This one isn’t in sight just yet but could be one day.
Back in my 1950s childhood there was a radio sf series called Journey Into Space. At the conclusion of the final serial (The World in Peril) the defeated “villains” set off for Proxima Centauri in a fleet of mobile asteroids (method of locomotion unstated but apparently not rocket propulsion). It is stated that the voyage will take about seventy years, indicating an average speed of around 0.06c.
What we have since learned about the amount of junk existing even in interstellar space suggests that this is how any such voyage would have to be done. At that sort of velocity even hitting a snowflake or sand grain could do serious (possibly fatal) damage to a conventional space vehicle, and even hitting smoke particles or similar could erode away the hull cover. Also, exposure to cosmic radiation over several decades probably wouldn’t do the crew any good.
So it would probably have to be an asteroid, with the crew well below the surface most of the time. Hundreds of feet - perhaps miles - of rock, sand and gravel would absorb the radiation and all except the worst impacts, though by journey’s end the forward-facing part of the surface might well be worn smooth.
Looks like Charles Chilton (or his technical advisor Kenneth Gatland) will prove to have been right on the button.
Seems one challenge would be accelerating (and decelerating!) something so massive. We’d have to come up with more thrust than ion drives and solar sails can offer.
An old favorite, Greg Bear’s Eon, has the asteroid Juno hollowed out, spun up, fitted with drive systems, and sent on a 60-year trip towards a habitable planet:
Asimov wrote a non-fiction essay (“There’s No Place Like Spome”) about how asteroid dwellers might drift into being interstellar travellers by stages, as their ability to maintain a self-contained ecology grew. First they’d leave the inner system for the Kuiper Belt and Oort Cloud and at some point one of the Oort cloud colonies would be ready for a trip to another star’s Oort cloud
Inded. And if the Oort Cloud in indeed two light years in radius, and other stars have ones of similar size, they could pass from Sol’s Oort Cloud into Alpha Centauri’s without any discernible break.
This might be a better way than going directly from star to star, as on present evidence most exxoplanets would seem to be very uninviting.
This is a problem with the sf concept of the “generation ship”. Quite simply, if any ship or habitat is comfortable enough for people to live in it for decades or centuries on end, then it is probably more comfortable than any planet they are likely to find. John Brunner’s Lungfish, Chad Oliver’s The Wind Blows Free and Clifford Simak’s Target Generation all touch on this in different ways.