Heat Shields - Things Kerbal Space Program Doesn't Teach

[@torybruno7952]

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

[@Arkaid11]

Reason #1947461 why Bruno>>>> Musk, Bezos & others

[@logantodd5943]

Very interesting, thanks for the response!

[@NizioCole]

Thank you!

[@juriaanv]

Very interesting stuff! What exactly is meant by 4D weaving of carbon fibers? My euclidian space only offers three orthogonal planes, so I would assume there are some non-orthogonal planes?

[@TULDSkySaac]

pog

[@adamc1713]

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.

[@scottmanley]

Thanks for the extra detail

[@jimbarino2]

I'm gonna have to go ahead and ask you: have you been using the new cover sheets when you file your reports?

[@Blox117]

are you saying I shouldnt use elmer's school glue for my heat shield tiles?

[@RobertSzasz]

@@Blox117 extra credit if the densifier was PVA

[@adamc1713]

@@jimbarino2 You know how many times I have heard that one over the years? :)

[@thejesuschrist]

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.

[@umarazam30]

Ahhhh there you are! videos feel empty without a comment from you

[@heatshield]

Hey boss

[@theredstonehive]

You will be the next Justin Y.

[@turtle2720]

Belated happy birthday ;)

[@mikicerise6250]

Wait until your father hears about this, mister.

[@Master_Ed]

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

[@merxellus1456]

Check out CuriousElephant,If u havent yet.. .Im Sure ull love him

[@tubularap]

Master Ed -- Yes, Scott Manley, (together with a handful of others), is my place to go for space-in-the-present. Scott gets to the point, and us updated, done. PS. I like the reference in your name to a TV-favorite of mine.

[@Aereto]

Pretty much why Matt Lowne inserts Scott Manley memes in some of his music videos.

[@pajn]

Hmm, fly safe!

[@Master_Ed]

@@tubularap thanks but this is what everyone called me anywhere I went, they still call me Master Ed

[@colingrain8793]

No talk of ablative heat shielding is complete without talking about the Russian ablative heat shielding of.... wood

[@scottmanley]

It’s not just Russian.

[@colingrain8793]

Scott Manley ohhh?? I thought they were the only ones who flew wood as an ablative heat shield.

[@klausvogler6710]

@@colingrain8793 As far as I know another good material for this is cork. It gets charred at the surface and forms a protective layer for the cork underneath. Takes very long to burn through..

[@quoniam426]

It is Chinese technology for you.

[@DanSlotea]

@@quoniam426 also known as rip-off Russian tech.

[@jerry3790]

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.

[@wierdalien1]

love it

[@jerry3790]

injustice fellow I posted mine 3 minutes earlier

[@jerry3790]

injustice fellow Don’t worry though, I forgive you

[@paulhoffmann4263]

lol

[@HarryL2020]

You both get a like ;)

[@MrRandomcommentguy]

9:55 "Supposed to be re-usable" - yes those words define the entire Shuttle program.

[@divedevil985]

Go to the Smithsonian Museum, Kennedy Space Center and the California Science Center to see 3 space shuttles with over 30 flights each. Keep in mind that all future spacecraft were based on this 1970's reusable technology. Show a little respect.

[@luke7503]

divedevil985 it was a bit of a big Oof is all, mad respect but yeah they had to be refurbished a bunch

[@Chuckiele]

@@divedevil985 yeah but reusing them was more expensive than not reusing them would have been, so that effort was pretty wasted.

[@youravaragejoe5102]

@@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

[@Chuckiele]

@@youravaragejoe5102 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.

[@matchesburn]

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.

[@mike4ty4]

Indeed. Even a bullet - perhaps the fastest thing in most people's minds when they think of speeds that are in some sense "relatable" - is in a sense dog-slow compared to a reentering spacecraft. A handgun round, for example, may travel at only 300 m/s or less (= km/ks, handguns especially are usually made to keep their rounds subsonic so as to minimize noise as a supersonic bullet makes a "snap" as it passes - effectively, a tiny sonic boom, and the speed of sound in air at the usual level where humans live is around 341 m/s or so, though varies a bit with pressure and temperature). Even a rifle bullet (which are "allowed" to go supersonic) only gets to about 1000 m/s or maybe a bit more. But a reentering spacecraft easily plows in at orbital velocity if not greater - that's over 8000 m/s! The (per-mass) kinetic energy dissipated and the pressures involved go up as a square and that makes them on the order of 64 times worse than a rifle bullet! 8000 m/s is fast enough - keep in mind - that it can be used to circle the earth in only about 5 kiloseconds (40000 km / 8000 km/ks = 5 ks, not counting orbital altitude and the thus slightly enlarged radius. The ISS's period is more like 5.5 ks IIRC.) - compare that to a typical international jet flight taking 36 ks (10 hrs) just to go a quarter of the way (10 000 km) around the globe! And what's happening to create all that heat? Effectively, you're _pounding the air so goddamn hard_ that it's not only creating a hypermegasonic deathwind against your craft but that deathwind is as hot a damned blast furnace due to the craft effectively acting like a piston and slamming all that air together in front of it as it's moving too fast for that air to simply flow out of the way, and thus causing it to compress dramatically and heat rapidly: think about a bicycle pump and how as you use it for a while, it warms up. Same thing here only far, far more violent. You're taking 8 km of air - a tube of air as long as a small city - then slamming it into a pancake (or at least a very short cylinder) in 1 second, _every_ second (so imagine in a single second zooming in a crazed blur from one end of your city to the other, buildings, parks, stadiums everything just flying by in the twinkling of an eye, and all that air, that would take you driving it perhaps 400 s or more at city speeds and would brush your hand held out the window like a wind, imagine encountering all that air virtually at once), so that by the time it gets around the edges it's like a blowtorch (this compression ratio reaches or even exceeds that of a diesel engine, I believe, which uses this effect to ignite its fuel instead of using a spark plug as in a gasoline engine, at least going by the temperatures attained.). Naturally this is why the bottom part is where the tiles are, since that's the part used to "attack" and thus compress the atmosphere, making it where the peak heat is reached.

[@markgerhard1362]

>> close to burning alive/structural failure that re-entry is Re-entry head: 1700 degrees. Temperature at which the most heat-tolerant glass melts: 800 degrees. But you still believe that a capsule with glass windows would survive re-entry.

[@matchesburn]

@@markgerhard1362 _"Temperature at which the most heat-tolerant glass melts: 800 degrees. But you still believe that a capsule with glass windows would survive re-entry."_ ...What are you getting at? That glass on space craft are a lie? That space travel is impossible due to glass and those clever disinformation agents at NASA were done in by none other than Mark Gerhard's clever thinking? "Glass beams can't jet fuel capsules" or something? ...You do know that glass isn't used as a heatshield, right? It's there... on the sides. Where the heat is much less and can be easily radiated away. And as far as that heating goes, I think the Shuttle utilized around 5 inch thick glass (of whatever type it was, I don't know). Now... Do you think that just perhaps it takes more heat to heat up thicker glass and takes longer? Strange concept, I know, but a small sliver of wood also burns much faster than a 5 inch round diameter tree, too.

[@markgerhard1362]

@@matchesburn >>You do know that glass isn't used as a heatshield, right? Your hero Scott Manley just said that it was. Check the thread above.

[@mike4ty4]

@@markgerhard1362 What "thread"? KZbin comments are not that organized, so I don't know where you're referring to. He sure hasn't commented in this particular set of replies (that to "matchesburn"'s top-level post).

[@therocinante3443]

I love how, "Fly Safe" came from Eve online.. I remember Scott explaining how the Dramiel was the fastest ship in Eve with the right fitting. I became an absolute KILLER in PVP with that thing. I put my Black-Ops battleships aside to fly pirate in a Drammy.

[@pegzounet]

Entered jupiter at WHAT ??? Gods, the sleepless nights for the shield engineering team...

[@imarchello]

Yup, 47.8km/s. Compare that to like 8km/s for LEO reentry. Insane speed isn't it? Explains why the heat-shield lost so much mass. It went from 47.8km/s to subsonic speed in less than 2 minutes. en.wikipedia.org/wiki/Galileo_Probe Radio contact with the probe ceased (due to the high ambient temperature) 78 minutes after entering Jupiter's atmosphere at a depth of 160 kilometers. At that point the probe measured a pressure of 22 bars and a temperature of 152 °C

[@PyroDesu]

48 km/s... the rule of thumb is an object moving at 3 km/s has kinetic energy equal to its mass in TNT. Kinetic energy equal to *16 times its mass in TNT.*

[@demoniack81]

@@PyroDesu Kinetic energy increases with velocity *squared.* It's not 16 times. You're actually looking at 1.15GJ/kg. TNT has 4.18MJ/kg. *275* times.

[@Thefreakyfreek]

@@demoniack81 hot damm the Rods from gods is a insane consept

[@UNSCPILOT]

@@Thefreakyfreek I'm thankful no one has been insane enough to make those o_o;

[@Rexrege7]

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!

[@Skull-in-the-house]

Yes I think so too

[@stevenclark2188]

"...a phenol-formaldehyde resin..." The Apollo heat shields were f'ing Bakelite? Bwahahahaha!

[@scottmanley]

Pretty much.....

[@dynamicworlds1]

It was an interesting time

[@mpcrazyscience7097]

well there were some wooden ones aswell

[@markgerhard1362]

Bakelite can't even stand a couple of hundred degrees, let alone a couple of thousand.

[@rogerwilco2]

Why not?

[@dgkcpa1]

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 me 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.

[@tarunantony1866]

A true person deserving of the role of astronaut!

[@LLH7202]

Isn't that essentially how the thermal system on the X-20 was designed to work?

[@dm12377]

"Aerothermodynamics: a fusion of aerodynamics and thermodynamics, something that will probably scare everybody." Yeah, that sounds about right....

[@dianapennepacker6854]

And chemistry. Space X... Just had huge portions of their BFG disintegrate... Feel like out of all things that would be the easier one to design against since we've been successful with materials to withstand standard reentry for a long time now. People say it is due to their fast iteration, and I get that. Yet Jesus. My confidence is waining with that, and the hardware failures. Yet it was a successful failure for sure as it still landed. The programmers for the flight controls are on an other level. Mad props for that team in particular, and Space X for getting things done.

[@drak-thul-3400]

"Please don't do that if its red hot, you'll burn yourself." I wish I had an opportunity like that!

[@ThatSlowTypingGuy]

Important safety tip!

[@homomorphic]

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.

[@Invisiblejihadi]

Spacex really missed out on an opportunity to call their heatshield material Pika 2

[@Mrdevs96]

pikaa

[@MonsterSound.Bradley]

PikaCHu

[@didiwin78]

Pika x2 = Pika Pika?

[@noname117spore]

That sounds like a Citation Needed ending joke (Pika 2 pikachu).

[@seriouslynot6420]

ah, ah, AH!!!!!!! Pikachoo!

[@junkmail4613]

Scott. I listened to this video 3 times, and I'm still stunned. I have no words to describe. Just AWE. What you speak is "absolute sorcery". Thanks.

[@FortyBot]

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.

[@telephas1c]

Scott, I watched some of your Kerbal stuff years ago, but this is a whole new level. Insta-subbed with extreme enthusiasm. You're the space-flight nerdism I didn't even realise I needed.

[@WillN2Go1]

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.

[@zbeekerm]

RE: 2:22 Hi Scott, super big fan and Mechanical/Aerospace Engineer PhD here. A minor clarification: shocks are NOT isentropic processes. The shock results in a large entropy rise and is a frictional, throttling process. So it’s not quite as simple as you make it sound/calling it a frictional loss isn’t 100% incorrect although that boils down to how you describe friction. The heating IS most certainly due to the shock layer and not a shearing type of frictional heating that most of us think of from our every day lives. You rock, keep making awesome content!

[@zbeekerm]

In my previous comment: “describe” -> “define”

[@zbeekerm]

RE: 10:10 Checkout the HYTHERM experiment images from STS-119! (Post Columbia 💔) They intentionally added a boundary layer trip on one of the aft wing tiles and filmed re-entry with an IR camera. Being further aft, the turbulent heating would be within design spec. However, gap filler, or some other unknown roughness source triggered early transition on the fore-body underside. Another hairy situation. The tile with the boundary layer trip is still in place on the space shuttle Discovery at the Smithsonian Air and Space Museum in Dulles VA. Also, another interesting property of C-C-C (carbon-carbon-composite) that the LE of the wing and nose patch is made from is that it is a highly an-isotopic material: the thermal conductivity varies by over an order of magnitude from through the thickness (EXTREMELY LOW) to in plane (higher conductivity, still extremely low).

[@zbeekerm]

Great vid. Highly recommend.

[@adamc1713]

@@zbeekerm You are talking about the BLT mod. A friend of mine bonded that tile. He still works with us in TPS. That was a neat experiment.

[@flamencoprof]

Ha! 08:00 I did that at age about 14 with an electric train controller and pencil. The contoller allowed me to dial up the current until the "lead" was red hot and the wood burnt, just like the video here! I followed the electrical direction and became a telecommunications tech, even though I was an avid sci-fi reader at the time. (Early 60's)

[@dathaniel9403]

Hi Scott, just wanted to say that as much as I miss the old KSP videos, I love the new direction in which you've taken your channel. Your knowledge of physics and engineering as it pertains to spaceflight made KSP a great teaching tool, but ultimately these types of involved-but-accessible videos about spaceflight technology are a much better showcase for your talents. Keep up the great work!

[@ryuk5673]

Poor guy no one read this

[@davidchen1397]

The science for cooking orbital breakfast with re-entry heat.

[@ChristopherWeaver1]

More like vaporizing

[@Vaasref]

Just ablate what you don't want to eat.

[@nathanaelvetters2684]

Pack it just underneath the TPS and the little bit of heat coming through should warm it up nicely.

[@faizanjanjua5397]

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!

[@scottmanley]

I have a few videos that cover bits of the RS-25 kzbin.info/www/bejne/aoK7i2WIr7OShdE kzbin.info/www/bejne/ombPZHZ-jNR7ias kzbin.info/www/bejne/q2fVe6N6hd2Mfbc

[@caydens.1250]

s p e e d y b o i

[@TheYoyozo]

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.

[@sethsims7414]

NileRed's video on Bakelite is interesting to see some of the chemistry behind the Apollo heat-shield.

[@tempname8263]

I was just thinking about what should I do with my free time. Thought of scrolling through KZbin, but such entertainment that lasts for a very short time would make me dizzy once again; and then for some reason I wondered if new video was released on this channel. Turns out it did. Nice.

[@ecophreak1]

TUFROC... nasa do love their acronyms don't they?

[@imarchello]

Tough....Rock....ToughRock. I get it now. Nice acronym.

[@1224chrisng]

ESA on the other hand has the Very Large Telescope

[@aritakalo8011]

@@1224chrisng ESO. European Space Agency vs European Southern Observatory

[@0ptera]

I keep wondering if NASA first decides on the acronym and then comes up with the full words.

[@phil4826]

@@0ptera Yes they do. It's called a backronym. See examples such as MESSENGER, INSIGHT, etc. It's really getting out of hand. Too many PR types on the payroll.

[@roflex2]

My favourite science channel. Covers the complex topics that mainstream channels wouldn't dare to touch. Not to mention your amazing voice/presentation style. I wish we could clone you.

[@luke7503]

I wouldn’t have discovered this man without having played Kerbal and god damn he’s godsent

[@flyboypuoi]

This is actually really helpful. I have an exam in a week and a half and re-entry is in it. Your diagram of hypersonic shock looks just like the ones in my lectures. Might I add while I'm here, my professor referenced you in a lecture. It was a diagram of asteriods in orbit I think.

[@Tonatsi]

_Thermaerodynamics_ sounds so much nicer

[@Tonatsi]

*_Howw???_*

[@TheRadioactiveBanana32]

ITS NOT.

[@MrAMandTM]

Sensitive hardware inside, i.e. the humans. God bless engineer brains

[@General12th]

Or as Gene called it, the "biological payload"!

[@sumreensultana1860]

And the main software is very powerful

[@nickvangeel]

Got to love the recap of my uni course aerodynamics Scott if you've got time, mind doing some thermodynamics in jet engines ?

[@sixstringedthing]

Seconding this, I haven't watched any good new airbreathing jet stuff in a while and I'm sure he'd do a great job.

[@adamtowse1]

Fascinating, and as a practicing engineer working in (non-space) thermal protection, can I congratulate you on your meticulous preparation. Thank you, please keep this up and I hope KZbin adequately compensates you for your time.

[@ryuk5673]

Bot

[@brianwyters2150]

I clicked on this video so fast I experienced reentry effects on my finger.

[@cheesegrease8247]

@D r . S p u d Probably not, just a black mark on the mouse or touchpad

[@cheesegrease8247]

@D r . S p u d Computer or not, something is still ending up severely burnt

[@cdrbmw]

This is the F...... best channel on KZbin

[@RCAvhstape]

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.

[@thebigitchy]

Helium Road take a look at the hush-hush X-37B

[@pseudotasuki]

Early Space Shuttle concepts were planned to use a metallic heat shield on top of a titanium hot-structure airframe. But as the orbiter design grew larger to meet USAF requirements, that became unfeasible and forced the switch to an insulating shield on top of an aluminum cold structure. That's also what makes me eager to see what SpaceX is attempting with Starship, since it's something of a best of both worlds by combining an aluminum cold-structure airframe with a metallic shield.

[@pseudotasuki]

@@thebigitchy That's largely the same design as the Shuttle.

[@Nowhereman10]

@@pseudotasuki The orbiters grew denser, not simply bigger in volume. In fact a number of the orbiter designs prior to the military involvement were bigger, but lower density because they were mostly big empty fuel tanks and were more like the X-37B in configuration with very small wings or no wings at all (true lifting body designs) since NASA did not need the super high 1500 nautical mile cross range capability.

[@adamc1713]

Sierra Nevada's Dream Chaser has alot of these upgrades you speak of.

[@fred_derf]

Your videos are always better than pretty much any "professionally" produced show on space and space travel.

[@get_emld]

1:20, what is that breaking up on re-entry?

[@cheesegrease8247]

I believe it was the ATV vehicle by the ESA, I think it was there to resupply the ISS.

[@proskywalker]

@@cheesegrease8247 ATV helped to keep the iss in its orbit not for resupply.

[@CarlosAM1]

@fenton bevan no... its an atv

[@xZise]

@Luke Skywalker Well both actually

[@OldCamaroNut]

To me it looked like a replay of Shuttle Columbia when it's reentry failed.

[@moistmike4150]

Absolute BEST channel to convey complex, scientific and physics to the world. You do a fantastic job! LOVE your channel Scott!

[@GeshronTyler1]

The defunct aerospace company "X-COR" developed a heat/combustion resistant composite dubbed "Nonburnite" for their Lynx suborbital spaceplane project, intended for protecting internal structures from hot engine parts as far as I know. The company had developed their own family of rocket engines, notable for using reciprocating pumps for fuel/oxidizer, along with their Rocket-EZE demonstrator aircraft.

[@Nevir202]

That hexagon fiberglass stuff is amazing. I worked that Hexcel in AZ where they made it one day. There was a scrap of it, about an inch thick and 6” square. It weighed just an ounce or two, yet I could stand on it in its strong orientation, as if it were solid as wood.

[@Nowhereman10]

There is another factor involved in the choices made for the Space Shuttle TPS that you didn't touch on and that is that the Shuttle orbiters wound up much denser on average than what NASA had originally intended. This increase in density happened in order to accommodate the various military requirements that got tacked onto Shuttle as well as the removal of fuel tanks from the orbiter and replacing it with the disposable external tank (done to reduce orbiter R&D costs). Because a lower density orbiters would have seen less heating, rugged metallic TPS made from columbium and inconel alloys would have sufficed for most of the vehicle's exterior areas, though reinforced carbon-carbon would still have been needed for the nose cap and leading edges. Another thing you left out was that TUFROC is also being used on Sierra Nevada's Dream Chaser lifting body vehicle.

[@Christopher28fair]

Does 'denser' mean heavier, here?

[@qzh00k]

The amount of engineering time that goes into these projects is tough to comprehend, and generally underestimated. I'm impressed, thank you.

[@signalworks]

Awesome! Love your videos, Scott!

[@ddegn]

Agreed! This one was particularly interesting.

[@XxPlayMakerxX131]

You are a really valuable channel for this videos and the fact that you upload much frequently is just amazing Thank you!

[@ryuk5673]

Bot

[@codebender9435]

Makes me wonder: At what speed would a raw egg need to enter the atmosphere to be prefectly cooked by the time it falls on the ground? :)

[@imarchello]

This might partially answer your question. From what height would you need to drop a steak for it to be cooked when it hit the ground? what-if.xkcd.com/28/

[@Thefreakyfreek]

Genius

[@rwilson1125]

3 minutes

[@robdow6348]

Probably a few nano seconds, totally hardboiled. Probably where flubber came from.

[@donjones4719]

Many science fair projects are competitions to see who can drop a egg from the greatest height. Your egg, perfectly cooked or not, would certainly beat the record!

[@AltereggoLol1]

Incredibly well researched. Thanks for doing these instead of "I fucking love science" clickbait, even though it must take a hundred times as much work and research.

[@mdava666]

I visited Kennedy Space Centre in November and met Jerry Ross (Mission Specialist on STS-27) and I asked him what was going through their minds when they discovered the Tile was missing. Let’s just say they didn’t think they were coming home...

[@dhurtt22]

Congrats on 800k! Keep doing what you do. This is my favorite channel!

[@mortiphago]

lets not forget that if spacex intends to solve orbital refueling, they could very well launch a fuel pod, dock on the return trip and just circularize back to earth before dropping into the atmosphere. They don't necessarily need to carry a big-ass shield to deal with interplanetary returns. (i'm aware that doing such an eccentric rendezvous and refueling would be a whole new engineering challenge in its own right)

[@rohanpotdar908]

That's actually a sensible idea, but wouldn't the interplanetary velocity be several times greater than the orbital velocity of the fuel?

[@chriskerwin3904]

@@rohanpotdar908 They would need to get the fuel tanker up to excape velocity to meet the incoming vehicle which would be pointless.

[@vladimirdyuzhev]

I wonder who's going to pay for that setup. I can't imagine payloads and projects valuable enough to justify that, IMHO.

[@hatman4818]

Or you could just take the time to bleed off energy through multiple orbits. So long as you can at the very least CAPTURE in that initial pass without destroying the craft, you can make as many passes as needed to slow yourself down to a LEO, where the speed on reentry is as low as possible.

[@chriskerwin3904]

@@hatman4818 Those far orbits would add at least several extra weeks to the time of the trip. May be worth it but, ISRU is the whole point of using this system and should enable the BFR to come back with a fair amount of delta-v.

[@fluffly3606]

The way I like to think of re-entry heating is that the object is approaching the speed where it would be better described as crashing into the atmosphere rather than flying through it

[@isaachenrikson3197]

Let me guess. On the way to look for Tory Bruno's comment?

[@CommyPlayz]

Nope!

[@drmantistoboggan2870]

Who?

[@Obi_Wan_Kenobi_027]

@@drmantistoboggan2870 Tory Bruno, the CEO of United Launch Alliance

[@josephrogers1282]

"It's very simple..." dude. It literally is rocket science. Excellent video as always, you always pitch the level just right.

[@scottmanley]

Rocket science is easy to understand after the fact, rocket engineering is hard.

[@josephrogers1282]

@@scottmanley I've always found the use of "Rocket Science" as a stand in for "something impossibly hard" quite ammusing. When it comes down to it, you don't need much more than Newtons laws of motion and the ideal gas equations. It's building a machine which will actually DO it reliably without exploding that's hard.

[@krakenburger56]

Another great vid by SCOTT -CENA- MANLEY! I love your vids! Keep the amazing work up!

[@NoNameAtAll2]

the man the myth the legend

[@Strike_Raid]

Early Chinese RV’s used wood as an ablator. As it kind of hints at in the title of the paper at 1:30, it’s much better to think of aerodynamic heating in terms of stagnation temperature instead of a raise of temperature due to pressure increase. The other paper referring to the temperature rise as due to friction is kind of misleading, but in that case the definition of ‘friction’, or what friction is, could be made pretty wide to make it almost ok; understanding that if there were no friction, the flow of gas would still be brought to rest in some geometries and the stagnation temperature (re-entry heat) would still be there.

[@ReginaldCarey]

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.

[@isimbulamadmqwe9972]

And since its pushing the plazma in front of the vehicle it would slow down even more

[@EricHallahan]

The talk of the space shuttle’s thermal protection system, particularly the image at 7:35, reminds me of a book I read in the 5th grade probably dating very early in the shuttle program. It had picture very similar to that one, and I remember being fascinated by the patterns that the thermal protection created.

[@Kumquat_Lord]

I'd love to see a TKSPDTY video on solid rocket boosters

[@sixstringedthing]

It's a shame he didn't call the series "Kerbal Space Program vs. Reality", then the acronym could have simply been KSPVR. :) Agreed about an SRB video, we always need MOAR BOOSTERS.

[@LineAlpine]

The thumbnail to this video also was the thumbnail to my Aerospace Engineering Aerodynamics course webpage.

[@thetntsheep4075]

TUFROC? I love NASA's abbreviations 😂

[@timothy8428]

They must have an entire team squirrelled away armed with dictionaries and thesauruses whose sole job is to come up with acronyms for the missions. Let's hope NASA never builds a Synchronous Helio-orbital Interferometric Telescope.

[@FluffyBlueCow]

Oh the best one is the P.O.E.S one, which is a VERY cude and terrible swearword in Afrikaans

[@Quantiad]

TUFROC deserves a place in KSP, for the acronym alone. "I'm Scott Manley, *exuberant flick of the brows* fly safe" :-) Cheers Scott. Merry Christmas and Happy New Year to you and your family.

[@petercherry2285]

How does one find Tory's comments?

[@parveshkhatri1027]

It's 4th comment shorted by newest

[@allenkemp3124]

@@parveshkhatri1027 Thanks!

[@fieryweasel]

17:04 Is it TUFROC or TUFORC? The expanded acronym doesn't seem to match.

[@AtomicFrontier]

Awesome video! Made something similar at NASA Johnson where I looked at the heat shielding material and did some experiments with a blow torch. It's called "Down to Earth" if you're interrested!

[@sixstringedthing]

Sounds interesting! Is it available to watch anywhere online?

[@AtomicFrontier]

Yep! Its on my channel (scroll down to "The Final Frontier" playlist) or you can find it by searching "Atomic Frontier Down to Earth".

[@sixstringedthing]

@@AtomicFrontier yeah... I suppose a search would have been the obvious option... but it's 2:30am in Australia and I'm rather drunk. :) Look forward to watching it, cheers and a happy new year to you and your family!

[@AtomicFrontier]

Haha, sounds like a good time. Happy new year to to too!

[@tubularap]

Thanks Scott, for a superb video: Great overview and well-chosen details for our understanding of heat shields.

[@ryuk5673]

Bot

[@TheMohawkNinja]

How do we know how much of Galileo's heat shield ablated away if it was discarded into Jupiter's atmosphere?

[@seanbush5313]

Math, like if you knew the temperature and the rate at which the ablative material ablates at a given temperature and the time duration you could figure it out

[@Mrdevs96]

the change in weight of the aircraft had to have something to do with it

[@Merlin1234-t2d]

My guess is that they analysed the change in deceleration due to the loss of mass

[@anderslolle2147]

I suppose if you know the pressure of the atmosphere you are in, it’s density and the rate of acceleration, and the weight before reentry, you can find out how much your mass changed in order to match your acceleration. Properly could tell after the deployment of the parachute.

[@Evolution56]

The follow-up mission of course, that found the heat shield at the bottom of Jupiter's atmosphere.

[@Rebar77_real]

Never thought about how entering different atmospheres would require different systems/configurations. Great vid Scott, thank you!

[@djbeezy]

Why do you think they don't re-design the space shuttle thermal tile system instead of replacing the heat shield every time? We flew those for over 30 years. I know they were brittle bit I would assume they would have figured something out by now. I'm no engineer or anything and I know my suggestion is easier said than done.

[@baronvonlimbourgh1716]

It probably is cheaper and faster to do it this way. The tiles where extremely labour intensive to maintain and replace.

[@NoNameAtAll2]

I remember seeing a video on youtube about flat thermal tiles as next generation research

[@chriskerwin3904]

Read about TUFROC which is exactly what you describe. It only became available in the last decade or so of the STS program.

[@jesusmora9379]

there was also some problems with bureocracy and politics, and they were not allowed to replace parts of the space shittle with more moderns ones because of it.

[@Martinit0]

If the Dragon heat shield is a single piece, like it seems to be, it's much easier to replace than thousands of individual tiles.

[@tinkmarshino]

that is some good information there Scott.. I had never thought there was so much involved.. as always well done!

[@dELTA13579111315]

I've been experimenting with NightHawkinLight's recipe for starlite, and it's some pretty cool stuff

[@xXTECHxKNIGHTXx]

All these breakthroughs are getting me all giddy about our future interplanetary exploration!

[@shachar2]

ok I'm sold! How much would it cost to cover ONE side of my apartment against the summer sun which reaches 30-35c here?

[@FluffyBlueCow]

Well, if you have large windows, you could just put a space blanket inside of the curtains, and keep them closed during the heat. People here used to do it with those thick old curtains, works quite well

[@davidgray6999]

Almost everything in that presentation was new to me. Wow - what a great thing; I wish I could give you two thumbs up on that one.

[@callsign_Elysium]

Dont mind me, just looking for Tory bruno's comment

[@drmantistoboggan2870]

Who the hell is this tony guy and why is everyone talking about him?

[@maddocentertainment8856]

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.

[@ftr98]

I was just reading your tweet when I got the notification by KZbin 😂

[@linuxguy1199]

Wow, you get notifications from KZbin, I didn't know that was possible!

[@ftr98]

You have to Subscribe and activate the bell next to the subscribe button

[@SteveChisnall]

@Scott Manley So, you're saying that an ablative material basically serves as a *sacrificial insulator* protecting the spacecraft from overheating, in the same way that a zinc bar on the outside of a boat or ship's metal hull serves as a *sacrificial anode* protecting the sea-going vessel from corrosion?

[@HotelPapa100]

So the Apollo heatshield was basically Bakelite...

[@ComradePhoenix]

Nah, I'd say it was pretty heavily baked.

[@SteveChisnall]

@Scott Manley Can you please cover how Falcon 9's lower stage (and by association, Falcon Heavy's core booster & 2 side boosters) use their exhaust plumes for thermal protection during re-entry to get away without a dedicated heat-shield?

[@garrettkajmowicz]

Short answer - they are going substantially less than orbital velocity. This means that more "conventional" aerodynamics apply. And, because the mission payload has already launched and this is "merely" recovery it can accept a fair bit more risk.

[@AttilaAsztalos]

Any time I see "pyrolysis layer" on a diagram I get a bit twitchy...

[@1_2_die2]

Fantastic video, as mostly. There are not many people able out there to condense this complex stuff into a formidable and easy to understand short video. Thank you a billion times (BILLION like Carl Sagan)

[@StormSilvawalker]

do not try to calculate the pipe density of the subsurface methane cooling system and the heat energy needed to be added to the tank pressure. It is a crazy long math problem.

[@seanbush5313]

Upload a video of it

[@Mrdevs96]

more pipes

[@michaelfarrell4824]

I think most of us did not need this advice Will Hunting...

[@sam-rs8wg]

R/iamverysmart

[@jesusmora9379]

it probably only works for a sphere in a void anyways.

[@TheTechovision]

Hey Scott, I love your videos and love how you've been diving into the deeper technical details. Keep up the great work!

[@Marc83Aus]

I wonder why they didn't just carry a caulking gun full of ablative thermal compound for filling up gaps where a tile was lost. Or alternatively I guess a loaf of bread would work just fine.

[@xponen]

maybe NASA is very afraid to even entertain a sense of humour.

[@randomnickify]

I remember reading they did considered something like that, technology probably wasn't there.

[@Marc83Aus]

The major difficulty is getting the stuff to adhere and not get knocked off by vibration ,pressure, expansion, etc.. It was always technically possible to have a layer of single use ablator underneath the tiles as an emergency measure in case the tiles broke off, but theres mass considerations. Perhaps a good solution would be to have mounting points underneath each tile, bolt somekind of support structure which can be cut to shape to those mounting points then laboriously fill it with caulk like the old apollo heat shield.

[@MrAnticlimate]

Scott (or Mr. Manley :) ) could you please make an episode solely dedicated to the materials used in rockets/spacecrafts (if there wasn't any yet). Plastics, composites, metals/alloys, ceramics etc. Advantages, disadvatages, recent developments, future... OK, it may be too broad a subject, just an idea. Anyways happy new year and thank you for the quality uploads!

[@tubanbodyslammer9125]

That’s why they call me mr Fahrenheit

[@Whitpusmc]

In a slightly related note I have cast lead Ingots and more complex shapes using dry balsa wood as the mold form. It was even reusable though the dimensions did slightly enlarge with subsequent uses which wasn’t critical for my application.

[@Kingfranz]

So even the tiles were classified? The paranoia/stupidity of the military is mind blowing

[@sillygoose210_6]

No, the mission was for the DOD meaning any and all details concerning it were classified. The tiles themselves weren't classified technology.

[@Garryck-1]

It was a different era.. the Cold War was in full swing. Paranoia was everywhere, and not just in the military.

[@roxxedk9897]

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.

[@fsmoura]

WHAT?! ( O.O) LIES! *KSP* TEACHES YOU _EVERYTHING_ !!

[@mikeohlsondefine592]

Scott you are the master of lucid and interesting explanations. We salute you in gratitude.

[@artysanmobile]

I had the incredible good fortune of a personal tour through the Vehicle Assembly Building during the final few weeks of assembly of a space shuttle vehicle. I remember the large days-to-launch banner high up on the interior wall of the building. Memory tells me it was somewhere in the medium-high 2 digits. I watched as men and women spent what must certainly have been weeks marking, removing, hand trimming, and replacing individual numbered thermal tiles to the under- and leading-edges of the shuttle’s port side wing. It brought home to me as no other narrative possibly could how time-intensive a process it was. The entire time I watched, which was probably less than half an hour, was used by one engineer on a single roughly brick-sized tile which was still not complete when I moved along. She treated that single tile as if it were the key to the entire ship’s success, which years later served as a terribly bittersweet memory.

[@mystixa]

The tile heat absorption was a pretty cool demonstration. They did with the public as well. I was in junior high school when astronauts did a space shuttle presentation at our school. They heated up a tile to red hot with a torch and had us kids hold them. I was one of the kids that got to hold one. It was very strange.

[@aqimjulayhi8798]

6:32 'You could crush them with your bare hands. Please don't do that if they're red hot, you will burn yourself' I was just about to burn a tile from the space shuttle in my backyard and do it. You saved me, Scott.

[@aby0ni]

Would super cooling the shield at the space station add any value in resisting heating? Or would that be ineffective and/or impractical?

[@mosiprop]

Excellent vid, Scott.. I learned a lot .. this coming from someone who makes ablative insulation professionally. Keep up the good work !!

[@rebelclause]

Thank you, Scott. Another piece of documentary excellence from your desk.