How much fuel do you need?
As you may have noticed, accelerating your spaceship to near-light
speed requires a lot of energy.
Your spaceship (with you on board) has a mass of 1000 kilograms
on Earth. If you wanted to accelerate to 0.866 times the speed
of light (about 260 million meters per second), you’d need
a hundred thousand trillion (100 000 000 000 000 000)
joules of energy. That’s
the equivalent of 2.5 billion (2 500 000 000) liters of gasoline.
As you go faster, your mass increases, and the required energy
Suppose you wanted to increase your speed from 0.9 to 0.99 times
the speed of light. You’d need almost five times as much
fuel as you used to reach 0.9 times the speed of light in the first
By the way, so far we’ve only talked about the energy you
need to accelerate your spaceship. Don’t forget that once
you get to your destination, you’ll need the same amount
of energy to slow it down!
|This graph shows how the
fuel you need increases with your speed. As you approach
the speed of light, the amount of fuel you need approaches
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