The breaking the sound barrier thread

[Sailor]

Breaking the sound barrier

At sea level a plane must exceed 741 mph to break the sound barrier, or the speed at which sound travels.

The change in pressure as the plane outruns all of the pressure and sound waves in front of it is heard on the ground as an explosion or sonic boom. The pressure change condenses the water in the air as the jet passes these waves. Altitude, wind speed, humidity, the shape and trajectory of the plane - all of these affect the breaking of this barrier. The slightest drag or atmospheric pull on the plane shatters the vapor oval like fireworks as the plane passes through.

Check out this F-18 Hornet video.
YouTube - F18 hornet

Here is my collection of photos of various aircraft breaking the sound barrier. The photos capture the moment.
Add you favorite aircraft here.

F-18 Hornet

F-8 Crusader

F-22 Raptor

F-14 Tomcat

B-2 Nighthawk

and just to show the Brylcream boys they can do it, a B-52.

B-1B Lancer

 

[Soham]

Good pics Sailor. Funny to watch a Buff in the midst of the sonic boom.
Just one question,
You said :

t sea level a plane must exceed 741 mph to break the sound barrier, or the speed at which sound travels.

The speed of sound remains the same anywhere in air, then why the mention of Sea level ?

 

[Auberon]

The speed of sound remains the same anywhere in air, then why the mention of Sea level ?

Air is a mixture of gases, air itself is not the same everywhere, density, temp., composition etc varies, all have an effect on the speed of sound.

 

[Sailor]

Because the air gets colder as you go higher. The toughest reading for an aircraft is at sea level and the official measurement is taken there..

Table: The impact of temperature on the speed of sound

−25 315.7 Speed of sound c in m/s
−20 318.9
−15 322.0
−10 325.2
−5 328.2
0 331.3
5 334.3
10 337.3
15 340.3
20 343.3
25 346.2
30 349.1
35 352.0

With the following formula you can calculate more exactly the speed of sound.

Speed of sound Schall in m/s; temperature Vartheta in °C

The speed of sound c depends on the temperature of air and not on the air pressure!
The humidity of air has some negligible effect on the speed of sound. The air pressure
and the density of air (air density) are proportional to each other at the same temperature.
It applies always p / ρ = constant. rho is the density ρ and p is the sound pressure.

 

[Soham]

Oh yes... Thank you for the clarification. T'was but a silly question.

 

[Sailor]

It was a good question Sol. It is from such questions that things are learnt.
I wonder how many here knew about temperature and air pressure in relation to the speed of sound?

 

[Known_Unknown]

Nice pics! Feels like the Starship Enterprise coming out of warp speed.

 

[prahladh]

Do passenger planes experience sonic booms, because they travel at way more than 740mph?

 

[Sailor]

Only the Concorde and the Tu-144 have flown at speeds exceeding the sound barrier Rimser. These were designed to do it.
The Boeing 747 for instance flies at around mach .85 with a top speed of mach.92

 

[prahladh]

Thanks sailor.
When I was on cathay pacific they showed a speed of 1225kmph which is mach1 I guess enough for a boom ?
Am I right!

 

[Sailor]

Rimser, all I can say is that you got that wrong. It isn't possible. I have had uncountable international flights and the fastest I ever saw on the screen monitor was 1005kph.