NASA Captures Unprecedented Images of Supersonic Shockwaves (phys.org)

As NASA looks into developing planes that can fly faster than sound without creating "sonic booms," the space agency has captured unprecedented photos of the interaction of shockwaves from two supersonic aircraft. Phys.Org reports: When an aircraft crosses that threshold -- around 1,225 kilometers (760 miles) per hour at sea level -- it produces waves from the pressure it puts on the air around it, which merge to cause the ear-splitting sound. In an intricate maneuver by "rock star" pilots at NASA's Armstrong Flight Research Center in California, two supersonic T-38 jets flew just 30 feet (nine meters) apart below another plane waiting to photograph them with an advanced, high-speed camera, the agency said. The rendezvous -- at an altitude of around 30,000 feet -- yielded mesmerizing images of the shockwaves emanating from both planes. You can view all of the photos via NASA.

Comments

Awesome

[JustAnotherOldGuy]

Awesome stuff, and some precision flying was needed too.

Gas Dyamics by Zuckrow

[140Mandak262Jamuna]

Remember seeing Schlieren pictures while doing the gas dynamics I course back in college.

The formula P by Po = ( 1 + (gamma - 1)/gamma * M^2) ^ (( gamma - 1)/gamma) I will never forget. Brain cells spent memorizing that formula are frozen for ever, can never be repurposed to do anything else, even if I have do earthly reason to calculate the total pressure in a supersonic flow ever again! The last Gas Dynamics examn I sat for was 32 years ago!

Re:Gas Dyamics by Zuckrow

[religionofpeas]

2nd link says this: "The images were captured during the fourth phase of Air-to-Air Background Oriented Schlieren flights, or AirBOS"

Re:Gas Dyamics by Zuckrow

[fazig]

I guess I've got to check all links, thank you.

BOS is an optical density visualization technique, belonging to the same family as schlieren photography, shadowgraphy or interferometry. In contrast to these older techniques, BOS uses correlation techniques on a background dot pattern to quantitatively characterize compressible and thermal flows with good spatial and temporal resolution. The main advantages of this technique, the experimental simplicity and the robustness of correlation-based digital analysis, mean that it is widely used, and variant versions are reviewed in the article.

Source: https://link.springer.com/arti...

Or for those who are not inclined to refuse Wikipedia as a source:

Background-oriented schlieren (BOS) is a novel technique for flow visualization of density gradients in fluids using the Gladstone–Dale relation between density and refractive index of the fluid. BOS simplifies the visualization process by eliminating the need for the use of expensive mirrors, lasers and knife-edges. In its simplest form, BOS makes use of simple background patterns of the form of a randomly generated dot-pattern, an inexpensive strobe light source and a high speed digital camera.

Source: https://en.wikipedia.org/wiki/...

Google schoolar places the earliest mention of this method into 2001, which is not that new: https://iopscience.iop.org/art...

Ear-splitting sound

[PPH]

Please. Stop already. I've heard plenty of sonic booms and I'd be hard pressed to describe them as 'ear-splitting'. If you live in the mid-west, Florida or other areas, thunderstorms create far higher sound pressure levels. And do more damage to windows and structures as well.

If we can't get the highly suggestible people over the idea that sonic booms are intolerably loud, because they have been told they are, we will never develop supersonic aircraft.

Re:Ear-splitting sound

[Anonymous Coward]

I've heard plenty of sonic booms and I'd be hard pressed to describe them as 'ear-splitting'.

You must have been far, far away from the sonic booms. I lived about 15 miles from a former military air base. Jet jocks were often goofing around and busting the sound barrier. The noise is LOUD and startling!

Re:These were presumably conventional

[pavon]

It is worth mentioning that these pictures were just a test of their improved imaging system, and not intended to provide any new information yet.