A photo of a sonic boom.

[Zuki Bandit]

Found this on the interwebby.


"The camera was set for manual exposure of F/5.6 at 1/1000 sec. John, the lucky and talented dog, caught this masterpiece with a single shot by
prefocusing at approximately 200-300 yards off the port side of the ship and then panning left to right as
the aircraft flew by."

[R6_kid:Me]

Is this actually a 'sonic boom'... the white 'cloud' is the compression (rarefraction) of the moisture in the air causing it to condense into what we see as a 'cloud'.

These are cool pictures non the less, but im sure they can be caught at sub-sonic speeds.

[Usarka]

it's aliens from the stargate!

[Bren]

looks like its wearing a Tutu

[peasea]

Found this on the interwebby.


"The camera was set for manual exposure of F/5.6 at 1/1000 sec. John, the lucky and talented dog, caught this masterpiece with a single shot by
prefocusing at approximately 200-300 yards off the port side of the ship and then panning left to right as
the aircraft flew by."

Seen a car doing it?

[RantyDave]

Is this actually a 'sonic boom'... the white 'cloud' is the compression (rarefraction) of the moisture in the air causing it to condense into what we see as a 'cloud'.

Yes it is. What you see here is a Prandtl Glauert singularity which, I am pleased to say, I spelt correctly first time through. It's actually the shockwave that builds up on anything astonishingly fast (not just aircraft) and which it has to pass through in order to go properly supersonic. The cone is caused by a region of low pressure forming behind the shockwave causing the water vapour to (briefly) condense.

I love them. They give me the horn and remind me of happy days when I gave a lot of a shit about fluid dynamics.

Here's a much cooler picture of someone having a lot more fun than me. Bastards.

Dave

[oldguy]

check the linkhttp://www.youtube.com/watch?v=-d9A2oq1N38

[Curious_AJ]

TAKE MY BREATH AWAAAAY!!

*come on... don't say you don't know what I'm on about...*

[Bren]

TAKE MY BREATH AWAAAAY!!

*come on... don't say you don't know what I'm on about...*

I think you are on about Maverick on a 1985 Kawasaki GPZ 900 Ninja

[Bass]

Yes it is. What you see here is a Prandtl Glauert singularity which, I am pleased to say, I spelt correctly first time through. It's actually the shockwave that builds up on anything astonishingly fast (not just aircraft) and which it has to pass through in order to go properly supersonic. The cone is caused by a region of low pressure forming behind the shockwave causing the water vapour to (briefly) condense.

Dave

Well, there you go. I had always assumed that the condensation cloud marked the region of high pressure of the shock wave itself. I had reached this conclusion because while I hadn't thought too deeply about it, I always drain a fair bit of water out of the receiver of my air compressor. So I assumed that compressing air increased the relative saturation and so caused condensation.
Now you tell me that decompressing the air does this and I can't disagree because, firstly, I had always thought that the shock wave should form further forward on the aircraft than the cloud does and secondly, I have often seen condensation trails on the top surface of the flap tips of landing 737's (obviously a low pressure area) in conditions of high relative humidity.
Somewhere around here, I have a psychrometric chart which probably explains this, but since I can't find it at the moment, can you tell me why a pressure shift in either direction appears to increase relative saturation?

[Curious_AJ]

I think you are on about Maverick on a 1985 Kawasaki GPZ 900 Ninja

well, I was just quoting a song from the movie, but close enough.. lol

[Ocean1]

Well, there you go. I had always assumed that the condensation cloud marked the region of high pressure of the shock wave itself. I had reached this conclusion because while I hadn't thought too deeply about it, I always drain a fair bit of water out of the receiver of my air compressor. So I assumed that compressing air increased the relative saturation and so caused condensation.
Now you tell me that decompressing the air does this and I can't disagree because, firstly, I had always thought that the shock wave should form further forward on the aircraft than the cloud does and secondly, I have often seen condensation trails on the top surface of the flap tips of landing 737's (obviously a low pressure area) in conditions of high relative humidity.
Somewhere around here, I have a psychrometric chart which probably explains this, but since I can't find it at the moment, can you tell me why a pressure shift in either direction appears to increase relative saturation?

There's water in your reciever because of the pressure drop as it moves from the compressor into the larger volume. There's also some thermodynamic stuff going on there, along with the fact that there's a lot of cold surface area inside the reciever. I always get confused between Boyle's law and Charles's law... looks... http://en.wikipedia.org/wiki/Gas_laws

I have heard of instances where the local dew-point has been right on the limit for fog and the the shock wave and subsequent local pressure drop has tripped the whole area into a whiteout. Must be both spectacular and fucken scary.

[Bass]

There's water in your reciever because of the pressure drop as it moves from the compressor into the larger volume. There's also some thermodynamic stuff going on there, along with the fact that there's a lot of cold surface area inside the reciever. I always get confused between Boyle's law and Charles's law... looks... http://en.wikipedia.org/wiki/Gas_laws

I have heard of instances where the local dew-point has been right on the limit for fog and the the shock wave and subsequent local pressure drop has tripped the whole area into a whiteout. Must be both spectacular and fucken scary.

OK.....Ummm.... I don't think that the ideal gas law helps much here and I have long forgotten most of my thermo. Also, if I go outside to the big factory compressor which is an oil flooded screw machine, it is basically a positively sealed progressing cavity pump. This means that the pressure in the screw elements never gets much higher than the receiver pressure. Also, the receiver gets quite warm. Yet I still drain lots of water out.

For the whiteout phenomenon you describe, I wonder if it's a supersaturation one. You are probably aware that air will supersaturate if it is very clean and very still, so that the moisture has no nuclei to coalesce on. This is what causes the long lasting vapour trails behind high flying aircraft when supersaturated air is both disturbed and polluted by their passage.
I wonder if your whiteout is a low altitude example of the same thing.
Either way, it would be a trifle inconvenient, hard out, mid corner on the bike.

[avgas]

English sucks - Boom = sound
Unless you are 2 and then everything looks boom.
Onamatapaia (dammed if i can spell it properly)
However Clap and the Clap are exceptions to the rule. hehe.
I wonder if the pilot farted?

[Ocean1]

OK.....Ummm.... I don't think that the ideal gas law helps much here and I have long forgotten most of my thermo. Also, if I go outside to the big factory compressor which is an oil flooded screw machine, it is basically a positively sealed progressing cavity pump. This means that the pressure in the screw elements never gets much higher than the receiver pressure. Also, the receiver gets quite warm. Yet I still drain lots of water out.

Nonetheless, the pressure in the reciever is lower than that in the compressor. If the air is close to saturated then any drop in pressure will cause condensation, there's just less mass there to saturate. Also, warm as the reciever is it's still way cooler than the incoming air, the compressor has just squished it into a tenth of it's previous volume. I can't be bothered looking it up but it'll be fuggen hot.

For the whiteout phenomenon you describe, I wonder if it's a supersaturation one. You are probably aware that air will supersaturate if it is very clean and very still, so that the moisture has no nuclei to coalesce on. This is what causes the long lasting vapour trails behind high flying aircraft when supersaturated air is both disturbed and polluted by their passage.
I wonder if your whiteout is a low altitude example of the same thing.

Seems likely, reports seem to be from low altitude at transition to supersonic. I heard of one such incident as an F18 flew past a carrier at under 40ft, the whiteout was instant and apparently extended for hundreds of metres. Temperature was sub-zero, don't know if that had any bearing on the outcome.