Just because something uses real physics and engineering materials that already exist, doesn't mean that it's actually possible in the real world & getting to the stars requires that we solve three or four very hard problems.
Impossible? Of course not. Much, much harder than the 'whee, we're all going to space!' crowd likes to think? I'm afraid so.
NB. GDP is not a good proxy for available energy for hopefully obvious reasons: Just because you have a high GDP doesn't mean that you have a lot of energy available, it may mean that you use the energy you have very effectively.