There a LOT of reasons why we will probably never be able to back in time, but it is certainly possible to go forward into the future. The Daedalus group has already designed several space ships capable of such speeds that if you rode in one for 10 yrs or so you would be in the future when you got back to earth. I realise this has no practical value, hence the gov. not involved, but why hasn’t some billionaire done it. Hell, if I had the $, I sure would. Can you imagine the trip-out factor? Would any one else here do it?
There is presently no way of cocking a human being in a spaceship for 10 years. That’s without counting the insanity factor. And that’s certainly not counting the fact that there is presently no way of propelling a spaceship fast enough to have a real influence on the traveller’s “timeline”. At 10% of the light speed, 1 year for the traveller would equal 1 year and 2 months in Earth’s time. And that’s at 10%!! That equals to 108 000 000 Km/h which in turn is roughly equal to 64 800 000 MpH. Time travel using relativity principles is simply out of our reach. For now…
Heck, you don’t need a space ship. In the morning, I leave home, get in my car, and drive to work. When I get there, it’s in the future! Usually about 10 to 15 minutes in the future, but it’s a start.
Hell, I’m constantly traveling forward through time, myself. At the rate of about 3600 seconds per hour.