Realistically, the starships presented in the Starships section are capable only of interplanetary travel, not interstellar travel. The reason for this is simple: Even the best engine can’t accelerate a ship to light speed, and without light speed, interstellar journeys take tens of thousands of years. The speed of light is 186,000 miles per second. That’s 1,116,000 miles per round, or 66,960,000 miles per hour. Maneuvering a ship at this speed is a tricky proposition; by the time you notice an object in your path, it’s probably too late to avoid it. One must also consider relativity: The closer the ship’s velocity comes to the speed of light, the greater its mass. A starship cannot achieve light speed via simple acceleration, no matter how powerful the ship’s engine, as increasing the power only increases the mass.
The greatest impediment to traveling between the stars is time: What would be the point of sending astronauts to Alpha Centauri, for example, if, by the time they arrived, no one on Earth could remember why they’d gone in the first place? Time dilation—the slowing of the passage of time in relation to an object traveling at close to the speed of light—becomes a factor. A few years might pass on board the ship, while a few hundred years might have passed both at the ship’s point of origin and its point of arrival.