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Abstract: One of the most important problems for performing a good design of the spacecraft attitude control law is connected to its robustness when some uncertainty parameters are present on the inertial and/or on the elastic characteristics of a satellite. These uncertainties are generally intrinsic on the modeling of complex structures and in the case of large flexible structures they can be also attributed to secondary effects associated to the elasticity. One of the most interesting issues in modeling large flexible space structures is associated to the evaluation of the inertia tensor which in general depends not only on the geometric ‘fixed’ characteristic of the satellite but also on its elastic displacements which of course in turn modify the ‘shape’ of the satellite. Usually these terms can be considered of a second order of magnitude if compared with the ones associated to the rigid part of a structure. However the increasing demand on the dimension of satellites due to the presence for instance of very large solar arrays (necessary to generate power) and/or large antennas has the necessity to investigate their effects on their global dynamic behavior in more details as a consequence. In the present paper a methodology based on classical Lagrangian approach coupled with a standard Finite Element tool has been used to derive the full dynamic equations of an orbiting flexible satellite under the actions of gravity, gravity gradient forces and attitude control. A particular attention has been paid to the study of the effects of flexibility on the inertial terms of the spacecraft which, as well known, influence its attitude dynamic behavior. Furthermore the effects of the attitude control authority and its robustness to the uncertainties on inertial and elastic parameters has been investigated and discussed. [Copyright &y& Elsevier]

Abstract: Low risk reentry vehicles, as recently proposed, may represent the right answer for the future demands of space exploration, Space Station operations, and space tourism. In this paper the low risk features of sharp reentry vehicles are discussed. In particular, the concept of boundary layer thermal protection is illustrated with reference to a three-dimensional nose-cone geometry. The flow field around the fuselage tip is found by Computational Fluid Dynamics (CFD) calculations. The critical aerothermal conditions in the velocity-altitude plane are identified, in terms of the highest temperature surface points that belong to the Thermal Protection System (TPS) (i.e. the stagnation point of the fuselage tip) and to the structural material (i.e. the point at the junction of the TPS with the structure). Typical reentry trajectories for a concept vehicle are computed according to this new descent philosophy, which comply with thermal boundaries. The influence of the chosen aerodynamic solutions on reentry heating and on downranges and crossranges is then discussed. [Copyright &y& Elsevier]

Abstract: The paper evaluates the disturbances on typical Fluid Physics experiments by numerical experimentation and shows how convective motions are originated by two vorticity production terms, one of which is related to the curl of the acceleration field. Isolation mounts may be responsible for the translation of linear g-jitter into pendular motions of the microgravity payload and therefore may induce convective motions also in an isodense liquid medium. Typical numerical results are shown of the different flow fields induced in an otherwise quiescent fluid cell by the different accelerations that characterize the ISS microgravity environment. Criticisms are made to the motivations at the base of the current ISS specification and different specifications are proposed that take into account the entire g-jitter spectrum and the presence of pendular motions of the fluid cell. [Copyright &y& Elsevier]

Abstract: The different acceleration components on the ISS that are responsible for the generation of convective motions in a fluid cell either in the presence of density gradients or in quasi-isodense processes, are analyzed. The NASA measurements of the quasi-steady and periodic acceleration on the ISS are considered and their effects on fluid-dynamic experiments are computed and discussed under different assumptions. In particular, numerical simulations are carried out to identify the relative importance of linear and pendular accelerations, due to possible rotations of the P/L around its center of mass. The effects caused by variable accelerations created by an isolation mount that exhibits an attenuation factor not constant within the payload volume, caused by the reaction forces of the umbilicals, are computed and analyzed. [Copyright &y& Elsevier]

This paper deals with the microgravity experiment on droplets, wetting and coalescence prevention, performed on the MAXUS 5 sounding rocket launched in April 2003 from the base ESRANGE located in Kiruna—Sweden. The aim of the experiment was to study wetting and coalescence prevention phenomena, induced by thermal Marangoni flows in drops bounded by a non isothermal immiscible liquid matrix.A failure in the on-board procedure occurred just after lift off, so the automatic experimental sequence did not start, but PI''s switched to the manual mode and managed to run the experiment by telescience operative mode directly from Naples. A hemispherical drop of silicone oil was formed under microgravity conditions in a matrix of Fluorinert. The drop was anchored to a moving metallic disk (10 mm diameter) held at controlled temperature. A temperature gradient was initially established in the liquid matrix controlling the temperature of a fixed plate. During the experiment, a thin liquid film (about 100 μm thick) could be observed at sufficiently large temperature difference between the moving drop and the fixed disk (wetting prevention). The decreasing of the film thickness, as expected, was detected when the thermal gradient was reduced until wetting occurred at a “critical” temperature difference. A similar behaviour was observed during the non-coalescence study (coalescence prevention).For the different conditions investigated, the Marangoni flows in the meridian plane of the drop were detected by two CCD cameras (with different fields of view) looking at the tracers particles illuminated by an orthogonal thin laser light sheet.The paper reports the preliminary results of the microgravity experiment and a number of numerical simulations aimed at explaining and correlating the experimental findings. [Copyright &y& Elsevier]

The paper wants to approach the problem of the disturbances mitigation on the International Space Station (ISS) from a purely scientific view point by evaluating and trying to minimize the effects (fluid-dynamic disturbances) more than trying to minimize some of the causes (as achieved by Isolation Mounts). A study case, consisting in a cylindrical test cell filled with a silicone oil in presence of a temperature difference ΔT, has been identified to reproduce the ISS microgravity environment (when in presence of a steady residual-g) on ground by properly changing the fluid properties, the dimensions and the imposed temperature difference. The orientation of the cell with respect to the vertical direction has been changed using an appropriate device that corresponds, in the MGE, to different angles between the cell axis and the residual-g. The maximum distortion of the temperature field has been evaluated numerically and experimentally by measuring the maximum temperature difference, in the mid-cross-section, between points that would exhibit the very same temperature in a purely diffusive, quiescent state. Further experimental tests have been performed, using a different configuration, to measure the surface temperature distribution with an infrared thermocamera. The correlation between experimental and numerical results are in good agreement and the results indicate that the experiment facility can be properly oriented to minimize the convection disturbances. Another experiment for the study of the temperature/concentration distortions induced by residual-g and g-jitter during experiments on diffusion/thermodiffusion is proposed. [Copyright &y& Elsevier]

The inulinase production by yeast K. marxianus var. bulgaricus growing in yacon extract was investigated. The microorganism showed good development in yacon, higher enzymatic activities were achieved at 30% and 40% (v/v) of extract. The cultivation temperature (20, 25, 30, 35, 40 °C) neither influenced the growth or the enzymatic activity. The optimum cultivation pH was 3.5. The highest activity was observed at 60 °C and pH 4.0. At temperature of 55 °C and 60 °C occurred sharp decrease in the enzyme activity. [Copyright &y& Elsevier]