Giancarlo Genta
Politecnico di Torino, Mechanics, Faculty Member
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Weapons appeared very early in human history. Indeed, we can say that technology began with weapons, at least those for hunting. It has been said that, from the beginning, humans felt the need to complete their diet with proteins from... more
Weapons appeared very early in human history. Indeed, we can say that technology began with weapons, at least those for hunting. It has been said that, from the beginning, humans felt the need to complete their diet with proteins from animals, but their physical structure was never designed to be a natural predator. Therefore, they had to resort to tools to make up for this serious handicap.
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The main scientific theme of the novel is extraterrestrial intelligence (ETI). Bioastronomy and SETI are, generally speaking, controversial subjects, because the basic issue of both, the existence of extraterrestrial life, is still an... more
The main scientific theme of the novel is extraterrestrial intelligence (ETI). Bioastronomy and SETI are, generally speaking, controversial subjects, because the basic issue of both, the existence of extraterrestrial life, is still an unproved statement. Even if there is a substantial difference of opinion, with astronomers and physicists generally for a positive answer and biologists for a more skeptical approach, many think that simple living organisms, comparable in complexity with our bacteria, are widespread in the Universe. More doubts are cast on the existence of extraterrestrial complex life and above all of intelligent extraterrestrials (ETIs).
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The history we have related so far has attempted to summarize the journey of homo sapiens from prehistory to the beginning of the conquest of space, paying particular attention to the events that saw Western civilization take on the role... more
The history we have related so far has attempted to summarize the journey of homo sapiens from prehistory to the beginning of the conquest of space, paying particular attention to the events that saw Western civilization take on the role of protagonist. The focal point of this path is the increasing role of the logical-rational component of humankind, which has been at the center of hopes and expectations over the future of our species since the Middle Ages. We have spoken, in this regard, of an authentic “faith in progress” that over the centuries, without interruption, has motivated millenarists, monks, merchants, capitalists and scientists. As we said at the beginning, humans are technological animals, and technology as we know it today is a product of rationality. Many innovations, from money to the wheel and from the airplane to nuclear energy, have been realized to answer to specific human needs, starting from a logical elaboration of the underlying problems.
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The application of the usual optimization techniques to the computation of low thrust interplanetary trajectories is made difficult by some criticality in the choice of the first approximation trajectory and thrust profile, needed to... more
The application of the usual optimization techniques to the computation of low thrust interplanetary trajectories is made difficult by some criticality in the choice of the first approximation trajectory and thrust profile, needed to start the numerical procedure. Some simple starting functions are here obtained with the aim of allowing to easily and quickly compute optimized interplanetary trajectories. General results regarding the relationship linking the travel time for the Whole interplanetary travel between the low orbits about the planets, the propellant consumption and the spacecraft performance can thus be easily obtained. The case of human Mars missions is studied in detail, and general considerations are drawn to identify some critical technologies which can allow to substantially shorten the travel time in case of human carrying interplanetary spacecraft or to greatly increase the payload, at equal initial mass, in case of slower cargo ships
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The variety of configurations for vehicles and moving robots not based on wheeled locomotion that have been suggested for the exploration of planets with a solid surface is so wide that it is impossible to deal with, or even just to... more
The variety of configurations for vehicles and moving robots not based on wheeled locomotion that have been suggested for the exploration of planets with a solid surface is so wide that it is impossible to deal with, or even just to mention, them all. Since the most common are those based on some form of legs, the present section is mainly devoted to walking machines. Apart from legged vehicles, only a few other approaches will be briefly described: wheels–legs hybrids, track–leg hybrids, jumping devices, vehicles on skis and apodal devices.
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Some type of housing must be used to maintain the flywheel in a vacuum and to provide personal safety from contact or, in the case of failure, from debris. Not all advanced flywheels need a containment structure. If the flywheel is... more
Some type of housing must be used to maintain the flywheel in a vacuum and to provide personal safety from contact or, in the case of failure, from debris. Not all advanced flywheels need a containment structure. If the flywheel is started beyond the earth's atmosphere, even the vacuum-tight housing is redundant. In other cases, it may be easier to protect persons or equipment with their own shields than to enclose the rotor in a burst-proof containment structure. The need for operating flywheels in vacuum usually only occurs with medium-energy or high-energy density types, and it is necessary for two reasons: (1) to reduce the energy losses because of aerodynamic drag and (2) to avoid overheating of the rotor. The aerodynamic drag increases rapidly with the peripheral speed and, hence, with the energy density. This chapter presents some spin-down tests undertaken on a flywheel and discusses their results. It further discusses the problem of aerodynamic heating of advanced flywheels.
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... The following two chapters deal with the study of the dynamics of ve-hicles modeled as rigid bodies. ... moment 120 3.5 Side force, rolling and yawing moments 125 3.6 Study of aerodynamic forces and moments 127 4. Longitudinal... more
... The following two chapters deal with the study of the dynamics of ve-hicles modeled as rigid bodies. ... moment 120 3.5 Side force, rolling and yawing moments 125 3.6 Study of aerodynamic forces and moments 127 4. Longitudinal dynamics 133 4.1 Load distribution on the ...
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Publisher Summary This chapter describes a transmission system as an important part of a kinetic energy accumulator. The transmission system is a compromise between many conflicting requirements. It must allow a continuous variation of... more
Publisher Summary This chapter describes a transmission system as an important part of a kinetic energy accumulator. The transmission system is a compromise between many conflicting requirements. It must allow a continuous variation of the transmission ratio and must operate efficiently under widely varying load conditions, often with the added problems of high-input rotational speeds. The need for high efficiency is particularly important during both the charge and the discharge modes. If the transmission efficiency is low, all the advantages of kinetic energetic accumulators can easily be lost. If the flywheel shaft is connected mechanically to a transmission, various types of variable-ratio transmissions can be used. The simplest solution is a variable-ratio belt transmission. It, however, has two main disadvantages: (1) the low value of the maximum transmissible power and (2) the limited range of transmission ratios obtainable. A reduction gear is usually needed between the belt transmission and the flywheel.
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Interplanetary missions are strictly dependent on the launch date. Mission planning requires a knowledge not only of the technological and cost constraints but also the study of the influence of the launch opportunity on the spacecraft... more
Interplanetary missions are strictly dependent on the launch date. Mission planning requires a knowledge not only of the technological and cost constraints but also the study of the influence of the launch opportunity on the spacecraft performance and on the feasibility of the mission. Pork-chop plots are effective tools to design interplanetary missions, providing a graphical overview of the relationship between the fundamental parameters of the mission design, namely, the launch date, the duration and the energy requirements. In this way it is possible to evaluate the best timing to accomplish the mission under current constraints. Plots of a similar type can be drawn also for optimizing missions based on low thrust or on propellantless propulsion—like solar sails. The cost function described in these plots may be the square of the hyperbolic excess speed, the ΔV, the ratio between the initial mass and the payload mass or between the mass of the propulsion system and the payload or the cost function J used in the optimization of the trajectory. In case of two-way missions, it is possible to plot a cost function of the same type, by adding the values related to the forward and the backward journeys, as a function of the duration of the two legs of the travel, once the stay on the planet has been fixed. In this way it is possible to optimize also missions which are intrinsically two ways, like human exploration missions or sample return missions.
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Human missions to Mars are still a goal for a more or less distant future. If we want to transform them into reality, then we must state detailed which address all the still unknown aspects and focus our efforts on the many details... more
Human missions to Mars are still a goal for a more or less distant future. If we want to transform them into reality, then we must state detailed which address all the still unknown aspects and focus our efforts on the many details remaining to be settled. The must not only address technological and scientific aspects, but must also concentrate on feasibility, affordability, and risk control if we are to transform a dream into an exploration campaign. It is likely that the road to Mars will involve the exploration and development of the Moon and that the experience gained on the Moon will be essential to later going on to Mars in a safe, affordable, and consistent way. As a means of assessing how feasible each project for human Mars exploration is at any moment in time, an index, the Human Mars Mission Feasibility Index (HMMFI), has been proposed.
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Mars is a small, arid planet of major geological and topographical complexity. Conditions on the surface in the remote past appear to have been rather more favorable to life than they are today. Whilst it is unlikely Mars still hosts... more
Mars is a small, arid planet of major geological and topographical complexity. Conditions on the surface in the remote past appear to have been rather more favorable to life than they are today. Whilst it is unlikely Mars still hosts life, particularly on its surface, things may have been different earlier on. The search for life, in particular for fossil life, is one of the reasons for exploring Mars, but it is not the main reason, and therefore if it turns out that life is absent, this must not be seen as a failure of Mars exploration.
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To travel to Mars, astronauts must spend several months in space. But space, and above all space beyond low Earth orbit, is a very harsh environment both for human beings and their machines, so it is essential to consider it in some... more
To travel to Mars, astronauts must spend several months in space. But space, and above all space beyond low Earth orbit, is a very harsh environment both for human beings and their machines, so it is essential to consider it in some detail. The danger of radiation is one of the factors that could cause us to postpone plans for a human Mars mission, or perhaps make it impossible. Whilst radiation is not necessarily a ‘showstopper,’ it must be considered very seriously. And if the vehicles for the mission are to be assembled in low Earth orbit, we must understand that environment too.
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More than half a century passed since the earliest serious plans for a human Mars mission and the perspectives are still unclear. While exploring Mars remains a fundamental goal for human space exploration, nobody is at present in the... more
More than half a century passed since the earliest serious plans for a human Mars mission and the perspectives are still unclear. While exploring Mars remains a fundamental goal for human space exploration, nobody is at present in the position of forwarding a serious prediction about a possible timeframe. In the last years, however, the several Space Agencies have forwarded new plans, the International Space Exploration Coordination Group (ISECG) has issued a Global Exploration Roadmap and even private organizations and companies made assessments on the subject. The aim of the present paper is summarizing the present situation with the aim of understanding the basic choices which planners of a human Mars mission must do
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A description of how the automobile evolved from its very beginning to our days would not be complete without a description of the evolution of the technologies aimed to design and build this product and of the evolution of the related... more
A description of how the automobile evolved from its very beginning to our days would not be complete without a description of the evolution of the technologies aimed to design and build this product and of the evolution of the related market. If this is true for any industry, this link between product, production process and market is even closer in the case of the automotive industry.