3D printing or additive manufacturing is ongoing revolution in manufacturing with its potential to fabricate any complex object and is being utilized from aerospace components to human organs, textiles, metals, buildings and even food. Additive manufacturing is defined by ASTM International as the process of joining materials together, layer by layer, based on three-dimensional model data.
Additive manufacturing is known to be a good prototyping method. It is allowing the manufacturers to make many iterations at a lower cost and quite quickly. Moreover, as you have to work on a CAD software to create your parts, you only have to make modifications on your 3D file if you need to change something. It is really allowing to work way faster than with other processes. The 3D printing technology is getting further boost in aerospace and aeronautics as many 3D printers which can print heat resistant materials are now entering the market.
For the last several years, aerospace companies have been examining ways to use additive manufacturing, or 3D printing, to aid the production of rocket engines. These industries are using this technology both for prototyping and production from motors to complete rockets.
The RS25 engine developed by Space Launch System has a 3D printed component called pogo accumulator, a shock absorber placed inside of the rocket engine. Aerojet Rocketdyne, has been working on printing components of its venerable RL10 engine. In early June, the company announced that a printed copper thrust chamber successfully completed a series of hotfire tests. The company isn’t alone in exploring new ways to apply additive manufacturing to propulsion and related systems.
Colorado-based company Agile Space Propulsion has a specific goal: to design and manufacture rocket engines using 3D printing technology. In particular, Barnes wants to develop thrusters, the small maneuvering engines used in rockets. According to Barnes, as rockets get cheaper, there is an increasing need for thrusters, and the miniaturization of electronics is spurring demand for more space vehicles for a variety of purposes.
Printer manufacturers are also developing large-scale 3D printers. Instead of components, it will be possible to print larger parts more easily.
Relativity Space, for example, is working to 3D-print entire rockets, including their engines, and has raised tens of millions of dollars to support its work. Kieatiwong, though, is hopeful that his company can achieve a breakthrough with its new approach to engine design.
SpaceX has built a rocket engine using 3D printing, it is called SuperDraco. This process has been used on different levels. First, for testing, 3D printing has been used instead of the traditional casting method. 3D printing has also been an advantage for the manufacturing process, and it really reduced the lead-time. The 3D printed parts were even more resistant than traditional ones.
NASA engineers, created a rocket engine prototype using two different metals: copper alloy and Inconel. They used a process called brazing, in order to join 2 different types of metal, creating a brand new component. This advanced process is offering promising possibilities for the future 3D printed metal parts.
Additive Rocket Corp. combines additive manufacturing with a tool called generative design
For Aerojet, using additive manufacturing helps to reduce the number of parts in engine components, and thus speed up production and lower costs. “You reduce the time to produce that part well in excess of 50 percent,” said Eileen Drake, president and chief executive of Aerojet Rocketdyne, in an April interview. “There’s less labor content, less supplier content, [fewer] parts that you have to put together that could cause an issue.”
The use of additive manufacturing is a key element in Aerojet’s updated version of the engine, the RL10C-X, intended to lower its cost without compromising reliability or performance. Aerojet is developing that engine with United Launch Alliance, who plans to use it in the upper stage of its Vulcan rocket under an agreement the companies announced in May.
“What additive manufacturing does is that it opens up the opportunities of design freedom and removes all the traditional barriers that engineers have to keep in mind,” said Andy Kieatiwong, co-founder and chief executive of Additive Rocket Corporation (ARC), during a presentation at the Space Tech Expo conference in Pasadena, California, in May.
ARC combines additive manufacturing with a tool called generative design, where computer algorithms develop thousands of different designs that meet a set of constraints and then iterate on them to find the optimal solution. That can result in designs that are not possible to produce without 3D printing and can even be beyond the imagination of conventionally trained engineers.
The exterior looks like a typical engine, but he showed cutaways of its interior that revealed dozens of channels carrying kerosene and liquid oxygen in patterns than he likened to blood vessels or a tree trunk. “That’s one of the best ways to move fluid through a system,” he said.
That “biomimetic” architecture is a hallmark of generative design. “The benefits of this system cascade up through the entire propulsion system,” he said. It lowers the pressure differential in the engine, so less energy is needed to move the fuel, which reduces the size of valves, pumps and tanks supporting the engine. It also improves the heat transfer through the nozzle to lower its temperature, increasing its lifetime.
Agile Space Propulsion Pursues 3D Printing for Rocket Thrusters
Barnes created Agile Space Propulsion because of a failure to land NASA grants to develop new technology, as Advanced Mobile Propulsion Test was viewed as a testing facility and not a design company.
Barnes has already developed a prototype thruster for a lunar lander for NASA. The thruster had languished in production for years without making much progress, due to the limitations of conventional manufacturing techniques. Using 3D printing, Barnes was able to come up with a prototype in merely nine weeks, and it performed better than the engine that had been in production for so long.
Agile Space Propulsion has already developed a 100-pound thruster and is currently working on a five-pound one. Barnes points to the use of 3D printing in much of aerospace, for both small and large engines.
“In traditional manufacturing, there are a lot of steps, a lot of parts, and there are restrictions on what you can do,” he said. “For instance, you can drill a straight hole, but you can’t drill a curved hole.” 3D printing, on the other hand, can create curved channels, and can cut down on the number of steps involved in making something like a thruster.
“The end product is more sophisticated, more capable and lighter, and that’s a really big thing,” said Barnes. “I can print in one day something that took months to make. Just the time savings alone is a big cost-saver.”
“Cost reductions have opened up opportunities,” Daudi Barnes said. “People are saying: ‘Wow, if all of this is more affordable, we can do more missions now.’” Rocket launches have been downsizing and becoming lighter and cheaper, partially thanks to 3D printing, which enables complex parts to be made in fewer components, or even in a single component. It also allows for a great deal of lightweighting. “Weight is everything in space,” said Barnes. “It costs $1 million to put 1 kilo on the face of the moon. If you can make a spacecraft half a kilo lighter, you’re saving a ton of money.”
Barnes is also the owner of Advanced Mobile Propulsion Test, which gives him access to that company’s rocket engine testing facility. This allows him to quickly iterate and test his designs. “We use 3D printing, but the other part we have is the testing facility,” he said. “We can learn a lot when we test here. We’re uniquely diagnostic. We have very specific equipment that gives you detailed information and more certainty in the information you’re getting. We are also focused on a quick turnaround. You can get back to an engine, modify it and quickly retest.”