Fabrisonic LLC, a manufacturer of Ultrasonic Additive Manufacturing (UAM) solutions, headquartered in Columbus, Ohio, USA, has partnered with Luna Innovations, Roanoke, Virginia, USA, a manufacturer of medical, telecommunications, energy and defence technologies, to gather data in cryogenic fuel pipes for rocket test stands at NASA Stennis Space Center for a NASA contract.
NASA’s goal is to collect data on pressure and temperature gradients inside of its fuel piping closer to the test article to better understand how a particular engine is behaving. Historically, NASA has mounted sensors to the outside of pipes using elbows and ports, which communicates some data. However, these do not give the same fidelity as sensors located adjacent to the fuel stream and can disrupt the fuel stream. Similarly, NASA has mounted sensors directly into the flow path using pass-throughs in the existing pipe. These ports and pass-throughs can, however, influence the fuel flow, adding uncertainty to the measurements.
According to Fabrisonic, the team assigned to this project additively manufactured sensors directly into the wall of the pipe. This allows a suite of sensors to be embedded in essentially the same space, giving a clearer picture of thermal and pressure gradients in the piping since no ports are required. All of the sensors used were fibre optic based sensors, provided by Luna Innovations. The team selected fibre optic sensors as they are small and thus don’t create a large impact on the structure of the pipe. The fibre-based sensors can also collect data over the entire length of the fibre allowing for a continuous length of sensing instead of a fixed point.
The company states that, as with many projects, Fabrisonic chose to only additively manufacture a portion of the pipe as AM is expensive and the team worked to minimise the amount of AM. The team started with an existing pipe and a flat section was milled into the outer diameter (OD) of the pipe creating a landing strip for embedding. A small groove was cut to positively locate each fibre and once the fibres were inserted by hand, Fabrisonic additively manufactured additional material over the landing strip to build the OD back up to specification. After the AM process, excess material was removed using standard CNC milling.
The team has reportedly tested the pipe at various pressures and temperatures to calibrate the sensor. This included boiling the pipe in water and filling it with liquid nitrogen to emulate cryogenic fuel. The pipe continued to provide solid data throughout all of the extreme conditions. The next phase of the project will include the Additive Manufacturing of a larger pipe section for use at NASA Stennis Space Center.