Wind-Tunnel Test of Flow Through Mars Pathfinder Lander

The Pathe nder Lander, launched in December 1996, is scheduled to land on Mars July 4, 1997. The Lander is a tetrahedron with open edges and corners, permitting a moderate e ow through the interior during parachute descent. One of its scientie c experiments isintended to measureambient temperatureand pressureduring parachute descent by use of sensors inside the Lander envelope. This location was required by safe landing considerations. Wind-tunnel and computational e uid dynamics studies were undertaken to determine whether valid atmospheric data could be obtained by sensors so constrained. Internal e ows through the window openings at the apex corners of the Lander were measured and computed. Internal e ow was found to be complex, recirculating, and highly turbulent with velocities as small as 0.1 that of the freestream. The temperature sensoris in a region of e uctuating, negative (upstream) velocity. This environment is clearly not optimum for atmospheric measurements, and temperatures measured in parachute descent are likely to be thermally contaminated. The data reported here will be ofvalueforevaluating themeasurements and identifying requirements for meaningful atmosphericmeasurements on future missions. They are also an interesting example of secondary e ow through a vented spacecraft. Nomenclature l = characteristic length, slant height of Lander vehicle side petal, equal to 1.14 m in full scale (the full-scale length of the edge of the tetrahedron inscribed in the Lander is 1.73 m ) p = freestream static pressure pt