Atlas V's Sonic Boom Made Visible By Sundog 99
Ross-Shire Geek writes "Atlas V lifted off on Feb 11 from Kennedy. As it goes supersonic through a sundog (aka parhelion) you can see (video link) wonderful visible ripples of the shock wave in the sky."
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4. In Soviet Russia, cookies turn YOU off!
5. I'm in Korea, you insensitive clod!
6. In Korea, only old people clod cookies
7. ???
8. PROFIT!
Wow (Score:3, Insightful)
Re:Wow (Score:5, Informative)
Indeed, and apart from that, the linked video is really, really cool.
Ripples in the sky FTW.
Re:Wow (Score:5, Funny)
A glitch in the matrix, nothing more.
Re:Wow (Score:4, Interesting)
I guess real life looks less real to me than special effects these days.
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It's just you. It's not CGI. Tip - get out of the basement for awhile, there's a whole other world out there.
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Is it just me, or does anyone else think this is CGI? My first thought was Photoshop!
I guess real life looks less real to me than special effects these days.
I thought it was claymation at first.
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Wallace and Grommit are more likely to re-visit the moon than the US !
Nice bit o' cheese Grommit !
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How convenient for you that we've just started a new one. (Decade).
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GIMP is better
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Are you serious?? Us artsy type grew up with Photoshop, and Gimp is FINALLY going to introduce a more photoshop-like interface after YEARS. Photoshop has been, and will continue to be the standard upon which all others will be judged.
I keed, I keed....
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Don't feed the troll.... :P
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I keed! (Kidding!)
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Just because it's real doesn't mean it's not computer-generated...
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Re:Wow (Score:5, Informative)
To skip the first ~2minutes and cut to the... ripples: http://www.youtube.com/watch?v=SsDEfu8s1Lw#t=1m51s [youtube.com].
And for even more karma whoring: "A sun dog is a prismatic bright spot in the sky caused by sun shining through ice crystals. The Atlas V rocket exceeded the speed of sound in this layer of ice crystals, making the shock wave visible from the ground."
So I guess the normal compression wave by a sonic boom is not enough to alter the way light goes through it (think flickering air when looking across a heated highway), but these ice crystals do the trick. Right?
Re:Wow (Score:5, Insightful)
No, the compression wave always alters the way light travels through it. It's just that normally there's no light going straight through the wave to you, or if there is it's uniform in color and brightness (i.e. blue sky) so altering the direction of the light slightly doesn't produce a visible change.
My guess would be that the sundog by its very nature means sunlight is at the proper angle at that location to be reflected back to you. A compression wave at this location alters the angle of sunlight being reflected off ice crystals . So the large variability in brightness as a function of small changes in angle makes the ripples visible. Kinda like if someone were trying to signal you with a mirror. If you're seeing blue sky reflected in the mirror, shaking the mirror still yields blue sky so you don't notice any change. But if you're seeing the sun reflected in the mirror, shaking the mirror makes it alternately reflect sunlight and blue sky, causing a strobing effect which is easily visible.
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After logging out 119 people the Troll mod has certainly been worth it.
Why? (Score:2)
Just a huge area with nothing of human value for lightyears.
Lucky miss (Score:5, Funny)
I thought that bird was going to get skewered a few seconds into the launch...
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Don't be silly. The bird might have been a roc [wikipedia.org]!
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Don't be silly. The bird might have been a roc [wikipedia.org]!
Clearly it wanted the launcher for its own purposes.
Yo Slashdot, Imma let you finish, but... (Score:1, Funny)
In 3D (Score:3, Interesting)
Re:In 3D (Score:5, Informative)
The shockwave is cone shaped rather than spherical for fast moving objects such as a rocket, I believe.
Very very cool though.
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The 2D aspect was a result of the shape of the clouds that formed the sundog, not the shape of the sonic wave. Sonic waves are indeed conical.
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A shock is indeed spherical right at Mach 1 (which certainly is not "stationary" LOL). As the Mach number increases further, it becomes a cone. The cone half-angle decreases with Mach number and starts at 90 degrees at Mach 1.
Second POV (Score:5, Informative)
Closer to the pad, and less shaky:
http://www.youtube.com/watch?v=q9S0z1ofcIc [youtube.com]
(it has the voiceover from NASA TV, but doesn't have the launch clock visible ... it might've been a camera angle that they didn't use live, as I don't remember seeing this on TV)
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t might've been a camera angle that they didn't use live, as I don't remember seeing this on TV
correct, I was watching NASATV too and waiting for a nice supersonic plume, but we only got a modest waver on the broadcast camera.
One of the recent Shuttle launches had one of those nice condensation clouds around the shockwave.
Not a sonic boom (Score:1, Interesting)
A sonic boom looks like a single shock wave. Those look like ripples. Engine sound maybe?
Re:Not a sonic boom (Score:5, Informative)
Not necessarily - different edges on the craft will generate additional shock fronts. There are usually two main ones from nose and tail but also from fin tips and even antennae.
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The sonic boom is what you hear when any aircraft going faster than mach 1 passes overhead, not just when it breaks the sound barrier.
The shock wave (very nice to see here: http://imgur.com/Cw5nS [imgur.com] (an F-22?)) only happens at around mach 1 when all the sound waves are on top of each other and don't diverge because the source is moving slower or faster than mach 1.
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Re:Not a sonic boom (Score:4, Informative)
Exactly [wikipedia.org].
The higher the speed, the more the shock waves become compressed into a series of cones stacked inside each other [google.ca] rather than the spheroids typical at slower speeds. Taken together, the passage of these shock waves through a plane perpendicular to the direction of travel would look a lot like circular ripples.
How incredibly appropriate. (Score:4, Insightful)
Parhelion (Score:2)
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Depends how hungry you are.
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Agree. Sundog sounds like some sort of a weekend snack at the Wienerschitzel.
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Isn't that a Mozilla product? Sunbird, Firefox, Thunderbird...
Any idea what that name is supposed to mean? After looking at the Wikipedia article, it seems to me that it would make about as much sense to call it a Sunhippo or Sunrhino...
Awesome (Score:1)
That's not a Sun Dog... (Score:3, Informative)
new waves below the rocket (Score:2)
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Just "waves?" Motorized cam; music choice (Score:2)
1) I don't think those are "shock waves," just ordinary very-low-frequency sound waves. I think shock waves occur when a pile of sound waves are forced to stack up on top of each other and create an actual pressure discontinuity.
2) I was fascinated to hear the background sounds of someone taking photos with a motorized SLR. That is, film... silver nitrate on polyester film. Is that a pro photojournalist? Do they still use film? Or just someone clinging to a nifty old piece of technology that still does the
Why the Imperial March? (Score:2)
Because it's bad-ass, just like this was.
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That sounded like the music from the awards ceremony at the end, I thought.
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No way to edit it, so I'll just say I was right.
http://www.youtube.com/watch?v=jSZB0NjRqzc [youtube.com]
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Film is still used, excellent resolution, expose now process later. it will always beat digital in rapid fire situations.
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You forgot that digital has to charge all of those teeny tiny capacitors in the CCD, auto-focus, expose them to light, then read the voltage on each one, store them in a computer read-able format, then apply the color correction and exposure factors, then store the image on the mass-storage device; for each picture. My favorite camera is a Canon FTbQL [wikipedia.org], 135 format [wikipedia.org], forty years old and has never had a film jam and the battery is only used for the exposure meter so it completely optional. I can expose 3 frames
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not that i'm disagreeing with your points, but i find it interesting that you respond to digital imaging tech with more tech, albeit film tech. i realise this is slashdot, but i think the mindset of which is technically better based on specs like film size is missing the point of photography. A photographer is someone that can take a great picture with whatever they have on hand, whether homemade pinhole or Mamiya 645 or digital P&S. I find it absurd that people turn their noses up to one format or a
1:54 (Score:2)
1:54 is really the sole reason we explore space.
Couldn't see that from my vantage point (Score:2)
FWIW, I really love this photo [flickr.com] of the launch which was taken by a guy in the same spot where I was. It captures the Atlas V flying past the sun which I thought was perfect given the natur
Cool - but probably not shockwaves (Score:5, Interesting)
Those look like regular acoustic waves to me.
I don't doubt the the rocket can go faster than the speed of sound (which gets lower as you get further from the surface), but those waves distinctly lead the rocket's motion, which means that they are the product of acoustic perturbations moving at the speed of sound in the medium.
If the rocket were moving faster than the speed of sound in that medium, then we would see the usual 'shock cone', where those waves would appear an a fairly narrow cone around the rocket as it passed though - certainly not before.
I qualify 'medium' since it is possible that the rocket is moving faster than the speed of sound (in the air) but not faster than the medium that the sundog constitutes. Liquids, for example, have much higher speed-of-sounds and it is (conceptually, not physically) fairly simple for something to be moving faster than the speed of sound in air at sea level but not be anywhere close to the speed of sound in a liquid that it is travelling - and thus producing the regular u-c, u+c acoustic waves.
However, as I understand them, sundogs are collections of ice crystals and probably don't have a higher speed of sound than the air around them. But anyway, waves preceding the motion of a body in a medium are certainly not shockwaves - if we could visualize the waves any object makes in the air, you would see acoustic waves arising from the object's motion before and after it.
Still neat-looking, though.
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At 2:01 you can hear the mission controller (or at least the same voice who was calling the countdown, ignition, etc) in the background saying, "Vehicle is now supersonic."
Just acoustic pressure waves (Score:3, Informative)
Another video of the launch with clean audio. Rocket isn't supersonic until roughly 2 minutes after launch.
http://www.youtube.com/watch?v=TRFWq7gcj2E&feature=fvw [youtube.com]
It didn't look like a shockwave to me from the start, as the name implies, it would be visible as a very sharp, immediate disturbance, not a bunch of ripples. Actually, would have been really cool if it *had* gone supersonic in that cloud layer.
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Not quite 2 minutes.
According to the ground loop audio, rocket goes supersonic at 1:38 in that video; launch is at 0:12. So mach 1 is at T+84 seconds or so. This matches my calculations in another thread, which I did using published Atlas rocket launch profiles.
The amateur video in the summary shows the phenomenon 75 seconds after launch. So while the rocket isn't yet supersonic, it's close. And that makes sense: in the transsonic region just shy of Mach 1, you get violent and irregular pressure-wave ph
Worst Camera Work Ever (Score:1, Troll)
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Here's what I don't get (Score:2, Insightful)
Every politician thinking about cancelling Ares needs to think about that. They wouldn't have cell phones and 3G internet and GPS if it weren't for the brave men and women who are, as Steve Buscemei so perfectly put it (minus the nuke):
"You know we're sitting on four million pounds of fuel, one nuclear weapon and a thing that has 270,000 m
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Once upon a time, men would have been sitting on top of that rocket.
I doubt it. It's only putting a satellite in orbit. Why'd anyone put men on that rocket?
My explanation (Score:3, Interesting)
I've looked at this a few dozen times. It's truly an amazing effect.
Being in the CGI effects business myself (and actually right in the middle of bidding some interesting atmospheric effects for a movie dogfight) I thought it was fake at first, mostly because I've never seen anything like this before. A spectacular display like this, I would have thought, would have been photographed many times if it was a normal occurrence. Some commenters have said that something similar happened on the Apollo XI launch, I haven't seen film that confirms that.
But no, it's clearly real. Many people saw it, several people filmed it.
What it is, is the shockwave moving through a thin layer of clouds and atmosphere. The shockwave disturbs that layer of clouds in some way (in the case of the sun dog, apparently disturbing the crystals orientation -- shockingly these sun dogs require the hexagonal crystals to be hanging more-or-less flat in the air) There are any number of films of airplanes flying above the speed of sound causing clouds to pop into existence and then disappear as the shockwave passes. Every nuclear bomb sequence has these kind of shock-induced clouds as well.
I suppose that clouds with exactly the characteristics to make this happen for rocket launches are rare, because I've watched film of hundreds of launches and never seen this. It always pays to look up!
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I love Mondays. On a Monday, anything is possible.
That is a genuinely novel and interesting sig. Is it a quotation from someone, or is it you?
Sonic boom or not? Math (Score:5, Informative)
Some debate here as to whether what we're seeing is a sonic boom, or just loud low-frequency sound waves. Let's do the math...
Basic question: is the rocket going at Mach 1 or greater when the phenomenon happens?
In the video, the launch happens at 0:38, and the ripples are seen at 1:53, 75 seconds later.
Here's a handy document [umd.edu] showing the launch profile of an Atlas V. It doesn't show velocity vs time, but on page 19 there's an acceleration vs time graph for the Atlas V 401, the specific vehicle [nasa.gov] used in this launch. It shows the average thrust during the first 75 seconds is 1.4 +/- .05 g's (uncertain because I can't read the graph that accurately.)
Subtract out 1 g for gravity pulling the rocket down, to get a vehicle acceleration of 0.4 +/- 0.05 g, which over 75 seconds will lead to a final velocity of 294 +/- 36 m/s.
The speed of sound is 330 m/s. So at the time we see the ripples, the rocket is riiiiight about at the speed of sound, maybe a little over, maybe a little under, impossible to tell.
This transition to supersonic flow is often chaotic and irregular, which would explain the intense but complicated ripples seen. If the rocket was going at mach 2 or 3, we'd see a perfectly shaped set of concentric rings; if it was going at far less than mach 1, we'd see nothing at all.
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