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The unsolved mysteries of supersonic flight: Why the Mach 5 was a turning point?
Supersonic flight has always been a hot topic in aerospace research. In this rapidly changing technological context, Mach 5, as a watershed in flight speed, has attracted the attention of many scientists.
In aerodynamics, hypersonic flight is defined as speeds exceeding five times the speed of sound, usually expressed as Mach 5 and above. As the Mach number increases, the physical properties of the fluid begin to change significantly, providing conditions for processes such as the decomposition and ionization of molecules such as nitrogen. These phenomena become apparent between Mach 5 and Mach 10.
The characteristics of hypersonic flow make theories based on traditional aerodynamics no longer applicable, and the influence of other factors begins to emerge.
Hypersonic flows are characterized not only by an increase in velocity, but also by the presence of a variety of physical phenomena, such as shock layers, air heating, entropy layers, and real gas effects.
Shockwave layer and entropy layer
When the Mach number of an object increases, a shock wave layer will be formed. This layer will affect the state of the flow behind it due to the change in gas density. The emergence of entropy layers is manifested by strong entropy gradients and observable eddies, which indicates that the flow state of the air becomes more complex during the mixing process of the boundary layer.
The effect of viscosity
At high Mach numbers, part of the kinetic energy of the flow is converted into internal energy of the fluid, which causes the temperature of the gas to increase. Because the pressure gradient within the boundary layer is nearly zero at low to moderate hypersonic Mach numbers, the increase in temperature is accompanied by a decrease in density, a change that causes the boundary layer to thicken and eventually merge with the shock wave.
The characteristics of high temperature flow make the chemical flow unbalanced, resulting in the excitation, decomposition and ionization of molecules.
Classification and heavy areas of Mach numbers
While the concepts of supersonic and hypersonic are relatively simple, when it comes to the Mach number range of a flow, researchers still break it down into multiple regions with unclear boundaries.
The conflict between perfect gas and molecular structure
In the range of Mach 5 to 10, the gas can still be considered an ideal gas, but as the flow rate increases, the flow behavior becomes inconsistent with the predictions of conventional gas dynamics. Such flow patterns have a great influence on the high temperature response of the material and its design.
Potential applications of hypersonic flowsHypersonic flight technology could open a new chapter for the future of commercial aerospace, with potential applications including rapid global travel and the development of space vehicles. From SpaceX to NASA, major aerospace organizations are actively exploring these technologies and seeking opportunities to commercialize them.
With the development of hypersonic flight, the challenges faced by researchers include not only technological breakthroughs, but also safety and high temperature resistance of aviation materials. These challenges need to be addressed urgently so that we can make greater leaps in this new field.
In future space exploration, will the breakthrough of Mach 5 be the starting point for mankind to conquer hypersonic flight?
