Engineering news
Nasa has used National Instruments SC Express and PXI hardware to create an advanced, distributed and flexible data acquisition system to meet the challenge of replacing legacy NEFF equipment in one of its largest human-rated environmental chambers.
The data acquisition system (DAQ) is capable of accurately synchronising and measuring more than 500 analog channels distributed throughout the chamber, without the need for additional external signal conditioning.
James Dean from Jacobs Technology, said: “For the first time, Nasa will no longer need the custom signal conditioning equipment in addition to its measurement hardware. With National Instruments (NI) SC Express hardware, they can achieve the ±3°F end-to-end accuracy requirements for thermocouples with commercial off-the-shelf technology."
Simulating Space on Earth
When Nasa needed to test various repair techniques and materials that astronauts could use to repair damaged tiles on the space shuttle, it used the Chamber B facility at the Johnson Space Centre (JSC). The human-rated chamber allowed an astronaut to apply the “goo” repair candidates to the tiles in a simulated environment to test their performance at the extreme pressures and temperatures in space.
At 10.7m wide and 13.1m tall, Chamber B is the smaller thermal vacuum chamber in building 32 at the Nasa JSC, but it is no less complicated than its larger next door neighbour. Features such as the removable top to allow for the insertion of larger test articles, a traversing monorail to provide weight relief to one crew member at a time and dual crew locks to enable easy access and crew member entry all contribute to the complexity of the chamber.
To provide a space-like environment, Chamber B must reach temperatures of 90 kelvin at 10-3 micron (~1x10-9 atm). A nitrogen-based cooling system runs through the walls of the chamber to ensure the proper temperatures are reached. Thermocouple measurements are made around the chamber to characterise the thermal environment, ensure that the desired temperatures are reached and verify that nitrogen flow is achieved throughout the chamber cooling system. Certain test articles also require dedicated temperature measurements to ensure they are behaving as expected in these environments. Pressure and flow measurements are also made in the facility and brought into the DAQ system. Overall, Chamber B has more than 500 analog signals, the majority of which are thermocouples.
Read the full case study here