Living Within Limits - Chapter 2

Overpopulation: Escape to the Star?
Question:  Can people colonize stars in the near future?

Hardin believes that modern society practices idolatry by worshipping at the 'Altar of Progress" - which equates to marveling at the ability of technology and economy to sustain perpetual growth (implied - to infinite).  The most common remedy to the inconvenience of overpopulation offered up by the Priests of Progress is the 'Dream of Extraterrestrial Migration".

Is it likely?  running the numbers...

Closest star to the Sun:  Alpha Centauri
Distance:  25 quadrillion (million million) miles
Speed of light:  671 million mph
DistanceLight Years:  4.37
Fastest man-made spacecraft:  Helios - 0.157 million mph (1/4300 speed of light)

Scientists Sabastian Von Hoerner postulated that the highest feasible speed for interstellar travel is approximately 3% of light speed - which translates to roughly 20,000,000 mph (roughly 128 times current top speed).  At that theoretical speed, it would take approximately 140 years to go from the Earth to Alpha Centauri.  In summary, we would need to create a vehicle that goes over 100x faster than the fastest one we have ever built, and then travel 140 years (5 generations). 

and the energy it would take...

The ship would require both fuel for acceleration/maneuvering, as well as energy to sustain life (human, animal, and plant... did you think humans could populate a planet by themselves?)  By the time the ship reached Neptune, the sun would begin to diminish, both physically and as a viable source of energy/fuel.  Most of the trip would be made in the dark of space, which as Hardin points out, is 'more romantic than nourishing'. 

how much would this cost...

A nuclear submarine costs approximately $1B, which translates to roughly $7M per sailor (excluding operating costs).  A spaceship that is able to support 5 generations, with supporting animals and plantlife, across 4+ light years is likely to cost significantly more than a nuclear submarine.
  
the problem is compounding faster than the (unlikely) solution...

The world economy (global GDP) is currently $61.1 Trillion dollars.  Assuming we could devote our entire economic output for a year to sending people to Alpha Centauri, and assuming it costs $7M per person (the same cost per person as a nuclear sub), then we can send roughly 8 million people every year.

The current estimate of population growth is 1.17%.  On the estimated base of 6.7B people, that means its growing at roughly 70M people every year.  Population growth outpaces spaceship sendoff rate by a 7:1 ratio (also not mentioning the fact that I would not want to be one of the ones left on Earth, when all its resources, year after year, is being devoted to a select few who are going somewhere else).

what would life be like aboard the spaceship...

It would be spartan.  The energy & economic costs of the trip would require that only the bare essentials be brought along.  In addition the impact that a tiny asteroid would inflict upon a vessel traveling at such high speeds would be catastrophic - it would require tremendous resources to carry out repairs.  There would need to be draconic measures imposed on the population of this ship, in order to insure its survival (3 kids?  Good luck...)

who is 'ideal' for the trip...

This final point is a philosophical one.  Due to the austerity measures, only some would be 'good' candidates for the trip.  Sadly, the same people who would be good for the trip, are the very ones whose behavior, if duplicated by the greater population, would have made the ship completely unnecessary!  Ultimately, it is this logical fallacy which reduces the 'space colonization' solution to the realm of science fiction.