Air density reaches critical mass at the speed of sound.

that's why it's the speed sound travels.

which seems obvious, but a surprising number of people don't really understand it.


sound travels at different speed through different gasses, and so an aircraft designed to travel a certain fraction of mach will travel a different linear velocity (MPH, or KPH<Km\h>) in different mediums (or in the same medium under different conditions, say, temperature, or altitude)

This is why Mach is described as Mach, and not "x mph"

it's a function (a non linear one even) not an absolute speed.



This speed is the speed of sound because at this point the air becomes sufficiently viscous that the pressure required to move past it steeply increases.

the sonic boom is born of a breaking of this viscous air.

you can actually replicate a sonic boom visually very easily at relatively low speeds in a much thicker medium (say, water)

 

ur so smart

 

Cool story bro.

 

Here's one. Why isn't a sonic boom heard after the shuttle launches and it goes supersonic?

Maybe the whole shuttle thing is just a fake and a conspiracy by the government.

.

 

Dunno what you're talking about. That condensate is where the air is collecting, and is indicative of a sonic boom. So, sonic boom, and, I've never heard of that phenomena before this moment, so any answer I gave you would just be speculation.

being that I do enjoy speculation.

first thought (in reality second thought, because first REAL thought is that you're making shit up, or passing along bad data) is that the wave pressure is insufficient to make the distance inverse square law and all that.(unlikely, because sonic booms are mean motherfuckers, and the shuttle is going fucking fast)

second thought would be that the other sound drowns out the sonic boom in some form or fashion, there is an incredible amount of energy being used to move the shuttle

third thought is mitigation, there were a lot of experiments in the sixties and seventies dealing with sonic boom mitigation, and some of them met with great success.

so far as I know, and every launch I've ever seen, there have been sonic booms.

but if there have been launches without them (which I do in earnestness doubt) seems like those three answers would be the only rational ones.

 

Earth rocks

 

Thanks for the heads up.

 

awesome man

 

just like when you talk about velocity you need to specify direction, otherwise youre just talking about speed.

 

i agree

 

Critical mass is a threshold value. Some people don't understand that.

 

Because directions around the aircraft's direction of travel are equivalent, the shock forms a Mach cone with the aircraft at its tip. The faster it goes, the finer, (more pointed) the cone. You have to be within the radius of the cone where it contacts the ground in order to here it.

 

im not a scientist. im an artist, and spiritual anarchist

 

it dosent go outward in a sphere?

 

No.

 

no, it ignites at 2pie to the 10th degree over 4.20 squared.

 

yeah, I used critical mass when I WASN'T talking about nuclear fission, I would be more precise if I were an absolute insufferable douchebag.

but I'm not, so a little imprecision here and there is completely acceptable

and I have a lovely picture of what sonic booms look like

 

Obviously you are not one of the some.

Precisely like the boat wake that you alluded to.

 

That's the explanation I was thinking of when I stated that apparently sonic booms of the shuttle aren't perceived at the ground level during launch. The axis of the Mach cone in that case is nearly vertical and the surface of the cone is expanding outward in roughly a horizontal direction. The cone wouldn't exist until the shuttle reached a particular elevation about 30 seconds or so into launch. So, observers on the ground in the vicinity of the launch site may never get intersected by the cone surface, which is what creates the perceived sonic boom.

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This animation depicts the Mach cone. Note that all the wavefronts are supimposed on the surface of the Mach cone. All those waves hit the observer at once. That creates the perceived boom.

For an aircraft going horizontal, an observer on the ground in the vicinity of the flight path is practically guaranteed to get intersected by the surface of the Mach cone and hear the boom.



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