Interesting note: Time dilation from earth for observers = 365 * 2 = 730 years.
Now I realise there is a big mistake somewhere, but I cant remember what it is, if someone smarter could tell me that will be great thank you. Please excuse the rudimentary math - thank you.
Matter travelling anywhere near the speed of light has a lot to contend with.
Proxima Centauri is ~4 light years away, not a half of a light year.
http://www.projectrho.com/public_html/rocket/enginelist3.php...
The numbers there indicate that the Orion design doesn't have the sort of exhaust velocity you'd want to get up to 0.95c
That site's also useful reading for all the OTHER downsides: for instance, traveling at 0.95c through space means that everything in your way is hitting the ship at 0.95c. Even stray hydrogen atoms are no picnic when they're arriving at that energy...