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# starship-design: FTL drive designs

```kyle writes:
> Another idea, perhaps the most promising aside from my earlier
> design, is forgetting FTL completely.

Oh, phew, I was hoping you'd get to that eventually :-)

> If you have to travel say 280 light years, at light speed this will
> take 280 years.

Well, that's the funny thing about relativity.  If something travels 280
light years from Earth, it can't get there any sooner than after 280
years of Earth time.  BUT, relativity says that it can be achieved in
arbitrarily short amounts of ship time, due to the effect commonly known
as "time dilation", as long as you have enough energy to accelerate and
decelerate the ship to velocities as close to c as desired.  The less
time you want the passengers on the ship to experience, the faster you
accelerate the ship.  Clearly this has limits based on the amount of
acceleration the occupants of the ship are capable of enduring and the
amount of energy you have available, but having it take one year of ship
time is completely physically possible.

As an example, if (big if) you are able to build a ship that can
accelerate at one g for 40 years continuously, it could cross the Milky
Way in those 40 years of ship time, but 100,000 years of Earth time.

Relativity doesn't rule out the possibility of getting anywhere in the
universe in a human lifetime, although a human might have to be
protected from hundreds or thousands of gs of acceleration to make the
longer trips.

Read _Spacetime Physics_ and you'll get the full details.

```