Heat Shields - Things Kerbal Space Program Doesn't Teach

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:

Background music:
Licensed under Creative Commons: By Attribution 3.0 License

[torybruno]

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

[adamc]

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.

[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.

[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

[jerry]

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.

[colingrain]

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

[MrRandomcommentguy]

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

[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.

[pegzounet]

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

[Rexrege]

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!

[therocinante]

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.

[dgkcpa]

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.

[drak-thul-]

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

[dm]

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

[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.

[stevenclark]

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

[Invisiblejihadi]

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

[Tonatsi]

_Thermaerodynamics_ sounds so much nicer

[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.

[ecophreak]

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