1. Research Progress Satellite Drag in Free-Molecular and Transition Flow Focus Area VIII October 26, 2011 Marcin Pilinski, Craig Turansky, Brian Argrow University of Colorado, Boulder Thanks to Scott Palo, Bruce Bowman, Ken Moe and Mildred Moe, Eric Sutton, and Eelco Doornbos

2. Focus Area VIII: Satellite Drag in the Re-Entry Region 10/28/20102 Objective: To significantly advance understanding of satellite drag in the transition and near-continuum regimes using state-of-the art numerical modeling, and to provide C D predictions under a broadened range of conditions YrMilestonesDeliverables 1Simulations of simple 3-D geometries with candidate GSI models. DSMC/GSI with atmosphere model 2Down-select/calibrate GSI models w/ satellite data DSMC/GSI w/ calibrated GSI options 3DSMC computation of transition-regime aerodynamic coefficients Code to compute C D in slip/ transition flows for range of geometries 4Create database of altitude-dependent C D for representative satellites in transition flow. Integrated simulation environment code to produce C D database 5Complete DSMC/GSI code for trajectory simulations w/ direct modeling of flow environment Integrated simulation environment code to simulate real-time application completed workongoing work M. D. Pilinski, C. Turansky, B. M. Argrow

3. Background: The Accommodation Coefficient 10/28/20103 [Doornbos. 2011] M. D. Pilinski, C. Turansky, B. M. Argrow Accommodation Coefficient a)α=1.00 b)α=0.80 c)Pilinski et al. 2010

4. Available Data: Fitted-Ballistic Measurements 10/28/20104M. D. Pilinski, C. Turansky, B. M. Argrow Data from 68 objects was provided by Bruce Bowman at AFSPC/A9A. Data spans 105 km to 520 km altitudes from 1969 to 2004.

5. Available Data: Tri-Axial Accelerometers 10/28/2010M. D. Pilinski, C. Turansky, B. M. Argrow5 aligned with boom towards Earth

6. 10/28/2010M. D. Pilinski, C. Turansky, B. M. Argrow6 SESAM Parameter Inversion Fitted-Ballistic Coefficients

7. Results: SESAM model comparisons 10/28/2010M. D. Pilinski, C. Turansky, B. M. Argrow7 fuel margin: -0.05% to 0.05% fuel margin: -3% to 0% fuel margin: -0.05% to 5.0%

8. Results: Comparison with Paddlewheel Measurements 10/28/2010M. D. Pilinski, C. Turansky, B. M. Argrow8

9. CHAMP-GUVI Comparisons 10/28/2010M. D. Pilinski, C. Turansky, B. M. Argrow9 α = 0.78 (+0.10, -0.13)

10. Tri-Axial Accelerometer Analysis Diffuse model with incomplete accommodation 10/28/2010M. D. Pilinski, C. Turansky, B. M. Argrow10 α = 0.89 (+0.02, -0.03)

11. Result Summary 10/28/2010M. D. Pilinski, C. Turansky, B. M. Argrow11

12. Spacecraft Simulation Goals 10/28/2010M. D. Pilinski, C. Turansky, B. M. Argrow12 Numerical Simulations (e.g. DSMC) Rigid-body dynamics (modeling/approximation) Full dynamic simulation (beyond drag) Redefine the problem from satellite drag to spacecraft fluid dynamics Treat spacecraft dynamics more like aircraft dynamics where possible

13. DSMC Development 10/28/201013M. D. Pilinski, C. Turansky, B. M. Argrow Bird’s “production” codes DS2V, DS3V Current, best available option for DSMC DS2V User Interface The Bad Limited geometry, BCs Requires a free-stream Difficult batch processing Only 2 GSI models Maxwellian diffuse Pure specular Closed source Can’t fix/extend it The Good Free, download at gab.com.au Highly reliable Verified by many people Chemical reactions/internal modes present

14. 10/28/201014 DSMC is a tool for rarefied/transition gas flows that we need Current DSMC tools are “dull” (insufficient and/or unavailable) New code: Voldipar created to act as a sharper tool Current state of Voldipar verified with benchmark problems Supersonic Flat Plate Hypersonic Cylinder NACA0012 DSMC Development M. D. Pilinski, C. Turansky, B. M. Argrow

15. 10/28/201015 Equations of Motion: 2D Source functions: x z q Gas forces from some model or simulation Take an example: Panel method in Free-Molecular (FM) flow to get X,Z,M What happens to an airfoil at Ma=10, Kn=100? Rigid-Body Dynamics M. D. Pilinski, C. Turansky, B. M. Argrow

16. 10/28/201016 separatrices limit cycles unstable trajectories Aircraft-like Dynamics Results NACA0012 in FM, Hypersonic flow: In-loop vs Sliding Taylor dynamic motion Ma=10, Kn=100, Argon 1000K M. D. Pilinski, C. Turansky, B. M. Argrow

17. 10/28/2010M. D. Pilinski, C. Turansky, B. M. Argrow17 Conclusions Seeking to better understand spacecraft motion beyond drag Want to make spacecraft as familiar as aircraft Developing better numerical tools – DSMC (Voldipar code) Starting to investigate how to apply this to rigid-body dynamics Examples in 2D show this is possible Future Add more to Voldipar code (GSI, 3D upgrade, better BCs, generalized) Examine new methods for approximation of dynamics Look into possible LBM-DSMC coupling for transition region Eventual Goal Provide “single file”, full-dynamic description of spacecraft motion due to rarefied/transition flow

18. 10/28/201018M. D. Pilinski, C. Turansky, B. M. Argrow Thank You