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George Welch - Who??? First Man to exceed the speed of sound depending on the parameters maybe


JohnT
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On 11/10/2021 at 9:47 PM, Graham Boak said:

Once the shock wave forms you get the boom - behind the shock the pressure drops but the entire aircraft is still flying at the same speed and the speed of sound hasn't changed.

 

 

the whole aircraft doesn't go supersonic at the same time, or maybe more accurately, the air around it doesn't. The more severe the surface and angle of the part of aircraft that's meeting the air is, the faster the air is forced to move out of its way. So, for example particularly with early era aircraft with a thicker wing, air moving over the top goes supersonic before air going underneath it. The tip of a propellor blade will create shock waves before the base, and so on. I'm pretty sure most supersonic aircraft create more than one shockwave because they have local ones form at high pressure points on various locations. For instance, one of the limitations NASA had when testing the blown laminar flow glove on the F-16XL was the shock wave from the bubble canopy interfering with the airflow over the wing. A second shock wave was coming from underneath... if I recall from the intake but I could be wrong.

 

Those high pressure areas will go supersonic first.

 

That, I believe, is what Dov was referring to, but once a shockwave forms at any point on the aircraft, including an overspeeding propellor which can happen while the aircraft itself is travelling well below the speed of sound, I believe you will get a boom (or more than one).

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27 minutes ago, kiseca said:

That, I believe, is what Dov was referring to, but once a shockwave forms at any point on the aircraft, including an overspeeding propellor which can happen while the aircraft itself is travelling well below the speed of sound, I believe you will get a boom (or more than one).

Aircraft such as the Harvard have their propeller tips exceeding the speed of sound, and are hence notoriously noisy.  However the noise was not, is not, and cannot be described as, a "boom". Recent research has suggested that aircraft such as the Whirlwind and Manchester suffered from supersonic flow near the tips of the propellers, and this would explain the performance shortfalls and vibration problems associated with these types.  However, I don't believe anyone reported sonic booms from them.  The shock waves associated with comparatively small local areas dissipate rapidly: it takes a large shockwave to reach the ground and make the distinct sharp report.

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1 hour ago, Graham Boak said:

Aircraft such as the Harvard have their propeller tips exceeding the speed of sound, and are hence notoriously noisy.  However the noise was not, is not, and cannot be described as, a "boom". Recent research has suggested that aircraft such as the Whirlwind and Manchester suffered from supersonic flow near the tips of the propellers, and this would explain the performance shortfalls and vibration problems associated with these types.  However, I don't believe anyone reported sonic booms from them.  The shock waves associated with comparatively small local areas dissipate rapidly: it takes a large shockwave to reach the ground and make the distinct sharp report.

 

 

Sonic cracks then maybe? :D

 

I also have never heard anyone describing sonic booms from prop tips, so fair point. I've heard, to my misfortune, a few Harvards in my time so can concur - bloody noisy thing, compounded by the fact that it's not particularly fast so the noise doesn't go away quickly either.... but definitely, as you say, not a boom.

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28 minutes ago, kiseca said:

I also have never heard anyone describing sonic booms from prop tips, so fair point

 

Or plan for supersonic prop tips and build the appropriately named Thunderscreech.

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To be supersonic:

If you have a bottle with air of 2 bar and an enviroment with the same temperature and with 1 bar and you open a valve at once, you have a supersonic condition.

The pressure relation of 2 causes supersonic speed.

The human body can do it easily, you know what I mean?

Sneezing, fart, klapping the hands (the air in between)!

Happy modelling

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On 11/1/2021 at 12:39 PM, JohnT said:

 

 

 

 

Can the Mods give Wellsprop and Dov a ban for making me feel really really really really stupid  :D  I struggle with a airbrush pressures but thats mind blowing:boom:

Thank God, I thought it was just me 🤣

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3 hours ago, dov said:

To be supersonic:

If you have a bottle with air of 2 bar and an enviroment with the same temperature and with 1 bar and you open a valve at once, you have a supersonic condition.

The pressure relation of 2 causes supersonic speed.

The human body can do it easily, you know what I mean?

Sneezing, fart, klapping the hands (the air in between)!

Happy modelling

 

 

A guy in my school days certainly had supersonic farts

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Nah! Nah!

You all got it wrong! Everyone knows it was a British test pilot, doing a high speed dive in a Swift (called the Prometheus)!

He experienced control lock with serious buffeting and recovered by pushing the stick FORWARD ! Hey presto! Boom!  Through Mach 1!

It was in a movie (The Sound Barrier) so , it must be right!!😉😂.

Incidentally, two of the test pilots credited for the flying sequences were John Derry and, Mike Lithgow - both killed in fatal accidents involving prototypes. Derry was killed only three months after the film was released.

 

John

 

Ps. Its actually a pretty decent film otherwise! 😊

 

Edited by Beermonster1958
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