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Psyche engineers discover and fix a major thruster problem only two weeks before launch

In a stroke of luck, the engineering team for the asteroid probe Psyche discovered an attitude thruster problem only two weeks before launch that could have destroyed the mission, and were able to fix it quickly.

The issue was discovered during pre-flight tests that showed the settings used to operate the thrusters were incorrect. At the planned 80 percent power level, analysis indicated higher-than-expected temperatures could cause damage.

As it turned out, the fix did not require any hardware or software changes. Just an updated table of parameters used by the probe’s flight computer, instructing it to fire the thrusters at what amounts to a lower power level. Maneuvers will take longer to complete, but that will not affect the mission.

Nonetheless, this problem should not have been discovered so late, and suggests that the management issues from other software problems that forced a year delay in the launch last year have not been completely solved. If I was the project scientist for this mission, I would be very uncomfortable about its future.

Hopefully, no more serious problems will occur, and after its Falcon Heavy launch on October 12 it will fly past Mars to aim for an August 2029 arrival at the metal asteroid Psyche.

Genesis cover

On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.

The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.

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"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News


  • David Eastman

    So the team was given inaccurate thruster data that worked out such that an 80% duty cycle would stay within the given temperature constraints, and wrote the flight management software accordingly. Then during final review, someone discovered that the data was incorrect, an 80% duty cycle would generate more heat than they were capable of dealing with, and they changed the software to limit them to a 30% duty cycle instead.

    I haven’t found an article that gives any details on how the discrepancy in the documentation happened and how it was discovered, but it seems to me that the current team is doing what it’s supposed to, and the actual problem was years ago when they were provided bad data and didn’t do whatever was just done to verify it.

  • Concerned

    There has been a steady erosion of engineering tribal knowledge all throughout the industry, except in pockets. Formerly rock solid engineering houses like Boeing, and now even the high pinnacle of JPL are now making bad mistakes that rarely snuck through to flight vehicles in the past. There simply hasn’t been consistent hiring and passing of that knowledge through the decades, and the best and brightest aren’t always choosing aerospace careers like was done post-Sputnik. Combined with replacement of engineers in upper management with finance, increasingly woke, types is a big factor in the degradation.
    I see it every day in my neck of the woods.

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