Free Fall Stability Analysis

Free Fall Stability Analysisof High Altitude BalloonReentry Vehicle Using CFD

J Snyder, C. Barnes, Jessica Rinderle, Oleg Shiryayevand Joseph Slater

Objectives

Release free fall capsule at 90,000 feetDeploy parachute at 65,000 ftDevelop launch/flight simulationCFD modeling of free-fallValidate CFD model Reduced order nonlinear rigid body dynamic model identified CFD from Compare to experimentally identified dynamic model

Background

5

th

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

FAA FAR 101 Subpart DNo flight permission required under exempt rules (must notify of launch and land)12 lb total payload limit6 lbs per package50 lb impulse max load capability… units?Stay out of controlled areasMany shades of gray in rules

HiBAL flight regulations

Experimental Setup

Styrofoam capsuleControl DTMFCut-down initiationParachute deploymentTrackingGPS/APRS via Micro-Track, Tiny TrackParachute

Free Fall Analysis

Data Acquisition System

VectorNav VN-100T sensor board

Temperature calibrated to 40

o

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 ftTwo cases of simulations were run High amplitude oscillating motion with selected descent velocitiesA = 900 ω = .5 rad/s3 m/s, 14 m/s, 28 m/s, 42 m/s, 55.8 m/sReynolds number from 15,690 – 291,836Low amplitude oscillation motion with over a set (grid) of angular frequencies and descent velocitiesA = 5o ω = 3 rad/s, 6 rad/s, 9 rad/s, 12 rad/s, and 15 rad/s3 m/s, 14 m/s, 28 m/s, 42 m/s, 55.8 m/s

Density,

ρ

(kg/m

2

) 0.122

Viscosity, µ (kg/m*s) 1.422 × 10

-5

CFD Model

3D teardrop is surrounded by a cylinder, which is in a larger rectangular domainThe cylinder allows for rotational motion as needed

y

x

z

inlet

outlet

teardrop

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

T

he 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 ResultsOscillation motions with varying velocity

y

x

z

y

x

z

y

x

z

y

x

z

Conclusion

CFD simulations are continuing Test flight was partially successful in required cut down methodsReady 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)