For starters, I recommend checking out this earlier thread I wrote on vapor cones and expansion fans as a lot of relevant points are covered there, so I won’t circle back to everything
This should explain the *transonic* vapor collar close to the rocket
Okay, so the audio in the original video is misleading. This event happened at about 9km altitude, so any wave generated at that instant would reach the ground roughly 30sec later. Not sure how the audio was synced but if it’s real time from the ground, it’s coincidental
Notice you don’t hear this “boom” in the original SpaceX audio
Now, the flash of white you see *is* associated w the vehicle reaching supersonic speed & the resulting shock wave that forms at the nose
NASA & @DJSnM have noted this is related to upper cloud layer ice crystals interacting with the passing shock wave
➡️ nasa.gov/mission_pages/…
Note that if you look closely you can even see the shadow of the rocket in the thin layer of clouds
I think there’s still some speculation as to the exact mechanism at play here but the NASA explanation tracks IMO
It’s worth clarifying that the shock wave & sonic boom are not transient processes—i.e. it’s not some instantaneous event that happens when you reach Mach 1 like an explosion/blast that then goes away
It’s a wave system that remains attached to the vehicle & moves w/ it
📷NASA
As a stationary observer you just hear a single boom when the wave moves past you
Hope that helps, please share and drop this in the replies to some of the posts going around!
Oh and if you want to see something a little similar to a shock wave system forming on a vehicle accelerating beyond Mach 1, here’s a schlieren video we recently recorded of a wedge during startup of our Mach 7 facility
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It's been a tough semester for everybody, so to lighten the mood and provide some extra credit points I posted a meme challenge to my fluid mechanics class
The submissions were BRILLIANT
Sit back and enjoy this nerdy fluids meme thread. Our @UTSA students rock #AcademicChatter
There were so many hilarious submissions (over 100!!) so I unfortunately can't highlight them all, but there are some that literally made me LOL
This one is a bit niche perhaps, but it was the perfect mix of educational, weird, and original that it made me laugh harder than perhaps all the rest
Came across a ram/scramjet review paper from the Stanford Center for Turbulence Research & it is an absolute treasure trove of wonderful illustrations related to hypersonics
A quick thread of my favorites, but first I got distracted w this simulation of scramjet combustion
Here’s a closer look at that animation, with links to the paper and YouTube source
What you’re seeing is an overlay of temperature, density gradient (analogous to schlieren), and velocity in a scramjet cavity at Mach 6.5
NASA just released some interesting preliminary data from their instrumentation onboard the #Mars2020 lander that delivered #Perseverance
Here’s a quick thread w some thoughts
[TLDR: Mars entry is HOT, but we made the heat shield too big (again)]
So to start, let’s turn back the clock to 2012. While you were watching The Walking Dead and the London Olympics, the good folks at NASA were measuring the aerothermal environment of Mars entry for the Mars Science Laboratory (MSL Curiosity) mission
They did this with an instrumentation suite called “MEDLI” which stands for Mars Entry, Descent, & Landing Instrumentation
This contained, among other things, a bunch of heat transfer, pressure, and temperature measurement devices in and around the MSL heat shield
Oh my goodness, this is video of the turbofan on a Boeing 777-200–flight #UA328 out of Denver—which experienced a serious engine failure after take-off.
Remarkably sounds like no injuries in the air or on the ground #AvGeek
Worth noting, twin-engine aircraft are designed to be able to fly safely with only one engine and pilots are trained for this (seems they did a phenomenal job here!)...but people and homes are NOT designed to withstand falling turbofan cowlings. Miraculous no one was hurt
Check out these images of #PerseveranceRover being dropped from the sky crane (left) and descent with chutes deployed via Mars Reconnaissance Orbiter! Incredible photos!
Folks, we just snapped of a photo of a spacecraft landing (possibly still at supersonic speed) on ANOTHER PLANET from a satellite also orbiting that planet. That is WILD
The extreme velocity of atmospheric entry will heat the surface of the heat shield to nearly 2,400 F (1,300 C) due to intense shock heating and aerodynamic forces
It’s a tricky part of the mission for many reasons, but our ability to predict/model the physics of these atmospheric entry events is currently limited—it’s a “multi-physics” problem which makes it tough even for our best super-computers to handle