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)