2012

Test Systems Ensure Structural Integrity of Orion Crew Vehicle

NASA is currently validating the Orion spacecraft design for human spaceflight. Three systems developed by G Systems were used for testing the new Multi-Purpose Crew Vehicle (MPCV). A custom pressurization and venting system enables engineers to apply pressure inside the test article for measuring strain. A custom data acquisition system synchronizes over 1,800 channels of analog data. This data, along with multiple video and audio streams and calculated data, can be viewed, saved, and replayed in real time on multiple client stations.

Data Distribution System" class="caption" align="right">NASA and Lockheed Martin engineers needed three test systems designed for performing structural tests on the Orion MPCV. G Systems used concurrent development, and leveraged off-the-shelf National Instruments (NI) hardware and software to deliver all three systems.

The first structural test for the Orion Ground Test Article (GTA) was successfully conducted in August of 2010. This proof pressure test at 1.05 atmospheres required three distributed systems that work together: a pressurization and vent (P&V) system for automated control of the pressure within the vehicle; a Data Acquisition System (DAS) for real-time collection of structural data as well as real-time calculation of virtual channels and analysis of limits and alarms; and a Data Distribution System (DDS) for real-time and post-test distribution of synchronized parametric, video, and audio data to test controllers and data clients.

The P&V system is responsible for precisely controlling the interior pressure of the crew vehicle during testing. The P&V system is a portable cart with high-pressure gas bottles that provide the gas needed for the pressurization process. This system has a control unit built around NI’s cRIO industrial computer, and controls pressure while simultaneously monitoring for critical faults or alarms. The cRIO with LabVIEW RealTime (RT) was selected to provide reliable control of this critical process. A “brick PC” with touchscreen provides a LabVIEW graphical user interface (GUI) in a removable pendant form factor so that the operator can control the pressurization process from a safe location.

The DAS is responsible for collection of parametric data, primarily for strain measurement. The heart of the DAS system is a PXI LabVIEW RT system that collects over 1,800 channels of synchronized data. In addition, the DAS has capability to calculate several thousand synchronized, user-defined, virtual channels while also monitoring alarm and limit levels that may trigger a test shutdown. A quad-core PXI RT controller performs all of these activities in parallel, and has been optimized to execute specific loops on each processor in order to maintain deterministic performance.

Maintaining calibration on high-channel-count systems is a challenge. For this purpose, G Systems developed a verification system that enables an operator to connect a cable to each of the 42 front-panel connectors and automatically run a calibration verification routine on each channel on that connector.

Collecting, synchronizing, and presenting several thousand channels of data in real time and post-playback can be a significant challenge. The DDS provides this capability. The DDS presents data from the P&V and DAS, and also from 32 IP cameras and eight microphones that are situated near the test article to observe the test in progress.

Six or more test observers use LabVIEW-based GUIs to view tests in progress or retrieve past test data. At any time, users can view real-time data for a test in progress, buffered real-time data, or logged data from previous tests.

Custom data acquisition and test systems
G Systems, L.P.
Richardson, TX
972-234-6000
www.gsystems.com

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