The most likely form of non-generational inerstellar travel is finding high efficiency methods to accelerate ships to high relatavistic speeds so that time dilation reduces the on-ship time to sub-generation scales.
This sounds appealing but there are a couple of major problems.
The first is that you have to get to a significant percentage of light speed for this to manifest itself. Even at 0.95c time is only traveling at 1/3 of normal speed [1].
Second, the energy cost for this is truly mind-boggling. Doing so when you carry the fuel seems highly impractical. The best bet are laser highways [2]. But, you need to build that first.
The upper limit of laser propulsion isn't really high enough for that level of time dilation.
Third, traveling at these speeds makes any potential impact within even a speck of dust potentially fatal.
Lastly, fun fact: such a ship actually needs to be aerodynamic. Why? Above 0.95c the drag of hydrogen atoms in the interstellar medium will start to slow you down.
The thing will also be a weapon of mass destruction of plannet cracking potential, one "parking accident" away from making planets uninhabitable.
On the other hand a civilisation producing such things should hopefully be technically immortal with lots of distributed backups for each individual potentially affected by such accidents & resources to fix up any affected infrastructure. So still, totally worth it, go fo it! :-)
(Less advanced neighbors might still be a bit on the edge, so please be considerate.)
You could get to the nearest star in a few years and to the other side of the galaxy well within a human lifetime with "just" constant 1 g acceleration. Obviously this is far from easy but it doesn't seem like it is necessarily out of reach given a few thousand more years of continued technological development.
The quotes you put round just are doing a lot of heavy lifting. If you had a perfect photon rocket you’d only need 1000000000 kg of fuel for each kg of payload to do 1g to the centre of our galaxy and slow down again.
Okay, maybe you can use a laser or something so you don’t have to carry the fuel with you, but you’ll still need a staggering amount of energy because the rocket equation is a harsh mistress, and the relativistic version is even worse.
Yes, and there are at least 76 stars (i.e. potentially interesting destinations) within 100 light years of us [0]. So, assuming you can set an arbitrary course at 0.95c, and decelerate without turning the humans inside your ship to organic goo, you can reach quite a few interesting places.
Absolutely, there are huge problems and it may not ever be feasible to reach sufficient relativistic speed to slow time by an order of magnitude or more. However, I find it far more likely that we will find a way to solve these concerns than that we will develop FTL travel.
There is an interesting book called Lockstep that explores how a civilization might work without light speed. Essentially they have perfected cryogenic sleep and the entire civilization moves in lockstep, sleeping for many years between waking up which allows for ships to move between.
The book itself is only so so but the concept is interesting non the less.
I've read a SF story like this once, woth effectively a caste of space going pilots and scientists that spend most of their time in cryosleep on board of ships going at relativistic speeds, exploring the universe and starting colonies.
As long as they don't have relations with normal humans outosde the caste they live quite normal lives, meeting their friends from the caste relativity often from subjective PoV, with potentially decades or centuries going one between such encounters.
Still if you say want to settle down and have children, you won't likely wont see anyone else from the caste ever again as the next time one of your friends ventures to the system you settled in they will only encounter your descendants, possibly a couple generations after your time.
Send a small autonomous robot; at the destination it builds a high-bandwidth radio receiver and factories; then 'upload' the colonists by radio. Much more practical if your civilization is reasonably advanced.
