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user3652621
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Here are my R calculation results. The first two columns are fractions (and multiples) of $c$.

Effect.Veloc.Astronaut  Starship.veloc.stationary   Joules.100000.kg.ship
0.01                    0.01                        4.50E+17
0.1                     0.0995                      4.50E+19
0.2                     0.196                       1.80E+20
0.5                     0.447                       1.10E+21
1                       0.707                       3.70E+21
2                       0.894                       1.10E+22
5                       0.981                       3.70E+22
10                      0.995                       8.10E+22
20                      0.9988                      1.70E+23
50                      0.9998                      4.40E+23
100                     0.99995                     8.90E+23
1000                    0.9999995                   9.00E+24
10000                   0.999999995                 9.00E+25
100000                  0.99999999995               9.00E+26

As you can see, humankind's energy output for a year early 21st century would barely suffice to accelerate a 100 ton craft to 0.2 c.

energy scales 5e20 Joules are about 1.5e13 watts. A mature type I Kardashev (so by the chart above humanity cca 2300) could get 1e17 watts, so output of 3e24 Joules. Even for a type I, relativistic interstellar travel is difficult.

A type II, about 900 years at 3% growth rates after Type I is reached, have 10e26 watts to play with, or 3e33 J, so launching a small ship at relativistic speeds would take no more than a few seconds' worth of the civilization's power output, similar to a Saturn V launch for 20th century mankind.

That does still leave a few major difficulties.

  1. Energy density of fuel.
  2. Deceleration.
  3. Shielding

(1) Can be alleviated somewhat by beaming power to the ship. (2) Remains open, and I have no idea how to get enough reaction mass to decelerate on board. Perhaps a payload consisting of a miniaturized AI with self-replicating machinery (a few grams), or a Bussard Ramjet could work as well. (3) A lot of ablation mass will be needed since each dust particle in the way will strike my ship like a shaped charge. Perhaps a powerful laser to clear the path?

As to where I'd go, I would probably go to the nearest Earth-like world, see what or who is there.

PS: I know it's generally bad form to give an answer to your own question, and all this might hinge on some miscalculation, but I got too excited about the effective FTL drive!

user3652621
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