Mars Pathfinder Rarefied Aerodynamics: Computations and Measurements

On July 4, 1997, after traveling close to 500 million km, the Pathfinder spacecraft successfully completed entry, descent, and landing at Mars. In the present paper, the focus is on the hypersonic rarefied portion of Pathfinder''s atmospheric entry where the synergy of flight measurements, aerodynamic calculations, and atmospheric modeling tools are used to extract Pathfinder''s attitude and the freestream density. Accuracy of the capsule aerodynamics directly impacts the inferred atmospheric properties extracted from deceleration measurements made by on-board accelerometers. The range of rarefaction considered in this study extends from the free molecular to continuum conditions and angles of attack from 0 to 30 deg. The aerodynamic computations are made with free-molecular and direct simulation Monte Carlo codes. The calculations show that Pathfinder is statically unstable for much of the transitional rarefied regime. Due to the relatively modest forces and the gyroscopic motion of the spacecraft, the angle of attack excursions were less than 5 deg as inferred from force measurements for the rarefied portion of entry and approached a nominal zero degree trim angle near hypersonic continuum conditions.

[1]  G. L. Brauer,et al.  Capabilities and applications of the Program to Optimize Simulated Trajectories (POST). Program summary document , 1977 .

[2]  P. Desai,et al.  Entry Dispersion Analysis for the Stardust Comet Sample Return Capsule , 1997 .

[3]  G. Bird.  Molecular Gas Dynamics and the Direct Simulation of Gas Flows , 1994 .

[4]  Richard G. Wilmoth,et al.  Aerothermodynamics for Mars Microprobe Capsules Direct Simulation Monte Carlo Calculations of , 1999 .

[5]  Richard G. Wilmoth,et al.  AERODYNAMIC FLIGHT MEASUREMENTS AND RAREFIED-FLOW SIMULATIONS OF MARS ENTRY VEHICLES , 1997 .

[6]  William M. Congdon,et al.  Mars Pathfinder entry temperature data, aerothermal heating, and heatshield material response , 1998 .

[7]  Walter C. Engelund,et al.  Mars Pathfinder six-degree-of-freedom entry analysis , 1995 .

[8]  G. R. Gladstone,et al.  A new model for Mars atmospheric dust based upon analysis of ultraviolet through infrared observations from Mariner 9, Viking, and Phobos , 1995 .

[9]  Hassan Hassan,et al.  Monte Carlo simulation of entry in the Martian atmosphere , 1993 .

[10]  Richard G. Wilmoth,et al.  DSMC Simulations of Blunt Body Flows for Mars Entries: Mars Pathfinder and Mars Microprobe Capsules , 1997 .

[11]  P. Kallemeyn,et al.  Mars Pathfinder Entry, Descent, and Landing Reconstruction , 1999 .

[12]  Robert D. Braun,et al.  Influence of sonic-line location on Mars Pathfinder Probe aerothermodynamics , 1996 .

[13]  G Wilmoth Richard,et al.  DSMC Grid Methodologies for Computing Low-Density, Hypersonic Flows About Reusable Launch Vehicles , 1996 .

[14]  Robert D. Braun,et al.  Mars Pathfinder Atmospheric Entry Navigation Operations , 1997 .

[15]  Robert D. Braun,et al.  Mars Pathfinder rarefied aerodynamics - Computations and measurements , 1998 .

[16]  James N. Moss,et al.  Survey of Blunt Body Flows Including Wakes at Hypersonic Low-Density Conditions , 1997 .

[17]  G Wilmoth Richard,et al.  Low-Density Aerodynamics of the Stardust Sample Return Capsule , 1997 .