Scott Manley - 2018-12-29
The science of Aerothermodynamics covers what happens during a spacecraft's fiery flight through a planetary atmosphere as it sheds speed, converting kinetic energy into thermal energy. This represents a complex interaction between fluid mechanics, thermal radiation and chemistry. The engineering required to shield hardware against this intense heating is an equally complex multi disciplinary art. If you want to learn the math then this course offered an excellent overview: https://tfaws.nasa.gov/TFAWS12/Proceedings/Aerothermodynamics%20Course.pdf Background music: "Ever Mindful" Kevin MacLeod (incompetech.com) Licensed under Creative Commons: By Attribution 3.0 License http://creativecommons.org/licenses/by/3.0/
thank you for what you do, I don't know anyone else that enlightens me quite the way you do in all things space flight.
How did you get verified as Jesus?
Happy Birthday Jesus. Hope you like crap.
Griefer Jesus going as far as chasing Matto in space, wew
How tf r u verified a Jesus
I believe in Christianity now I thought you were fake a myth but I was wrong and your real amen
I work in TPS manufacturing, actually in the building your hot tile cube video is taken from. I find all your videos to be fascinating and informative. I would like to offer one point of note relating to silica tile on the Space Shuttle. I used to work on the Shuttle TPS system as a technician, and the known cause for the early tile shedding you showed on the OMS pod was not only structural flex as you have mentioned. On STS-1, many of the tiles did not have densification applied to the inner mold line where the Strain Isolator Pad is bonded to the tile. What this causes is a very weak bond that would allow the SIP to debond and take a thin layer of tile with it as it debonded. Think of putting masking tape on a dusty surface and peeling it back off again. The weak bond allowed any force that could get under the tile to pull it off, and this was especially easy on the OMS pods where the tiles were large and thin. The solution was a chemical which I can't remember the name of, that makes a thin "densified" layer on the IML of the tile and allows the SIP to stick incredibly well, dramatically increasing the bond strength. I hope this explanation didn't come across as to knit-picky. Thanks for the great content.
But how didn't the cube transfer the temperature to the demonstrator's fingers? Isn't it heated from surface, so that it was the glowing-hot part that was touched? It must mean the temperature was low enough, as the heat is tranfered to the heat conducting fingers, and not to the low heat conducting cube.
@FatiTank Eris These tiles are over 95% air by volume, so the rate they transfer heat is very low. I understand that the temperature is very high (over 2000 F), but it isn't really temperature that burns you. The rate of heat flow, or BTU/hr is what burns you. If it is a 2000 degree cube that can only transfer a few BTUs to your fingers, it won't heat up your fingers to a temperature that will burn them. You can feel the heat radiating off the cube just like when you open an oven door, but it doesn't transfer to your hand quick enough.
@Robert Szasz It was not PVA. The densification was accomplished by brushing on a slurry made of LUDOX and silica.
@Brian Larkin STS-1 was not as “close call” as you state.
@divedevil985 where did that take place?
Im proud to be subscribed to you, none of your videos are click bait, the videos are educational and you don't repeat anything over and over again, the videos are also fun to watch
He would get more views if he was photogenic and had a hair tranplant from italy for 5000lira
He doesn't even ask to subscribe and like his videos.
@esecallum Lira? Bit of a dated currency, don't you think?
@J.J. Shank - 500 dēnāriī ?
:-)
@Christopher Carr ME TRADE TWO DEER FOR SIX SHARP ROCKS
This is something I've always been interested in and which has sadly not been given the attention if deserves. Material science has greatly benefitted space travel in ways like this. And we rarely see just how difficult the perils of space travel are with the demands placed on the materials used. Think of the melting (660 degrees Celsius) and boiling point (~2,400 Celsius) of aluminum and how the temperatures of re-entry compare to that. It's amazing to think of close the margins are of the numbers and how close to burning alive/structural failure that re-entry is. The forces involved are just not normal and comprehensible by normal, everyday human understanding of temperature.
@Ivo Ivanov My point is that the glass would melt, which I think we have established.
@Mark Gerhard, your exact point was, that glass will melt at 800 degrees. And I proved it wrong.
@Ivo Ivanov You didn't 'prove' that glass doesn't melt at 800 degrees. You claimed, with no evidence, that 'special' glass was used in re-entry capsules. I pointed out that, even if this were true, it would still melt.
So the astronauts would have burnt up, just like everything else that falls through the atmosphere.
@Ivo Ivanov Correct me if I'm wrong, but wouldn't cold water have worked better since liquid nitrogen tends to (just about) instantly boil even at room temperature, leading to that pocket of steam that protects your hand from the minus 200 degrees liquid nitrogen?
It's not that close at all. The only way that temperature reaches the orbiter is if the boundary layer is disturbed by turbulence in the airflow.
9:55 "Supposed to be re-usable" - yes those words define the entire Shuttle program.
@divedevil985 yeah but reusing them was more expensive than not reusing them would have been, so that effort was pretty wasted.
@Chuckiele Bruh. Are you serious or are you joking? While thats the case with the SRB's the Orbiter and the ET... Not so much
@Your avarage Joe The SRBs were just the tip of the iceberg, where refurbishing basically meant stripping them apart and rebuilding them entirely with only the casing being actually reused and that was damaged badly by the salt water. The Orbiter had two major issues as well. The first one being that the original design had less cargo but internal fuel, the design they eventually went with had much more cargo and no internal fuel so that it needed an external tank. However for some reason they forgot to move the engines below the external tank. Instead they were dead weight on the orbiter once the tank was dropped. The engines themselves were extremely expensive to refurbish because they were a very complicated design. Expendable engines strapped to the external tank would have been cheaper while achieving the same result, except that the Orbiter would have been lighter as well. The second issue was the heatshield which was very expensive yet very fragile and thus every tile had to be checked and replaced if needed after every flight which was very labour intensive and stripping off an ablative heatshield and reapplying it entirely wouldnt have been more effort but would have been way cheaper in material costs.
@Chuckiele The bulk of he cost was the man-hours not the material. From what i understand the shuttle tiles turned out way less durable than was expected during design.
@darthkarl99 yes, labour tends to be more expensive than materials but both could have been cut down significantly if they hadnt gone for a reusable design. Dont get me wrong, reusable launch systems are clearly the future, they will eventually be able to reduce price and turnaround time significantly but the shuttle failed at that. It was known from the beginning how fragile the tiles are btw. you could easily crush them in your hand.
Many thanks for this and other informative videos. Regarding the X-15, its ablative coating had the unintended effect of trapping heat in the X-15's airframe, which otherwise acted as a heat sink. See Milt Thompson's book "At the Edge of Space" An individual who worked on the X-15 project told how there was some talk of putting the X-15 in orbit, but try as they might, none of the X-15 pilots could fly the simulator from orbit to landing without burning up. A non pilot asked to try, and succeeded on his first attempt. Everyone wanted to know how he did it. Simple, he said, he watched the temperature gauge. If the plane got too hot, he climbed; when the plane cooled, he descended, and gradually worked his way down to a safe landing.
No talk of ablative heat shielding is complete without talking about the Russian ablative heat shielding of.... wood
@One Sky Dog cofk is not wood but bark.
@One Sky Dog nark
Speaking of wood and carbon foams, there is a way to build a heat shield for a one-way Mars cargo lander that is a hybrid of ablative heat shield and active cooling. Imagine you have a metal surface - the bottom of the vehicle. Attached is a relatively thin layer of carbon foam - using via standoffs or engineered to allow channels for the coolant. Into the space between the metal surface and the carbon foam you pump liquid methane. Re-entry heating boils the liquid methane and methane gas then finds its way through the open cell carbon foam and also through the joints.
Liquid methane is an excellent coolant. As its temperature increases, its specific heat increases. Eventually it will dissociate and the resulting soot will act as a further optical barrier (absorbing some of the radiated energy from the shock front). So long as you keep sufficient flow, the metal of the vehicle will remain cold. And where the carbon foam wears locally, the flow increases and thus its self correcting.
End result is a much thinner and lighter heat shield. Yes you do have to provide coolant, but the nice thing is that as the mass of coolant is depleted, the vehicle gets lighter as a result, meaning your landing burn can use less fuel and you can also dispense with usual jettison of the heat shield - which further simplifies and lightens the vehicle. No heat shield jettison means you're not raining heavy junk onto potentially inhabited locations, so its safer.
This method of cooling is also enabling in that it allows rocket nozzles that are flush with the heat heat shield surface (again, kept sufficiently cool with a small flow of liquid methane). It also enables landing feet are part of the heat shield and can project through the heat shield in preparation for landing.
@fuzzywzhe in the early years of aviators their efforts were also ridiculed as entertaining but of no practical use. In my opinion humans will need to leave the earth or face extinction. Better to learn now.
@Francisco Osuna The reason aviation is useful is that most people can't take 3 days to travel cross country, or a week to move intercontinentally. It's cheaper to move quickly than it is to take that much time off from work to go that distance for most people.
Aviation is PRIMARILY for moving people around to go meet other people. It's primarily for business and to meet up with family and sometimes friends.
Until there's an actual COLONY on another planet or in low Earth orbit, it's not useful. There's talk of doing asteroid mining. I find this to be silly, because we really don't know what is in asteroids. We have landed ONE PROBE on one, and although it was a pretty impressive technical feat, it didn't reveal anything about its internal composition.
The main reason governments want to get to space is for military applications - for war.
Excellent rundown of the subject! I always thought that as technology and operational experience advanced they could build a Space Shuttle 2.0 that would correct for many of the deficiencies in the 1970s design someday, and heat shield tech would be a major part of that.
@Helium Road Many of NASA's original Shuttle design requirements still mixed crew and cargo with a baseline 25,000 lb (11 tonnes) to LEO payload and the ability to bring bring a similar amount back in addition to as many as 12 astronauts. All this was before the military's requirements got slapped on and the Shuttle's only purpose was to be a logistical vehicle for a very large space station. A space station that would've been made up of 100 tonne modules launched separately by Saturn 5s. In turn the space station's purpose would not have been limited merely to research, but also serve as an assembly depot for manned Lunar and Mars ships.
And yes, it is quite true that the 30 tonne to LEO at 28.5 degree inclination, 15 tonnes to near polar inclinations, and 1500 nm cross range was indeed all mandated by the Air Force and Department of Defense as well as by the National Reconnaissance Office and Central Intelligence Agency for their spy satellites. All of that made the Shuttle heavier, more difficult to research and develop, and far, far more expensive.
@Helium Road I agree that the Dream Chaser does not match the capability of the Space Shuttle and is not designed to. I was more referring to the idea that many of the material and technology advancements discovered since the Shuttle era are being applied to Dream Chaser. I say this as a former Shuttle technician and current manufacturer of components for Dream Chaser.
@Adam C True that. There were lots of ideas for upgrading STS over the years that never got the funding to go ahead. Liquid flyback boosters to replace the SRBs, for example. Stuff like that would be a no-brainer for an STS 2.0, where all the lessons of 30 years of operating STS could be applied.
@Helium Road I started working on the Shuttle program right around the time they were considering 5 segment boosters that would supposedly eliminate the necessity of RTLS in the case of a main engine failure. We had also been told that RTLS was more of a hope than a guarantee anyway. People have a hard time accepting that space flight is inherently risky and they want endless contingency plans.
@Adam C Yeah, that's true, but the fact is that STS really was kind of dangerous. When it was designed the idea was to limit it to a catastrophic accident about once every 1000 flights or so, which is totally unacceptable by commercial aviation standards, and that turned out to be wildly optimistic. The actual accident rate was about 1 in 60, with almost no hope for crew survival or rescue during most of the flight. Now that may be acceptable for a test plane with test pilots, like an X-15 type program, but for a vehicle that is to be the core of the nation's space access and which risks 7 people at a time, that's too much to ask. Especially since the Shuttle had a huge public profile and had the emotions of millions of Americans (and quite a few American friends and partners) riding on it, watching 7 people die live on TV is unsustainable. Would've been better had, say the USAF operated it and kept it mostly hush hush, SR-71 style. I'm just rambling now, of course, the real world did not and does not work that way. Friend of mine worked on the Challenger mission that failed. To this day he still feels guilty even though he had no part in the mistakes that caused it. That's a heavy load to bear.
Spacex really missed out on an opportunity to call their heatshield material Pika 2
More like pika 9
Pika pika?
Pika 2!!!
Well i still gave credit to spaceX for naming their roket "Falcon". So they can named it larger version BFR "Big F Rocket". As F stand for Falcon.
Pika Pika!
Hey Scott! I recently saw a fun fact about the RS25 (space shuttle main engine) saying that the exit velocities of the exhaust gases were 13 times the speed of sound. Could you make a video talking about this, or the RS25 in general? Thanks!
I have a few videos that cover bits of the RS-25
https://www.youtube.com/watch?v=4QXZ2RzN_Oo
https://www.youtube.com/watch?v=l5l3CHWoHSI
https://www.youtube.com/watch?v=u6rJpDPxYGU
s p e e d y b o i
I live near Kennedy Space Center and when I got to watch a launch from about 7 miles away I was surprised at the weird sounds that were made.
The lack of realism in ksp gets Scott Manley pretty heated sometimes.
Edit: no I did not steal injustice fellow’s comment. Mine was posted first.
Nothing to say, just equalising the comments.
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At the time I saw these two they were right next to each other with Jerry's on top lol
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Badum-tsss
Thanks for the warning about crushing the thermal tiles from the space shuttle while red hot. I was just grabbing a tile from the kiln when you mentioned that.
NileRed's video on Bakelite is interesting to see some of the chemistry behind the Apollo heat-shield.
Thanks Scott, this is great info. I would love to see a video regarding the history of materials and internal rocket structure considering Spacex's change to stainless steel.
Entered jupiter at WHAT ??? Gods, the sleepless nights for the shield engineering team...
@Rohan Selvan Going off of the 16², a 300kg projectile entering at 46 odd Km/s it would have the kinetic energy equivalent to just shy of 77kT of TNT, or a little shy of 3½ times the energy of the Trinity test
@PyroDesu My condolences, dude. This probably gets pretty annoying lol.
@Nathanael Vetters honestly, $200M per shot is not a bad deal. $2B to put 10 in orbit, each one can basically level a city with the quake, I would be surprised if there wasn't one of these things kicking around up there.
Hell they said challenge accepted.
@Nathanael Vetters it MIGHT violate, as with all human terms and mouth sounds it all comes down to semantics ><
Hey Scott, I love your videos and love how you've been diving into the deeper technical details. Keep up the great work!
Sensitive hardware inside, i.e. the humans. God bless engineer brains
Or as Gene called it, the "biological payload"!
And the main software is very powerful
"Aerothermodynamics: a fusion of aerodynamics and thermodynamics, something that will probably scare everybody." Yeah, that sounds about right....
What a great video, thanks Scott. I love your knowledge and enthusiasm.
There are also radiatively-cooled heat shields used on some ICBMs and the Mercury space craft. They were designed for short, suborbital reentries and simply soaked up the heat and radiated it away after reentry. They aren't used much today because the heat shield needs a lot of mass to absorb all the heat.
Thanks, this is terrific. I think you missed an opportunity. The change from Apollo to Space Shuttle is to start with carbon instead of producing it. Part of this change was probably breaking down the steps of an Apollo reentry burn, and noticing that they could probably save some weight if nothing had to burn away to leave the carbon. I really like the way you covered so much of the problem and the methodologies. I hope there are some young engineers and chemists who see this and think, this could be an amazing subject to work on.
Great video! Well researched, good pace and super informative
Thanks Scott, for a superb video: Great overview and well-chosen details for our understanding of heat shields.
Hi Scott love the channel thanks for your hard work this year. Can i ask where did you get your model rockets from?
God you’re amount of information and research abilities is just wonderful. Love all of your videos and appreciate the time that it must take to make them. Keep it up and we’ll keep learning
I wonder if we could generate an electromagnetic field around a vehicle entering the atmosphere that would tend to push the plasma farther from the vehicle surface - an active heat shield.
I wouldn’t have discovered this man without having played Kerbal and god damn he’s godsent
Awesome episode Scott! Thank you for the fascinating information!
Great video as always! I heard that starship switched to a heat shield from the methane cooling. Could you elaborate?
I am an aerospace engineer and i love your videos: so detailed without being boring at all. And i think this one is my favourite, it's super well done. Congratulations!
Thank you for the very informative video Scott. I have a question. As reentry generates a layer of plasma per the hypersonic aerodynamics mechanism that you explained, it reoccurred to me the following idea:
What if the space vehicle were “encased” in a high density magnetic field that flipped its polarity (the plasma is composed of both positive and negatively charged moieties, no?) at a high enough frequency to effectively repel (both the (+) & (-) charged ions) the majority of the plasma and push the boundary layer even farther away from the surface of the vehicle? I’m thinking of this concept as sort of an inverted Tokamak.
Are there any privately or publicly funded aerospace science and engineering groups that have considered this and/or experimented with this “magnetic thermal deflector shield” concept?
I can’t be the only person who has considered this. I recall having a “what if” moment right after the STS-107 Colombia tragedy where the idea of having a more effective and efficient engineering solution was needed and conceived this magnetic field plasma “deflector” idea.
Thanks Scott, very informative.
A real reentry-shield could be accomplished, by doing pre-ionizing the entry vector.
That should extent the shock layer away from the vehicle.
But we have no efficient and powerful energy system, that could provide that.
Agian, you make great video! Thank you. Scott, this made me think of a Kerbal challenge for you. Using the Realism Overhaul, can you make a "kerballed" spacecraft that can return without a heat shield. You can use cheat mode on fuel if needed.
Great video! I'd like to know if an object enters the atmosphere faster then it needs more shielding. So, if that same object enters the atmosphere slower, would it need less shielding?
You are a really valuable channel for this videos and the fact that you upload much frequently is just amazing
Thank you!
Hey, that was my question a few videos back! I'm sure you get asked about the shape of the Apollo re-entry capsules often, so thanks for the detailed explanation :)
Wow, amazing heat shield documentary. Well done, thanks Scott!
Great video, I learned a lot.
Should have already known, but it's always great to learn from you Scott.
Thanks for a great video, of course all your videos are of a very high standard, but this one was particularly interesting :-)
Thank you Scott, for making these things easier to understand😉😁
One of your best videos yet. So much great info!
Beautifully explained and great archive footage as usual.
That was really interesting - thank you for such a detailed explanation of a very neglected subject.
The amount of engineering time that goes into these projects is tough to comprehend, and generally underestimated.
I'm impressed, thank you.
I could listen to Scott fill my brain with space knowledge forever, so interesting and easy to understand!
Great videos! Hey what do you consider to be the max acceptable skin temperature for a SpaceX Starship during atmospheric entry?
Thanks Scott, this was informative.
Seems like SpaceX is still making major architecture level changes, I don't know how they're going to fly when they say they are going to, if they can't settle some things down and build.
Scott, your videos are Excellent - you provide detailed illustrations and explain things perfectly - I’ve just become a subscriber and look forward to watching the rest of them. If I may ask, what is you background? Teacher or scientist or both? Thank you for producing such a wonderfully entertaining educational resource 👍
Great video, very informative. Thanks Scott.
Tory Bruno - 2021-03-17
Scott,
Another great video and a very clear explanation of the difference between supersonic and hypersonic applications!
Here's a little more background on what we mean when we use the term of art, "carbon carbon". As you covered, this refers to a graphite and fiber reinforced composite material. We generally will use this in three distinct forms: 2D, 3D, and 4D C-C. This refers to the number of planes that the fibers are placed in.
In a 2D CC part, we place (weave) high purity rayon fibers in 2 orthogonal directions (ie; x and y). A filler material is often present as a matrix which will graphitize during processing. BTW: the most sensitive and demanding applications like solid rocket nozzle throats are often made from NASA's reserve of very high purity rayon left over from the Space Shuttle Program, although other sources are now increasingly sought, as the stockpile is depleting.
The billet is then densified through successive cycles of heat and pressure to convert the block to nearly pure carbon, which will retain the morphology of the original fiber matrix. Densification can take many months. This generates a material of exceptional erosion and thermal resistance, such as would be needed for an ITE (integrated throat exit) which contains the flow of very hot gas entrained with aluminum particulates through a normal shock. Once fully processed, the billet is machined to its final design shape.
3D CC has 3 orthogonal planes of fibers (x,y,z). 4D has 4. We chose the type and other details based on the loads that will be encountered in a specific application.
-Tory
Tom Vaughan - 2021-04-04
Hi Tory :D
armr6 - 2021-04-17
Watch the "Going nuclear" series (just for the pleasure of it) and start working on that NERVA bus to open up the Moon.
master shooter64 - 2021-07-06
oh wow it's tory bruno
Paul Michael Freedman - 2021-08-10
@Arkaïd Why does one always have to be better than the other?
Tory Bruno has a lot of knowledge, but look at the cost of what ULA builds compared to what Musk launches (F9) and is building (Starship - fully reusable). look at how fast or how slow one is compared to the other. Both companies have positive and negative traits. ULA has NOTHING reusable. At most refurbishable. Bruno would love to design and build a fully reusable rocket, but alas the pencil necks above him say otherwise. And can't even admit it outright because of the ramification of such statements.
Dare you really say one is better than the other? It's like comparing apples with pears.
AyeBraine - 2021-09-20
@Juriaan Vanmechelen They are planes, not spatial dimensions. You can have lots of planes intersecting each other in the same 3D material space we're all inhabiting. One plane, two planes, five planes.