
Nasa captures images of supersonic shockwaves - lelf
https://phys.org/news/2019-03-nasa-captures-unprecedented-images-supersonic.html
======
wolfram74
As mentioned by others, the photography technique looks like (and apparently
is a software enabled variant of) Schlieren photography. This(1) is a neat
example of an old school Schlieren set up capturing shockwave formation during
whip cracks. I highly recommend it.

(1)
[https://www.youtube.com/watch?v=AnaASTBn_K4](https://www.youtube.com/watch?v=AnaASTBn_K4)

~~~
nate_meurer
Very cool. They didn't mention this in the video, but I immediately see one
groundbreaking new phenomenon that they uncovered: at the exact moment the end
of the whip goes supersonic, it is being accelerated by something other than
the tension of the rope. It looks as though it's accelerated by the
shockwaves, of which there appear to be two -- one on each side of the whip
end, with a vacuum in between. It's as clear as day in the video. The rope in
front of it clearly goes lax, and the whip end even changes direction to align
with the shock wave propagation.

~~~
nate_meurer
I thought about this and watched the video again, and I've changed my mind
just a bit. It looks like, instead of being accelerated, the whip end is
experiencing reduced drag in the vacuum between the two shock waves. We can
see that it travels right behind the first shockwave, not lagging at all, and
this is exactly what you would expect if it is both the source of the
shockwave and the beneficiary of the vacuum behind it.

------
skykooler
How are these images captured? They look like Schlieren photography, but as I
understand it that requires a mirror on the other side of the target being
photographed.

~~~
devb
It is a Schlieren technique, but in this case a series of images taken over a
textured background are then processed with software in a way that amplifies
the differences in air density. This page goes into a little more detail:

[https://technology.nasa.gov/patent/TOP2-271](https://technology.nasa.gov/patent/TOP2-271)

~~~
skykooler
Thank you, that's really interesting!

------
melling
More on NASA's attempt to solve "quiet" supersonic flight.

[https://www.nasa.gov/QSF18](https://www.nasa.gov/QSF18)

------
jarmitage
Anyone found hi-res versions of these images?

~~~
Bluestrike2
NASA has somewhat larger versions linked on this article, though they aren't
really sufficient for larger wallpapers or prints:

[https://www.nasa.gov/centers/armstrong/features/supersonic-s...](https://www.nasa.gov/centers/armstrong/features/supersonic-
shockwave-interaction.html)

The photos aren't yet listed in their image database[0], unfortunately. They
also publish[1] high-resolution versions on Flickr, so it's possible the
photos might make their way there in the near future. Alternatively, they give
a phone number (202-358-1900) to inquire about media use of specific
images.[2] Maybe I'll give them a call later if someone doesn't beat me to it.
Or the high-res photos will make their way onto Flickr, since they already
posted to Instagram as of yesteray.

0\.
[https://nasasearch.nasa.gov/search/images?affiliate=nasa&que...](https://nasasearch.nasa.gov/search/images?affiliate=nasa&query=)

1\.
[https://www.flickr.com/photos/nasahqphoto/](https://www.flickr.com/photos/nasahqphoto/)

2\.
[https://www.nasa.gov/multimedia/guidelines/index.html](https://www.nasa.gov/multimedia/guidelines/index.html)

------
ByThyGrace
I really wonder who makes the decision of starting work on this kind of
research, and how it goes.

I hope it's not in the lines of "Alright team, we've got two idle supersonic
jets, a high speed camera, and enough jet fuel to burn for a day, so how about
some ideas?"

~~~
iscrewyou
It’s probably “we now have two idle supersonic jets”. Everything else they
already had. And good budget planning always helps.

~~~
ThenAsNow
> It’s probably “we now have two idle supersonic jets”.

It's likely not. This kind of thing takes a lot of planning and coordination.

------
SEJeff
I suspect the idea of quiet supersonics are also very interesting to the
Department of Defense as well (for relatively obvious reasons).

------
djtriptych
I wish there were video :(

------
coin
NASA is a an acronym and not a word

