No abstract

No abstract

Several techniques have been developed to obtain optimum trajectories with low-thrust propulsion. However, few low-thrust guidance schemes have been investigated to fly the reference optimum trajectories. The guidance algorithm successfully employed in the DeepSpace1 mission was the first approximation through the presented guidance schemes, valid for various interplanetary low-thrust trajectories, independently of the optimization technique they result from. A method is presented to transform any given thrust profile to a thrust law defined by a finite set of control variables. This law allows the definition of a control vector to be optimized for the guidance purposes. Simulations were carried out to compare the performances of the algorithms to very different missions, such as SMART-1 and BepiColombo. The good performance of the enhanced guidance schemes prove the generic applicability of the algorithm. Parametric analysis allows the assessment of stability and robustness of the schemes and the sensitivity to certain parameters. Table.

An improvement of the MacCready speed-to-fly theory used in sailplanes cross-country flights is outlined. Two different parameters characterizing the thermal are introduced (the vertical speed of the air inside the thermal and the thermal radius) and a universal dimensionless model is proposed, which can be applied to any sailplane. The maximum average cross-country speed, the optimum airspeeds in descent and climb, the rate of climb in the helical trajectory and other flight variables are calculated versus two abbreviated parameters condensing thermal and sailplane data.

No abstract