This video is supported by KiwiCo If you’ve been following Starship from the
very beginning, you will know that it didn’t always look this good. The first Starship prototypes looked incredibly
rough, not like something that could ever survive a journey into space. The Starships that SpaceX produce now look
much more sophisticated, with smoother metal work and welds that are much less noticeable. So how did Starship go from looking like this
to this in just a few years? And will it ever look completely smooth and
shiny like it does in the renders? To answer this question, we need to look at
why Starship looks like this in the first place, more specifically, why it’s big and
shiny instead of white and thin like most rockets. Starship wasn’t always destined to look
like a 1940’s sci-fi rocket. In fact, it was originally meant to be made
from carbon fiber and production had already begun in California. This seemed like the most logical plan since
carbon fiber is extremely strong and SpaceX already had most of their workforce based
in California. So it shocked everyone when a stainless steel
Starship popped up in a small village in Texas. But over time, people started to realize what
a great decision this was. Although carbon fiber is very strong, it starts
to break down at around 200 degrees. Therefore, it would require a very thick heatshield
in order to survive the 1600 degree temperatures during multiple reentries. Although stainless steel is heavier, it can
deal with much higher temperatures, and so only a very thin heatshield would be required. Stainless steel is also much cheaper than
carbon, costing just 3 dollars per kg compared to an incredible 150. But this wasn’t the first stainless steel
rocket to be made. Back in the 60’s, NASA made an Atlas rocket
out of incredibly thin stainless steel. This was so thin, that unless the rocket was
constantly pressurized, gravity alone would completely crush it. And it did! But even if SpaceX had gone with carbon fiber,
it’s hard to see how Starship would have actually been made. In order to manufacture carbon composites,
the fibers have to be layered in a very specific way, in order for the material to be strong
in every direction. Then the composites need to be cured in an
enormous pressure oven. For Starship’s 9 meter wide sections, SpaceX
would need an oven larger than anything that exists at the moment. This is where stainless steel excelled. It could be put together quickly, using the
most basic and affordable methods. And so, SpaceX began working on the world’s
shiniest rocket. But for some reason, it wasn’t so shiny! One of the biggest challenges with the initial
Starship prototypes was the welding. Initially, each ring was being made out of
several sheets of 301 stainless steel, which were around 4.5mm thick. Don’t forget that the original Starship
crew was contracted from a water tower company and didn’t have any experience with building
rockets. So the welding standards were, well, not great. But what exactly is welding and why is it
so difficult to get right? The Office: Webster's Dictionary defines wedding as the fusing of two metals with a hot torch. The early Starship prototypes used a welding
method called flux-core. With this method, a voltage is passed through
a metallic wire which forms an arc between it and the metal, causing it to melt. The tip of the metallic wire also melts and
falls into the now molten stainless steel, filling up any cracks or air bubbles. With flux-core, the metal wire is surrounded
by a solid material that burns and releases a protective gas around the weld. This protects the weld and stops it from reacting
with the oxygen in our atmosphere, which would cause corrosion. This works well when you’re inside a controlled
environment. But SpaceX’s main problem at the time was
that they didn’t really have a proper factory, just a fairly large tent. And so, with most of the welding being done
outside by welders that had no rocket experience, it's no surprise Starship looked so bad. The welds on the first mark 1 prototype were
heavily corroded, with cracks and rough edges on the surface. In order to improve these welds, SpaceX started
grinding them down until they were flush with the surface. Although this seemed like a poor attempt to
restore some shininess, this process was actually done to strengthen the welds. These sharp edges and tiny cracks act as pressure
points which could lead to much bigger cracks once Starship is pressurized. And so, grinding the surface removed these
defects and reduced the chance of a weld failing. In theory, each weld should be as strong as
the surrounding metal. But the initial Starship test proved that
it wasn’t. Mark 1 exploded when one of the horizontal
welds failed and sent the bulkhead flying. And so, SpaceX brought in some major improvements
to the next Starship prototype. Each ring was now made from thinner single
sheets of stainless steel which required much less welding. They also moved from 301 to 304L stainless
steel which was much more resistant to corrosion when welding. At this point, they also upgraded to TIP-TIG
welding, which gave them more control over the welding arc, allowing the welder to tighten
it up and weld much deeper into the metal. This produced much thinner welds and didn’t
warp the surrounding metal nearly as much. SpaceX also started to buy robotic welding
machines from companies Liburdi and Kuka, similar to the ones seen in Tesla factories. With these upgrades, SpaceX automated a large
chunk of the process and started to produce cleaner and more precise welds. They also began installing more stringers
on the inside of Starship's hull, to stop the metal from buckling under its own weight. But SpaceX didn’t stop there. By now, SpaceX has likely moved onto laser
welding for many of Starship’s sections. With laser welding, the heat is much more
concentrated and goes deeper into the metal, allowing the ring segments to be welded in
a single pass. But in order to really improve the strength
of each weld, another process has to be done. You see, when Starship’s stainless steel
is produced in its factory, it goes through a process called cold rolling. This involves passing the metal through a
series of rollers which compress it down and stretch out the grains in the metal. This makes the material stronger and harder. However, when Starship is welded, the heat
causes the metal in that area to soften up again. This is where SpaceX’s giant planishing
machine comes in. Planishing involves hammering the welds down
and compressing them until they match the hardness of the surrounding metal. This has the added benefit of smoothing the
finish of the welds and improving their look. But will Starship ever have a completely smooth
finish like a mirror? To answer this, we need to go to Chicago to
look at the famous Bean sculpture. Made from several stainless steel sheets,
this structure went through an 8 month polishing process, involving a crew of 24 people using
many different grades of sanding grit. In order to do this on Starship, the entire
body would need to go through this process to avoid having any visible lines around the
welds, so it's unlikely that SpaceX will ever do this. Either way, SpaceX is throwing everything
into Starship and it's amazing to see this project come together so quickly. Speaking of amazing projects. KiwiCo creates super cool hands-on projects
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see you in the next video.
This is from the "Primal Space" channel on YouTube. My first suspicion was that it was one of the many clickbait channels attempting to capitalize on the high interest in SpaceX. I now see that it has original, thoughtful content. So my first suspicion was wrong. After watching this video, I am now a subscriber to the channel.
Are they actually doing laser welding and planishing now?
Primal Space is a good space youtube channel. I remember really liking his video on why they were trying out something other than landing legs - I didn't know they added so much mass.
Great video. Shame the cover image looks like spam