sonic boom

[bonzo]

I have been troubled for years with the question of where the boom occurs. My readings suggested the boom occurs when the sound leaves the airplane, the boom occurring at the point on the ground where the shock wave hits as this happens. Others contend that the boom follows the path of the airplane for its entire supersonic flight.
When the shuttle came back over Santa Barbara or near there, we could hear the boom in the San Fernando Valley as the shock wave and the craft reunited. Written accounts stated as I remember that the boom would happen that point. I don't think that a boom was heard when the craft was farther north and still supersonic.
In the fifties I was able to witness an F104 at an airshow at Nellis bomb range. go supersonic to start the show. When he came by the grandstands later at what seemed like eye level, we could see the shock wave far behind the aircraft, but my memory says we didn't hear a boom after he passed, but just the tremendous noise from the engine, which was by all means startling after he passed in complete silence.
Given all this, I maintain that it does not go boooooooooooooom across the country, but is only on going supersonic, and returning.
Anybody have thoughts, theories, or facts on this?

[DoraNineFan]

The boom isn't a sound but a pressure wave and any object (bullet or airplane) that reaches supersonic velocity will produce that pressure wave. The pressure wave will dissipate over time and distance and will not be heard farther away. I think the F-104 flight you describe was the effects of transonic flight and not supersonic flight because strange things happen as an aircraft approaches the speed of sound.

[Clifford Bossie]

The boom will follow the path of the aircraft. The phenomenon is created as long as the airplane is supersonic. To quote Wikipedia: "Contrary to popular belief, a sonic boom does not occur only at the moment an object crosses the speed of sound; and neither is it heard in all directions emanating from the speeding object. Rather the boom is a continuous effect that occurs while the object is travelling at supersonic speeds. But it only affects observers that are positioned at a point that intersects an imaginary geometrical cone behind the object. As the object moves, this imaginary cone also moves behind it and when the cone passes over the observer, they will briefly experience the boom."

[Chris Brame]

That makes sense... the few times the shuttle landed at Vandenberg, we could hear the boom in downtown L.A. where I worked (it sounded like somebody dropped a large heavy cardboard box on the ceiling).

[ZRX61]

That makes sense... the few times the shuttle landed at Vandenberg, we could hear the boom in downtown L.A. where I worked (it sounded like somebody dropped a large heavy cardboard box on the ceiling).

Edwards, they never landed at Vandenberg.

[BigGrey]

The shuttle also gave off twin booms over L.A. When CY flew overhead at Edwards in an F-15 on the 50th anniversary of his first supersonic flight he was high up and the boom wasn't that loud.

[ZRX61]

We get them all the time up here in the AV. Sometimes we get over achievers who rattle the entire town, set off car alarms, get the dogs barking etc. Roomie had the shower door rattle when she was in the shower one morning. Few weeks back they were reports of broken windows in Rosamond. Helps to have a scanner so you get a bit of warning when a flight of 3 F35's requests supersonic flight coming back from China Lake etc, then we get over-lapping double booms. Last month we have a series of 5 booms, one was REALLY loud so I guess that was two at the same time.

[bdk]

There is a shock wave at the front and the back of a plane, so there are actually 2 sonic booms. You may hear it as a "pop-pop."

When you see the vapor cone on airplanes lower down, that is a phase change from the humidity in the air condensing, not a supersonic shock wave.

[DaveG]

We get them all the time up here in the AV. Sometimes we get over achievers who rattle the entire town, set off car alarms, get the dogs barking etc. Roomie had the shower door rattle when she was in the shower one morning. Few weeks back they were reports of broken windows in Rosamond. Helps to have a scanner so you get a bit of warning when a flight of 3 F35's requests supersonic flight coming back from China Lake etc, then we get over-lapping double booms. Last month we have a series of 5 booms, one was REALLY loud so I guess that was two at the same time.

And I'm here thinking

[Chris Brame]

Edwards, they never landed at Vandenberg.

Edwards, dammit - how embarrassing...

[ZRX61]

Edwards, they never landed at Vandenberg.

Edwards, dammit - how embarrassing...

They did extend the runway at Vandenberg for them though, there was even talk of landing them in Palmdale if they were due back at Plant 42 for work. The idea was it would save the (alledged) $1M cost of putting them on the 747 over at EAFB & ferrying them 25 miles.

[Blackbirdfan]

When I was a kid I used to hear the SR-71s coming off the tankers north of Susanville CA. They would rattle the windows sometimes, but usually nothing more. The higher they were, the less loud the boom was. Heck, the last flight of the SR that happened at Edwards they did a flyby at Mach 3 at 80(ish) thousand feet. The boom was noticeable, but not all that loud. Yes, the boom will follow the the plane, but if its high enough, its like someone slamming a door, from across the street. 30K feet, its noticeable, 80K, not so much. I have to admit, I miss hearing those unmistakable double sonic booms letting me know the fastest thing in the sky was not far away.

Will