Free Fall Stability Analysis
of High Altitude Balloon
Reentry Vehicle Using CFD
J Snyder, C. Barnes,
Jessica Rinderle, Oleg Shiryayev
and Joseph Slater
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
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
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
Experimental Setup
• Styrofoam capsule
• Control
▫ DTMF
▫ Cut-down initiation
▫ Parachute
deployment
• Tracking
▫ GPS/APRS via MicroTrack, Tiny Track
• Parachute
Free Fall Analysis
Terminal Velocity vs. Altitude
350.00
300.00
Velocity, MPH
250.00
200.00
150.00
100.00
50.00
0.00
0
2
4
6
8
10
12
14
16
18
20
Altitude, Miles
Capsule
Drag Chute
Main Chute
Parachute Deployment Altitude
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)
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
Test Flight Configuration
Data Processing
• Pre-processing
▫ 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
Sample Data From Test Flight
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
Simulations Methods
• All simulations were run with air at 60,000 ft
Density, ρ (kg/m2)
Viscosity, µ (kg/m*s)
0.122
1.422 × 10-5
• Two cases of simulations were run
▫ High amplitude oscillating motion with selected descent
velocities
 A = 900 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
 3 m/s, 14 m/s, 28 m/s, 42 m/s, 55.8 m/s
CFD Model
• 3D teardrop is surrounded by
a cylinder, which is in a larger
rectangular domain
• The cylinder allows for
rotational motion as needed
outlet
y
teardrop
z
inlet
x
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.
Coarse Mesh
• The course mesh has
approximately 41,000 elements
• To the right is a zoomed in view
of the mesh near the teardrop
Refined Mesh
• The refined mesh was
created to verify mesh
independence of the
solution
• The refined mesh has
1,199,314 elements
Simulation Results
y
Oscillation motions with varying velocity
Lateral X Force vs. Time
V = 55 m/s
z
x
15.000
10.000
Force (N)
5.000
0.000
0.000
5.000
10.000
15.000
-5.000
-10.000
-15.000
Time (s)
20.000
25.000
30.000
fine mesh
coarse mesh
y
Vertical Y Force vs. Time
V =55.8 m/s
x
z
30.000
25.000
Force (N)
20.000
15.000
fine mesh
coarse mesh
10.000
5.000
0.000
0.000
5.000
10.000
15.000
Time (s)
20.000
25.000
30.000
Orthogonal Lateral Z Force vs. Time
V = 55.8 m/s
2.000
y
x
z
1.500
1.000
Force (N)
0.500
0.000
0.000
5.000
10.000
15.000
-0.500
25.000
30.000
fine mesh
coarse mesh
-1.000
-1.500
-2.000
-2.500
-3.000
20.000
Time (s)
y
Orthogonal Lateral Z Moment vs. Time
V = 55.8 m/s
x
z
1.500
Moment (N m)
1.000
0.500
fine mesh
0.000
0.000
5.000
10.000
15.000
-0.500
-1.000
-1.500
Time (s)
20.000
25.000
30.000
course mesh
Conclusion
• CFD simulations are continuing
• Test flight was partially successful in required cut down
methods
• Ready to obtain flight data from reentry vehicle
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 0837677
• Wright State University Physics Department and
Cornerstone Research Group (equipment)
• Wright State University (curriculum innovation funding)