script.rb can't run from rails controller

Hi,
I wrote script to execute remote commands using net/ssh.
my script works fine when I run it from command line.
But when I try to execute it from rails controller I got an error.

`require': no such file to load -- net/ssh (LoadError)

can anybody help me to understand what I am doing wrong.
Thanks

Rails controller
@result=system "ruby script.rb"
