BrainStuff Classics: How Does Captain America's Shield Work?

Captain America's indestructible shield may be a work of fiction, but that won't stop us from trying to figure out how it might work in the real world. Learn more about the history and science behind Cap's shield in this episode of BrainStuff.

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Episode Transcript

Speaker 1 (00:01):
Welcome to brain Stuff production of iHeart Radio. Hey brain Stuff.
I'm more in Vogelbaum, and today's episode is a classic
from our former host, Christian Sagar. The team here around
the currently virtual office loves a comic book and has
been delighted that Marvel has been bringing that love to
a wider audience with its cinematic universe. So today let's

(00:23):
get geeky with a deep look into how Captain America's
signature shield would work if it, you know, really existed.
Hey brain Stuff, I'm Christian Sager. The official Marvel Comics
database says that Captain America's shield is a metal disc
that's approximately two point five feet in diameter and weighs

(00:45):
twelve pounds, but Rhet Elaine at Wired Magazine did some
math and figured out that it would be more likely
to weigh forty three point nine pounds, despite the shield
being made of a unique alloy combining vibranium, which is
a fictional metal, steel, and an unknown third component. Elaine
also figured out that the density of the shield would

(01:07):
be somewhere between eight thousand, seven hundred and sixty seven
and four thousand, three eighty three kilograms per meter cubed
that is somewhere between the density of iron and titanium. Now,
in the Captain America comics, the story goes that Dr
Myron McLean was attempting to replicate Hercules golden mace by

(01:28):
fusing vibranium with an experimental iron alloy. Some say it
was a steel alloy, but even McClain didn't know what
it was because he fell asleep when an unknown catalyst
was introduced to the process. He was never able to
duplicate the process, so the government painted the disk and
gave it to Captain America. But how would you forge

(01:48):
such a thing, especially since metallurgy is so complicated. Just
the forging temperature alone depends on the materials carbon content,
it's alloy composition, maximum plasticity, and the out of reduction required.
Was it heated by induction or by continuous fuel fired furnaces.
With a material this unique, you would have to carefully

(02:09):
control the heating process. Now, forgibility is how easy or
difficult a material resists deformation, And since Captain America's shield
is indestructible, it would have to be a very narrow
forging temperature range, meaning it could only be forged for
a short time after heating. With metallurgical factors like crystal structure,

(02:31):
chemical composition, and grain size at play, the only way
McClain could have diminished their influence would be by adding
alloying elements, possibly compounds that easily dissolve within the metal.
There are all types of elements that could have been introduced,
but it's likely that Captain America's shield was forged like
a super alloy. This is how metall are just referred

(02:54):
to iron based, nickel base and cobalt based alloys, specifically
the ones that offer very high strength at high temperatures.
These really high strength metals and iron based grades are
the least difficult ones to work with, so that would
narrow down McClain's experimental alloy to iron. Super alloys are
really difficult to forge because of their narrow temperature range.

(03:17):
You can't even use regular sizing presses and hammers on
them because they'll deform. They even wear down the tools
designed for forging them pretty easily. They're also extremely expensive,
like ten times the price of carbon steel. Sounds a
lot like Captain America's shield, right, But how do we
explain the shield's ability to absorb kinetic energy, supposedly from

(03:39):
the vibranium in the alloy. Usually materials absorb kinetic energy
through other mechanisms like plastic or elastic deformation or dynamic
fluid flow, but cap shield doesn't seem to be an
elastometric material, and it's not organic like polyurethane in the movies.
It actually seems to reflect vibration rather than absorb it,

(04:02):
like when Thor hits it with m Olner in that
first Avengers movie and the shock wave flattens a whole forest.
Perhaps that was because the shield reached its absorption limit.
Another thing that's tough to explain is how aerodynamic the
shield is. If it really weighed forty three point nine pounds,
it would be difficult to throw, even for a guy

(04:22):
in peak physical condition like Steve Rogers. In the comics,
Tony Stark actually puts electro magnets under the shield to
help control it in midflight, but Captain America later ditched
them because they upset the shields natural balance. It seems
like the soldier and the shield are made for each other.

(04:47):
Today's episode was written by Christian and produced by Tyler Klang.
For more on this and lots of other topics that
shout excelsior, visit how stuff works dot com. Brain Stuff
is a production of my heart Radio. For more podcasts
to my heart Radio is the i heart Radio app,
Apple Podcasts, or wherever you listen to your favorite shows.

(05:14):
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