Speaker
Mr
Lorenzo Bucci
(Politecnico di Milano)
Description
Nowadays interest on large structures, ISS like, to serve for a long time as orbiting outposts place in strategic, possibly long-term stable locations, is increasing. They can serve as a support for far target robotic\manned missions, for planetary tele-operated robotic surface activities, as scientific labs for sample return missions in preserved environment avoiding contamination, for astronauts training, for refueling and maintenance of deep space vessels. Whatever the exploitation is such large structure would undergo numerous docking\undocking activities with a time dependent matrix of inertia; it should require a large lifetime along with orbital stability and, being the structure extended, a strongly coupled attitude\orbital dynamics is expected. Lagrangian points are an evident appealing location for such an infrastructure, offering stable trajectories together with well suited relative positioning with respect to the Sun and the other planets to be considered in the three body system [1].
The investigation of Large Structures coupled dynamics, whenever located in Lagrangian points proximity, is the topic of the paper. The configuration design\6 DOF dynamics coupling is deeply investigated to, eventually, drive the infrastructure system and operational design. Because of the wideness of possible practical applications in the incoming decade, the Earth Moon Lagrangian points system is here considered.
The paper firstly shows the natural periodic orbit-attitude solutions, introducing maps to visually identify the regions where those solutions exist, under the CR3BP approach. The maps are parametrized over the infrastructure inertia properties, and solutions are classified with respect to the number of attitude rotations per orbit. This taxonomy supports preliminary mission design and operations analysis, in verifying the impact of variations in inertia properties (e. g. after docking/undocking of a module) on the attitude and orbital motion. Practical applications of such solutions are discussed, with attention to future missions (e.g. ARM, HERACLES) which could benefit from a full exploitation of the coupled orbit-attitude dynamics. Distant retrograde orbits (DRO) are investigated with greater detail, since their stability properties are appealing for numerous applications. Extension to other orbit classes is then briefly discussed, underlining differences and similarities with the presented results and suggesting new fields of investigation.
The aforementioned discussion introduces then to the rigid body finite extension enhancement in the model, to assess its effect on the orbital motion and analyze modifications in the stability regions. Solar radiation pressure (SRP) disturbance is part of the model enhancing as well, assessing its effects on stability regions as a disturbing action on the whole coupled 6DOF dynamics. Design parameters and drivers are obtained from SRP analysis, with some conclusions on critical aspects and possible requirements for a large structure in the Earth-Moon system. The need of an active attitude control is preliminarily discussed, with attention devoted to requirements needed to guide the control strategy and system design.
Effects of flexibility in the large infrastructure are then introduced in the model; energy principles and linear modal analysis are the mathematical approaches exploited to assess whether orbital and attitude motions could excite/be excited by small vibrations of flexible structures.
Preliminary considerations are deduced from the classical flexible dumbbell model, and are extended to lumped mass models of given complexity.
[1] B. Hufenbach, K. C. Laurini, N. Satoh, C. Lange, R. Martinez, J. Hill, M. Landgraf, A. Bergamasco, International missions to lunar vicinity and surface - near-term mission scenario of the global space exploration roadmap, 66th International Astronautical Congress, 2015.
| Applicant type | First author |
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Primary author
Mr
Lorenzo Bucci
(Politecnico di Milano)
Co-author
Prof.
Michelle Lavagna
(Politecnico di Milano)
