Structural analysis of a frangible nut used on the NASA Space Shuttle
A structural analysis methodology has been developed for the NASA 2.5-inch frangible nut used on the Space Shuttle. Two of these nuts are used to secure the External Tank to the aft end of the Orbiter. Both nuts must completely fracture before the Orbiter can safely separate from the External Tank. Ideally, only one of the two explosive boosters contained in each nut must detonate to completely break a nut. However, after an uncontrolled change in the Inconel 718 material processing, recent tests indicate that in certain circumstances both boosters may be required. This report details the material characterization and subsequent structural analyses of nuts manufactured from two lots of Inconel 718. The nuts from the HSX lot were observed to consistently separate with only one booster, while the nuts from the HBT lot never completely fracture with a single booster. The material characterization requires only tensile test data and the determination of a tearing parameter based on a computer simulation of a tensile test. Subsequent structural analyses using the PRONTO2D finite element code correctly predict the differing response of nuts fabricated from these two lots. This agreement is important because it demonstrates that this technique can be used to screen lots of Inconel 718 before manufacturing frangible nuts from them. To put this new capability to practice, Sandia personnel have transferred this technology to the Pyrotechnics Group at NASA-JSC.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 10106327
- Report Number(s):
- SAND--93-1720; ON: DE94003672; BR: GB0103012
- Country of Publication:
- United States
- Language:
- English
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