Other companies have built rocket engine parts, most notably Elon Musk's SpaceX, but now Aerojet Rocketdyne says they've successfully completed a series of hot-fire tests on their Bantam demonstration engine and it was built entirely with additive manufacturing processes.

"We're not just making a stand-alone chamber or injector derived from traditional design approaches. Rather, we're integrating the full capability of additive manufacturing processes to evolve a proven, reliable, affordable design," said Jay Littles, director of Advanced Launch Propulsion Programs at Aerojet Rocketdyne.

Such engines are normally made up of dozens of parts, but the Baby Bantam consisted of only three additive-manufactured components; the injector and dome assembly; the combustion chamber; and a throat and nozzle section.

Dubbed the Baby Bantam, the liquid oxygen and kerosene-fueled engine boasts a thrust of 5,000 pounds. The other engines in the Bantam line extend up to 200,000 pounds of thrust and can be adapted to use various fuels, including kerosene, ethanol, methane and storable propellants.

Atlas Sustainer engine

Adapted from the design of the company's Atlas Sustainer engine, this latest entry was made to adhere to additive manufacturing capabilities. The total design and manufacturing time for the Baby Bantam was reduced from over a year down to two months, and the process reduced the cost of the engine by approximately 65 percent.

This latest engine test came as part of a multi-year Aerojet Rocketdyne additive manufacturing development cycle which included process development, design tool evolution, component fabrication and component hot-fire tests.

"The key to the technology is that it has the ability to replicate very detailed features, in most cases where we combine a lot of details into one assembly, and now you have the opportunity to consolidate that into one large component without having to join all of these details together. So the key that we had to produce was those fine-featured details," said  Jeff Haynes of Aerojet Rocketdyne. "We have a design optimization group for additive manufacturing at Aerojet Rocketdyne that is looking to understand those limitations, and as we get into new design solutions, these are key considerations in our tool box that we're developing. So our designers have to open their framework from what they are used to, to understand this new manufacturing process – to be able to accept and adopt it."

Haynes says the alloys used in the completion of the Baby Bantam are nickel-alloy-based super alloys, and that the company is exploring other alloys, such as those using titanium, aluminum, and copper.

3D printed injector

"I had a simple part that I wanted to produce today, say a single element. If it's forged or machined, you have to wait for that forge upwards of about four months. Once you get that forging, it takes about two weeks to make that part so-to-speak. Now if you have a complex assembly like these injectors that have hundreds of details within them – but you can print them in one or two details – then you've eliminated that full-value stream of waiting and support time," Haynes said. "In the case of that one part, once you've got the forging, it's kind of a one-to-one trade off. But if you want to construct a full assembly with hundreds of details in it … like on this injector, we built that with about a 70 percent savings in terms of both time and cost to make that assembly part. While it really depends on the complexity of the part, we're really looking at the value added to this process where you are able to take these very complex assemblies and you're now able to print them in one or two pieces."

Aerojet Rocketdyne is an aerospace and defense firm which focuses on propulsion and energetics for the space, missile defense and strategic systems, tactical systems and armaments markets in support of domestic and international markets.