Test & measurement
Still image from video of USC Rocket Propulsion Lab “Graveler II” rocket test
a rocket into space. As part of an unofficial space race among international universities, Tewksbury and his team don’t just want to be the first team to successfully launch; they want to reach an altitude of 100 km (330,000 ft) above sea level with a rocket made up completely of components that they manufacture themselves. They only get to build one or two rockets every year, so testing components on the ground is essential to building viable rockets. As par t of his application to obtain a launch
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window from the Federal Aviation Administration (FAA), Tewksbury needed to validate that his space-shot rocket could safely make the trip. Par t of that validation process took place at a Mojave Deser t test site. Tewksbury needed to test the integrity of the thermal protection system of the rocket’s motor case as well as the carbon-phenolic nozzle design. “We have to guard the case, which actually can’t survive very high temperatures because it’s carbon fiber,” Tewksbury says. “The biggest new addition to this static fire
was the nozzle. We completely redesigned the nozzle with new materials, new processes,” Tewksbury adds. “We wanted to see how well that performed. We used a special ablative technology on the nozzle to hopefully whisk
BATES Grains still evident after the rocket test
eil Tewksbury and his team at the University of Southern California Rocket Propulsion Lab want to blast
Validating thermal protection before a space-shot launch
How do you gather thermal management data when testing rockets? A team at the University of Southern California Rocket Propoulsion Lab has been using thermal cameras from FLIR Systems to do the job. The company’s thermal cameras provided valuable data at a level unattainable with thermocouples to measure performance of rocket thermal protection system during engine firing
away as much of the heat as possible to protect our thermally sensitive case.” Called Graveller II for “ground” and “traveler,” this was to be a static test of the rocket motor on the ground. In past static tests, Tewksbury relied
on thermocouples to gather thermal management data. Where as thermocouples could provide specific spot data, he needed a solution that could gather more comprehensive data for this test. “We really wanted to see if there were any hot spots both on the case and on the nozzle. We can only use a finite number of thermocouples,” Tewksbury says.
SOLUTION On 17 February 2018, the USC Rocket Propulsion Lab successfully tested Graveler II, the largest composite-cased amateur rocket
FLIR T540 Professional Thermal Camera
motor ever successfully fired to date. The 8inch diameter, 80.5-inch long R-class solid rocket motor delivered a total impulse of 42,000 lbf-sec. Graveler II was fired in a carbon-epoxy motorcase with a carbon- phenolic nozzle, all of which were designed and fabricated by USC students.
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August 2019 Instrumentation Monthly
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