I think I understand your question now, Success_Machine. You're looking at it in terms of how many people will actually be able to participate in any future space program.

The answer for a very long time to come will be, not many, compared to the population of the Earth. It would take millions of launches per year to simply keep pace with population growth, if you think in terms of emigration. There are millions of commercial aircraft flights per year, so it's not inconceivable that space flight could someday achieve that level of traffic. But it won't be within my lifetime or yours.

I have accepted that I will never personally benefit from the space program. Yet I support it strongly, and as a citizen I'm willing to support making sacrifices that might impact me personally. It's simply the right thing to do.

Someday our descendents will benefit from what we do today. Collectively we should think like parents who work to build a better future for our collective children. We should be happy at the thought that they will reap the rewards from what we sow.

Humanity won't spread throughout the universe through emigration. We'll spread through propagation, sending out small numbers of humans to found colonies, whose members will reproduce and "stock" the new worlds with humans "grown" on the spot.

The object of the exercize is to spread our DNA and our memes, not our bodies. In the most basic sense, humanity is a concept too, whose physical characteristics are described in DNA and manifested temporarily in bodies; and whose intellectual and spiritual achievements are recorded in the knowledge and cultures and beliefs our colonial children inherit from us and take with them. We are the parents of a spacefaring civilization.

No individual can live forever, but humanity can.

I believe that a "spacefaring civilization" is really all about humanity's need to reproduce. We must heed the call of life itself to grow and spread.