Subject: Is it possible to build a nuclear starship?

Iam hard sci-fi writer, and I am interested in interstellar travels.
 Ive read a lot about spacecraft propulsion, especially nuclear pulse engines, 
such as Project Orion, Medusa, MagOrion and Mini MagOrion. But I still dont 
know how fast could actually travel -  some write about 1% c, some even 10%, so 
its quite unclear.
The same is true about some other concepts, such as VISTA, ICAN, VASIMR etc. 
I need to know whether some of these are able to reach sufficient speed (I mean 
for generation or sleeper ships, speed 1-15% c.)
How much propellant would be needed?
Ive asked this question before, but you told me, that there already was an 
answer on your site. Well, it wasnt there, so I send it to you once again.
Thank you for your patience.

Re: Is it possible to build a nuclear starship?