Supersonic Flight and Sonic Booms

Discussions on high/extreme altitude and mach busting rockets.

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Re: Supersonic Flight and Sonic Booms

Postby Space Mark » Fri Mar 21, 2014 3:10 pm

Wow, I wouldn't have thought that a 747's structure would handle high transonic/mach, nevermind flaming out the engines. I'd love to read more about that one! I love it when planes do crazy things, like those fedex pilots that were fight a hijack and flew it almost inverted.
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Re: Supersonic Flight and Sonic Booms

Postby SpaceManMat » Fri Mar 21, 2014 5:09 pm

rocket_troy wrote:I heard once that someone put a 747 into a nose dive to exceed Mach. That would've provided a nice audible report :)


All of the big airliners would be tested this way, they all have cruising speeds in the 800-1000km/h range. Bottom line is they are powerful enough to break Mach in a powered decent, so designers have got to know that it can be flown safely in those conditions.

Space Mark wrote:Wow, I wouldn't have thought that a 747's structure would handle high transonic/mach, nevermind flaming out the engines. I'd love to read more about that one! I love it when planes do crazy things, like those fedex pilots that were fight a hijack and flew it almost inverted.


I believe they also do inverted flight tests, apparently a good test pilot can roll a 747 and the passengers could not tell if they weren't able to see outside.
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Re: Supersonic Flight and Sonic Booms

Postby Fadge » Sat Mar 22, 2014 11:18 pm

rocket_troy wrote:I heard once that someone put a 747 into a nose dive to exceed Mach.


This probably refers to China Air Flight 006 that went into a dive and is reported to have exceeded 1.0M.

There is a NTSB report which states it "... exceeded the airplane's maximum operating speed (Vmo). Vmo is 0.92M"

Abstract of the report: "About 1016 Pacific standard time, February 19, 1985, China Airlines Flight 006, a Boeing 747 SP-09, enroute to Los Angeles, California from Taipei, Taiwan, suffered an inflight upset. The flight from Taipei to about 300 nmi northwest of San Francisco was uneventful and the airplane was flying at about 41,000 feet mean sea level when the No. 4 engine lost power. During the attempt to recover and restore normal power on the No.4 engine, the airplane rolled to the right, nosed over, and entered an uncontrollable descent.
The captain was unable to restore the airplane to stable flight until it had descended to
9,500 feet. After the captain stabilized the airplane, he elected to divert to San Francisco International Airport, where a safe landing was made. Although the airplane suffered major structural damage during the upset, descent, and subsequent recovery, only 2 persons among the 274 passengers and crew on board were injured seriously.
"

"The maximum vertical acceleration forces recorded during the descent were 4.8Gs and 5.lGs as the airplane descended through 30,552 feet and 19,083 feet, respectively."

Full report can be found at: http://www.rvs.uni-bielefeld.de/publica ... R8603.html
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Re: Supersonic Flight and Sonic Booms

Postby Fadge » Sun Mar 23, 2014 8:46 am

Forgot to mention, the report also states the aircraft sustained major structural damage.


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Re: Supersonic Flight and Sonic Booms

Postby jase » Fri Sep 26, 2014 9:22 am

Watched a couple of interesting (old) clips about supersonic airflow etc...

This one, demonstrates the heating effect during hypersonic flights (which apparently you have to watch via youtube here: http://youtu.be/RChlt5wdqBs playback disabled on other websites):



This one demonstrates the basics:



Nostalgic and very educational 8)
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Re: Supersonic Flight and Sonic Booms

Postby OverTheTop » Fri Sep 26, 2014 9:53 am

Just to clarify, in case anyone is unclear, what "transonic flight" means. It is the portion of the flight where at least some of the airflow over the vehicle is supersonic. The mainstream flow may not be supersonic yet, but perhaps some of the more turbulent areas are.

This can occur at surprisingly low speeds, depending on the aircraft.
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Re: Supersonic Flight and Sonic Booms

Postby jase » Fri Sep 26, 2014 10:14 am

Indeed... What did you think of the "Vortex Generators"? Wondering if they would/could be applicable to rocketry...?

Also watched this one, amazing how much damage a ping pong ball can do travelling supersonic :shock:



Been giving Nic's fins a lot of thought - extraordinary really!

There is a more comprehensive video of the above here: https://www.youtube.com/watch?v=tqP-VqZqp_o
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Re: Supersonic Flight and Sonic Booms

Postby OverTheTop » Fri Sep 26, 2014 1:14 pm

Vortex generators are good at improving airflow and generating lift IIRC, subsonic. We fly rockets, not aeroplanes, so the vortex generators would probably help generate more lift at AoA other than zero. That implies we could use smaller fins for the same corrective moment, which implies minor improvements in drag due to fin frontal area. Given the vortex generators probably add a bit of drag I suspect we hit the law of diminishing returns quickly.

The airflow improvements may assist in the air staying attached as AoA increases, but I suspect gains would be minimal.

Once at mach+ the aerodynamics change anyway and most of the lift is generated on the side of the fin facing the airflow so vortex generators in the lew would be fairly ineffective I think. They would also set up shock fronts which could be good or bad.

I don't recall seeing missiles with much in the way of vortex generators so they are probably not worth the effort, or detrimental
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Re: Supersonic Flight and Sonic Booms

Postby jase » Fri Sep 26, 2014 1:48 pm

OverTheTop wrote:The airflow improvements may assist in the air staying attached as AoA increases, but I suspect gains would be minimal.


Yes, as demonstrated in the video - more about getting the air flow to 'reattach' so the trailing edge/control surfaces are effective, for aircraft.

But on both sides of a rocket fin, maybe some improvements?

Obviously adds drag, but I am wondering if at a certain point, say Mach +2 or higher there maybe performance benefits? Say for example, if by having them you are adding to the surface area of the fin, increasing stability you could save in other areas...

Kind of like (in principle) the 'winglets' on many commercial airliners these days, for example - you look at them and think 'hrm, probably doesn't do much' but in fact they have a significant effect...

Would look cool too 8)
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Re: Supersonic Flight and Sonic Booms

Postby jase » Thu Sep 24, 2015 9:07 am

Just had to share this 8)

Every now and then you see something online that just blows your mind - not only is this a freaking awesome image (and I've had to re-sample this one a few times to get it to upload here, my apologies to NASA), consider how this image was acquired!

From: http://www.nasa.gov/feature/ground-base ... n-and-moon

"The Air Force Test Pilot School at Edwards provided a supersonic T-38C to serve as a target aircraft. Air Force test pilots Maj. Jonathan Orso and Col. Glenn Graham worked with NASA in planning how to precisely align the jet’s flight path to capture the schlieren images. The aircraft needed to be in the right place at the right time in order to eclipse the sun relative to the imaging system on the ground. The pilots had to hand fly the airplane to hit a specific point in the sky to within approximately 300 feet, while travelling faster than the speed of sound. This had to be accomplished within a two-minute window as the sun’s relative position in the sky changed due to Earth’s rotation."

cak-f2-p2.jpg
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I've seen Schlieren images before but this one, just WOW!!! 8) 8) 8)
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Re: Supersonic Flight and Sonic Booms

Postby OverTheTop » Thu Sep 24, 2015 9:26 am

They are doing some neat Schlieren images these days by flying aircraft past cliff faces. The fine detail in the rocks on the face allows post processing of the images to render a schlieren image without having to have exacting conditions to make it visible in the first place. Very clever stuff :D
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Re: Supersonic Flight and Sonic Booms

Postby OverTheTop » Fri Sep 25, 2015 7:42 am

AIAA Daily Launch 24SEP2015
Gallery Shows Use Of Schlieren Photography Helps Make Planes Quieter.
Jake Ellison at the Seattle Post-Intelligencer (9/23) posts a gallery of NASA images showing how it is “toying” with schlieren photography “supercharged with new computing power and visualization technology to figure out a way to make planes quieter.” Ellison thinks that while the research is “sure” to improve civilian lives, it will likely have “a military application” as well.

Good article with additional images here:
http://www.seattlepi.com/national/article/NASA-reveals-shockwaves-in-amazing-flight-photos-6524316.php
schlieren.png
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Re: Supersonic Flight and Sonic Booms

Postby Lister » Fri Sep 25, 2015 10:20 am

Thats some great info for people wanting to break into mach flight. Thanks.

With new shell fuels and lubricants the planes of tomorrow will go faster.. so thats what we need for rockets :)

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Re: Supersonic Flight and Sonic Booms

Postby jase » Thu May 05, 2016 1:53 pm

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Re: Supersonic Flight and Sonic Booms

Postby OverTheTop » Thu May 05, 2016 2:19 pm

The Concorde was speed limited to a maximum speed of mach 2 or 127degC at the nose, whichever it got to first!
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