You have to go really, really fast to get 100:1 time dilation (like, 99.99% c) -- probably fast enough to make interstellar travel hazardous in a "collide with

You have to go really, really fast to get 100:1 time dilation (like, 99.99% c) -- probably fast enough to make interstellar travel hazardous in a "collide with a hydrogen atom, it hurts" kind of way. Also, the energies involved are absurd.