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Cone Angle Choices For Atmospheric Entry Vehicles: A Review Michael Tauber ELORET Corp.

Cone Angle Choices For Atmospheric Entry Vehicles: A Review Michael Tauber ELORET Corp. NASA-Ames Research Center Michael Wright Kerry Trumble Reacting Flow Environments Branch NASA-Ames Research Center IPPW-6 Atlanta, Georgia June 23-27, 2008.

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Cone Angle Choices For Atmospheric Entry Vehicles: A Review Michael Tauber ELORET Corp.

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  1. Cone Angle Choices For Atmospheric Entry Vehicles: A Review Michael Tauber ELORET Corp. NASA-Ames Research Center Michael Wright Kerry Trumble Reacting Flow Environments Branch NASA-Ames Research Center IPPW-6 Atlanta, Georgia June 23-27, 2008

  2. Why Do Cone Angles Of Entry Probes And Landers Vary from 45o To 70o? • Parameters that affect cone angle choices - packaging, atmosphere, heating, stability, etc. • Advantages of 45o cone angle • Packing of pressure vessels • Can decrease heating rates • High-speed dynamic stability • Larger cone angles • Decrease entry heating duration • Can increase heating rate, especially radiation • Increase descent heat conduction • Can decrease dynamic stability

  3. The thin conical shock layer, ∆<<, sharp nose, =0, =1/2<<1 • Aerodynamic stability, <<  • Entry trajectory and heating Boundary layer; lam n=0.5, turb n=0.8 Radiation; inner planets n=1.19-1.22 Radiation; outer planets n=1.17-1.45

  4. Shock Layer Temperature and Pressure Distributions at Cone Frustum Midpoints V = 10.871 km/s, altitude = 61.761 km

  5. =70o Sphere-cone 60o Sphere-cone 50o Sphere-cone Variations of Stardust Capsule

  6. Heat Conduction During Descent • Simplifying assumptions: terminal descent, exponential atm. density variation with altitude Since sin 1 and , where  is atm. density scale height Now the approximate descent time, td, becomes Where o is the atm. density where heat shield is discarded • Note that heat conduction time is reduced by decreasing the CD, or cone angle. In contrast, during entry the heat load is decreased by increasing the CD, or cone angle • Also, note the effect of atm. density, o, and scale height, , on the descent time

  7. Mars Pathfinder Entry Dynamics Total off-axis acceleration recorded during 100-s interval surrounding peak dynamic pressure. Gnoffo, et al, “Prediction and Validation of Mars Pathfinder Hypersonic Aerodynamics Database,” Journal of Spacecraft and Rockets, Vol. 36, No. 3, May-June 1999, pp. 367-373

  8. Davies, C., “Planetary Mission Entry Vehicles”, Version 2.1, NASA Ames Research Center

  9. Conclusions

  10. Back-up Slides

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