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Jordan Taylor Profile picture
@Jordan_W_Taylor
Dec 13, 2022 • 14 tweets • 6 min read • Read on X
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1/This is a thread about metallurgy's secret cheat code, and how it's used by the aerospace industry to accomplish things that no material should.

In particular, how that cheat code is enabled on the humble, but amazing, jet engine turbine blade. Image
2/This is our friend, the high pressure turbine blade. It lives inside your everyday turbofan engine and helps you go on holiday. It also casually takes 20,000G of force and operates about 200C above it's own melting point.

I have a separate thread about that, but I digress. Image
3/Zoom into any metal, real close-like, and you'll see this. Countless tiny crystals, forming a complex grain structure. The size and uniformity of these grains has a *huge* effect on the tensile strength and fatigue life of the material. Image
4/When the metal is casted it cools from a molten state, but it doesn't do so uniformly. Tiny crystals form and grow as the metal cools and solidifies. The size and uniformity of the crystals is dictated by the speed and uniformity of the cooling. Image
5/Broadly speaking the smaller the grain size, the better. Grain boundaries inhibit crack propagation and so the more of them there are, and the more uniform there are, the harder it is for defects to propagate. In a turbine blade, subject to insane stress, this is crucial. Image
6/Except there is an exception. At very high temperatures, thermal creep starts to become an issue which can dominate over cold tensile strength. For a blade operating right next to it's melting point this is a big deal.

Creep is enhanced by grain boundaries. What to do? Image
7/With this exception comes a countermeasure. A cheat code if you will. Rather than small or large crystals, why not a single crystal with no grain boundaries at all? Not perfect for fatigue, but ideal for continuous load at high temperature.

Well, easier said than done. Image
8/Enter the strange world of single crystal investment casting. First a wax turbine blade is produced, with a ceramic core inside held in place with platinum wires. Image
9/Then a robotic arm dips it repeatedly in ceramic slurry, which dries to create a ceramic mould (the wax will later be melted out). This is the mould that will enter the vacuum furnace and cast the Nickel superalloy. Image
10/The ceramic mould, filled with molten Nickel superalloy, is lowered from the vacuum furnace onto a chiller plate. This forces crystallisation to start from a single point. Image
11/The crystals move up through the mould as it is lowered slowly from the furnace. They move through a tight 'pigtail' which causes one crystal to dominate before it enters the rest of the mould. The pigtail is then removed. Image
12/The casting is removed from the mould and the core leached out. It is cleaned and etched to reveal the crystal structure for inspection, to ensure that impurities haven't caused multiple crystals to form that would threaten blade integrity. Image
13/The blade is the barrelled for a super polished finish and sent to turbine blade machining, leaving the foundry. After much additional processing, coating & inspection the blade is finished. A literal crystalline jewel, ready to take you overseas. ImageImage
More fun engineering threads:

New & upcoming gas turbine trends:

The open-rotor engine:

Turbine blade film cooling:

Tidal energy basics:

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More from @Jordan_W_Taylor

Jordan Taylor Profile picture
Jan 24
Rare earths: They're silvery magnetic rocks with strange properties and almost every high-tech good in the world depends on them.

And China controls 90% of the supply. What are they, how are they made and how can we fix this?

The rare earth thread! Image
What are they?

They're a group of 17 chemically similar metals with magnetic, mechanical, catalytic and optical properties that make them crucial.

For example: Neodymium, a powerful permanent magnet, used in compact motors, generators & actuators everywhere. Image
Are they rare?

Kinda, but not quite. Some rare earth elements (REE) are rare, others are as common as copper. On average REEs are about as common as lead.

Their rarity comes from being an absolute devil to mine & refine, and until recently it was China that grasped the nettle. Image
Read 19 tweets
Jordan Taylor Profile picture
Dec 11, 2025
Where is the talent coming from?

There are approximately 14.6 million working-age people with STEM degrees in the United States, plus arrivals from outside. There are 29 million in the EU & UK.

But this is a sideshow to the real action in the East… Image
Image
I used Grok Expert to create a series of estimates for STEM educated populations across the world, excluding social sciences, then used population data to predict changes over time. I analysed USA, China, EU+UK, India, Russia & Japan.

Let's get into it… Image
USA!

14.6 million.
A low volume of engineers at about 3.7-5.6 million (depending on definition) is powerfully made up for in the sciences, particularly biology & biomedical (2.9 million) and computer science & IT (4.1 million).

Appropriate for the industries of the future! Image
Read 15 tweets
Jordan Taylor Profile picture
Aug 30, 2025
It's the greatest story never told: It's the story of how a frugal county in the North of England invented the modern world.

Put on a flat cap and call up the whippet, because this is a thread about my home county, and the inventions that came out of Yorkshire! Image
Image
Steel!

Benjamin Huntsman invented high homogeneity crucible steel in Sheffield in the 1740s, firing with coke to fully melt the steel and homogenise the carbon content.

This became used… everywhere, and supercharged the ongoing industrial revolution. Image
Steam trains.

Steam locomotion had been in development for some decades by 1812, but arguably the world's first commercially successful steam locomotive was Matthew Murray's Salamanca. To him, we owe speed. Image
Read 14 tweets
Jordan Taylor Profile picture
Aug 26, 2025
A liquid rocket boost stage needs to pump fuel and cryogenic oxidiser to the combustion chamber at a rate that beggars belief: The 33 engines on the boost stage of SpaceX's monstrous ‘Superheavy’ booster each chew through about 700 kg of propellant every second. Put all those engines together and the flow rate of liquid fuel & oxygen would be sufficient to empty an Olympic swimming pool in under 2 minutes, if you could find an Olympic swimming pool for cryogenic propellant.

Can you think of any conventional lightweight pump that can do this? Me neither. You need something special…

The turbopump comprises a typically-axial turbine powered by hot, pressurised gas flow that powers centrifugal compressor pumps that pump the colossal quantities of propellant required and pressurize it to, potentially, hundreds of standard atmospheres.

It's a handy, lightweight way to provide pumping power, but it does require that you have a source of hot, high-pressure gas to work with.

Now, where would you find that in a rocket engine?

Indeed. In order to burn fuel, we must pump it. In order to pump it, we may have to burn some of it.

Um…Image
Image
The Gas Generator Cycle.

A small quantity of the pressurised fuel & oxidiser flows are tapped, brought to a small combustor, vaporised, ignited then expanded through a turbine that powers the fuel and oxygen compressor cycles.

Inevitably the gas generator can't run with a completely nominal fuel:oxy mix, as it would get so hot that it would melt the turbine blades, so typically a gas generator will trade off some efficiency and run fuel rich to power the turbopumps.

-Why not oxy rich? Because fuel has a higher specific heat at constant pressure (Cp) and so you need less mass flow through the gas generator if it's fuel rich than oxy rich, meaning more useful propellant goes to the main combustor & nozzle that moves the rocket.

So the upside of a gas generator cycle is relative simplicity and robustness, which is why it's used on the most reliable rocket motors around, the SpaceX Merlin. The downside is that you trade away efficiency by throwing away some of your propellant, meaning that the tyranny of the Tsiolkowsky rocket equation will kick you where the sun don't shine.Image
Image
Staged combustion attempts to address this, by taking either a fuel rich or oxy rich preburner, operating at a much higher flow volume than a standard gas generator, and routing the hot gases that leave the turbine straight to the combustion chamber so that they're not lost. This not only increases the average propellant exhaust velocity (since none of it is lost) and therefore efficiency, but also allows a lower average temperature in the preburner and turbine, since there's a higher volume throughput instead.

On the flipside you must deal with hugely increased engineering complexity, an increased potential for feedback control problems between the different parts of the engine, and also a much higher pressure preburner, since it will still need to deliver high working pressures to the combustion chamber after the losses of the turbine and injectors.

The Soviets got there first, and some of their genius manifested in the Russian RD180 oxy-rich staged combustion engine, which was bought by the Americans and used in Atlas rockets for many years. Its unique oxy-rich staged combustion cycle was efficient but not without drawbacks, as high temperature gaseous oxygen is brutal to exposed metal surfaces, demanding an enamel coating on many parts of the engine.

And it gets even more complex than that…Image
Read 5 tweets
Jordan Taylor Profile picture
Jul 18, 2025
Last month Rolls-Royce won the UK's small modular reactor competition to develop and build SMRs in the UK. It could be a new dawn for nuclear power.

But who else was in the competition, what was special about each design, and which is your favourite?

An SMR thread… Image
What's an SMR?

A small modular reactor is a way of beating the brutally high capital costs of building nuclear power: By simplifying assembly (modularity) and minimising subsystem size so almost all of it is factory built you harvest industrial learner effects and low costs. Image
Boiling water vs pressurised water reactors.

All designs in this list are either PWRs or BWRs, the most common reactor styles today. I've a thread on the basics if you need it, but otherwise on with the show!
Read 21 tweets
Jordan Taylor Profile picture
Jul 4, 2025
In April on a mountain in Chile the Vera Rubin observatory gathered first light, and this telescope will be world-changing! -Not because it can see the furthest… but because it can see the fastest!

The Vera Rubin telescope thread! The value of speed, and unique technology… Image
Who was Vera Rubin?

She first hypothesized the existence of dark matter, by observing that the rotation speed of the edge of the galaxy did not drop off with radius from the centre as much as it should. The search for dark matter, and other things, will drive this telescope… Image
Does it see a long way?

Yes, but it’s not optimized for that: The battle of the big mirrors is won by the Extremely Large Telescope which, yes, is meant to see a long way. Vera Rubin is not that big, but that doesn’t matter because it has a different and maybe better mission. Image
Read 22 tweets

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