Slashdot Mirror
Atlas V's Sonic Boom Made Visible By Sundog
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."
There is something incredibly belittling about trying to comprehend the vastness that vehicles like that help us explore.
I thought that bird was going to get skewered a few seconds into the launch...
http://michaelsmith.id.au
Dr. Evil's rocket launch was so much better. http://www.youtube.com/watch?v=vkTv8DGlrok
More impressively - the sonic boom "waves" effect is actually a three-D object - imagine if we could see it from multiple POVs, a spherical wave instead of 2D one :)
-- Sig down
A sonic boom looks like a single shock wave. Those look like ripples. Engine sound maybe?
Very appropriate, it seems to me, that a rocket carrying the Solar Dynamics Observatory should make pretty with a sundog.
I think the word "parhelion" sounds better than "sundog".
It's been years since I saw something spectacular like this, thanks for reminding me!
The creative use of technology just boggles the mind...
probably has cookies turned off
I posted this days ago but Timothy gets priority on the homepage? Thanks guys
Holy fuck Batman, that was awesome!
What the Saturn V encountered was an Iridescent Cloud
"The truth points to itself." - Kosh, Babylon5
...if a ball-lightning did a Hadouken to the rocket afterwards.
At 2:00 it looks like there are new wavefronts being generated far below the craft. Reflections from the ground? Can't think of any really good explanation.
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 job?
3) Why would anyone choose the Imperial March from Star Wars, inseparably associated with Bad Guys, as background music?
"How to Do Nothing," kids activities, back in print!
1:54 is really the sole reason we explore space.
A work that expires before its copyright never enters the public domain and thus enjoys eternal copyright protection.
Because it's bad-ass, just like this was.
A work that expires before its copyright never enters the public domain and thus enjoys eternal copyright protection.
Closer to the pad, and less shaky:
http://www.youtube.com/watch?v=q9S0z1ofcIc
(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)
Build it, and they will come^Hplain.
I drove over to the Canaveral National Seashore for this launch. The position of the sun made it very hazy from where I was. This shot is geotagged if you're so inclined to see exactly where it was taken. I didn't see that sonic boom wave and no one I was with made any mention of it either. That's really spectacular.
FWIW, I really love this photo 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 nature of this mission.
-S
--- What parts of "shall make no law", "shall not be infringed", and "shall not be violated" don't you understand?
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.
You know, after getting up in the wee small hours of the morning, driving miles to find a spot to observe the launch and having paid good cash for a video camera (and PC and editing software), you'd think that the joker that took the video would learn **how to pan with the moving object**!. That's "pan with the object" not wait until the object has left the frame and then jerk the camera up until it's at the bottom. And you know, you can buy cameras these days with image stabilization (or even stabilize in post). *very* frustrating video.
Rich people are eccentric. Poor people are strange. Me, I'd be happy with odd.
Once upon a time, men would have been sitting on top of that rocket. Men with no fear, who couldn't give a shit about politics. They just wanted the ultimate ride.
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 moving parts built by the lowest bidder. Makes you feel good, doesn't it? "
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!
I love Mondays. On a Monday, anything is possible.
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 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 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.
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
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.
argument follows.
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!
In soviet Russia, God creates you!
They are blind to what they dont want to see. They have been spoon fed this shit since they were little by their parents, their teachers, their religious leaders and their politicians, and they buy the entire thing hook line and sinker. The more they fight for it, the more liklely they will never come to their sences. These people cant see what everyone else does, cause that just means that they, their parents, their politicians, and their god is all wrong. THey would have nothing to live for. Their life would mean nothing. I say we stop trying to convince them, and just banish them all to Texas, Louisana, Mississippi, Alabama, and depending on space requirements Oklahoma, Arkasas, Georgia, and Florida. We surround these area with electrified fence, and just put all the republicans down there. They can have their little Neo-Con self governing area, and the rest of us can finally get something done. The Democrats will get all the countrys debt from years with a democrat in the white house, and the republicans will get the debt from the years a republican was a president. YAY
Just a huge area with nothing of human value for lightyears.
If Google really cared they would fix Android Chrome to reflow text, instead of discriminating
It's at about 11 km above the ground after 75 s. At that height, the speed of sound is 295 m/s (WolframAlpha). So it is a sonic boom.
Karma fed to this user will be promptly burnt. Be warned; be wary.
PS. Really impressed at how deeply you looked into this. Respect.
Karma fed to this user will be promptly burnt. Be warned; be wary.