(Georgia Institute of Technology, 2014-01)
Dutta, Soumyo; Braun, Robert D.
The Mars Science Laboratory spacecraft landed an approximately 900 kg rover on Mars
on August 5, 2012 while using the largest aeroshell and supersonic parachute ever utilized
by a planetary entry mission. Similar to past Mars missions, the spacecraft recorded inertial measurement unit data and radar altimeter measurements during its descent through
the Martian atmosphere, but its aeroshell was also instrumented with ush atmospheric
data system sensors that captured the pressure distribution on the vehicle during hypersonic and supersonic flight regimes. The rich data set enabled a comprehensive post flight analysis of the vehicle's trajectory. This paper shows the vehicle's reconstructed
trajectory, aerodynamics, and atmospheric conditions using several statistical estimation
methods, specifically the Extended Kalman filter, Unscented Kalman filter, and adaptive
filter. The statistical estimation methods allow for both state estimation and uncertainty
quantification of model errors, which could improve design of future Mars entry missions.
(Georgia Institute of Technology, 2014-01)
Hart, Kenneth A.; Dutta, Soumyo; Simonis, Kyle R.; Steinfeldt, Bradley A.; Braun, Robert D.
Fast, high-fidelity trajectory propagation of objects in near-Earth orbits is a key capability for space situational awareness and mitigating probability of collisions on orbit. This
high-fidelity analysis requires accurate aerodynamics prediction for objects in the free-
molecular regime of flight, but most tools for aerodynamic prediction for this regime either
are found using assumptions or are computationally intensive. Symbolic manipulation
software can be used to analytically integrate expressions for pressure and shear pressure
coefficients acting on a general body in free-molecular regime to derive aerodynamic force
and moment expressions. The analytical aerodynamics prediction method is described and
relations have been developed for the sphere, cylinder, panel, and rectangular prism. The
NASA-developed Direct Simulation Monte Carlo Analysis Code is used to validate the analytical expressions and it is shown that expressions are accurate within 0.38%. These generalized analytic expressions in terms of angle of attack, sideslip angle, freestream conditions,
wall temperature, and accommodation coefficients allow near-instantaneous computation
of the rarefied aerodynamics and enables space situation awareness analysis.