Over the past 2 years Addaero has been fortunate to work with some of the most prestigious companies in the world and we have been able to work on some amazing projects. With confidentiality being paramount in the industry we are rarely able to show what we work on. Recently we asked the question, what if we tackle some of these projects on our own. Below is the start of one of those projects.
Addaero Manufacturing’s in-house rocket project took its first major step with the printing of its first nozzle design. The Ti6Al4V nozzle was manufactured using the ARCAM A2X Electron Beam Melting machine this summer.
The nozzle has a design thrust of 1,500 pounds, with liquid oxygen and kerosene propellant. The desired burn time is 30 seconds, and rectangular coolant passages run the length of the walls of the nozzle. The nozzle will be dump cooled using water as coolant. Dump cooling will decrease the noise profile of the engine while simultaneously providing cooling. The nozzle was designed to model Rao’s ideal nozzle profile and to slightly under expand exhaust to avoid shock waves at the nozzle exit. The nozzle has a 10-degree exit angle and expansion ratio of 5.37. Design flow rate of liquid oxygen is 1.7 kg/s and the design flow rate of kerosene is 0.76 kg/s. The nozzle as-fabricated is roughly 11 inches in height, 4.38 inch diameter across the combustion chamber, 1.62 inch diameter across the throat, and 3.76 inch diameter at the exit. Ti6Al4V was selected as the material for this project. Although it is not the ideal material for a rocket engine it was chosen for a variety of reasons including availability, test duration, and post processing ability.
The nozzle design was done mostly in MatLab. Nozzle geometries were back calculated from performance requirements, yielding a set of radii for the inner and outer diameters of the nozzle. Using downloadable toolboxes, STL files of both the nozzle as well as the coolant channels were generated directly from MatLab. Using Materialise Magics, these STL files were then combined, smoothed, and optimized for use in the ARCAM A2X. The whole design of the nozzle was optimized for additive manufacturing. Nozzle geometry was developed to avoid the need of supports, and coolant channels were designed without any geometrical restriction, as nearly any geometry is made possible with additive technology. The engineering factor for this component was 8 as this was for ground test only and weight was not a concern.
The build took 60 hours to complete. Preceding the successful build, the nozzle was powder blasted, and steel wire was used to remove powder from the coolant channels. The nozzle was then sent to REM Surface Engineering to chemically remove any powder remaining in the channels and to improve the surface finish uniformly across the nozzle. With improved surface finish, the engine will experience fewer losses due to friction.
The next steps will be to design and fabricate the injector assembly. Stay tuned for more updates and don’t hesitate to ask questions!