The more detailed public summary published by NASA yesterday can be found here: NASA Investigative Summary: Taurus XL T8 and T9 Mission Failures https://www.nasa.gov/sites/default/files/atoms/files/oco_glory_public_summary_update_-_for_the_web_-_04302019.pdf(copy also attached)
Naively, I would have assumed that a weaker than specified frangible joint rail would have fractured more easily, perhaps doing so prematurely. Is there a more detailed public report which explains the mechanism of how substandard material properties (lower than specified Minimum Yield Strength and Ultimate Tensile Strength) led to a frangible joint rail failing to fracture?
Quote from: AnalogMan on 05/01/2019 11:01 amThe more detailed public summary published by NASA yesterday can be found here: NASA Investigative Summary: Taurus XL T8 and T9 Mission Failures https://www.nasa.gov/sites/default/files/atoms/files/oco_glory_public_summary_update_-_for_the_web_-_04302019.pdf(copy also attached)Naively, I would have assumed that a weaker than specified frangible joint rail would have fractured more easily, perhaps doing so prematurely. Is there a more detailed public report which explains the mechanism of how substandard material properties (lower than specified Minimum Yield Strength and Ultimate Tensile Strength) led to a frangible joint rail failing to fracture?
Quote from: kdhilliard on 05/02/2019 02:17 pmQuote from: AnalogMan on 05/01/2019 11:01 amThe more detailed public summary published by NASA yesterday can be found here: NASA Investigative Summary: Taurus XL T8 and T9 Mission Failures https://www.nasa.gov/sites/default/files/atoms/files/oco_glory_public_summary_update_-_for_the_web_-_04302019.pdf(copy also attached)Naively, I would have assumed that a weaker than specified frangible joint rail would have fractured more easily, perhaps doing so prematurely. Is there a more detailed public report which explains the mechanism of how substandard material properties (lower than specified Minimum Yield Strength and Ultimate Tensile Strength) led to a frangible joint rail failing to fracture?Novak is correct about the basic materials properties involved.I worked briefly on Pegasus many years ago, and my memory is admittedly suspect, but the frangible joint they used was designed by an Orbital MechE named Gary Harris, and was informally called the Harris joint at Orbital. I'm fairly sure the Harris joint was carried over from Pegasus onto Taurus.Hard to describe without a drawing, but imagine a cross-section like two tuning forks laid flat facing each other, with their "U" ends touching, formed as a single piece of metal with a notch where each "U" end joins the other. Now imagine a semi-flattened stainless steel cylinder (which is actually a long sealed tube in 3-D) inside the two U's. The tube contains pyrotechnics that cause the tube to expand, pushing out on the arms of the U's and causing the metal to fracture at the notches where the U ends join.If the metal of the U arms is too soft, they'll just deform without fracturing as the expanding tube pushes them outward, and the the joint won't fully separate. That's basically what happened with the failed joints. The aluminim extrusions were just too soft to fracture completely.I just found a link to Gary Harris' patent application for his frangible joint. Figure 2 shows the cross-section I described above.https://data.epo.org/publication-server/rest/v1.0/publication-dates/19940511/patents/EP0596400NWA2/document.html
Is this the highest $ loss due to material supply chain issues to NASA?CRS-7 was a notably smaller number, including cargo.