Aerojet Rocketdyne Completes Hot-Fire Tests of First Entirely 3D-Printed Rocket Engine: A Q&A With Dr. Jay Littles, Aerojet’s Director of Advanced Launch Propulsion Programs

Aerojet Rocketdyne recently completed a series of hot-fire tests on its ‘Baby Bantam’ liquid rocket demonstration engine, that was entirely constructed with additive manufacturing processes, also known as 3D printing. Image Credit: Aerojet Rocketdyne.
Aerojet Rocketdyne recently completed a series of hot-fire tests on its “Baby Bantam” liquid rocket demonstration engine (pictured above), which was entirely constructed with additive manufacturing processes, also known as 3-D printing. Image Credit: Aerojet Rocketdyne.


The advent of additive manufacturing technologies, better known as 3-D printing, has been an ongoing trend in industrial manufacturing in recent years, with a growing number of industries, including aerospace, embracing its use in their attempt to innovate and further reduce their manufacturing costs. Having become a standard tool in the R&D efforts of private space companies and government space agencies alike, 3-D printing technologies have found many applications in the construction process of various rocket and spacecraft hardware. Now, in what represents an important milestone in the further development of additive manufacturing and a first for the U.S. private space sector, leading rocket propulsion manufacturer Aerojet Rocketdyne has recently completed a series of hot-fire tests of a Bantam demonstration engine that has been entirely constructed with 3-D printing.

Additive manufacturing is a term comprising the set of technologies by which solid 3-dimensional materials can be constructed from a digital computer model. Contrary to the conventional subtractive manufacturing methods that are used today, where objects are fabricated through the subtraction of undesired parts from different types of raw materials in order to produce the desired finished product, additive manufacturing creates objects through the successive layering of raw materials that are laid down on top of each other. Its many advantages over traditional manufacturing processes are impressive and hold the potential of completely revolutionising the space industry, where construction costs remain high and the reduction of launch costs is an imperative. For instance, 3-D printing produces almost none of the waste byproducts of conventional manufacturing. In addition, this technology can combine different raw materials together in ways that aren’t possible in subtractive manufacturing, resulting in lighter and cheaper objects whose properties like strength and temperature resistance can be highly customised according to their intended use. Furthermore, 3-D printing can reduce the number of moving parts of space hardware systems significantly, resulting in more streamlined, low-cost end products, compared to their conventional counterparts.

NASA has been on the leading edge of the development and integration efforts of additive manufacturing processes into the U.S. manufacturing industry, with the results of these efforts being freely available to private space companies. These include a series of successful hot-fire tests last year of a subscale model of the agency’s iconic RS-25 rocket engine that had some of its parts made with 3-D printing technologies at the Marshall Space Flight Center in Huntsville, Ala. Outside of NASA, the California-based Space Exploration Technologies, or SpaceX, has been one of the high-profile private space companies to also acknowledge the value of additive maufacturing, by employing it in the construction of the SuperDraco, the engine that will power the company’s next generation Dragon V2 spacecraft, whose combustion chamber was manufactured with 3D-printed materials.

A hot fire test of a joint NASA/Aerojet Rocketdyne 3-D printed rocket engine injector, at the space agency's Glenn Research Center. Image Credit: at NASA/GRC
A hot-fire test of a joint NASA/Aerojet Rocketdyne 3D-printed rocket engine injector at the space agency’s Glenn Research Center. Image Credit: at NASA/GRC

Now, carrying rocket propulsion additive manufacturing to the next level, Aerojet Rocketdyne announced that it successfully completed a series of hot-fire tests at the company’s facilities in Sacramento, CA, on a liquid oxygen/kerosene Bantam demonstration engine, the first rocket engine to be entirely constructed with 3-D printing. “The demonstration of this engine, made completely with additive manufacturing, is another significant milestone in our path to changing propulsion affordability,” said Dr. Jay Littles, director of the company’s Advanced Launch Propulsion Programs, in a statement earlier this week. “We are not just making a stand-alone chamber or injector derived from traditional design approaches. Rather, we are integrating the full capability of additive manufacturing processes to evolve a proven, reliable, affordable design. We are doing so with technical depth and rigor to meet our unparalleled quality and safety requirements.”

Aerojet Rocketdyne is no stranger to additive manufacturing. The company has had an extensive partnership with NASA under an unfunded Space Act Agreement, which had led to a previous series of successful hot-fire tests in 2013 of a 3D-printed liquid rocket engine injector system at the agency’s Glenn Research Center in Cleveland, Ohio. Being part of Aerojet Rocketdyne’s multi-year additive manufacturing development efforts, these earlier tests opened the way for the development of their new entirely 3D-printed engine, affectionately called “Baby Bantam” for being at the low-end of the company’s Bantam family of liquid rocket engines, capable of producing a thrust of 5,000 pounds. The 3-D printing method that was used for its construction, called Selective Laser Melting, or SLM, constructs 3-dimensional metal parts by utilising a high-power laser beam to fuse together successive layers of fine metallic powder and melt them into a homogenous part. This process led to the 3D-printed Baby Bantam engine having some impressive advantages over its conventional counterparts: its production cycle was reduced from approximately a year to a couple of months, while the engine’s moving parts were reduced from a dozen to just three, including the entire injector and dome assembly, the combustion chamber and a throat, and the nozzle section. This streamlined approach helped to reduce production costs dramatically as well, which according to Aerojet Rocketdyne were more than 65 percent lower than that of more conventional manufacturing processes.

Following up on this recently announced impressive achievement by the company, we had a chance to have a small Q&A with Dr. Littles regarding the development of the 3D-printed Baby Bantam engine, as well as the role of additive manufacturing in the company’s future development plans.

Dr. Littles, before we start we’d like to thank you for taking the time to answer some questions for our readers. The advent of 3-D printing, or additive manufacturing, in recent years has led to a growing number of companies embracing it for their design and manufacturing processes. What role has 3-D printing played in Aerojet Rocketdyne’s rocket engine development efforts, and what have been the benefits so far compared to more traditional manufacturing processes?

It’s my pleasure. Aerojet Rocketdyne continues to work on a range of technology efforts focused on improving affordability, as well as enabling new products. Additive manufacturing is an example of one tool that AR is using to both enable new designs and improve product cost, as well as reduce lead times for both new and legacy products. The Baby Bantam engine demonstration effort provides a good example; AR’s lean design tools, combined with the use of Additive Manufacturing, reduced this overall effort to approximately 20 percent of a traditionally approached similarly sized engine demonstration effort in terms of schedule, and at approximately 30 percent of the cost. The specific benefits will vary by application, but these tools really are changing the way we can perform rapid technology development and feasibility assessments of new designs and configurations.

The recently tested Bantam demonstration engine has been the first rocket engine to not just have some of its parts constructed through 3-D printing, but has been entirely built with additive manufacturing processes, which certainly represents an important milestone for the private space industry. Can you give us some more details about the 3-D printing technologies being used?

The Baby Bantam engine was manufactured using a powder bed Selective Laser Melting (SLM) technique. This process has the ability for sufficient control of fine geometrical features to enable manufacturing of some of the most critical components within the engine. Prior to this engine demonstration, AR had performed process development to ensure repeatable material properties as a function of manufacturing process parameters and material characterization within the pertinent operational environments.

Aerojet Rocketdyne's fully 3D-printed 'Baby Bantam' demonstration liquid rocket engine, during a hot-fire test on April 10. Image Credit: Aerojet Rocketdyne.
Aerojet Rocketdyne’s fully 3D-printed “Baby Bantam” demonstration liquid rocket engine during a hot-fire test on April 10. Image Credit: Aerojet Rocketdyne.

What are Aerojet Rocketdyne’s plans concerning the possible applications of its 3D-printed engine designs? Could we expect a whole new family of entirely 3D-printed rocket engines completely replacing more traditionally constructed ones on the U.S. space industry’s launch vehicles in the future?

Additive manufacturing opens up new design space, as well as enabling drastic affordability and lead-time benefits. That said, with the current state-of-the-art, AM does not offer these benefits to every application or component type. Depending on the material being used and the complexity of the specific component, it may be more cost-effective and timely to utilize traditional manufacturing processes. Further, the SLM process is currently size-constrained to only allow us to capture components that fit within the build envelope of the existing machines. The Bantam Family of engines, however, is appropriately sized to allow the maximum utilization of these processes. Within some of our legacy products, AR is working plans to implement AM for select components to achieve affordability and lead time improvements. With all of that said, the AM processes themselves are evolving quickly and the next generation of processes will open up the envelope to an even broader range of applications.

Aerojet Rocketdyne has been closely collaborating with NASA on the testing of various 3D-printed engine parts in recent years. Could the successfully tested 3D-printed design of the company’s Bantam engine potentially be used on the space agency’s Space Launch System heavy-lift vehicle as well, which is currently under development?

Aerojet Rocketyne is proud to be supporting NASA on the development of the Space Launch System (SLS). The heavy lift, yet flexible, capability to be provided by SLS is absolutely critical to achieve the range of Exploration Missions that NASA continues to develop and evolve. The SLS vehicle will utilize the very high-performance RS-25 engines on the core, and is currently baselined to use the J-2X upper stage engine that has recently completed testing at Stennis Space Center. While there are no current plans to utilize the Bantam engine on SLS, the AM technologies demonstrated on the Bantam program are being evaluated for future affordability enhancements on the SLS propulsion systems.

Before closing, Dr. Littles, we’d like to thank you again for taking the time to talk with us.

It’s been my pleasure. I was happy to assist you.


The author would like to thank Aerojet Rocketdyne’s Communications Specialist Miss Jessica Pieczonka for her overall assistance.

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    • Thank you Tom,

      The hot-fire tests took place at the company’s operating facilities in Sacramento, a detail which I originally omitted from the article. Thanks to your question, I updated the article accordingly.

      Best regards.

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