1. Jesii Doyle 2/28/2008 Internal Structures, Inter-Stage Skirts, Shear Stress Calculation, CAD Final Skirt Design
AAE 450 Spring 2008

2. Inter-Stage Skirt Configuration
Variable parameters:
Thickness of stringer
Number of stringers
Number of ring supports
Constant parameters:
Aluminum skin/stringers
Slope angle = 10°
Outer skin thickness = 4mm
Stringer depth = 2cm
Shear Stress Analysis Incorporated
Co-authored by Vince Teixeira
Figure 1 by Jesii Doyle
AAE 450 Spring 2008
Structures

3. Sample Skirt Configurations
SB-HA-DA-DA
Stringer thickness (mm) [ ]
No. of stringers: [ ]
No. of ring supports: [ 2 2 ]
MB-HA-DA-DA
Stringer thickness (mm): [ ]
No. of stringers: [ ]
LB-HA-DA-DA
Stringer thickness (mm): [ ]
No. of stringers: [ ]
No. of ring supports: [ 3 2 ]
Future Work
Implementation of final design
AAE 450 Spring 2008
Structures

4. Backup Slides MAT Code Version 4.0 Analysis Rocket Design Inputs
Model Name: SB-HA-DA-DA
Delta V = 7000
Delta V Percentages = [ ]
Inert Fractions = [ ]
Max Gs = 6
Model Name: MB-HA-DA-DA
Delta V = 8100
Delta V Percentages = [ ]
Inert Fractions = [ ]
AAE 450 Spring 2008
Structures

5. Backup Slides MAT Code Version 4.0 Analysis (Cont.)
Rocket Design Inputs
Model Name: LB-HA-DA-DA
Delta V = 9800
Delta V Percentages = [ ]
Inert Fractions = [ ]
Max Gs = 6
AAE 450 Spring 2008

6. Backup Slides Shear Stress Calculation Variables
t_skin θ y Sy
Shear Stress Calculation
Variables
t_skin = 0.004m (Const.)
θ = angle between stringers (rad)
yr = vertical dist. from shear center to stringer r (m)
Ar = area of stringer r (m^2)
r = stringer number
Ixx = area moment of inertia (m^4)
qr = shear flow through stringer r (N/m)
σr = shear stress through stringer r (Pa)
Sy = shear force at shear center (N)
AAE 450 Spring 2008

7. Backup Slides Shear Stress Calculation (Cont.)
Maximum Shear Stress – radius = radiusmin
Br = Ar + (t_skin*radius*θ/6)*(2 + yr+1/yr) + (t_skin*radius*θ/6)*(2 + yr-1/yr)
Ixx = Σ(Br*yr^2)
qr = -(Sy/Ixx)*Br*yr
σr = qr/t_skin
σcrit = maxi(σr) < σsu
AAE 450 Spring 2008

8. Backup Slides Stringer Axial Stress Equations AAE 450 Spring 2008 P h

9. Backup Slides Skin Critical Load Analysis E = Young’s Modulus
γ = 0.33 = const. valid for 10° ≤ α ≤ 75°
v = Poisson’s Ratio
AAE 450 Spring 2008

10. References
Bedford, A., Fowler, W., and Liechti, K.M., Statics and Mechanics of Materials, Pearson Education Inc., Upper Saddle River, New Jersey, 2003.
“Conical Shells,” Astronautics Structures Manual, NASA, 1976.
Megson, T.H.G., Aircraft Structures for Engineering Students, Vol. 3, Elsevier Butterworth-Heinemann, Burlington, MA, 1999, Ch
AAE 450 Spring 2008