This thread got me to thinking about the actual feasibility of traveling into the significant future. And by significant, I mean at least a couple of hundred years.
Here are the limitations as I see them:
Taking enough fuel
Taking enough provisions
Going fast enough to make it possible
So suppose the US decided to try to get someone to the year 2210 and was willing to spend the funds for it could current technology do it. If we built our fastest ship, loaded with supplies for say a 50 year trip (out and back), and further suppose you could refuel after leaving earths orbit before starting would it be possible? If not, how far into the future could we send someone with current technology?
We don’t have the technology to achieve a significant fraction of the speed of light, so no relativistic time effects. With that, I’ll answer 122 years.
The fastest space probe we’ve ever launched is traveling about 1.5 kilometers per second.
If we somehow were able to launch a probe that could travel 10,000 times faster than that (15,000 km per second) that still would only be 1/20th the speed of light.
At 1/20th the speed of light, the time dilation is about 1/10 of one percent. That would shave about a month off the travel time for a 100-year trip.
Don’t forget that time and space are related. If you don’t take into account the earth’s rotation(along with the motion of the earth around the sun, the sun’s rotation around the galactic center, etc.) when you get to the desired time, the space could be totally elsewhere.
When you have the technology to arrive at the “same” spot you left, you’ll also have the tech to plop yourself wherever you want to be.
You’re talking about time travel as the “poof we’re there” theoretical - and totally imaginary - kind of time travel. Since nobody has a clue as to how that would work, nobody can say ahead of time what the technical requirements would be.
The motion of the earth, sun, and galaxy are sufficiently well known that a relativistic speed trip through space that returns to an aged earth with a still young crew of the sort the OP refers to wouldn’t be any problem. We’re going to be in approximately the same place a mere 200 years in the future.
It’s my understanding that you need to be close to the speed of light or in really intense gravity for large differences in the relative passage of time to show up. We aren’t close to being able to travel that fast, and there aren’t any supermassive black holes conveniently nearby.
I expect that, long before we achieve the ability to build spaceships which can reach that kind of relativistic speeds while sustaining human life, we will have the ability to freeze people and revive them hundreds of years later. Or even to achieve immortality so that you can travel forward in time “the long way round”. Those would seem to me to be more practical forms of time travel.