radar waves to refract back and forth between the walls, consuming energy and greatly weakening the radar scattering signal in the direction of the intake duct, reducing the probability of being detected by the opponent's radar. Numerous advanced fighter jets have enhanced their battlefield survivability and stealth assault capabilities through the DSI intake design. The "bulge" of the intake duct is a manifestation of aviation functional aesthetics, which replaces the bulky mechanical structure of the past. With a simple and smooth surface, it integrates cutting-edge requirements such as shock wave management, boundary layer control, and radar stealth, allowing fighter jets to unload heavy loads, stabilize "breathing", and hide in high space, ultimately integrating surging power and deterrence into the figure that pierces the sky. (New Society)