OK I'm not sure if this is the proper place to post this question, but since there probably is no correct definitive answer but hypothesis ....here goes... What is the fastest speed in the form of percentage of light speed, that we will realistically probably ever be able to get a spacecraft going? NO warp drives,..no FTL drives like in the movies or on SciFi (not SyFy).because I understand there is No law of physics preventing those from hypothetically being possible but I have never heard even an incling of an idea how one could even begin to actually make those possible.What I mean a space craft large enough to carry a crew and everything needed to support it,or even seceral space probes.Using any one of the various different propulsion types, different engines that have been designed and tested and even some of the ones that have not quite been built because technology is not quite there yet but will realistically exist in the future. Combined with sources of energy that will realistically exist at some point. What's the fastest speed we can realistically count on being able to explore the galaxy at SOMEDAY. For example will we be able to get a craft going at 10 to 20% the speed of light?? I just wonder because if we could get a craft going to 20% the speed of light than we could send probes out to our closest neighbors in the galaxy.the alpha centauri stars. They are what 4 light years away, so at 20% Light speed it should take what?.. 20 yrs to get there approximately? And then data and pictures could be sent back at the speed of light. So in under 30 yrs we could have the answer to the question is there life around our closest neighbors.And on to each star in our neighborhood. If we could get going that fast we could realistically find out the answers to a lot of questions in just a single or just or up to a few life times...and not 100,000 yrs or whatever it would take going the speed of what is now our fastest moving space craft, the new horizons probe. just to get 4 light years away. It seems like it is a matter of power...energy... that would decide how fast we could get a craft going using one of the propulsion systems we have or have some understanding of how to actually make work. So I guess I'm just wondering if any of you have ever heard this question or something like it ever asked or discussed before by someone knowledgeable in a field relative to this..someone much smarter than myself!