The Aviation Thread [Contains Lots of Awesome Pictures]

Oh well, still very cool.
 
SpitfireMK461 said:
Mach 1.07 will produce a much weaker shock then an SR-71 flying at 3.5. The strength of a shock (that is the pressure difference between the front and back sides of the shock) is a function of the square of the Mach number, so shocks are increasingly stronger as Mach increases.

To put it in numbers, the static pressure ratio of a normal shock at Mach 1.07 is 1.1691. The ratio at Mach 3.5 is 14.125. Where as the F-18 flyover could only be noticeably heard at a few hundred feet (the engine noise will drown out the shock eventually), the shock from an SR-71 at speed could be heard for miles.

The Mythbusters results are what one would expect.
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That's what I was wondering, because I would have expected to continually hear booms once it flew past and not just the single boom.
 
P1 aviation is free on the iPad if anyone is interested in business aviation.
 
Look what my dad got me! I don't know nothing about it but it' in pretty good shape and needs some cleaning and disinfecting.

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Now you just need the suit that goes with it.
 
Hmmm, how did a U-2 helmet end up in that part of the world?

Pentagon: Aircraft flew at 20 times the speed of sound


The Pentagon released video of a test flight of an unmanned experimental aircraft as it sped through air at 13,000 mph this month above the Pacific Ocean.

The video was ?captured from a hand-held camera operated by a crew member aboard the Pacific Tracker ? the first sea-borne telemetry collection asset able to visually monitor? the aircraft in its test flight.

In the test flight, the aircraft, known as the Falcon Hypersonic Technology Vehicle 2, was launched Aug. 11 from Vandenberg Air Force Base, northwest of Santa Barbara, into the upper reaches of Earth's atmosphere aboard an eight-story Minotaur IV rocket, made by Orbital Sciences Corp.

After reaching an undisclosed suborbital altitude, the aircraft jettisoned from its protective cover atop the rocket, then nose-dived back toward Earth, leveled out and was supposed to glide above the Pacific at 20 times the speed of sound, or Mach 20.

The plan was for the Falcon to speed westward for 30 minutes before plunging into the ocean near Kwajalein Atoll, about 4,000 miles from Vandenberg. But the Pentagon?s research arm, known as the Defense Advanced Research Projects Agency, or DARPA, which was responsible for the test, lost its data connection with the arrowhead-shaped plane.

Subsequently, the Falcon failed three minutes into the flight and splashed down in the Pacific.

But on Thursday, DARPA issued a release saying that the flight wasn?t a complete failure, and that more than 20 air, land, sea and space data collection systems were operational.

?Scientists believe that very high-quality data collected from the combined test range assets will aid our further understanding of this unique flight environment,? DARPA said. ?The footage released today shows how rapidly a vehicle can travel from horizon to horizon at Mach 20.?

It was the second and last scheduled flight for the Falcon program, which began in 2003 and cost taxpayers about $320 million. Both flights failed to go the distance.
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[video=youtube;uVFNLdTuN-s]http://www.youtube.com/watch?v=uVFNLdTuN-s&feature=player_embedded[/video]
 
Did a little investigative researching, its NOT a U-2 helmet, but looks to be an old MiG-25 Foxbat helmet:

http://gauntletinternational.com/helmets/GSh-6A.htm

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http://blog.starwreck.com/category/world/nazis/page/2/ (1/4 way down)
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The helmet is an original Mig-25 fighter pilot?s helmet. Basicly it?s a space suit, since the Mig-25 was designed to reach altitudes around 25 kilometers. It?s also one of the fastest aeroplanes ever built, with a top speed of Mach 3.2 (that?s 3500 km/h or 2,170 mph). Back in it?s day it was considered so awesome that the Hollywood propaganda machine sent Clint Eastwood to steal it?s fictional successor in the film Firefox. Sadly it was quickly made obsolete by missiles, so these days only couple of third-world airforces operate the plane and there?s even two of them sitting here at the Tampere airport, just rusting away.
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Cold Fussion said:
That's what I was wondering, because I would have expected to continually hear booms once it flew past and not just the single boom.
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That's not how it works. The boom you hear is just the normal sound of a jet but stacked up on-top of each other -- all of the normal noise that you would hear before the jet reached you. I think at least...

Once the boom hits, then it's all just normal noise as the source is moving away from you.
 
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This thread needs more business aviation:

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http://imageshack.**/photo/my-images/251/asddbz.jpg/

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Bonus F-18 pic:

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Viper007Bond said:
That's not how it works. The boom you hear is just the normal sound of a jet but stacked up on-top of each other -- all of the normal noise that you would hear before the jet reached you. I think at least...

Once the boom hits, then it's all just normal noise as the source is moving away from you.
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The boom is the sudden change in pressure experienced at the front and rear of the aircraft, which happens all along the flight path. I've been reading up on it and it can only be heard when it's above you because the width of the boom is very narrow.
 
Cold Fussion said:
The boom is the sudden change in pressure experienced at the front and rear of the aircraft, which happens all along the flight path. I've been reading up on it and it can only be heard when it's above you because the width of the boom is very narrow.
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More accurately, the boom is caused by the pressure change across the shockwave itself. How audible the shock is depends on the Mach number and the shape of the aircraft (different shapes will create different shockwaves). You don't have to be below the aircraft to hear the shock, I just imagine it is strongest there on fighter jets due to the largely flat shape of most fighters.

Viper is somewhat correct though. At subsonic speeds, the air is able to transfer energy faster than the aircraft is moving, so the air ahead feels it coming before it gets there. At supersonic speeds, the air cannot transfer that energy faster, so the air ahead experiences the aircraft only when it gets hit by the plane, so there is an essentially instantaneous transfer of all that energy. In essence, you can imagine a sonic boom being caused by the sound of the plane stacking up at the shockwave. Once the wave has passed, you will hear the normal sound.

Something else to keep in mind is how many shockwaves are created. At transonic speeds (~ Mach 0.9-1.1) you could have numerous waves coming off the vehicle because an initially subsonic flow will accelerate over a piece of bodywork (such as wings) and reach Mach 1 or greater. In this situation, you might not hear a clearly defined sonic boom as the plane goes by. This picture is the best I know of showing transonic behavior. There is a higher res version, even in this thread, but I'm too lazy to find it.

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Notice how there is no shock coming off the nose. They all come off later pieces of bodywork such as the canopy, the fuselage, and the wings. Actually, the coolest element of this picture is how the later shocks eventually coalesce into a singular shock at the edge of the photo (the bottom shock interacting with the water, awesome). I imagine there is a quite but still audible approach followed by a quick yet still gradual rise of noise.

At higher Mach numbers, there will typically be one dominate shockwave, the one that is coming off the nose of the plane. The nose will have been designed to send the shock away from the rest of the bodywork so it will not interrupt the airflow on the wings and create more shockwaves. This situation is when you hear nothing and then get the massive boom. Again, though, the Mach number determines the strength of the shock which will determine how loud the boom is, and thus how far away you can hear a boom.
 
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That is pure win.

flyinhawaiian said:
I love me some Falcons!!!
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Same here - they're like fighter jets that just happen to look like business jets.

Having said that, there arent many here. Most of the bizjets i have seen are either gulfstream or Bombardier. VLJs are really taking off too.
 
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