1. In order to assess the guidance and control system robustness as well as its performance, 2000 4DOF and 2000 6DOF simulations were performed. The system uncertainties we have considered are separated into 4 main blocks: mission, aerodynamic, mass properties and atmospheric uncertainties. The variation assumed for the first three of these is shown in the table below. The atmospheric uncertainties are internally generated in the atmospheric model used,forwhich adifferent seed numberis set at thestart of each simulation.
2. Initial Longitude(deg) 338.1691 0.19 Gaussian
3. In the 4DOF simulations, the aerodynamic moment coefficients and center of gravity are perturbed in the same way as for 6DOF simulations, such as to ensure that the trim angle-of-attack perturbations will be realistic. The simulations are carried out starting from a perturbed initial entrystate at r = 3522200m, and stopped when either the range ratebecomes positive andthe vehicle is still within aset ofdesignlimits,or whenthesedesign limits approach pre-selected values. In our simulations we have set limits to the deployment altitude (5-13km), the Mach number (1.4-2.0)andthe dynamicpressure(between 350-750N/m2).
4. D. Results Figure 10. Parachute deployment latitude and longitude dispersion. Data computed from 2000 4DOF simulations, including all system perturbations.Perfect navigation is assumed. Figure 11. Parachute deployment latitude and longitude dispersion. Data computed from 2000 6DOF simulations, including all system perturbations. Perfectnavigationis assumed.