A Test Chamber that is a National Historic Landmark

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Adam Bahret

Have you seen a test chamber so important in developing numerous historically significant products that it was designated a “National Historic Landmark”? It means in the course of country’s history, this test chamber has played a key role in shaping the trajectory we are on. It is located in NASA’s Jet Propulsion Laboratory in Pasadena, CA and is called “25-foot-Space Simulator”

Testing is a huge part of Reliability Engineering activity. We conduct tests on products to measure reliability and improve reliability. Testing is done on specialized equipment or chamber that can simulate the desired stress conditions. These chambers themselves are technological marvels. I have personally used numerous chambers (HALT Chamber, Vibration shaker, Shock Chamber, Dust Debris) in my work helping develop robust products, but not anything like the 25-Ft Space Simulator.

It was built to test products for out-of-the world usage. I mean it literally. Nicknamed the “torture chamber”. It is a cylindrical chamber of 25-ft diameter x 85-ft height capable of thermal conditions from -195C to 120C approx. Can simulate the vacuum of space, sun exposure through Xenon Arc lamps, and control the values precisely to ramp up & down. Instrumentation attached to it enables us to monitor the product in real-time. What an impressive test arrangement!

NASA has conducted tests in this chamber to validate satellites from early Ranger (Moon 1960s) to Perseverance (Mars 2020). These missions have been successful and it hides the fact that the chamber played a key role in mission approval. Functional test and Reliability tests of the satellite are conducted in the chamber. The extreme temperatures of outer space are simulated inside to see if the product (satellite or Rover) performs satisfactorily. Once a functional test is completed, the unit can be tested for Reliability. I can think of myriad ways of conducting a HALT test using this chamber to make the rover robust. Temperature cycling under vacuum conditions while the rover is operating will torture it to uncover the weakest link. Failures observed are investigated and design improvements are made.

Under these extreme conditions, the margins for components are tight. Tolerance is small. So, any variation in sourcing, assembly, or material build will cause a failure. And failure is insanely expensive. It would mean the entire mission is failure costing likely billions! Building each component in the system with highest precision and adding large safety margin for stress is a way to make it reliable. But building it this way would make it overrun budgets and schedule, which unfortunately, has occurred in the past. I can sympathize when I read a news article that the launch is delayed.

These program conflicts are captured in the figure Ratio Factor in my book Devastate the Competition. The takeaway for us, doing in-the-world engineering, is that the Testing program is shaped by the product Ratio Factor. How do we test and validate the reliability of our product within budget & time? A Perfect Test Plan will be drafted to meet these targets.

In Part 2 of this article, we will cover how do we get units for testing, when you can build only one satellite.

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