1. 1 Jesii Doyle 3/20/2008 Internal Structures, Inter-Stage Skirts, Shear Stress Calculation, CAD Final Slides!!

2. 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 Structures Figure 1: 200g Launch Vehicle – Stage 2 Skirt (Jesii Doyle)

3. 3 Inter-Stage Skirt Configuration  200g Launch Vehicle –Stringer thickness: 3mm –No. stringer: [ 35 14 ] –No. ring supports: [ 7 1 ]  1kg Launch Vehicle –Stringer thickness: 3mm –No. stringer: [ 29 15 ] –No. ring supports: [ 6 1 ] Structures  5 kg Launch Vehicle –Stringer thickness (mm): [ 5 3 ] –No. stringer: [ 42 14 ] –No. ring supports: [ 8 1 ]

4. 4 Backup Slides  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) t_skin θ θ y SySy

5. 5 Backup Slides  Shear Stress Calculation (Cont.) –Maximum Shear Stress – radius = radius min B r = A r + (t_skin*radius*θ/6)*(2 + y r+1 /y r ) + (t_skin*radius*θ/6)*(2 + y r-1 /y r ) I xx = Σ(B r *y r ^2) q r = -(S y /I xx )*B r *y r σ r = q r /t_skin σ crit = max i (σ r ) < σ su

6. 6 Backup Slides  Stringer Axial Stress Equations P L b h

7. 7 Backup Slides  Skin Critical Load Analysis –E = Young’s Modulus –γ = 0.33 = const. valid for 10 ° ≤ α ≤ 75° –v = Poisson’s Ratio

8. 8 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. 10.2.