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Jessica Schoenbauer 2/7/08 Skirts Skirt Code. r1. l. α. r2. Inputs/Outputs for Skirt Code. *made to work with “Model Analysis Code” Inputs: 1) Axial load – mass of upper stage(s) and payload 2) Radius of upper stage 3) Radius of lower stage 4) Material of skirt
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r1 l α r2 Inputs/Outputs for Skirt Code *made to work with “Model Analysis Code” Inputs: 1) Axial load – mass of upper stage(s) and payload 2) Radius of upper stage 3) Radius of lower stage 4) Material of skirt 5) Material of stringers/support rings 6) Length of nozzle Outputs: 1) Mass of skirt 2) Length of skirt 3) Cost for raw materials Geometry by Jessica Schoenbauer Diagram courtesy of http://mix.msfc.nasa.gov/IMAGES/MEDIUM/9902050.jpg Structures Group
The Skirt Code Skirt Code Inputs Length > nozzle Length < diameter Calculate skirt length Calculate critical axial load Choose semivertex angle Choose thickness yes no no Critical > applied Calculate critical bending, pressure, and torsional load no Calculate mass & cost yes Outputs Structures Group
Backup Slides - References 1. “NASA Space Vehicle Design Criteria (structures): Buckling of Thin-walled Truncated Cones,” NASA SP-8019, September 1968. 2. “NASA Space Vehicle Design Criteria (structures): Buckling of Thin-walled Doubly Curved Shells,” NASA SP-8032, August 1969. 3. “NASA Space Vehicle Design Criteria (structures): Staging Loads,” NASA SP-8022, February 1969. Structures Group
Backup Slides - Equations Axial Compression: = correlation factor to account for difference between classical theory and predicted instability loads E = Young’s modulus t = thickness α = semivertex angle of cone ν = Poisson’s ratio Structures Group
Backup Slides - Equations Bending: = correlation factor to account for difference between classical theory and predicted instability loads E = Young’s modulus t = thickness r1 = radius of small end of cone α = semivertex angle of cone ν = Poisson’s ratio Structures Group
Backup Slides - Equations Pressure: = correlation factor to account for difference between classical theory and predicted instability loads E = Young’s modulus t = thickness L = slant length of cone t = thickness Structures Group
Backup Slides - Equations Torsion: = correlation factor to account for difference between classical theory and predicted instability loads E = Young’s modulus t = thickness l = axial length of cone ν = Poisson’s ratio t = thickness Structures Group