This blog was written by Mr. Tom Bryan ES31\ GNC Hardware Team Lead – RF, Electromagnetic Effects, GNC Hardware Branch, Senior Engineer, Flat Floor Robotics Lab & 6 DOF Dynamics Sim Lab for NASA. He worked on the Navigation system for the Artemis SLS system and did the testing for it with our motion base. His words are as follows:
The small compact 6DOF Motion Table was used for the “End to End [Control] Polarity Test” demonstration or as the nickname of “Tilt the SIL”.
For smaller launch vehicles, once all of the sensors and control actuators are installed on the launch vehicle and the final software is loaded, the launch vehicle can be rotated to demonstrate and check that when the vehicle is “tilted”, the polarity from the gyroscopes into the computers and out to the steering actuators actually activate to steer the vehicle back onto the correct course. However, the SLS (Artemis) core stage being the largest launch stage ever built is too big for such a test demo. But here at MSFC, the entire avionics system is built into the SLS Integration Laboratory ( or SIL) including all of the gyroscopes, computers, software, two working Thrust Vector Control Actuators and simulators used to steer the 4 main engines, and the two Solid Rocket Boosters during ascent (liftoff).
Even though earlier standalone tests of the Gyro sensors had been performed in various labs on various motion tables, everyone wanted to run a more thorough polarity test before the first flight. The concept of “tilting” each of the three Gyro sensor packages while they were connected via extension cables to the rest of the integrated avionics was conceived. Servos & Simulation small compact 6DOF Motion Table (PN: 710-6-500-220) was selected due to its flexibility and ability to fit through the available openings in the SIL Lab and have safe motion constraints for the equipment and personnel. The software protocols and table commands were verified in a simulation command development facility before the 6DOF Motion Table was trucked over to the “SIL” lab, bolted to the floor, and aligned to “True” North for accurate Gyro package performance before being connected to the SIL Simulation Control system.
After a carefully modified and isolated version of the SLS Flight Software was loaded into the SLS Avionics Integration Lab, each of the 3 Core Stage gyro packages was taken off of their normal SIL rack mounts. Then they were bolted on to test fixtures mounted to the 6DOF motion table and reconnected back into the avionics. When each of the gyroscope packages was tilted in Roll, then Pitch, and Yaw, everyone watched with anticipation to see the readouts from the avionics, but more importantly, that full-scale Thrust Vector Control Actuators moved according to design to keep the SLS on its proper course. It worked!! We now knew that the polarity and channels of all of the sensor data were correct and that the software correctly processed the sensor inputs into the correct vehicle Control commands to steer the SLS during ascent!
And in the early morning of Nov 16, 2022, as SLS lifted Orion into space for the first Artemis mission, we saw the proof that the “End to End [Control] Polarity Test” demonstration was correct and that Servos & Simulation’s 6DOF motion table allowed NASA MSFC to “Tilt the SIL” one critical piece at a time!
We are honored to have been utilized as a small part of getting Orion and Artemis into space. Thank you Tom Bryan for the write-up.
We look forward to seeing just how far the Artemis program will advance us into the future. Good Luck and God Speed!!
Rachel Baker
