Tests Confirm Potential Launch Vehicle Weight, Cost Savings
Initial results from a series of tests suggest that the designs for NASA’s next generation of launch vehicles may be modified to significantly reduce weight and cost which would lessen development and performance risks.
The NESC Shell Buckling Knockdown Factor (SBKF) Project was established to develop and validate new analysis-based shell buckling design factors for Ares-I and Ares-V metallic and composite launch vehicle structures. The analysis makes use of improved “knockdown factors” that allow for a less conservative design.
The NESC funded design and fabrication of a large-scale test facility and the first series of large-scale buckling test articles, programmatic and technical support, peer reviews and advocacy. In addition, the NESC helped coordinate activities between NASA’s Langley Research Center and Marshall Space Flight Center, the two primary centers involved in this project and has enabled an efficient working relationship between the centers.
The new facility, completed in FY08, is capable of testing 8-foot-diameter cylindrical shell structures subjected to combined axial compression and bending. Two 8-foot-diameter, 2195 Al-Li orthogid cylinder test articles were designed, fabricated and tested in the facility at MSFC in early FY09. (See Fig. 1)
|Figure 1: Shell Buckling test facility to be constructed at MSFC, Bldg 4619. Upper left inset: Checkout test article. Lower left inset: Lower test fixture assembly.
Sub-component tests of 2195 Al-Li orthogrid stiffened panels are being conducted at LaRC to investigate local skin pocket buckling and stiffener crippling behavior. (See Fig. 2) Test data are being used to assess current design approaches for these structural details and to validate new high-fidelity numerical simulations of common Ares-like structural details.
|Figure 2: Measured buckling displacement contour super-imposed on Al-Li stiffened panel test article. Test article subjected to uniform compression load. Full-field displacement and strain measurements obtained by using a 3-D video image correlation system.