Space metals – Which metals are tough enough for lift off?

The forces you get when a space rocket takes off are quite something, especially during the phase of ‘maximum aerodynamic pressure’ when the rocket’s actually thrusting through the earth’s atmosphere. Despite these powerful forces the craft’s liquid fuel systems have to stay at very low temperatures.  In contrast the combustion and exhaust sections of the rocket must reach extremely high temperatures. Then there’s ‘hydrogen embrittlement’ to take into account.  

The fact that every component in a rocket also has to be really light and you can see there are all sorts of tricky challenges to handle, especially since most metals are naturally pretty dense.  So which metals are rufty-tufty enough to take rockets up into space without falling apart, melting, or exploding? 

About the metals used to make space rockets  

A high density metal can’t be made thin enough to be as light as it needs to be, and parts made from dense metals are inevitably massive. So how about using light metals like aluminium, lithium and magnesium? They’re all used in space in one way or another but they also have a big downside in the form of a very low melting point – and that’s no good when metals in space get superheated. 

These metals are also very chemically reactive, which means they’re about as much use as a chocolate fireguard when it comes to being in contact with cryogenic fuel or the searing hot gases expelled from a space rocket’s exhaust.

Ceramics and ceramic composites can be extremely strong and stable. But they can also be too brittle to cope with high mechanical loads. At the end of the day four common metals turn out to have the right features for space rocket manufacture, even though they’re comparatively dense. We’re talking nickel, cobalt, iron and chromium.

Elon Musk’s take on space rocket metals   

Space-obsessed Elon Musk is going to build his Starship and associated rocket booster from stainless steel, which he rates higher than any advanced carbon fibre structure. In his world stainless steel 301 is the best solution, used to integrate the structural elements of the rocket with its heat shield. Because the alloy has such a wide temperature range it can be used in anything from sub-zero cryogenic temperatures to super-hot 1100 K. It actually outperforms aluminium and carbon fibre alternatives and it’s also the lightest choice. 

Most of a rocket’s mass is focused around the propellant tanks, which can have a load-bearing responsibility. They have to deal with moderate pressure at extremely low cryogenic temperatures while handling mechanical loads. Rocket designers often use a stiffened aluminium alloy shell to support the weight whether or not the interior is pressurised. The aluminium 2000 series is ideal, a blend of aluminium-copper alloys.

 Inside these alloys, a compound called CuAl2 adds strength.  Including silicon, lithium, and tiny amounts of manganese, magnesium, and titanium make the alloys easier to forge and less likely to corrode when stressed. They also, oddly, have a high tensile strength at very low temperatures. 

What are the pipework and feed lines in a space rocket made from? 

Pipes and ducts demand high ductility and strength even at cryogenic temperatures. And they have to be able to withstand the fluids conducted along the lines and pipes as well. This is where hydrogen embrittlement comes in. Rocket pipes made from corrosion-resistant 321 stainless steel come with a lot of chromium included, as well as nickel. The whole thing is stabilised by a dash of titanium. 

Finally, there’s the rocket’s turbo pump blades and the actual casing, both made from a clever titanium-based alloy. 

All the metals you need – except for space travel 

We have all the metals you’re likely to need for a multitude of applications… excluding space travel!  Walk this way for quality 6061 aluminium square bar and aluminium 7075t6-t651 plate. We’re trusted brass square bar suppliers and there’s nothing we don’t know about aluminium tooling plate. That’s just the tip of the Metalex metals supplier iceberg. How can we help you? 

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