Well, the hull problem is there at 1% or 15% of c or whatever is reached. You don't get to wave how you get to the 1% of c speed away either, so let's not set d

Well, the hull problem is there at 1% or 15% of c or whatever is reached. You don't get to wave how you get to the 1% of c speed away either, so let's not set double standards; interstellar transport for humans _is_ all scifi-land. IMO, we simply can't get there with chemical rockets as we know them. Continuous acceleration in space is just any kind of engine that keeps running and provides thrust. We're not talking cars here. The estimation of the energy needed is easy to make sense of - what does it take to have a rocket (or more likely, some other engine) hover over the ground for 4 years using some kind of thrust? When we have that capability, we can pretty much do non-suicidal interstellar transport. But it requires new technology and for me, that constitutes sci-fi. Doesn't mean a conversation can't be remotely serious though, IMHO. But the point I actually wanted to make was, that whenever people talk of cruise-speed in interstellar transport, it seems to me like they haven't grasped the scope of interstellar travel with an intent of conquering it. Rather, they are implying it just can't be done - without arguing for it. The term 'cruise-speed' itself becomes an annoying passive-aggressive attack on the notion of interstellar transport. That was my original reason for posting.