About the Arc Jet

The Arc Jet complex at NASA Ames in Mountain View, CA performs high intensity and high energy material testing for the thermal protection systems of spacecraft re-entering the atmosphere. To do this, the facility is able to simulate the environment of re-entry by using an electric arc to superheat a gaseous fluid (usually air or CO2) and firing it out of a nozzle into a vacuum test chamber. Test articles are mounted on sting arms which are inserted into the flow in order to study ablation and recession. 

​

Primary Role

During my 18 month internship, I worked as an assistant to up to three test engineers at a time in two facilities that operated successively. My core responsibilities were to inspect test instrumentation prior to arc jet testing to ensure accurate data would be collected. I used a multimeter to confirm electronic isolation of calorimeter sensors, aligned pyrometers and infrared cameras to their target location on the test article, and operated infrared data collection software during test runs. I was also responsible for creating comprehensive data reports which included sensitive test data, all relevant documents, and photo/video footage.

 

3D scanner and QA Inspection Software

On my off time, I evaluated  3D scanning equipment to determine if it could be another service the facility could provide to the clients. The goal would be to obtain a detailed 3D scan of a test article before arc jet testing and another after it had been tested. We would then superimpose the two scans and apply a deviation map to identify areas of greater recession. 

​

First, we needed to understand the behavior and limitations of the 3D scanner and how to use the inspection software. I went to the cafeteria and bought an apple. I then set the 3D scanner on its maximum definition settings and obtained a complete 3D scan of the apple. Then I took a bite out of the apple and put it back on the scanner and took another high definition scan. I uploaded the scans into an inspection software we wanted to test out and learned how to create a colored deviation map which provided a detailed visual representation of the bite I took. I was able to measure deviation with a resolution of 1 mm.

​

However, while I was able to obtain the results we wanted, the scanner had its limitations. It was, after all, on the lower end compared to what is on the market. The high definition scans took about 45-60 minutes to complete. It scanned the apple in 12 sections which had to be stitched together manually by identifying surface features that were present in multiple scans and aligning the scans to them. This process took several hours and left a significant amount of room for human error. The resulting 3D meshes still required post-processing in order to appropriately represent the object. Since the facility was looking to use this equipment for exact measurements, we did not move forward with it. Still, it was a fun challenge for an engineering intern! Just before my internship ended, I was able to attend a demonstration for 3D scanning equipment that was leaps and bounds more advanced than the one I worked with. These scanners were basically handheld and obtained high definition scans instantly without any manual stitching. They came, of course, at about 100x the price of what I tested.