Perhaps the most critical factor in any attempt at space travel is propulsion. The distances we must travel are enormous, the speeds we can reach are puny, and it is very expensive. NASA’s Space Shuttle costs $1 billion to launch and can travel at an amazing 27 800 kilometres per hour. However, it would take the Shuttle five and a half days to get to the Moon. Getting to the nearest star is all but impossible with today’s technology – hence the interest (not only in science fiction) in more exotic methods of spaceflight.

Much more advanced technologies are based on systems that do not require reaction mass, the stuff that pushes the rocket forward. The control of gravity is very popular here. David Weber describes a powerful drive in “Path of the Fury” (1992). Each ship can generate a small black hole in front of itself. As the ship falls toward the hole, the hole is moved by the ship – thus the ship continuously falls and accelerates. The concept of building lighter space vehicles with larger fuel tanks has nearly reached its limit. New engines with new fuels will be required to explore our own Solar System more fully and develop permanent outposts in space. Going to the stars will require a great leap in the conversion of known science into usable tools.

| Index | Space Stations and Space Colonies |