[Guardian]

anyone done any time dilation calculations for travel time?

Nope!

right now if you get the right slingshot orbit with a solar sail ship you can get approx .7C or 70PSL.
figuring in the time dilation factor it's about 14 years on ship for every 20 years traveled. or close to 25% slowdown.

given that I wouldn't mind making the trip out to Alpha centauri in cryo sleep on a sufficiently advanced ship, after all 40 years there and back isn't nearly as bad as 10,000 years.

Crazy to think about. Would be pretty insane, but we need to get some interest in space exploration going first. Until then, no incentive for some research into getting specifics right. I'm sure there's plenty of opportunity to monetize, it's just a huge risk with no guaranteed return.

basically it's an earth sized space cannonball.

...and its terrifying when you put it like that. Imagine a planet getting smacked with that one? Yikes.