Rocket Materials: Magic of Metal Alloys
Let's learn about the different alloys used in making rockets.
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In previous article we had a brief overview on the different materials used in construction of a rocket. In this article, we will explore the different types of alloys used in rocket construction, and their specific applications in rocket components. We will also discuss the advantages and limitations of each alloy, as well as their potential impact on rocket performance and safety.
Different metal alloys are selected for their specific properties in regards to following constraints—
High temperature ranges
Corrosion resistance
Strength-to-weight ratio
Thermal conductivity
Electrical conductivity
Safety in handling
Let’s discuss the different alloys one by one.
Aluminum Alloys
Aluminum alloys are lightweight and strong, making them ideal for use in rocket structures. They are also highly resistant to corrosion, making them ideal for use in space. Some of the most common types of aluminum alloys used in rocket construction include —
2xxx series: These alloys contain copper as the primary alloying element and are often used in structural applications where strength is critical, such as in rocket frames, skins, and bulkheads.
5xxx series: These alloys contain magnesium as the primary alloying element and are often used in applications where high strength and good corrosion resistance are required, such as in rocket tanks and fuel lines.
6xxx series: These alloys contain magnesium and silicon as the primary alloying elements and are often used in applications where good formability and weldability are required, such as in rocket skins and panels.
7xxx series: These alloys contain zinc as the primary alloying element and are often used in applications where high strength and good fatigue resistance are required, such as in rocket frames and structural components.
The SpaceX Falcon 9 rocket uses a variety of aluminum alloys in its construction, including 2014, 2219, and 7075 alloys. Fuel tanks are made from an aluminum-lithium alloy and the rocket's landing legs are made from another high-strength aluminum alloy. The rocket's interstage, is made from an aluminum honeycomb sandwich structure, providing high stiffness and strength while minimizing weight.
Titanium Alloys
Titanium and its alloys are widely used in rocket construction due to their high strength-to-weight ratio, excellent corrosion resistance, and ability to withstand high temperatures. Some of the most common types of titanium alloys used in rocket construction include:
Ti-6Al-4V (also known as Ti-64 or 6-4 titanium): This is the most commonly used titanium alloy in rocket construction due to its high strength, good ductility, and excellent corrosion resistance. It is often used in rocket engine components, such as turbine blades, compressor discs, and high-pressure fuel lines.
Ti-5Al-2.5Sn: This alloy has good strength and toughness and is often used in rocket engine components such as compressor discs and turbine blades.
Ti-3Al-2.5V: This alloy has good ductility and is often used in rocket skins and structures.
Ti-15V-3Cr-3Al-3Sn: This alloy has good strength and is often used in rocket engine components such as compressor discs and turbine blades.
Overall, titanium alloys are often used in rocket construction due to their high strength, corrosion resistance, and ability to withstand high temperatures, making them ideal for use in the hot, high-pressure environment of rocket engines.
The F-1 engine on the Saturn V rocket used titanium alloys in its combustion chamber.
Titanium vs Aluminum Alloys
Overall, the choice between titanium and aluminum alloys will depend on the specific requirements of the rocket and its intended use. If high strength and corrosion resistance are critical, titanium alloys may be the preferred choice, while if weight and cost are more important factors, aluminum alloys may be a better choice. Titanium alloys have a higher melting point and better thermal stability than aluminum alloys, which makes them ideal for use in high-temperature applications, such as in rocket engines.
Inconel Alloys
Inconel is a family of high-performance nickel-based alloys that are commonly used in rocket construction due to their excellent mechanical properties, high-temperature strength, and resistance to corrosion and oxidation. Some of the most common types of Inconel alloys used in rocket construction include:
Inconel 625: This is a high-strength, corrosion-resistant alloy that is often used in rocket engine components, such as combustion chambers, exhaust nozzles, and turbine blades. It is also used in rocket fuel lines and tanks due to its excellent resistance to corrosion and oxidation.
Inconel 718: This is a high-strength, corrosion-resistant alloy that is often used in rocket engine components, such as turbine blades, compressor discs, and high-pressure fuel lines. It has excellent resistance to corrosion and oxidation at high temperatures.
Inconel X-750: This is a precipitation-hardened alloy that is often used in rocket engine components, such as turbine blades and compressor discs. It has good strength at high temperatures and excellent resistance to corrosion and oxidation.
Inconel 600: This is a high-temperature alloy that is often used in rocket engine components, such as combustion chambers and exhaust nozzles. It has excellent resistance to oxidation and can withstand high temperatures.
Overall, Inconel alloys are commonly used in rocket construction due to their high-temperature strength, excellent resistance to corrosion and oxidation, and mechanical properties, making them ideal for use in the hot, high-pressure environment of rocket engines.
The Space Shuttle's main engine used Inconel alloys in its high-pressure fuel and oxidizer turbopumps.
Nickel Alloys
Nickel alloys are commonly used in rocket construction due to their excellent mechanical properties, high-temperature strength, and resistance to corrosion and oxidation. There are several types of nickel alloys used in rocket construction, each with different properties that make them suitable for different applications. Some of the most common types of nickel alloys (apart from the above discussed Inconel alloys) used in rocket construction include:
Haynes: Haynes alloys are a family of nickel-based alloys that are often used in rocket engine components, such as combustion chambers, exhaust nozzles, and turbine blades. Haynes alloys are known for their excellent strength, high-temperature properties, and resistance to corrosion and oxidation.
Waspaloy: Waspaloy is a nickel-based alloy that is often used in rocket engine components, such as turbine blades and compressor discs. Waspaloy has excellent high-temperature strength and good resistance to corrosion and oxidation.
Rene: Rene is a family of nickel-based alloys that are often used in rocket engine components, such as turbine blades and compressor discs. Rene alloys have excellent high-temperature strength and resistance to fatigue, making them ideal for use in the high-stress environment of rocket engines.
The RD-180 rocket engine, used on the Atlas V rocket, uses nickel alloys in its combustion chamber and nozzle.
Other Alloys
Along with what we discussed above alloys of copper, beryllium and magnesium are also used in rocket construction, although in relatively lesser and limited quantities. Beryllium alloys are known for their high stiffness, strength, and thermal conductivity, as well as their resistance to corrosion and fatigue. High-purity copper alloy is used in electrical components, such as wiring and connectors, due to its excellent electrical conductivity. Magnesium alloys offer excellent machinability along with high strength-to-weight ratio, hence, often used for manufacturing of components with intricate shapes and features.
Restricted Alloys
As materials science has progressed and the potential risks associated with certain materials have become better understood, many countries have put in place regulations and restrictions on the use of these materials in order to protect the health and safety of workers and the environment.
One example of a metal that was used in earlier rockets but is now prohibited is beryllium. Beryllium was used in rocket construction due to its unique properties, including its high stiffness, strength, and thermal conductivity. However, beryllium is a toxic material that can cause lung disease and cancer when inhaled, and therefore its use in rocket construction is now strictly regulated.
Another example is cadmium, which was used in rocket engine construction as a plating material to protect against corrosion. However, cadmium is a toxic material that can cause lung and prostate cancer, and its use is now heavily restricted.
Similarly, lead was also used in earlier rockets in applications such as radiation shielding, but its use is now heavily restricted due to its toxicity and environmental concerns.
We hope you found this article informative. In next newsletter we will cover more details on the different materials used in rocket construction.