Shell Buckling Knockdown Factor (SBKF) Project Update
The SBKF project expects to significantly reduce structural mass in buckling-critical launch vehicle (LV) shell structures and help mitigate future vehicle development and performance risks. One of the objectives of this project was to test the External Tank Test Article (ETTA)-1 to provide critical data to help determine the effects of scale on the buckling of large LV barrel components and also to provide data needed to relate test data obtained from sub-scale test articles to full-scale LV components.
The SBKF conducted a re-planning effort in April 2011 for the stiffened metallic LV shell structure to be complete and ready for use by mid Fiscal Year (FY) 13. FY 13 is the earliest possible Preliminary Design Review for a heavy-lift vehicle.
27.5-ft-diameter orthogrid barrel, ETTA-1, was tested at Marshall Space Flight Center in March 2011
Third Annual SBKF Workshop planned at Kennedy Space Center (KSC)
- The test was a great success!!! ETTA-1 was the largest barrel tested by the SBKF team, and the ETTA test met the test objectives.
- Twenty guests from industry attended the test.
- Test was broadcast live on NASA TV for 4 hours as a part of the Science, Technology, Engineering, and Mathematics (STEM) education programming. The test was subsequently run on CNN and Fox websites.
- Administrator Bolden received a tour of the test facility after the successful test.
- Currently, the SBKF team is processing the test data and correlating that data with predictions.
Advanced Aluminum Alloy Assessment
- First SBKF workshop with industry to present the SBKF project and receive feedback
- Preliminary ETTA1 test and analysis correlation will be presented as well as results from some detailed design studies on-going for heavy lift vehicles (Ares-V-based design).
- Industry participants will be invited to present information on design, qualification, and certification challenges for metallic and composite structures.
Technology Development and Implementation
- SBKF Advanced Aluminum Alloy Assessment has spun off into a Small Business Innovation Research activity to investigate material properties and structural design optimization for heavy lift LV cryotanks constructed from Al-Li 2050.
- Al-Li 2050 cryo tanks and dry structure can show as much as a 20-30% weight savings over Al-Li 2195 and has a much lower technical risk and significantly lower cost than the composite alternative because this material is already used extensively in several commercial aircraft.
- Two technical reports were presented at the AIAA/ASME/ASCE/ASC Structures, Structural Dynamics, and Materials Conference in April 2011 at Denver CO
- Schultz et al, Compression Behavior of Fluted-Core Composite Panels, AIAA-2011-2170
- Bushnell and Rankin, Use of GENOPT and BIGBOSOR4 to Obtain Optimum Designs of an Axially Compressed Cylindrical Shell with a Composite Truss-Core Sandwich Wall, AIAA-2011-1811
- To view other Shell Buckling reports click here.
- SBKF Trade Study activity is complete.
- The project is continuing to pursue an activity to develop and validate new lower-bound buckling load calculation methods for preliminary design.