SpaceX’s SX 500 Superalloy Passes a Big Test

By on August 29th, 2019 in materials

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 SpaceX’s StarHopper flying with a 3D printed rocket engine [Source: SpaceX]
SpaceX’s StarHopper flying with a 3D printed rocket engine [Source: SpaceX]

This week SpaceX demonstrated the power of 3D printing in very dramatic fashion.

They successfully performed a test flight of their Starship flight demonstrator, the “Starhopper”, using the new and highly advanced Raptor rocket engine. This engine is known to be made from 3D printed parts, which vastly simplifies the design, production and assembly. It also substantially increases reliability due to the complex design having fewer seams where failures could occur.

But before you read further, please watch the official video of this fascinating test launch:

Inconel Superalloys

What’s also notable about this test in regards to 3D printing is the use of a new superalloy developed by SpaceX: SX 500. SpaceX chief Elon Musk tweeted about it some time ago, saying:

 Elon Musk tweeting about the SX 500 superalloy [Source: Twitter]
Elon Musk tweeting about the SX 500 superalloy [Source: Twitter]

Inconel is considered a superalloy, as it has several “super” properties. The most important one is that it is resistant to corrosion through oxidation. Most metals combine with oxygen and deteriorate — rust is a form of this effect, as you may have seen.

However, Inconel is able to overcome this. Wikipedia explains:

“Inconel alloys are oxidation-corrosion-resistant materials well suited for service in extreme environments subjected to pressure and heat. When heated, Inconel forms a thick, stable, passivating oxide layer protecting the surface from further attack. Inconel retains strength over a wide temperature range, attractive for high temperature applications where aluminum and steel would succumb to creep as a result of thermally induced crystal vacancies.”

SX 500 High Pressure

But what’s most amazing about the SX 500 material is that it can withstand pressures of 800 atmospheres, or 810 Bar. This is an incredibly massive specification. To put it in perspective, that’s equivalent to the weight of a column of water eight kilometers tall! The atmosphere of pressure-cooker sister planet Venus is “only” 93 bar.

These characteristics are necessary to ensure the Raptor engine’s turbo pumps can supply fuel and oxidizer to the combustion chamber, which is designed to operate at very high pressures. Worse, the oxidizer pumped through is liquid oxygen, perhaps the most corrosive scenario one could imagine.

The SX 500 material was evidently 3D printed into Raptor engine parts, assembled and fired into the air this week in south Texas at SpaceX’s Boca Chica site.

And it worked.

Open Materials for Metal 3D Printers

3D printing was key to SpaceX’s success here, but also the materials used. This is a classic case of how a 3D printer operator was able to experiment with different materials to achieve a result quite different from the standard materials available for a given 3D printer. Yes, standard materials are useful for common, everyday items, but sometimes they are not.

That’s definitely the case with SpaceX, which is pushing the envelope of materials (and a few other things). Their success is partly due to the ability to use any materials in their metal 3D printers.

Open materials is the future.

By Kerry Stevenson

Kerry Stevenson, aka "General Fabb" has written over 8,000 stories on 3D printing at Fabbaloo since he launched the venture in 2007, with an intention to promote and grow the incredible technology of 3D printing across the world. So far, it seems to be working!