T-38C passes in front of the Sun at supersonic speed, revealing shock waves | Hacker News Reader

T-38C passes in front of the Sun at supersonic speed, revealing shock waves

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37 pointsmaxcan12 comments

In case you are also wondering what a T-38C is, it is a plane. https://en.wikipedia.org/wiki/Northrop_T-38_Talon

I didn't realize it was supersonic:

Maximum speed: Mach 1.3 (858 mph, 1,381 km/h)

The T-38 was an offshoot of the N-156F lightweight supersonic fighter ( F-5 to the USA and its allies ) and basically underwrote that project.

They've been in service since 1961, which means they've lived through a lot of history. Here is Werner von Braun stepping-out of one of NASA's T-38Ns:

https://www.flickr.com/photos/my_public_domain_photos/700014...

For a while the Portuguese flew the T-38 as a trainer which was faster than their front-line combat aircraft, the A-7!

It's based on the late '50s-early '60s F-5: https://en.wikipedia.org/wiki/Northrop_F-5 and supersonic capability was a must by then. We bought a bunch of T-38s as, I gather, the default supersonic trainer aircraft, the Thunderbirds switched to them after the first oil shock (and the Blue Angels to A-4s, although an attack aircraft that's not carrying any ordinance is pretty hot...), and full circle, I recall reading the Pakistanis armed some for one of the wars with India, and they did pretty well as long as they were able to stay low.

Neither did I. Is it customary for trainers to be capable of supersonic flight? The T-6 we use in the Navy is a turboprop whose flight envelope is well under transonic speeds, let alone supersonic ones.

It was a fad of the era which followed on from the excitement of all-jet training ( which itself declined in the 1970s ).

The British RAF looked at the T-38 as inspiration but the subsequent Jaguar turned out as an attack aircraft.

The Japanese then looked at the original supersonic training concept of the Jaguar and cloned it as the T-2, larger than the T-38 but likewise still in service.

The few other forces who ended-up using T-38s did so as a result of FMS credits rather than actual need or validity, since the US had nothing to offer comparable to the subsonic Hawk and Alpha Jet.

For a second there I thought it was a comet, and the thought of those leaving shockwaves in space was very confusing.

This is known as Schlieren imaging. The refraction of the light changes with the density of the air, resulting in a nice way to visualize the shockwave.

Seeing multiple parallel lines (I'm guessing condensation from the pressure wave?) makes me wonder if the boom you hear is actually multiple nearly simultaneous booms.

I believe there is one wave caused by each leading and trailing edge of the plane's structure.. so there are 5 waves, 1) nose of plane, 2) leading edge of wing, 3) trailing edge of wing, 4) leading edge of vert stabilizer, 5) trailing edge of vert stabilizer / back end of the plane.. the angle tells you the mach number it is traveling at.. see here: https://en.wikipedia.org/wiki/Oblique_shock

it does -- and designing the plane to shape the shockwaves can reduce the perceived boom volume http://www.nasa.gov/aero/centers_tackle_sonic_boom.html

When I was a child (Gosh, nearly thirty years ago now - where did it all go wrong?) I used to draw relatively snub-nosed planes that had an array of lasers firing so that they settled on a movable point ahead making a 'virtual nose'. The lasers could then diverge and move the concentrated focal point forward as it went faster, making the 'nose longer'.

I always wondered whether there was anything in that, but I'm too stupid to work it out.

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