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NASA completes investigation into the failure of the OSIRIS-REx drogue parachute

When the sample return capsule brought OSIRIS-REx’s Bennu samples back to Earth on September 24, 2023, it appeared that the drogue parachute never released prior to the release of the capsule’s main parachutes. Fortunately, those main parachutes were able to do the job, putting the capsule down unharmed but a minute early.

NASA has now completed its investigation into the drogue chute failure. According to its press release:

After a thorough review of the descent video and the capsule’s extensive documentation, NASA found that inconsistent wiring label definitions in the design plans likely caused engineers to wire the parachutes’ release triggers such that signals meant to deploy the drogue chute fired out of order.

The drogue was expected to deploy at an altitude of about 100,000 feet. It was designed to slow and stabilize the capsule during a roughly five-minute descent prior to main parachute deployment at an altitude of about 10,000 feet. Instead, at 100,000 feet, the signal triggered the system to cut the drogue free while it was still packed in the capsule. When the capsule reached 9,000 feet, the drogue deployed. With its retention cord already cut, the drogue was immediately released from the capsule.

In other words, engineers wired the thing incorrectly so it cut its cords before it was released. To further confirm this conclusion engineers will inspect the system thoroughly once scientists have completed removing the Bennu samples from the capsule.

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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.

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  • Andi

    There’s an extra R in the title

  • Ray Van Dune

    Last time it was an accelerometer mounted backwards, and it prevented any chute deployment at all. I guess this is progress.

  • MDN

    IMHO this kind of assembly error is inexcusable given the ability to fully integrate and document the entire spacecraft in a 3D computer model nowadays. And the design should have used distinctly different connectors for the deploy and separation circuit control loop wiring to insure the impossibility of such a mistake anyway. We are extraordinarily lucky we didn’t lose the entire spacecraft in a crater because of this.

    I want to say whoever managed the assembly team, and that team, should never work in the industry again.. But realistically I suppose this screw up weighs heavy on their minds now so they’re likely the best choice instead because now they’ll be a lot more rigorous in sweating the details.

  • cm smith

    I’m reminded of an early (If not the first.) crash test of a prototype auto airbag system. The airbag failed because it was wired wrong.

    Airbags. The devices that we were promised would make seatbelts unnecessary.


    Thanks Mr. Z,
    I’ve worked around NASA-ites long enough to know the Drogue chin wage game going on in conference rooms, and on the construction floor. While trades exchange catcalls on the floor, conference rooms have the “Poobahs” pouring over As-Builts with furrowed brows – as the bean counters request more funding to correct this anomaly.
    Science is a harsh Mistress.

    Mike Buford from Michoud

  • pzatchok

    I can make a bat that they know exactly who designed the connectors, who approved them, who made them, who installed them and exactly the day and time this was all done.. In triplicate. The system lives on paperwork and detailed documentation.

    They have more than likely talked to the guy who installed the device and he told them the plugs were not marked clearly. the engineer who marked the plugs told them he understood it perfectly why didn’t the stupid tech understand it., and the manufacturer just said they did it all by the designs approved by the engineers.

    Musk knows the real culprit in the engineer who designed it. NASA knows this also but will blame the installer but since he can not be fired by union rules they are just taking the safe route in blaming him.

    And do not believe that the guys who made the mistake will now be on their guard and more detail oriented. The mistake will fade from his conscious and he will soon make another similar mistake.

  • Edward

    MDN wrote: “IMHO this kind of assembly error is inexcusable …

    True. There are supposed to be several opportunities to identify and correct these kinds of errors before flight.

    And the design should have used distinctly different connectors for the deploy and separation circuit control loop wiring to insure the impossibility of such a mistake anyway.

    The article said “inconsistent wiring label definitions” may have been the problem at the design level. It is not clear whether this is a case of mislabeled connectors or crossed pins within a single connector (mislabelled on the interface drawing — and, yes, I have seen this, too, but someone caught it on an interface drawing, like we were supposed to do, and it may have been a cross-wired test cable drawing rather than flight cable). Either way, this should have been discovered during ground testing, or preferably before. If a single connector contained both pins (likely, given that the signals were going to nearby locations), then the ground testing may have been inadequately planned or designed to discover this kind of error.

    In the design plans for the system, the word “main” was used inconsistently between the device that sends the electric signals, and the device that receives the signals. On the signal side, “main” meant the main parachute. In contrast, on the receiver side “main” was used as a reference to a pyrotechnic that fires to release the parachute canister cover and deploy the drogue. Engineers connected the two mains, causing the parachute deployment actions to occur out of order.

    So, it seems to be a communication problem on the interface drawing. It could have originally been a systems engineering failure to make sure terminology was clear, consistent, or otherwise well understood. It also suggests that the two teams were not communicating well with each other, making sure that everything was clear and properly designed on both sides of the interface. I still believe testing should have discovered it, too.

    … I suppose this screw up weighs heavy on their minds now so they’re likely the best choice instead because now they’ll be a lot more rigorous in sweating the details.

    Maybe, but it was not an immediate lesson, and it is not clear that it is a single person’s screwup,* so it does not sink in as well as in the tale of a JPL engineer who almost killed the Spirit Mars rover:

    His lesson was immediate, scary, and very memorable. As I commented in that post, a better method is for the whole organization to take error prevention very seriously. Everyone makes mistakes. Make sure yours are few and minor.
    * Come to think of it, it is a screwup of everyone who should have found the problem before flight. So, which of those people is going to take the ownership of his own portion of the overall screwup and learn the lesson? How few of them will even realize that they should have discovered the problem? Was there even systems engineer? Which might make it a management failure.

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