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30 Jun, 4 tweets, 2 min read
I posted this thread on the @ReactionEngines SABRE combined-cycle engine 1 year ago and thought I would provide a quick update

As we predicted, the most immediate impact has been the spin-off of some of the subsystems

For example, the @ReactionEngines heat exchanger was recently integrated into the UK/@esa National Space Propulsion Facility
aerospacetestinginternational.com/news/engine-te…
There have also been recent successful tests of the HX3 micro tube heat exchanger and the hydrogen preburner subsystems

I’ll be honest this is really impressive progress in a COVID year IMO and exceeded my expectations
aerospacetestinginternational.com/news/engine-te…
With that said, one year ago tests of the engine core were anticipated within a year—that has not happened and a test date is still not being provided publicly.

Given the success of the spin-offs I imagine there’s maybe a bit less pressure to finish the core fast

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More from @DrChrisCombs

Chris Combs Profile picture
28 Jun
🌪From the weekend, this is one of the most violent tornado videos I think I’ve ever seen🌪

This was from a tornado outbreak in, of all places, the Czech Republic

The way those trees topple over is unbelievable. That is some incredible wind speed
From a bit further away, this gives you some perspective on the strength of this storm and the level of danger present in the first video

This is the scene afterwards, it looks like a bomb went off. Really bad situation

Read 9 tweets
Chris Combs Profile picture
27 May
There’s been a lot of confusion centered around this (very cool) video of yesterday’s Falcon 9 launch so I wanted to jump in and clear some things up

Short thread…
#AvGeek #Falcon9 #SpaceX @elonmusk
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
Read 10 tweets
Chris Combs Profile picture
22 Apr
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
Read 18 tweets
Chris Combs Profile picture
20 Apr
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

🎥
📄 web.stanford.edu/group/ctr/ResB…
So back to the review paper, a bunch of these figures caught my attention

First up since we’re already on scramjets, a great illustration of a combined-cycle turboramjet + dual-mode scramjet

Gets you from takeoff to Mach 10!

📄 annualreviews.org/doi/abs/10.114…
Read 8 tweets
Chris Combs Profile picture
2 Apr
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
Read 13 tweets
Chris Combs Profile picture
20 Feb
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
I mean, just look at these photos...
#AvGeek #ua328
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
Read 12 tweets

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