Straddling the Kármán line
Getting results both inside and outside Earth’s atmosphere
By Luke Morris
The Kármán line, named after Hungarian American engineer and physicist, Theodore von Kármán, is the boundary between Earth’s atmosphere and outer space. Broadly, most experts say that space starts at the point where orbital dynamic forces become more important than aerodynamic forces so designing structures or aircraft to be used on our side of the line typically requires different types of testing and analysis to those on the outside. But it’s still possible to use the expertise of the same engineers on both sides if you have the right tools for the job.
Expanding the International Space Station
The Bartolomeo platform, produced by Airbus, is the newest payload hosting platform designed to explore the potential commercial use of the International Space Station(ISS). When it came to the critical and complex testing phase of the project, Airbus turned to DLR for help.
The Institute of Aeroelasticity, based in Göttingen, is part of Germany’s space agency, Deutsches Zentrum für Luft- und Raumfahr (DLR). It is a leading research centre that focuses on structural dynamics, unsteady aerodynamics, and dynamic loads. Traditionally, it has worked on aircraft, including ground vibration testing (GVT), multi-axis vibration excitation, and test rigs for wind tunnels, but more recently has evolved to include modal survey tests (MST) for the space industry.
DLR used the 192-channel Simcenter SCADAS Mobile hardware equipment for a modal survey test to update the finite element simulation model of the Bartolomeo platform. This was crucial to the project as it allowed for the simulation and prediction of aspects such as how the platform would couple with the ISS. Reliability and accuracy were vital as in space the tiniest miscalculations can have serious consequences. Simcenter SCADAS Mobile enabled the capture of accurate experimental data to validate and improve the fidelity of the FE model by measuring 192 signals simultaneously.
Having recently switched from Simcenter SCADAS 3 to Simcenter SCADAS Mobile this was DLR’s first major application of the new system, but as Julian Sinske, Structural Dynamics Testing Lead, says, they had no doubts in its capabilities. “In our experience, Simcenter SCADAS has always been issue-free and reliable, so we were extremely confident in the updated system.”
Sinske says that Simcenter SCADAS Mobile provides extra flexibility for handling not only MST, but different types of tests such as GVT thanks to the versatility of the data acquisition system. He also points out the advantages of using it alongside another tool from the Simcenter portfolio: “Simcenter Testlab is well-suited to large-scale tests like this one, particularly with the flexibility to customize what it offers.”
This customization allowed DLR to run its own algorithms alongside Siemens’ PolyMax algorithm to satisfy their specific testing needs. DLR engineers also customized the user interface and projected the results onto the wall of the laboratory so that everyone could track test progress. This all led to significantly quicker results than comparable testing scenarios, with the first measurements available less than an hour after setup.
Image provided by Airbus
Delivering results fast
The complete test results were delivered in less than four days – unprecedented based on previous projects. The structural dynamic data set produced by DLR enabled Airbus to determine the appropriate modal model, identify nonlinearities, and update the finite element model.
“Airbus had very high expectations,” Sinske says, “which thanks to having the right tools available to us, we were able to meet. The entire test went according to plan. We needed to work as fast as possible to swiftly deliver the data that was required. Simcenter SCADAS Mobile and Simcenter Testlab helped us achieve this.”
The future has just begun
Now they’ve done it once, the engineers from DLR’s Institute of Aeroelasticity will be able to do it again and again. They’ve created a replicable testing approach that can be used in either aviation or space. “We use the same hardware and software for both GVT and MST and we have a plan in place,” says Simske.
But they’re not standing still and basking in their achievements. DLR is already hard at work developing new testing methods and technologies for the future, including the use of automation and artificial intelligence.
So, whichever side of the Kármán line a project is focused on, DLR now has a blueprint for fast, effective, and reliable testing. And it’s all thanks to the agility of Simcenter SCADAS Mobile and the flexibility of Simcenter Testlab.