Earlier, in deep space, the time dilation would have been greater.
With time dilation, that was about 450 years for research and development.
You wondered why the time dilation was only two hundred percent?
Because of time dilation, however, the trip seems to the travelers only to last two years.
There are two kinds of time dilation, and both can operate together.
Fletcher should have been in the same age group, but due to time dilation, he is four or five years older.
However, there is no known theoretical way to cause such time dilation independent of these conditions.
Hope that time dilation puts many years between each of your battles.
Time dilation would allow events at the edge to appear to have happened billions of years in the past as seen from earth.
Due to traveling at near light speed, time dilation made it seem like less than that to them.