3D printed rocket motors the technology driving the private sector space race

3D printing technology, which uses heat-resistant metal alloys, is revolutionizing rocket development by trial and error. Entire structures that previously would have required hundreds of separate components can now be printed in days. This means you can expect to see many more rockets explode into small pieces in the next few years, but the parts they're actually made of are set to get bigger and fewer in number as the private sector space race intensifies. .

Rocket engines generate energy equivalent to the explosion of a ton of TNT every second, directing that energy into an exhaust that reaches temperatures well over 3,000 degrees Celsius. Those engines that manage to do this without quickly destroying themselves in an unscheduled manner take at least three years to design from scratch, most of which is taken up by the cyclical process of redesign, rebuild, restart and repeat. This is because rocket engines are incredibly complex.

The Saturn V F-1 engines that took Neil Armstrong to the moon in 1969 each had 5,600 manufactured parts, many from different suppliers, with the need to be individually welded or bolted on by hand, taking a long time.

This lengthy and costly process could have gone well in the 1960s, with the US government pouring money into NASA to fuel the race to space, but for private companies it simply takes too long.

The key to rapid engine development is to reduce the number of parts, which reduces the time it takes to assemble the engine and the disruption caused by supply chain delays. The simplest way to do this is to modify the manufacturing processes. Space companies are moving away from subtractive manufacturing processes - which remove material to model a part - to additive manufacturing processes which build a part by adding material to it little by little, basically the principle of 3D printing.

Increasingly, engineers are favoring a process called selective laser sintering to 3D print rocket engine parts in an additive process. The process works by spreading a layer of metal powder, before fusing the shapes into the powder with lasers. The metal binds where it is molten and remains dust where it is not. Once the form has cooled, another layer of powder is added and the part is built layer by layer. An Inconel copper superalloy powder is used for rocket engines, capable of withstanding very high temperatures.

The use of 3D printing also helps manufacturers reduce the weight of the complete rocket, as they are fewer nuts, bolts and welds are needed to produce their complex structure. 3D printing is particularly useful in the production of an engine's regeneratively cooled nozzle complex, which directs cold fuel around the hot engine to simultaneously cool the engine walls and preheat the cold fuel before combustion.

A redesign of the Apollo F-1 engines using 3D printing reduced the number of parts from 5,600 to just 40. It is undeniable that 3D printing has led to a new era of fast and responsive rocket engine development.

Virtually all new rocket companies and space startups are adopting metal 3D printing technology. Accelerate their development phase, helping them survive the crucial years before they can bring anything into space. Of note are Rocket Lab, which uses its 3D printed engine to launch rockets from New Zealand, and Relativity Space, which 3D prints its entire rocket. In the UK are Skyrora and Orbex, which aims to launch a rocket using a 3D printed engine as early as 2022.