Can we please implement some sort of rule that KoC has to stop posting completely irrelevant posts?
As far as I'm aware asteroid belts aren't actually that populated, it's just that relative to the rest of the universe there are more bodies. It shouldn't be too hard to navigate through them though.
Problem with building a ship in outerspace is that you'd still need to move all the materials up there in the first place, in which case you may as well build it on earth, where you don't need to bring your own oxygen for welding, and any changes in the plans won't require another launch.
Problem with going anywhere outside of the moon is that it'll take such a long time to get anywhere. The next closest solar system is Alpha Centauri, which is about 4 light years away. Obviously we can't travel at the speed of light, so let's say even 10% the speed of light. First off, that would be 40 years of travel, a long, long time, and very easy for something to go wrong. A 40 year journey would mean a very large ship, of mass ~90000000kg. So the energy required to get to that speed with something that big is .5*(90000000)*(.1*3000000)^2
That's roughly 4*10^22 J, or about 100 times the current world usage. That is completely impossible.
So to go anywhere, we'd need to come up with a completely new way to either make energy, or something else entirely new. So new that I couldn't even say what it is, but it would also have to revolutionise our understanding of modern physics. It might be possible, but I'm extremely sceptical about it all