A stressful test
As I stood watching the static loads test of the MAVEN spacecraft structure, my thoughts went back to my high school physics class, where we built bridges out of balsa wood. To see which bridge was the strongest, the teacher applied a force to the center until the bridge broke. Each student would cringe as the pressure increased, waiting for the sound of splintering wood. I had that same feeling now.
The static test is one of the key tests for the structure. It’s designed to ensure that the structure will withstand the extreme forces of launch. The structure provides the framework that supports all of the pieces that together make up the MAVEN spacecraft. Science instruments, computers, batteries, radios, solar arrays, propulsion—nearly everything gets attached to the structure. It has to be strong enough to withstand the intense shaking and acceleration during launch, but light enough for a single Atlas V to lift it, and the other equipment, away from Earth and send it all the way to Mars. An all-metal structure would be too heavy, so we make it primarily out of composite panels. The core structure weighs less than an average NFL lineman, but it has to support a fully-fueled spacecraft weighing as much as a full size SUV, all while the rocket is accelerating it six times faster than a Ferrari.
The static test is conducted by using hydraulic rams to apply controlled force to critical points on the structure. Load cells, strain gages, and displacement transducers are used to precisely measure the effects. The forces we apply are higher than what we expect to actually see at launch. We always design and test with this margin because of the unexpected. The total forces from all of the rams we applied during the most stressing test exceeded 35 tons. The success criteria is simple: if the structure does not break and its deflections match our computer models, then we know it was properly designed and built correctly.
I listened to the groans of the structure as the test progressed and wondered if I would hear the sound of splintering composite panels, just like the sound of my bridge breaking all those years ago. I didn’t hear it. The structures team had done an outstanding job designing and building the structure, and we passed the test with flying colors. The structure was now ready to be handed over to the propulsion team so that they could start installing the fuel tanks, thrusters and propellant tubes. I could breathe a little easier, at least for awhile.
–Guy Beutelschies, MAVEN Flight Systems Manager, Lockheed Martin«Return to the Features, News, & Events page