What happens when a plane slows down from hypersonic speed?

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In summary, the shockwave created by hypersonic flight disappears when the aircraft slows down from hypersonic speed.
  • #1
Mustafa Bayram
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Is it results in a new shockwave or does the shockwave continuously created by hypersonic flight suddenly disappear? I guess slowing down from hypersonic speed will cause a lot of vibration on the plane.
 
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  • #2
Welcome, @Mustafa Bayram !

I don't know for sure, but it seems to me that slowing down should be a more peaceful transition, which nature is passing from a high-demand-energy condition (compressing-heating surrounding atmospheric air) to a condition that requires a lot less energy (non-compressed cooler air).

Copied from
https://www.grc.nasa.gov/www/k-12/airplane/mach.html

"There is no upstream influence in a supersonic flow; disturbances are only transmitted downstream."

 
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  • #3
Mustafa Bayram said:
slowing down from hypersonic speed

"Hypersonic" is usually defined as above Mach 5. "Supersonic" is defined as above Mach 1. Is that what you mean?
 
  • #4
Mustafa Bayram said:
Is it results in a new shockwave or does the shockwave continuously created by hypersonic flight suddenly disappear?
At, or above, the speed of sound, shockwaves radiate energy from the aircraft.
Below the speed of sound, a shockwave is not generated.

The problem with accelerating through the speed of sound is changes in vehicle stability, and the generation of sufficient thrust.
Decelerating through the speed of sound, changes vehicle stability and wastes energy.
 
  • #5
I don't really understand the question. There will always be a shock of some kind at the leading edge/tip of a vehicle if ##M>1##, and that shock will smoothly change in character as a vehicle accelerates or decelerates through various Mach numbers unless conditions are near the shock detachment point. In that situation you might get abrupt changes between attached oblique shocks and bow shocks.
 
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  • #6
hutchphd said:
"Hypersonic" is usually defined as above Mach 5. "Supersonic" is defined as above Mach 1. Is that what you mean?
didn't know that thanks, I mean supersonic
 
  • #7
boneh3ad said:
I don't really understand the question. There will always be a shock of some kind at the leading edge/tip of a vehicle if ##M>1##, and that shock will smoothly change in character as a vehicle accelerates or decelerates through various Mach numbers unless conditions are near the shock detachment point. In that situation you might get abrupt changes between attached oblique shocks and bow shocks.
one of my students asks if a second shockwave is created when a plane slows down from a supersonic flight. I think this can be a good answer; a continuous shock wave created at equal or above the speed of sound. when it slows down from the speed of sound vibrations downgrade and the shockwave is disappear.
 
  • #8
Mustafa Bayram said:
one of my students asks if a second shockwave is created when a plane slows down from a supersonic flight. I think this can be a good answer; a continuous shock wave created at equal or above the speed of sound. when it slows down from the speed of sound vibrations downgrade and the shockwave is disappear.
But that's not what I said. I'm not sure what you mean by "vibrations downgrade." I didn't even mention vibration.
 
  • #9
Mustafa Bayram said:
one of my students asks if a second shockwave is created when a plane slows down from a supersonic flight. I think this can be a good answer; a continuous shock wave created at equal or above the speed of sound.
Yes, I think there is a common misconception around that the boom you hear is the plane breaking the sound barrier - as if there's no boom for an already supersonic plane. That isn't correct; the boom is just the continuously created shock wave passing you as it sweeps across the ground/sky.
 
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  • #10
Lnewqban said:
Copied from
https://www.grc.nasa.gov/www/k-12/airplane/mach.html

"There is no upstream influence in a supersonic flow; disturbances are only transmitted downstream."
So, I take that to mean that one observer will hear a bang but the next guy along the road will not but no one will hear the bang 'stopping' lol. Makes sense, though; a set of recordings made along the path of the aircraft will have a range of different bangs - the last ones would be a 'quieter bang' perhaps.
 
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  • #11
I might be easier to visualize what happens (at least for me) if one realizes that the only reason that a plane slows down at all is due to the drag caused by that onrushing air. The engines power down and the force on the leading edges of the craft cause the craft to slow, allowing the shockwave to advance, smoothing out the gradient.
 
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  • #12
DaveC426913 said:
I might be easier to visualize what happens (at least for me) if one realizes that the only reason that a plane slows down at all is due to the drag caused by that onrushing air. The engines power down and the force on the leading edges of the craft cause the craft to slow, allowing the shockwave to advance, smoothing out the gradient.
There is only one impulse wave travelling over the ground (or perhaps a double). Before it arrives, you don't hear it. When it passes you, you hear it. When it's gone past you no longer hear it cos it's going away from you.
 

1. What is hypersonic speed?

Hypersonic speed is defined as any speed greater than five times the speed of sound, or Mach 5. It is typically achieved by high-speed aircraft or missiles traveling at speeds of Mach 5 to Mach 10.

2. How does a plane slow down from hypersonic speed?

There are several methods that a plane can use to slow down from hypersonic speed. These include using airbrakes, turning the aircraft to increase drag, or using a parachute. The specific method used will depend on the type of aircraft and its capabilities.

3. What happens to the temperature of the plane when it slows down from hypersonic speed?

When a plane slows down from hypersonic speed, the temperature of the aircraft will decrease. This is because at hypersonic speeds, the friction between the air and the aircraft creates intense heat, which dissipates as the speed decreases.

4. Can a plane slow down from hypersonic speed while in flight?

Yes, a plane can slow down from hypersonic speed while in flight. However, this process must be carefully planned and executed to ensure the safety of the aircraft and its passengers. Pilots and engineers work together to determine the best method for slowing down the aircraft based on its capabilities and the current flight conditions.

5. What are the potential dangers of slowing down from hypersonic speed?

Slowing down from hypersonic speed can be a dangerous process if not done correctly. The intense heat generated at hypersonic speeds can cause structural damage to the aircraft, and sudden changes in speed and altitude can also put stress on the aircraft. Additionally, the sudden decrease in speed can cause turbulence and affect the stability of the aircraft. Therefore, it is important for pilots and engineers to carefully plan and execute the process to ensure the safety of the aircraft and its passengers.

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