Sonic booms – Concorde exempt?

[Eric Mc]

davepen said:

durbster said:

When they first broke the sound barrier, did they know it would boom?

It'd be bloody terrifying if not

I think that was the least of their problems, I'm sure there is an old B&W film, based on the de Haviland tests - lots of "cannot hold it" and trips to cemetery. Fixed by the "flying wing" concept.

Quick look on wiki - it was based on Geoffory de Haviland jr and the film was called The Sound Barrier, obviously enough. http://en.wikipedia.org/wiki/The_Sound_Barrier

It was also a fashion to force a boom at the Farnborough Airshow - until one crashed in 1952.
Also used to get booms in Southern Germany in the 1980's, possibly USAF.

I don't think teh sonic booms at Farnborough were stopped because of John Derry's DH110 crash. They were stopped a few years later because of complaines from the locals. Derry's DH110 broke up when the plane was making a subsonic pass.

[daz3210]

Mave said:

daz3210 said:

TEKNOPUG said:

daz3210 said:

I'm gessing during OP's permission isn't a worry. If they are in enemy territory do you think they are there with permission?

No but I'd expect it to be easy to track

Would it though?

I thought the sonic boom came AFTER the object that created it. Thus you only know where it has been.

Still useful though, isn't it? If you can track where it's been, you can work out where it's going; turning circles are quite large at Mach 2+!!

I would say not, only where it won't be.

Turns can be in two directions (left or right) and only at less than a certain circumference. The aircraft could even go straight forward. Hence you can only reliably predict an ever changing cone.

[RizzoTheRat]

Hugo a Gogo said:

yes, surely the boom is travelling AT the speed of sound, and SR71 is going mach 2 point whatever

It travels away from the aircraft at the speed of sound, but will travel across the ground at the same speed as the aircraft. Think of it like a bow wave from a boat. I think the Russians generally knew the Blackboard was there, they just couldn't do anything about it.

Our neighbour many years ago was a concord pilot and held the transatlantic speed record.

[Eric Mc]

RizzoTheRat said:

Hugo a Gogo said:

yes, surely the boom is travelling AT the speed of sound, and SR71 is going mach 2 point whatever

It travels away from the aircraft at the speed of sound, but will travel across the ground at the same speed as the aircraft. Think of it like a bow wave from a boat. I think the Russians generally knew the Blackboard was there, they just couldn't do anything about it.

Our neighbour many years ago was a concord pilot and held the transatlantic speed record.

For an airliner, I presume, since the absolute trans-Atlantic speed record is held by the SR-71. I hour 55 minutes, set in 1974 on its way over to the Farnborough Air Show.

[RizzoTheRat]

Yeah, I assume it was a civilian record.

Was that the one where they apparently didn't come off the throttle soon enough and ended up over Norway or is that an urban myth?

Edit: a quick Google shows they set another record for London to Los Angeles on the way back, and there were complaints of broken windows in LA due to the boom, so no wonder overland supersonic runs were limited.

Edited by RizzoTheRat on Wednesday 14th March 16:30

[Eric Mc]

RizzoTheRat said:

Yeah, I assume it was a civilian record.

Was that the one where they apparently didn't come off the throttle soon enough and ended up over Norway or is that an urban myth?

Sounds like an urban myth to me. They did have a large turn though which took them almost to Paris as they swung around back to land at Farnborough.
The Blackbird paid a few more trips to Farnborough but never tried to set any records on these later visits.

[Mave]

daz3210 said:

Mave said:

daz3210 said:

TEKNOPUG said:

daz3210 said:

I'm gessing during OP's permission isn't a worry. If they are in enemy territory do you think they are there with permission?

No but I'd expect it to be easy to track

Would it though?

I thought the sonic boom came AFTER the object that created it. Thus you only know where it has been.

Still useful though, isn't it? If you can track where it's been, you can work out where it's going; turning circles are quite large at Mach 2+!!

I would say not, only where it won't be.

Turns can be in two directions (left or right) and only at less than a certain circumference. The aircraft could even go straight forward. Hence you can only reliably predict an ever changing cone.

Don't know what you mean by "less than a certain circumference"?

I think the SR-71 had a turning radius of about 100 miles, so any manouevres take minutes rather than seconds....so the prediction cone has quite a narrow angle.

[Glosphil]

When an apprentice at British Aircraft Corporation I spente a short time in the Flight test department and was given the job of answering and logging telephone calls complaining about the Concorde's noise or sonic boom. One day a lady phoned to say that the sonic boom had just shaken her very expensive tea set off the shelf and smashed it on the floor. She wanted compensation. She got most upset when I said that her claim would be rejected as Concorde had not flown that day! We often received complaints regarding damage, farm animals 'spooked', etc. on days that Concorde didn't fly.

[kooky guy]

Surely the SR-71 flew so high that there would be insufficient air to generate a sonic boom...?

And Concorde come to that, once it was up to cruising height...? (60000ft if I recall correctly - and > 70000 for the SR-71)

[steve y]

Rather sketchy memory from school near Southend in the earlier 1960's I remember an aircraft (possibly a English electric Lightening) flying up the Thames estuary deliberately setting off sonic booms to test public reaction! I am sure the older folks may have disliked it but us kids thought it was brilliant! anyone else remember those tests? (cue eric Mc!)

[dr_gn]

Le TVR said:

Frimley111R said:

I couldn’t figure out why the US plane could cause a sonic boom near/affecting residents of cities/town. Surely it’d be way up in the sky? Also, if it did for whatever reason, why didn’t Concorde do the same?

How much over-pressure is generated depends on the mass of the object not just the speed.

Depends on the MASS of the object?

Why is mass relevant to over pressure?

[Eric Mc]

steve y said:

Rather sketchy memory from school near Southend in the earlier 1960's I remember an aircraft (possibly a English electric Lightening) flying up the Thames estuary deliberately setting off sonic booms to test public reaction! I am sure the older folks may have disliked it but us kids thought it was brilliant! anyone else remember those tests? (cue eric Mc!)

Living in Ireland back then, the nearest we ever got to a noisy jet was a BEA Trident taking off from Dublin Airport.

[IroningMan]

There were few qualms about sonic booms in the Eastern bloc: living in Cold War Berlin the East German and Russian airforces seemed to particularly enjoy supersonic overflights on Christmas morning.

[RizzoTheRat]

dr_gn said:

Depends on the MASS of the object?

Why is mass relevant to over pressure?

Because mass is directly proportional to the amount of lift generated.

[dr_gn]

RizzoTheRat said:

dr_gn said:

Depends on the MASS of the object?

Why is mass relevant to over pressure?

Because mass is directly proportional to the amount of lift generated.

So a Concorde completely stripped of all unecessary weight would create a weaker boom than a a Concorde loaded to it's limit, flying under otherwise identical situations?

How does that work?

[Asterix]

Eric Mc said:

durbster said:

When they first broke the sound barrier, did they know it would boom?

It'd be bloody terrifying if not

Yes.

Natural items have been breaking the sound barrier since time began. People may not have understood what was happeneing of course when they heard the bangs.
Ernst Mach solidified the science of transonic and supersonic effects in the 19th century (which is why we have Mach Numbers). Cannonballs, artillery shells and rifle bullets were already man made supersonic objects decades before Chuck Yeager broke the sound barrier in 1947.
The German V2 rocket was actually HYPERSONIC (4,000 mph plus) - and it first flew in 1942, five years before Yeager broke the sound barrier in the Bell X-1.

The tip of a whip breaks the sound barrier when 'cracked' - the oldest supersonic device?

[Tango13]

dr_gn said:

RizzoTheRat said:

dr_gn said:

Depends on the MASS of the object?

Why is mass relevant to over pressure?

Because mass is directly proportional to the amount of lift generated.

So a Concorde completely stripped of all unecessary weight would create a weaker boom than a a Concorde loaded to it's limit, flying under otherwise identical situations?

How does that work?

The intensity of a sonic boom depends on various factors, the aircrafts weight, length, its pitch ie whether it's climbing or diving and the density of the air it's flying through.

[Eric Mc]

Asterix said:

Eric Mc said:

durbster said:

When they first broke the sound barrier, did they know it would boom?

It'd be bloody terrifying if not

Yes.

Natural items have been breaking the sound barrier since time began. People may not have understood what was happeneing of course when they heard the bangs.
Ernst Mach solidified the science of transonic and supersonic effects in the 19th century (which is why we have Mach Numbers). Cannonballs, artillery shells and rifle bullets were already man made supersonic objects decades before Chuck Yeager broke the sound barrier in 1947.
The German V2 rocket was actually HYPERSONIC (4,000 mph plus) - and it first flew in 1942, five years before Yeager broke the sound barrier in the Bell X-1.

The tip of a whip breaks the sound barrier when 'cracked' - the oldest supersonic device?

Already been mentioned. It is perhaps the oldest human made sound barrier breaking device.

There is a theory that the dionosaur Diplodocus could crack its tail like whip.

[Asterix]

Eric Mc said:

Asterix said:

Eric Mc said:

durbster said:

When they first broke the sound barrier, did they know it would boom?

It'd be bloody terrifying if not

Yes.

Natural items have been breaking the sound barrier since time began. People may not have understood what was happeneing of course when they heard the bangs.
Ernst Mach solidified the science of transonic and supersonic effects in the 19th century (which is why we have Mach Numbers). Cannonballs, artillery shells and rifle bullets were already man made supersonic objects decades before Chuck Yeager broke the sound barrier in 1947.
The German V2 rocket was actually HYPERSONIC (4,000 mph plus) - and it first flew in 1942, five years before Yeager broke the sound barrier in the Bell X-1.

The tip of a whip breaks the sound barrier when 'cracked' - the oldest supersonic device?

Already been mentioned. It is perhaps the oldest human made sound barrier breaking device.

There is a theory that the dionosaur Diplodocus could crack its tail like whip.

Ah, sorry - didn't see it mentioned.

[RizzoTheRat]

Think of it as the amount of energy it imparts to the air. Virtually all the energy used by the engines is to force it through the air, so anything that reduces fuel use (less weight, less air density, shape, etc) reduce the amount of energy put in to the air, and hence the amplitude of the shock (massive simplification but it gives the gist)

As said, a whip was probably the first man-made supersonic boom, but thunder also a shock wave.

You can also hear the shock wave quite well from bullets, you get the crack of the shock passing before you hear the thump of the weapon that fired it.