(Georgia Institute of Technology, 2011-04-05)
Wells, Grant
The primary importance of trajectory reconstruction is to assess the accuracy of pre-flight predictions of the entry trajectory. While numerous entry systems have flown, often these systems are not adequately instrumented or the flight team not adequately funded to perform the statistical engineering reconstruction required to quantify performance and feed-forward lessons learned into future missions. As such, entry system performance and reliability levels remain unsubstantiated and improvement in aerothermodynamic and flight dynamics modeling remains data poor. The comparison is done in an effort to quantitatively and qualitatively compare Kalman filtering methods of reconstructing trajectories and atmospheric conditions from entry systems flight data. The first Kalman filter used is the extended Kalman filter. Extended Kalman filtering has been used extensively in trajectory reconstruction both for orbiting spacecraft and for planetary probes. The second Kalman filter is the unscented Kalman filter. Additionally, a technique for using collocation to reconstruct trajectories is formulated, and collocation's usefulness for trajectory simulation is demonstrated for entry, descent, and landing trajectories using a method developed here to deterministically find the state variables of the trajectory without nonlinear programming. Such an approach could allow one to utilize the same collocation trajectory design tools for the subsequent reconstruction.
(Georgia Institute of Technology, 2006-05-01)
Wells, Grant
The purpose of this investigation is to begin forming a dataset to be the basis of a Mars
entry, descent and landing mission design handbook for planetary probes. The premise of
the project is that Mars entry, descent and landing can be parameterized with five variables:
(1) entry mass, (2) entry velocity, (3) entry flight path angle, (4) vehicle aeroshell diameter,
and (5) vertical lift-to-drag ratio. For combinations of these input parameters, the following
trajectory information will be determined: peak deceleration, peak heat rate, heat load, and
the altitude at which Mach 2 is reached (for parachute deployment).