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19 Feb, 5 tweets, 7 min read
WOOWWWWW

Check out these images of #PerseveranceRover being dropped from the sky crane (left) and descent with chutes deployed via Mars Reconnaissance Orbiter! Incredible photos!

#Mars2020 #Perseverance #NASAPerseverance #NASA #Mars ImageImage
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

#NASAPerseverance #NASA #PerseveranceRover #Perseverance #Mars2020 #ScienceTwitter Image
I just can’t believe this image—am I right that we’re seeing some of the dust plume from the retro rockets? This is like a baroque painting Image
A color photo from the surface now!

#Mars2020 #Perseverance #PerseveranceRover #NASA #NASAPerseverance #Mars Image
By the way, just buckle up because we’re going to have some truly remarkable photos and videos trickling in over the coming days (JPL teasing a video maybe Monday). Here’s a great thread from @elakdawalla outlining the imaging equipment onboard

#NASAPerseverance #Mars2020 #NASA

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More from @DrChrisCombs

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 11 tweets
Chris Combs Profile picture
18 Feb
NASA is LIVE with coverage of the Perseverance landing, happening around 2:55p US CT, this is the place to be

Percy about to hit the atmosphere at 3.5 miles/sec (5.5 km/s) and create some serious heat
#CountdownToMars #MarsPerseverance #Perseverance

pscp.tv/w/cv11hDFsWkVw…
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
Read 5 tweets
Chris Combs Profile picture
23 Nov 20
It’s November which means we’re getting into GRAD SCHOOL APPLICATION SEASON so I thought I’d take a break from my usually #AvGeek/rocket threads & talk some #AcademicChatter with my personal advice for those considering grad school. A thread...

#AcademicTwitter @AcademicChatter
All the usual caveats apply: I’m in engineering and while there are many different paths & perspectives I’ll be giving advice based on my personal experience. With that said hopefully it’s helpful to many of you w/ broad applicability outside of engineering
First: don’t pay to go to grad school. Many faculty have paid research assistantships (GRAs) and will provide tuition + stipend. You’ll still be underpaid but it’s really difficult to economically justify the benefit of grad school vs lost income if you pay your own way
Read 33 tweets
Chris Combs Profile picture
1 Sep 20
THIS IS NOT A SONIC BOOM

Okay folks, it’s been long enough. Time to finally address the biggest point of confusion on #AvGeek twitter: what exactly is going on with vapor cones?

Let’s just say much of what you’ve read is (probably) wrong. Wonder no more: a thread... 1/n
2/n We’ve all seen the photos & videos—whether it’s a jet flying over the beach or a rocket during its ascent—with the beautiful vapor cone (you also hear shock collar or even shock egg). Inevitably the exclamations follow: “sonic boom!” “Mach 1” & “breaking the sound barrier”
3/n And I totally understand. It’s a nuanced concept & a quick Google search brings up all kinds of misinformation. I could not find a single article that seemed to truly “get it”. So no shaming here—it’s debunking time
Read 25 tweets
Chris Combs Profile picture
11 Aug 20
DETONATION ENGINES THREAD

It’s been too long since a good propulsion thread. With enticing potential for supersonic & hypersonic flight, pulsed & rotating detonation engines are an exciting possibility for future high-speed vehicles. Let’s discuss 1/n

🎥 credit @PurdueEngineers
So the top-line big number is the potential 25% theoretical efficiency improvement from pulsed & rotating detonation engine concepts (PDEs & RDEs, respectively) & ISP > 8000s for hydrogen fuel up to hypersonic Mach numbers, far exceeding other air-breathing and rocket engines 2/n
And this is in no way a new concept—detonation engines were theorized way back in the 19th century! With initial RDE experiments performed in the 1950s. But recent advances in experimental and computational methods have started to make this complex problem more tractable. 3/n
Read 26 tweets
Chris Combs Profile picture
25 Jul 20
A quick and funny story from the lab this week that I think does a nice job encapsulating the day-to-day in experimental work/#phdlife...

#AcademicChatter #AcademicTwitter @AcademicChatter #SaturdayThoughts
So we had a subsystem test planned for our hypersonic wind tunnel and as we’re going through the checklist our high-pressure air compressor for some reason won’t turn on. Grad students are baffled. Nothing has changed since the last test!
I ask (seriously) “is everything plugged in? Is everything turned on?” Because trust me I’ve spent hours debugging a problem in the lab only to find out something wasn’t plugged in. So frustrating when it happens. This is the type of insight you get from a PhD 😂
Read 5 tweets

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