In the field of engineering, the first manufactured prototype always looks rough.
Suppose you've seen the various versions of SpaceX starship; you will notice that SpaceX
engineers gradually advanced a starship that looks incredibly rough to much more sophisticated
model with smoother metal walls and welds that are less noticeable.
The welded joints look shinier and smoother than the rough, ugly surface finishing they've
been manufacturing before.
So how did the Starship improve from looking like an ugly masquerade to a well-detailed,
smooth surface?
Stick to the end of this video as we answer this question, and we'll also discuss why
the Starship was rough in the first place.
To answer this question; Well, you will agree that the Starship is the first structure that
looks this tall and cylindrical, about 390 feet tall, having its nose cone up in the
sky.
The first welders who fabricated the first prototypes of starships that looked rough
were welders that worked as reservoir welders in oil companies and water tanks.
SpaceX has to recruit these guys to work on the Starship fast.
Like the saying, if you mean to start something good, don't think much about it.
Rather do it.
So, the first starship prototype was fabricated by non-experienced welders, when it comes
to cylindrical sky-scrapper-like structures.
So, they may not have gotten any first-hand knowledge required to work on tall hollow
and wide structures like this.
But what exactly is welding, and why is it so difficult to get it right?
According to Webster's Dictionary, welding can be defined as fusing two metals with a
hot torch.
Thus, what did SpaceX do to change the game of rough surface welding into something smooth?
A welding technique known as flux-core was utilized in the construction of the early
Starship prototypes.
This technique involves sending a voltage through a wire made of metal, which results
in the formation of an arc between the wire and the metal, forcing the metal to melt.
The end of the metallic wire also melts and falls into the stainless steel that has become
molten, which fills in any cracks or gaps that may have been visible.
When using flux-core welding, the metal wire is wrapped in a solid material that, upon
combustion, produces a shielding gas around the weld joint.
This shields the weld and prevents it from reacting with the oxygen in the surrounding,
which could potentially cause it to fail.
Each stainless-steel ring is fabricated from a single, much thinner sheet.
Thin sheets like this will reduce the high melting point of steel during the weld.
Hence, the engineers switched from stainless steel type 301 to stainless steel type 304L,
which is also more resistant to sudden brittleness during the welding process.
Again, SpaceX welders also upgraded to TIP-TIG welding, which aids them with greater control
over the welding arc.
This enabled the welder to tighten the arc and weld much deeper into the metal than when
the previous welding method was used.
Moreso, SpaceX discovered the importance of buying robotic welding machines from companies
like Liburdi and Kuka.
With the help of robotic welding, SpaceX could automate the major challenging welding process
and begin producing cleaner and more precise welds.
SpaceX has likely switched to laser welding for many of the Starship's sections.
Because the heat generated by laser welding is more concentrated and penetrates the metal
to a greater depth, it is possible to weld the ring segments in a single pass.
However, another process needs to be completed to improve the strength of each weld.
Again, the stainless steel that Starship uses in its manufacturing goes through a process
known as cold rolling after being cut before it is welded into rings.
The question is, what exactly is cold rolling?
You see, Cold rolling is done by moving the metal through a set of rollers, which compresses
the metal structure, and spreads out the grains that make up the metal.
This operation makes the metal material more durable and robust.
Also, after welding, the welded portion tends to become malleable due to the heat.
So, the plashing machine will come into play by strengthening all welded joints to enhance
strength.
In the process of plashing, the welds are pounded down and compressed using a hammer
until they reach the same hardness level as the surrounding metal.
After which, the appearance of the welds will be improved, and an additional smooth look
will be noticed on the welded joints.
To get the point straight, the job of SpaceX welders entails nothing more than using class
A equipment to weld, cut, trim, fit, and fabricate metal components to the specified dimensions
to build and assemble, but this may not be all the case, for the Starship, a good standard
for surface finishing is always maintained.
When planning welding operations in an area where procedural information is not available,
it is necessary to analyze engineering drawings and specifications.
And to accomplish this, you can't rely on inexperienced workers who don't know how to
fabricate anything using metal sheets.
That is why SpaceX has to train amateur engineers who are only good at welding oil reservoirs
or metal water tanks and anchor them with professional welding skills to an advanced
level.
Most of these welders are retained as full-time staff in SpaceX today.
Now, coming to what happened that made the Starship look rough and ugly on the first
try.
The rough and bad look of the previous Starship was a result of improper fitting and bad techniques
for controlling heat input.
It should have been done with pulse mig if done by hand.
Ultimately robotic pulse tig or laser is the best method having the heat/arc more concentrated
with a continuous weld.
A welder can only go so far before having to reposition or change something on the machine
when done by hand.
SpaceX has a pretty good recent track record with their Goofy Prototypes—the Falcon Heavy
stuck its first go—but rocket engineering is hard, and Starship is trying many new,
untested technologies all at once.
You'll be correct to call it a first-generation rocket.
Everything about the Starship is an experiment.
Nobody has ever tried anything like it before.
It's groundbreaking in at least half a dozen basic technologies.
Do you expect it to look like a finished work?
Of course not.
SpaceX isn't just building a starship; they are making them in thousands, around 1,000
to 3,000 of them - so the rapid assembly process and the chances to spread these processes
along a production line are sure to be considered.
And that is a big factor in the material used in producing the Starship.
And rolling off the stainless steel into diameter "rings" and then robotically welding them
to form long tubes without having to cut or bend the material is a very compelling way
to easily mass produce starships.
Like you should one day take a stroll and see how it's being done at Boca Chica - there
is one large "tent" where they just rolled out stainless steel as many times as possible.
There is another area where they weld the rings into larger cylinders - and another
where nose cones and hemispherical bulkheads are made, possibly by hand.
Do you remember the manual fabrication thing?
After deciding to switch to stainless steel, SpaceX started to see more benefits of the
shiny stainless steel gifted nature - no need to paint it, stainless steel gets a lot stronger
at "cryogenic temperatures" - which is fantastic news when you have liquid oxygen/methane at
stupidly low temperatures exerting huge pressure on the structure.
They can also "friction/stir weld" the structure - which robots are good at.
The melting point of the steel is higher than the temperature experienced during reentry.
So, the structure won't lose strength if any of the heat tiles fly off during reentry.
And without forgetting that stainless steel is incredibly cheap.
It's a good cost-effective material, a goal very important to Elon Musk and SpaceX.
That's reusability.
The type of steel grades used in production of the starship are also used for making kitchen
utensils, such as pots and pans.
So it's an easily available metal.
If there were a better/cheaper alternative - you'd expect SpaceX to have found and used
it by now.
But why not carbon fiber in the case of a commercial airplane?
Now think about this a moment.
Suppose SpaceX uses carbon-fiber material, and it works, it will save the quantity of
fuel used to fire the Starship into orbit since the carbon fiber may be lighter than
stainless steel metal.
Why did SpaceX finally dump the carbon-fiber haven used it for the Starship prototype?
To answer this, let's look at the first case scenario of the Starship that utilized carbon
fiber.
Until it was discovered that carbon fiber was a poor choice for a vehicle that had to
deal with temperature extremes ranging from -180 degrees Celsius to 1600 degrees Celsius,
especially during multiple reentries, the carbon fiber could not withstand high temperatures
like this, even though the original "BFR" concept used carbon fiber as the basic construction
material, yet it was later abandoned.
You need pretty thorough insulation and heat shielding system to account for this if you
want this composite to survive at high temperatures above 1000 degree C.
Contrarily, stainless steel is quite content in a much wider temperature range, is stronger
at cryogenic temperatures, and crucially retains a good amount of strength even at a high temperature
of 1000 degrees C and above.
This significantly lowers the need for insulation and a thicker heat shield.
The price difference between stainless steel and carbon fiber, which can be used in a system
that can be deemed more cost-effective, is another important consideration.
Hope you learned a lot in this video today, when do you intend to visit spacex factory
at Bocha Chica Texas, to see the starship production process yourself?
You can also take a look into SpaceX Great Improvements From Starship S20 to S24 That
No One Talks About Are INSANE.