The beginning of the Maxwell Empire Books.
Back in 2015 when I first wrote about humans expanding to other solar systems I had them travelling in cylindrical spaceships as long as from Albury to Melbourne, that is 300km, and with a diameter the same as Bendigo to Bright. The details of this can be seen at https://www.besteducationtours.com/index.php/max-blog/item/34-maxwell-next-stop with a couple more two weeks later, by which time I had concluded that sending humans was not feasible.
Robots were the answer, taking the DNA information of all Earth life. The importance of storing said DNA was obvious because the runaway population growth of humans is resulting in some species becoming extinct. A second matter is to store the DNA in places more than 70m above present sea level because global warming is going to melt all the ice and sea levels will rise. When this has happened before the sea has gone up that far on present sea levels.
It was then necessary to reproduce the life from the DNA. This is invented in 3108 by Diane Hunter which means Earth 2, 3, 4, …, 234, are possible.
You will have noticed that the initial calculation of the time to get to a planet ten light years away was quite short. This assumed continuous burning of the rocket engines but the fuel necessary is excessive. My subsequent calculations have five years of acceleration and five years of deceleration. The latter will be a bit shorter because of reduced mass from fuel use.
The present interest in sending humans to Mars is a waste of resources. All research should be on producing robots adequate to do the necessary tasks. The future spreading of humans throughout the universe requires robots developed to do everything so we need to concentrate on this. Not R2D2 types but more K-Nine as humanoid robots will result in animosity as all jobs are done by robots.
Hence advice to young people, become a robotics engineer, not an astronaut.