Looking out from the continent-sized cities and vast game preserves that may be our future on this planet, youngsters will dream that when they are grown, if they are very lucky, they will catch the night freight to the stars.
Carl Sagan, The Cosmic Connection (1973)
By the end of the 21st century we will have imaged Earth-like planets (if these worlds exist) orbiting nearby stars, and our probes will have reached the heliosphere, and at least, the inner fringes of the Oort Cloud.
Fission propulsion will probably be incapable of carrying humans to these beckoning new worlds; fusion-pulse may remain politically and socially unacceptable, solar sailing is too slow and antimatter too expensive. This will be a time of vast change on Earth as our population peaks and nation states begin to give way to a true global civilization. Is there any hope, then, for a propulsion system that could take at least a few humans to habitable worlds orbiting nearby stars, on missions that begin late in the 21st century?
As it happens, there is one star-travelling approach that may become feasible by the middle of the century. Figure 7.1 presents the various aspects of this approach -beamed-energy sailing. A solar powered station is located closer to the Sun than the starship. Solar collectors focus sunlight on a solar pumped beam projector attached to the solar collector array. A laser beam or particle beam is generated by the power station. This is directed at the distant starship with the beam divergence angle shown. The starship, which consists of payload attached to a sailcraft, accelerates to its cruise velocity by the exchange of momentum with the impinging beam.
As the starship approaches the destination star, it applies a magnetic field (or magsail) for the first stage of deceleration. The magsail reflects interstellar ions, acting as a magnetic dragbrake. For the final deceleration stage, the craft decelerates to planetary velocities using a solar sail directed at the destination star. Similar magnetic techniques may have application in changing spacecraft direction in
Sail craft accelerated by impinging beam
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Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.