1. STRUCTURAL ANALYSIS OF SOUNDING ROCKET FINS
Presenter: Aris Iturbe Hernándeza
Daniel Alejandro Hernández Záratea, José Luis Xancopinca Trejoa, David Cisneros Gonzáleza, Sergio Raúl Rojasa, Gerardo Saucedo Zárateb
aUniversidad Aeronáutica en Querétaro, Colón, Querétaro C.P , México
bINMUE A.C President
Contact:

2. INTRODUCTION - Many problems could cause a sounding rocket breakage
INTRODUCTION - Many problems could cause a sounding rocket breakage. - One of them is the possible failure of their structural components Analysis of the bending-torsion flutter in sounding rocket fins a) b)
Lenght
6 m
Empty Weight
51 kg
Total Weight (loaded)
115 kg
Thurst
> 4000 Nf
Time propulsion
28 seg.
Max. Speed km
Max Height
70-90 km
Range
24 km (86 degrees)
Supersonic parachute
95 km/hr waterland
SPECIFIC OBJECTIVES
Determine the flutter velocity.
Simulation of rocket trajectory.
Determine a safe operating range rocket.
Calculate the critical relation that may permit a systematic separation of safe and unsafe fins.
Determine the natural frequency response of the fin subjected to bi-directional vibratory movement.
Obtain a numerical model to simulate de natural frequency response of the fin subjected to bi-directional vibratory movement.
Fig. 1 a) Sounding Rocket JFCR-200A, INMUE A.C, Sounding Rocket JFCR-200A characteristics INMUE-UNAQ

3. METHODOLOGY Bending-Torsion Criterion End Start
Mission simulation (Obtain max. rocket velocity)
Design plans
JFCR 2000A Flight Data sheet
Geometric Parameters Definition
Flutter velocity calculation
Comparative between rocket velocity and flutter velocity
Is abs( Vrocket- Vflutter) > 0
Yes No
Determine the biggest positive difference of abs( Vrocket- Vflutter )
Is it possible to modify the geometry?
Change of material to augment flutter velocity of the biggest difference
Change geometric parameters to augment flutter velocity of biggest difference
Generate design plans and CAD figures of modified fin
Modal analysis with laser vibrometer
Modal analysis with numerical software (FEM)
Generate analysis report
End
METHODOLOGY
Bending-Torsion Criterion
This allows us to determine the fins performance in a rocket.
Leaving this study as a first step aero-elastic analysis.
Diagram presents the a methodology for rocket fins analysis under dynamic and static conditions.

4. BENDING-TORSION CRITERION
Considering: Static pressure = Stagnation Pressure
1. Material can not be changed ---> Geometry can be changed
𝑉𝑓 a 2 < 3.77x ∗ 𝑃 P0 ∗ 𝛌+1 2
2. Material can be changed ---> Geometry can not be changed
𝑉𝑓 a 2 < 5x x106
3. Parameters can not be changed
𝑉𝑓 a 2 < 3.77x ∗ 𝑃 P0 ∗0.9564
Based on the TN 4197 NACA Report

5. DESIGN PLANS MODELS MISSION SIMULATION JFCR 2000A DATA SHEET
Fig. 3 Variables evolution during rocket´s mission
Fig. 2 Design plans of the fin
Rocket velocity at different altitudes
JFCR 2000A DATA SHEET
Designed following Normative: ECSS-E-ST-10-02C

6. MODELS FLUTTER VELOCITY CALCULATION GEOMETRIC PARAMETERS DEFINITION
Theoretical: Safe climb operational range on NACA TN 4197 report
Root Chord
21 in
Tip Chord
12 in
Semispan
9 in
Root thickness
3/8 in
Tip Thickness
1/4 in
Taper Ratio
0.899 [1]
Panel Aspect Ratio
0.55 [1]
Table 1. Fin geometric characteristics
Root Chord
Tip Chord
Semispan
𝑉𝑓𝑙=𝑎∗ 𝐺 𝐴 𝑡 𝑐 3 ∗ 𝐴+2 )(( 𝜆+1 2 ))( 𝑝 𝑝 𝑜 𝐆
Shear Modulos. 𝐀
Panel Aspect Ratio 𝐭
Thickness 𝐜
Root Chord 𝛌
Taper ratio 𝐩
Pressure at a given altitude
𝐩 𝐨
Standard Pressure 𝐚
Speed of sound at a given altitude
𝐕𝐟𝐥
Speed in which flutter may occur for a given state of the rocket
Symbols for flutter speed equation.
Fig. 4 Principal Geometric Parameters

7. MODAL ANALYSIS WITH LASER VIBROMETER
MODELS-RESULTS
MODAL ANALYSIS WITH LASER VIBROMETER
Fin´s material: Aluminum 6061 T6
Excellent joining characteristics, good acceptance of applied coatings.
Combines relatively high strength, good workability, and high resistance to corrosion; widely available
Figura 7. Experimental Setup.
Natural Frequency
Hertz I
145 II
298
III
456 IV
713
Table 2. Experimental model solution
Figura 6. Rocket fin with reflectors and accelerometer
Fig. 5 Aluminum 6061-T6 mechanical properties

8. MODAL ANALYSIS WITH NUMERICAL SOFTWARE (FEM)
MODELS- RESULTS
MODAL ANALYSIS WITH NUMERICAL SOFTWARE (FEM)
Table 3. FEM Model Solution
Frequency [Hz]
Modes number
Figure 8. Total Deformation evolution

9. CONCLUSION X Aluminum 6061-T6
Shear Modulus psi
1.04
3.7e6
From contrast the numerical and experimental values. The critical mode to cause failure is: 3, 713 [Hz]
From current values for X and material: Aluminum 6061-T6 is recommended to use different material, options: titanium alloy but low density, composites materials, X
Mode
Natural Frequency
Experimental
FEM
% Error I
145
182 25 II
298
276 7
III
456
487
6.8 IV
713
767
7.5
𝑋= 𝐴 𝑡 𝑐 3 ∗ 𝐴+2

10. New material consideration (higher shear modulus)
FUTURE WORK
Adapt the numerical model to experimental model with mesh adapting and constrains.
New material consideration (higher shear modulus)
Classify vibrating rocket components and estimate their frequency
Simulation of the aerodynamically forces over the fin corrected with presented methodology

11. THANK YOU

12. BACK UP To Prevent fluttering are several ways, one of them is
Decouple the movement of bending and twisting
Modifying the distribution of mass to move the center of gravity close to the center of rotation