National Aeronautics and Space Administration Unsteady Pressures on a Generic Capsule Shape Jim Ross & Nathan Burnside NASA Ames Research Center 53rd AIAA Aerospace Sciences Meeting Kissimmee, FL January 5-9, 2015 Outline •  Background •  Test Objectives •  Test Description – Model design – Instrumentation – Flow conditions tested •  Unsteady Pressure Processing •  Selected Results •  Concluding Remarks 2 Background •  Agreement between CFD and experiments for Orion CM was poor below Mach 0.7 –  Uncertainty in the CFD-determined capsule flow –  Wind-tunnel and CFD did not match low-M results from pad- abort flight test •  Wind-tunnel testing of Orion showed boundary-layer state on heat shield significantly affected CM aerodynamics –  Reynolds number sensitive for Mach numbers below about 0.7 –  Method of tripping flow also had an effect on the aerodynamics •  NASA Engineering and Safety Center funded study to make measurements on and around an idealized Orion Crew Module shape •  General test overview and preliminary results –  Ross, J. C., et al., “Comprehensive Study of the Flow Around a Simplified Orion Capsule Model,” AIAA paper 2013-2815, 31st AIAA Applied Aerodynamics Conference, San Diego, CA, . June 24-27, 2013 3 Objectives •  Detailed characterization of the flow around a capsule shape for subsonic/transonic flight •  Document effect of heat-shield roughness –  Post-entry Avcoat is very rough •  Comprehensive measurement suite –  44 Unsteady pressures around heat-shield shoulder and on back shell –  Wake velocity from near the capsule to ~5.5 capsule diameters downstream - Particle Image Velocimetry (PIV) –  Detailed pressure over entire model surface - Pressure Sensitive Paint (PSP) –  Boundary-layer transition and separation locations - IR Thermography –  Boundary-layer profiles at one location on the heat shield –  High-speed shadowgraph videos (6,000 frames per second) 4 Model Description •  Model is axi-symmetric based on Model Definition the analytic description of the Orion CM – Smooth heat shield – Rough heat shield to represent post-entry Avcoat roughness pattern •  Struts used for support – Side entry to keep the strut wakes out of measurement plane – Stiff support to minimize model deflections and motion – Provide optical access for all of the cameras 5 Heat Shield Details º Φ≈0 º Φ≈330 •  Two-layer heat shield fabrication º Φ≈270 –  ¼” aluminum structural layer –  ¼” polycarbonate outer surface •  Provides enhanced IR º signatures for Φ≈180 transition/separation visualization 6 Rough Heat Shield 7 Micrograph of Dimpling •  Hex pattern scaled from post-entry Avcoat honeycomb roughness (Orion and Apollo) 0.050” •  ~75,000 dimples machined 0.005” into plastic outer layer deep •  PSP coating ~0.002” thick 8 Tunnel Installation Stabilizing Cables 9 9 Test Conditions for Various Measurements PSP, IR Thermography, Unsteady Pressures, Shadowgraph Heat  Shield   Angle  of  A0ack   Mach  0.3   Mach  0.5   Mach  0.7   Mach  0.9   Mach  1.05   Smooth   30°   1.3x106   1.3x106   Smooth   30°   5.3x106   8.7x106   10x106   10x106   6.6x106   Rough   15°   5.3x106   8.7x106   10x106   10x106   6.6x106   Rough   30°   1.3x106   1.3x106   Numbers in green boxes indicate Rough   30°   5.3x106   8.7x106   10x106   10x106   6.6x106   Reynolds number Boundary-Layer Surveys, Skin Friction, IR Thermography tested Heat  Shield   Angle  of  A0ack   Mach  0.3   Mach  0.5   Mach  0.7   Mach  0.9   Mach  1.05   Black boxes indicate conditions Rough   0°   5.3x106   8.7x106   10x106   not tested Rough   15°   5.3x106   10x106   6.6x106   Rough   30°   5.3x106   10x106   6.6x106   PIV, Unsteady Pressures, Shadowgraph - Rough heat shield Model  PosiDon   Angle  of  A0ack   Mach  0.3   Mach  0.5   Mach  0.7   Mach  0.9   Mach  1.05   Downstream   15°   5.3x106   8.7x106   10x106   Upstream   15°   5.3x106   8.7x106   10x106   10