The big trick is that if you could build a space craft that could accelerate continuously at one gravity you could be anywhere in the galaxy in a couple of years. One year of accelerating at one gee would bring you pert near the speed of light, and while your velocity measured relative to Earth might not increase much after that, you and and everyone else aboard the ship would start to experience extreme time dilation, i.e. time would slow down for you, so you would need to keep a sharp eye on your clock in order to determine when to start slowing down so you don't miss your destination. One minute at the speed of light with a time dilation factor of 10 will take you 600 billion feet, or a little more than one AU (astronomical unit, the distance from the Earth to the Sun, about 93 million miles or eight light minutes).*
So how do you build a spaceship that can accelerate continuously at one gee? The trick is you need a very high exhaust velocity, and for that nothing beats a linear accelerator, the big old monsters physicists are using to explore subatomic particles. Feed it a steady diet of iron particles for magnetic reaction mass and power it with a nuclear power plant from a submarine and off you go.
- Light travels 186,000 miles per second. Let us round that up to 200,000 miles per second to make things easy on ourselves.
- Multiple by 60 seconds per minute and we get 12 million miles per minute.
- Multiple by 10 for our arbitrary time dilation factor and we get 120 million miles, which is a little more than the distance from the Earth to the Sun.
How to get started in space exploration, in five easy lessons: