How can a jet break the sound barrier?
Author: admin Category: 5
Ok I understand that the plane is going faster then the speed of sound. But why cant sound go faster, and if you are going faster and then slow down does the sound catch up with you? Sorry I was thinking about this last nite and it got me curious.
Good question. Not an easy answer. Actually there is no such thing as a "sound barrier". That term was invented during WWII when some fighter aircraft approached the speed of sound in a dive and lost all control. Those pilots who survided the ordeal came back and told stories about this barrier that if you tried to punch through, you were doomed.
Good ol’ Chuck Yeager proved them all wrong when he flew the Bell X1 that he named Glamorous Glennis after his wife, past mach one, the speed of sound and once he was there, the controls smoothed out and the rest is history.
The complicated part about your question though is just exactly what is the speed of sound. You see, it varies depending on the density of the fluid that you are in. The air is a fluid but so is water and sound travels different distances and speeds in water than it does in the air. And even if we’re just talking about the air where they thought the sound barrier exists, sound travels at different speeds based on the density of the air. The biggest factors affecting the density of the air in our atmosphere are altitude and temperature. At sea level, at a temperature of 21 °C (70 °F) and under normal atmospheric conditions, the speed of sound is 769 mph. On that same day if you were to climb to thirty thousand feet, the speed of sound would be only 673 mph. Jet aircraft rely more on what "mach number" that they are flying at than indicated airspeed or true airspeed. [entirely different subject so don't get me going.] For instance, long range cruise of the Boeing 727 executive jet that I fly is Mach .80, or eighty percent of the speed of sound. The speed of sound being Mach 1 of course. Because the wing and controls are affected by the shock wave that builds up over the wing as you approach the speed of sound, knowing the mach number is crutial. It is also the most useable speed indication since the effects of temperature, altitude and humidity are already accounted for.
Hope this makes sense but like I said, your question is a complicated one. But a good one.
July 30th, 2009
sound can only go the speed it goes….the sound waves are slowed by air… is sound goes mach 1 and plane goes 1.5 plane leaves sound behind…..same with lighting…you see flash and some secounds later u hear thunder.
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July 30th, 2009
On average, sound travels 769 mph at sea level with 50% humidity. The speed of sound changes depending on humidity and altitude, but is usually between 680mph and 750mph at the various altitudes where jets fly.
If you can imagine a stone being thrown into a pond, it leaves ripples in concentric circles around it when it splashes. Sound travels in waves, much like water. If you can imagine the jet standing still and making engine noise, the waves of sound, (if you could see them) would travel out from the jet in all directions in conctric circles. As the jet approahes the speed of sound those waves become compressed very small at the nose of the plane and become very elongated at the back of the jet. Once the jet begins to travel faster than the sound, it make a very loud bang called a sonic boom. A that point, if you could see the sound waves, they would all be generated behind the plane. So if the plane is going faster than sound and it passed you by, you would see the plane coming and going past you; then at some point after the plane passed you by, it’s sound would be heard following.
Then once the plane slowed down below the speed of sound, the sound waves will catch up to it.
I hope this makes sense, it’s hard for me to explain without visual aids.
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July 30th, 2009
Sound travels at a fixed rate that is known. Sound is a vibration of molecules through air or liquid. Sound vibrations move through air one molecule at a time until it reaches your ear. In the thin air at high altitudes the sound travels slower because there are less air molecules to transfer this vibration from one to the other. What this mean is a plane like the Concorde that traveled at 60,000.00 ft. had to travel even faster than it would to break the so called sound barrier than if it were trying to break it at sea level.
Sound travels faster in water than it does in air because it’s thicker meaning the molecules are more densely packed together.
References :
July 30th, 2009
Good question. Not an easy answer. Actually there is no such thing as a "sound barrier". That term was invented during WWII when some fighter aircraft approached the speed of sound in a dive and lost all control. Those pilots who survided the ordeal came back and told stories about this barrier that if you tried to punch through, you were doomed.
Good ol’ Chuck Yeager proved them all wrong when he flew the Bell X1 that he named Glamorous Glennis after his wife, past mach one, the speed of sound and once he was there, the controls smoothed out and the rest is history.
The complicated part about your question though is just exactly what is the speed of sound. You see, it varies depending on the density of the fluid that you are in. The air is a fluid but so is water and sound travels different distances and speeds in water than it does in the air. And even if we’re just talking about the air where they thought the sound barrier exists, sound travels at different speeds based on the density of the air. The biggest factors affecting the density of the air in our atmosphere are altitude and temperature. At sea level, at a temperature of 21 °C (70 °F) and under normal atmospheric conditions, the speed of sound is 769 mph. On that same day if you were to climb to thirty thousand feet, the speed of sound would be only 673 mph. Jet aircraft rely more on what "mach number" that they are flying at than indicated airspeed or true airspeed. [entirely different subject so don't get me going.] For instance, long range cruise of the Boeing 727 executive jet that I fly is Mach .80, or eighty percent of the speed of sound. The speed of sound being Mach 1 of course. Because the wing and controls are affected by the shock wave that builds up over the wing as you approach the speed of sound, knowing the mach number is crutial. It is also the most useable speed indication since the effects of temperature, altitude and humidity are already accounted for.
Hope this makes sense but like I said, your question is a complicated one. But a good one.
References :