Lockheed Martin engineers began investigating alternatives to traditional supersonic inlet concepts in the early 1990s. They tried to eliminate the complex mechanisms associated with boundary layer control: boundary layer barriers, bleed systems, bypass systems. By eliminating these mechanisms, designers were able to save approximately 300 pounds of weight from the aircraft. The final result of this research is today's DSI, or bulging air intake. The boundary layer separation panel has been removed on the DSI and the air intakes are integrated into the front fuselage design. There is a three-dimensional surface (bulge) designed in front of the air inlet. The function of this bulge is to act as a compression surface while increasing the pressure distribution to "push" the boundary layer air away from the intake duct. The design features of the inlet cowl lip allow the main boundary layer airflow to escape to the rear fuselage. The entire DSI has no moving parts, no boundary layer isolation panels, and no bleed or bypass systems. In other words, DSI is actually a modification of the air intake portion of the conventional air intake. The carefully designed three-dimensional compression surface combined with the air inlet can not only complete the function of the traditional boundary layer barrier, but also provide air flow pre-compression, thereby improving the efficiency of the air inlet at high speed and reducing resistance. With the elimination of the intake duct adjustment system, weight is naturally reduced. What is more important for future combat aircraft is that after the elimination of components such as boundary layer barriers and compression ramps, the aircraft's RCS may be significantly reduced, which is obviously beneficial to improving the aircraft's stealth capabilities - the advancement of the F-22 The air duct still has a traditional boundary layer partition, which requires a lot of effort in design; while it uses a fixed air inlet, stealth requirements account for a considerable part of the factors considered.
DSI was developed and refined on Lockheed Martin's own computer modeling tools following advances in computational fluid dynamics (CFD). CFD is the science of developing digital solutions to the governing equations of fluids and can describe important flow fields in space or time and further improve the solutions. CFD solutions illustrate how engineers can represent complex flow fields and evaluate the performance of their designs.
In late 1994, Lockheed Martin conducted studies on an aircraft configuration that would later become the configuration for their JSF prototype. The study focused on investigating the advantages of DSI over F-22 or F/A-18E/F type swept inlets. DSI allows the aircraft to perform better due to reduced weight (approximately 300 pounds); DSI also reduces production and operating expenses - by eliminating complex components, each aircraft can save $500,000, which is a significant benefit . In order to maintain technological leadership, engineers applied for 2 U.S. technology patents during this period, which were approved in 1998.
Today, only China and the United States use DSI air intakes.
In addition to the previously disclosed Xiaolong fighter jets and F-35 fighter jets, the J-10B test flight at the end of 2008, and China's new generation stealth fighter "J-20" witnessed by netizens at the end of 2010 also use DSI Air intake. In addition, the United States once tested this inlet on the F-16 but did not continue.
Today, only China and the United States have developed this technology. Its technical difficulty is actually very high. First of all, designing this bulge requires extremely high levels of aerodynamics and computer technology. Secondly, its manufacturing precision is very high, and it is very difficult to process metal materials. Composite materials are currently used.