ASROC MISSILE FIN FLUTTER VELOCITY
Copyright 1999-2017 John Cipolla/AeroRocket


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Flutter velocity performed for the ASROC missile determined using the FinSim Ug method. Table-1 presents a comparison between various flutter velocity methods and the Ug method used by FinSim. Table-2 displays FinSim input data derived from ASROC fin dimensional information presented in Figure-4. Figure-1, Figure-2 and Figure-3 display FinSim flutter velocity results using fin dimensional data presented in Table-2. Please see NACA RM SL58H08a, Test 38 for detailed information about the windtunnel method used to determine ASROC fin flutter.
 
UF METHOD, TABLE-2 FLUTTER VELOCITY (UF) DIFFERENCE
FinSim_Ug Mach 1.20 -7.7 %
FinSim main screen analysis Mach 1.33 + 2.3 %
NACA TN 4197 equation Mach 1.319 +1.5 %
NACA RM SL58H08a (windtunnel) Mach 1.3 NA

Table-1, Flutter velocity computation methods compared to the FinSim Ug method

 

FINSIM INPUT DESCRIPTIONS

VALUES

NOTES

Semi span (b)

3.42 in Fin input geometry screen

Root chord (cr)

8.91 in Fin input geometry screen

Tip chord (ct)

6.44 in Fin input geometry screen

Sweep length

4.22 in Fin input geometry screen

Fin thickness (t)

0.05 in Fin input geometry screen

Maximum body diameter near fins

4.0 in Fin input geometry screen
     

Fin Materials

Aluminum, main screen pull down

Shear modulus (G)

3759398 psi Fin material, aluminum

Elastic modulus (E)

10E6 psi Fin material, aluminum

Poissons ratio

0.33 Fin material, aluminum

Material density

0.098 lb/in3 Fin material, aluminum
     

Rocket simulation altitude (P) @ max Mach

29,000 ft Pressure, main screen pull down
     

Supersonic Airfoil Lift Slope

  Main screen pull down menu

Aerodynamic center location (A.C.)

0.50 0.5 for supersonic, main screen
CN-alpha method, NACA TN 4197   Supersonic lift slope method used
     
Aeroelastic input variables   E.A. and C.G. main screen inputs

Elastic axis location (E.A.)

0.50

Attachment centroid, main screen

Center of gravity location (C.G.)

0.694

Measured or computed, main screen

     

FinSim Results

   
FinSim main screen flutter analysis Mach 1.33 See Figure-1

U-g Torsion-Flexure flutter velocity

Mach 1.2 See Figure-3

Table-2, FinSim input variables for performing supersonic flutter velocity analysis

 

Figure-1, FinSim main screen

 


Figure-2,  Fin input geometry screen

 


Figure-3,  Flutter velocity (UF) computed using U-g method (Windows 10 image displayed)
 

Figure-4,  ASROC annotated fin dimension worksheet from NACA RM SL58H08a, Test 38