1. Free Fall Stability Analysis of High Altitude Balloon Reentry Vehicle Using CFD
J Snyder, C. Barnes, Jessica Rinderle, Oleg Shiryayev
and Joseph Slater

2. Objectives Release free fall capsule at 90,000 feet
Deploy parachute at 65,000 ft
Develop launch/flight simulation
CFD modeling of free-fall
Validate CFD model
Reduced order nonlinear rigid body dynamic model identified CFD from
Compare to experimentally identified dynamic model

3. Background 5th year of High Altitude Balloon program
“Our laboratory is at 100,000 feet”
Cost-effective near space experimentation
100% recovery rate (15 flights)
Prior experiments
Reliable balloon tracking systems
Deployment of shape memory composite tube
Three dimensional deployable truss using shape memory composites

4. HiBAL flight regulations
FAA FAR 101 Subpart D
No flight permission required under exempt rules (must notify of launch and land)
12 lb total payload limit
6 lbs per package
50 lb impulse max load capability… units?
Stay out of controlled areas
Many shades of gray in rules

6. Experimental Setup Styrofoam capsule Control Tracking Parachute DTMF
Cut-down initiation
Parachute deployment
Tracking
GPS/APRS via Micro- Track, Tiny Track
Parachute

7. Free Fall Analysis

8. Data Acquisition System
VectorNav VN-100T sensor board
Temperature calibrated to 40o C
Accelerations
Angular rates
Magnetic sensors
Output to SparkFun Logomatic V2 Serial Data Logger
Quaternion (via EKF)
Acceleration X, Y, Z
Angular rates (via EKF)

9. Test Flight
Ran a flight to test the ability of the data acquisition system
Also tested cut down system
Need to reliably cut down the reentry vehicle from the balloon to obtain correct free fall data
Test flight consists of the data acquisition system enclosed in a Styrofoam cooler
Numerous parachute deployment tests

10. Test Flight Configuration

11. Data Processing Pre-processing Stability Analysis
Removal of corrupted lines
Removal of bias
Smoothing
Stability Analysis
Visualization of spatial orientation of the capsule
Estimation of aerodynamic forces and moments
Correlation with CFD data

12. Sample Data From Test Flight

13. CFD Analysis
The 3 Dimensional reentry vehicle is forced to oscillate rotationally about the z axis.
Analysis provides moments and forces as a function of rotation and angular velocity that will be used to identify the rigid body dynamic equations

14. Simulations Methods All simulations were run with air at 60,000 ft
Two cases of simulations were run
High amplitude oscillating motion with selected descent velocities
A = ω = .5 rad/s
3 m/s, 14 m/s, 28 m/s, 42 m/s, 55.8 m/s
Reynolds number from 15,690 – 291,836
Low amplitude oscillation motion with over a set (grid) of angular frequencies and descent velocities
A = 5o ω = 3 rad/s, 6 rad/s, 9 rad/s, 12 rad/s, and 15 rad/s
Density, ρ (kg/m2)
Viscosity, µ (kg/m*s) × 10-5

15. y x z
CFD Model
3D teardrop is surrounded by a cylinder, which is in a larger rectangular domain
The cylinder allows for rotational motion as needed
inlet
outlet
teardrop

16. Discontinuous Mesh
SC/Tetra has a discontinuous mesh setting, which allows flow field states to transfer between two separately created meshes that have adjacent faces.
The two model portions are meshed separately with an unstructured grid, and then combined to form the final mesh model.
For the simulations two final meshes have created so far, a coarse grid and a finer grid.

17. Coarse Mesh The course mesh has approximately 41,000 elements
To the right is a zoomed in view of the mesh near the teardrop

18. Refined Mesh
The refined mesh was created to verify mesh independence of the solution
The refined mesh has 1,199,314 elements

19. Simulation Results Oscillation motions with varying velocityx z

20. y x z

21. y x z

22. y x z

23. Conclusion CFD simulations are continuing
Test flight was partially successful in required cut down methods
Ready to obtain flight data from reentry vehicle

24. Acknowledgements
Industry advisors: Bruce Rahn, Steve Overmeyer, Steve Mascarella
Other faculty advisors: George Huang, John Wu
Brent Guenther, Besmira Sharra and other team members
Ohio Space Grant Consortium
NSF CCLI Award
Wright State University Physics Department and Cornerstone Research Group (equipment)
Wright State University (curriculum innovation funding)