A group of scientists and engineers recently got together in Dallas, Texas for this year's Starship Congress. Their goal was to examine the major challenges of extrasolar space flight and how we might meet them in the future. A lot of crazy, awesome proposals were put forward during the conference, but in the area of human colonization, one proposal took the cake: Ken Roy's Shell Worlds.
Roy begins his proposal with the very real probability that the first humans to arrive in an alien solar system won't exactly be capable of simply putting up tents on whichever rocky planet they choose. If we ever hope to set up a permanent home out amongst the stars, we'll have to modify its atmosphere to suit our needs. How Roy plans on affecting this change, however, is straight out of sci-fi — comedy sci-fi.
To terraform an entire planet, Roy proposes encasing it in a protective sphere — ostensibly the equivalent of Planet Druidia's air shield from Mel Brooks' cult classic Spaceballs. Roy's version of the air shield would be constructed from layers of Kevlar, soil and steel. Inside this shell, colonists would be safe from radiation and would be capable of creating an artificial cycle of day and night.
Roy imagines a planet with cities hung like plants from massive moorings affixed to the shell's surface. Just as in Spaceballs, there would be a hatch that allows colonists to enter and exit the shielded atmosphere, possibly even one with an impossibly simple five-digit lock code.
All of that's well and good, but constructing a shell large enough to encase an entire planet and its atmosphere would be a ridiculously massive undertaking. Roy's theory of importing the materials needed to construct it would likely mean the strip mining of whole worlds. Even with some kind of army of spacefaring 3D printers, the project would take generations. People would be born and die waiting for their home's shell to be completed. They'd also have to bring their own starter atmosphere with them — something like seven percent of Earth's atmosphere, as well as a lot of water.
With all this in mind, Roy still believes that his shell worlds would provide the best chance for humans to survive on exoplanets. We're not so sure. After all, it took a Shwartz-wielding hero in a Winnebago to keep Planet Druidia safe and we don't see a budget set aside for defending against Mega Maid anywhere in Roy's plans.