Blast Resistant Design of Explosive Containment Chamber
Abstract
Hypervelocity projectile rail guns require instantaneous electrical switching of extremely high energies. To achieve the necessary switching speed, cord explosives are used to drive strips or slats out of aluminum switch plates creating precise gaps which allow the electrical energy to arc. This paper describes the dynamic design of aluminum containment vessels for the explosive switches. The switching mechanism for the rail gun consisted of four 30" x 84" switch plates for main current diversion and two final interrupt switches to dissipate any current remaining after the test. Configuration of the electrical bus bars attached to the switches could not be interrupted which required separate half cylindrical vessels. Large magnetic fields produced by nearby inductors required that the vessels be fabricated from aluminum. Use of this material for blast loads produced special problems with fabrication and structural response which necessitated close examination of the localized stresses, especially in areas which were welded. The containment vessels were designed for a test frequency of two per week for a 5 year life. Due to the testing frequency, the vessels had to be easily removed for cleaning between shots. Cord explosive used to open the switches consisted of 8 lines of 100 gr./ft PETN. The blast pressures and fragments produced by detonation of the cord were required to be contained to protect personnel and equipment. In addition to the blast loads from the explosives, the electrical energy passing across the switch created additional blast pressures. It was found that the energy per unit length of the switch arcs approximated that of common lightning bolts. Pressure prediction formulas for this strength of energy dissipation were used to predict blast loads. The paper describes design requirements, load prediction techniques, structural analysis methods, material response, and operational considerations.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1994
- Accession Number
- ADA514961
Entities
People
- Darrell D. Barker