Throughout history, our biggest leaps in technology have occurred as a result
of new materials becoming available. I've shown you how it took humankind centuries
to master iron and steel, culminating in the explosion
of growth during the industrial revolution; how the accidental discovery of age hardening allowed aluminium to take humans
into the stratosphere in droves; and how silicon forms the backbone
of this age of information. But today, we're going to discover
the next great leap in material science: carbon fiber reinforced plastics. Carbon fiber, and its even more futuristic brother,
carbon nano tubes, have been touted as the next great innovation that will allow humans to build amazing structures
that were once unimaginable. Elon Musk recently revealed an enormous
carbon fiber-reinforced plastic cryogenic fuel tank, the largest fuel tank
that has ever been created for spaceflight. Building spaceships of this size is not an easy task. The larger the spaceship,
the more fuel you need to escape the Earth's gravity. The more fuel you need,
the bigger the fuel tank needs to be to hold it, which just adds more mass to the rocket. Carbon fiber reinforced plastics
provided a new way to keep the weight down while maintaining the strength needed
to withstand the internal pressures. But building a structure like this
from carbon fiber is no easy task. This is the sort of material that
if it crash-landed on Earth just 70 years ago,
it would have been a completely alien object, and we are still learning a lot about its mechanics. The fact SpaceX have created a structure this size
out of carbon fiber reinforced plastics that has already been tested at two thirds
of its bursting pressure is astounding by itself, but we've yet to see whether it can resist
the blistering cold temperatures of the liquid fuels without cracking and leaking, and do it repeatedly. After all, the whole point of SpaceX rockets
is to be reusable. Building a cryotank out of composite materials is without a doubt the most difficult part
of building a spaceship of this size. Don't believe me? Listen to the man himself say it. Nevertheless, the material will be pivotal
in reducing the weight of our craft enough to escape the gravity prison
that has kept humans as a single-planet species. Even though we are still learning a lot about the material, carbon fibers by themselves
are not as new as you may think. The first carbon fibers were produced
by Thomas Edison and Joseph Swan for use as filaments
in their new electric incandescent lamps. The carbon fibers they created were produced by carbonizing plant threads like
cotton, wood, and bamboo. This material did not have the tensile strength
of today's carbon fibers, but they allowed Edison and Swan to replace
the expensive Platinum filaments being used earlier. The carbon bamboo filaments Edison developed
lasted up to 1200 hours, and they were the norm for 10 years
until tungsten filaments replaced them. Not much thought was put
into carbon fiber as a structural material until the late 1950's:
when the Union Carbide Corporation, a company that manufactured light bulb filaments, began investigating replacements
for tungsten filaments. They started using Rayon,
an artificial, cellulose-based material. popular as a cheap alternative to silk
and cotton as the base ingredient for carbon fibers. This was a breakthrough moment for the start
of the modern carbon fiber era as a resulting materials
showed potential as a structural material. Researchers all over the world took notice, and just a month later,
the Japanese Industrial Research Institute began investigating how to make their own fibers from Polyacrylonitrile or "PAN" for short. The majority of today's carbon fiber
is produced with PAN, even though it is
an expensive byproduct of oil production. It yields a fiber with a much higher percentage
of carbon than Rayon, and it's easier to manufacture. Dr. Shindo created long strands of this PAN material, which he stabilized by first heating it
to around 250 degrees for up to two hours. This rearranges the chemical bonding to create a thermally stable ladder bonding. These fibers were then heated again
to around 1,000 degrees in the absence of oxygen, which expels the non carbon atoms
in the material leaving tightly-bonded carbon atoms
arranged mostly in the direction of the fiber. This material was both heat and chemical resistant.
It had fantastic tensile strength, and didn't rust. Specialized industries, like aerospace,
immediately saw its potential to help spacecraft break the grip of Earth's gravity. And when Gay Brewer won
the Taiheiyo Club Masters' Golf Tournament in 1972, using a carbon fiber composite shaft,
the material captured the world's attention too. The sporting goods manufacturers all over the world
began creating carbon fiber products. Golf clubs, tennis rackets, and racing bikes started to be made with the cheaper off-spec fibers
that the aerospace industry could not use. Despite its high price,
demand for the material kept growing, and by 1980,
1,000 metric tons were being produced a year. But it was still
a notoriously difficult material to work with, and many still doubted
its ability as a structural material. During the development of the McLaren MP4/1, one skeptical engineer had said to have picked up
a piece of carbon fiber composite just like this and easily snapped it in half, declaring that the material was too weak and brittle to be used for the ambitious
carbon fiber composite monocoque. But he was breaking the material across the fibers; if he had attempted to break it along the fibers,
he would've had serious difficulty. You see, carbon fiber is made
from these tiny thin fibers. This is a picture showing the size difference
between a carbon fiber and a human hair. The carbon fiber is the smaller one. These tiny fibers by themselves
can't be used as a material, we first have to bind
these long strands of fiber together with a plastic resin. Otherwise, they're just a flimsy fabric
that can't hold any load other than tension. Here you can see a solid piece of carbon fiber
where the fibers are surrounded by white resin, but this technique causes some problems for engineers
when designing a product with this material because the plastic is weaker than the fibers. This is a unidirectional layer of Carbon fiber
held together with resin. If we pull it this way along the fibers, it has fantastic strength because the fiber is
in the same direction as the load, and, thus, can resist it. But if we pull it this way,
there is no continuous run of fibers to resist the force. Instead, the resin matrix gets pulled apart,
and the fibers add very little strength to the material. To combat this, engineers will layer
the fibers on top of each other. Here we have a zero degree layer
on top of a 90 degree layer, so, the material properties are the same
in those directions. But now, the 45 degree direction is weaker. We can keep adding more layers until
we have similar stiffness in all directions. But eventually, the thickness
of the material will become too great. We reach another problem: when we remember there is nothing
but the resin matrix holding these layers together, and sometimes that fails,
and we get de-lamination of the layers. This is why you often see the carbon fibers
woven into a fabric like this. But again, woven fabrics can only be so thick. We also need to worry about
the drapeability of the material, as these fabrics need to be shaped over molds, and a very thick material like this
can make that job very difficult. These issues create a whole lot of work
for engineers working with composites. But with experience, we've learned to use these unique material characteristics to our advantage. The designers of the MP4/1 managed to create
such a strong monocoque with the material that when the car did crash,
it silenced many of its doubters. We can tailor the fiber directions
to optimize the material properties. Here, we perform the tensile tests
on a tiny piece of carbon fiber composite with fibers only in the direction of the force, creating an incredibly rigid structure
that barely deformed through the test and managed to hold 5.3 tonnes before breaking. But stiffness like that is not always desired. For example, in the event of a crash, you want your car to crumble and deform
to absorb as much energy as possible. And so composite noses of F1 cars are designed
to fragment into millions of tiny bits, and this helps absorb energy
and decelerate the car more slowly. Pressure vessels like the Dreamliner fuselage are wrapped in layer after layer of resin-soaked carbon fiber by a robot that places it in the exact right position, making the structure perfect
for withstanding internal pressure. One of the big problems
when building a structure this big with composite, is that they need to be placed in an autoclave
to get the best quality material. An autoclave applies heat and pressure
to the material to set the resin and forces the air and other voids that weaken
the material out of the resin during the curing process. The autoclave Boeing uses
for the Dreamliner is massive, and there isn't an autoclave in the world big enough
to fit the tank SpaceX created. It's hard to know how they did it, but they almost certainly used an automated tape-placement robot, like the one in Boeing use
to create their own smaller cryotanks, which can cure the resin with a laser
as it lays the pre-preg carbon fiber tape down. But it's very hard to create
quality parts with this method, as the pressure of the autoclave is essential for removing voids in the resin, And this is such a huge concern for composite manufacturers, that parts are often scanned with ultrasound technology to check that the resin has cured
with a tolerable amount of micro-voids. This machine sends ultrasound into the part through a jet of water, and detects the voids in the material. These voids are an even bigger
concern for this application because the biggest problem for the material is cryogenic fuel leaking through micro-cracks and voids. Looking at the outside of the tank, I would say with a fair bit of certainty
that the tank was made in two halves that could fit in an autoclave,
and was then riveted and welded together which I would imagine will be removed
for the final version as this just creates weakness in the structure, but this is all guess work. buh-buh-buh-buh-buh buh-breaking news, yeah! So, while I was making this video, pictures were posted to the SpaceX subreddit by u/Death_Cog_Unit showing the remains of the cryotank after being tested. It failed exactly where I said it was going to fail, but SpaceX have yet to make a formal announcement about the results of this new test. This does not mean failure of the project. We test things to learn more, and it's fantastic that SpaceX are pushing the boundaries of what is possible. I still have so many questions about how this thing was made, which just makes it more frustrating that all the questions being asked in the Q&A session after the big reveal were so stupid. This advancement, if we can make it work, will be the most significant leap in rocket technology we've seen in recent memory. Boeing stated that their cryotank provided 40% weight savings over traditional aluminium fuel tanks. That is going to allow us to launch larger vehicles into orbit, reach further into our solar system, and hopefully, not in the too distant future, it will help humans become a multiplanetary species. Thanks for watching! And this episode is once again brought to you by SquareSpace, who helped me make my next move with my website. In my last video, I revealed
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Stumbled upon this one looking for filament winding machines.
Surprisingly good video - all about ITS tank!
Hearing more of a materials engineering perspective on a core technology of the BFR/S was very interesting. It is easy to get caught up in economic, political, or existential debates, but a post like this is one I can imagine even Elon appreciating for it's focus on 'first principles'. Technologies such as this truly are the cutting edge of human understanding.
Seeing the scale of that is insane. God I can’t wait to see this thing lift off
I think I've seen the video a long time ago. Anyway it seems like a tank for a BFR sized rocket is now well within the capabilities of SpaceX.
That tank is unbelievably huge!
The tank might already work. They pushed it to the point where it actually did fail.
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:
Decronym is a community product of r/SpaceX, implemented by request
3 acronyms in this thread; the most compressed thread commented on today has 28 acronyms.
[Thread #987 for this sub, first seen 21st Mar 2018, 11:24] [FAQ] [Full list] [Contact] [Source code]