There's absolutely no reason to believe that anti-gravity technology is not already in use for space travel. Personally, I don't buy the idea that we cannot already travel to mars.
Automobiles haven't changed in over 100 years! Just 4 wheels and gasoline. Meanwhile, we make plenty of other tehcnological advancements and we're supposed to believe we don't have ships that can cruise around our solar system? Laughable.
NASA is talking about "progress", I'm talking about progress.
Don't let science fiction films distort your sense of how far along we are.
I'm speaking from research, however it's not really important or anything I obsess about.