Many early prototypes stuck in dirt banks and end up decorating tops of trees. This is due to the volatile nature of space rocket engines. Rocket scientists have devised a way to describe unintentional explosions, called rapid unscheduled destruction (or RUD).
Each time a rocket engine explodes, it is necessary to identify the cause. The cycle continues until the engine’s failure is fix. A new, improve engine is design and manufacture. It is then ship to the test location and fired. This is one of the major causes of delays in developing rocket engines for a rapidly growing space industry.
Today’s 3D printing technology uses heat-resistant metal alloys to revolutionize trial-and-error rocket design. In just days, whole structures that use to require hundreds of components can now print. As the private sector space race intensifies, you can expect to see more rockets breaking down into smaller pieces over the next few years. However, the parts that they actually made of will become increasingly scarce.
Rocket engines produce the equivalent of releasing a tonne worth of TNT per second and then direct that energy into an exhaust which reaches temperatures well above 3,000. It takes at least three years to build an engine from scratch that can do this without disassembling in an unscheduled manner.
Rocket engines are extremely complex. Each of the 5,600 parts that made Neil Armstrong’s 1969 rocket to the Moon with F-1 Saturn V engines had 5600 each. Many of the parts from different suppliers so each one had to individually weld and bolted together manually. This took time.
In the 1960s, this lengthy and expensive process was fine as the US government funneled money into Nasa to fund the space race. But for private companies, it is simply too slow.
Rocket Fuel Can Be Add Space
Reduce the number of components is key to speeding up engine development. This reduces the time required to assemble the engine, and reduces disruptions caused by supply chain delays. Modifying manufacturing processes is the best way to achieve this. Space companies are moving away from subtractive manufacturing, which involves removing material to form a part, to additive manufacturing processes. These processes add material bit by bit to build up a part.
This means 3D printing. Engineers are increasingly using selective laser sintering to create 3D printed parts for rocket engines in an additive process. The process involves first coating the metal powder and then melting the shapes with lasers. The metal will bind to the areas it has melted and remain powdery where it is not. After the shape is cooled, another layer is added of powder and the part is assembled layer by layer. Because it can withstand extremely high temperatures, Inconel copper superalloy powder is recommended for rocket engines.
Selective laser sintering makes it possible to print multiple parts in-house as one part in just days. Engineers can fix a RUD using 3D modeling software. They can also integrate complex parts into new rocket engines that are ready for testing firing within days.
3D printing helps reduce the overall weight of the rocket by requiring fewer nuts, bolts, and welds to create their intricate structure. 3D printing is particularly useful for manufacturing complex regeneratively cool nozzles that cool and heat the fuel.
The number of parts required to redesign the Apollo F-1 engines was reduced from 5,600 down to 40 by 3D printing. Although no company has yet to reduce the number of parts to one, it is clear that 3D printing has enabled a new era in rocket engine development.
This is important for private space companies. It is expensive to build a rocket. As the RUD pile grows, investors may become feisty. When faulty rockets force companies to delay their launch dates, it can be a serious PR blow to those who are trying to launch payloads in space.
Virtually every new space startup and rocket company is using 3D metal-printing technology. It speeds up their development and helps them to survive the critical years before they can get into space. Rocket Lab uses its 3D-printed engine for rocket launches from New Zealand and Relativity Space 3D prints its entire rocket. Orbex and Skyrora are two of the UK’s most prominent 3D-printed engines. This latter group aims to launch a rocket with a 3D-printed engine by 2022.
It remains to see if a complete rocket, including its engine can be 3D print in one piece. This is the clear direction of travel in an industry where light-weight, complex and in-house manufacturing will determine which payloads are placed in orbit. These payloads may also end up disassembling at an inopportune time.