At 100 feet per second how long does it take to get to Mercury from earth?

Answer 1

On average, Earth is 1 AU from the Sun, and Mercury is 0.4 AU from the sun.

1 AU is approximately 491 billion feet.

The shortest distance between the Earth and Mercury is 0.6 AU (when all three bodies are in a line with Mercury in the middle).

0.6 AU * 491 billion feet per AU is approximately 300 billion feet. 300 billion feet / 100 feet per second (velocity) is 3 billion seconds.

However, because the planets are in constant motion at different velocities around the Sun, the shortest distance between Earth's orbit and Mercury's orbit is not necessarily the path that takes the least amount of time (you would need to spend time to overcome the velocity of the earth to get on a straight line toward the sun and then catch up to the velocity of Mercury in order not to smash into it, or you would need to wait for Mercury to swing around). Most inter-planetary trips are curved, and you'll need to accelerate and decelerate gently which makes the total travel time somewhat longer then 3 billion seconds.