TIL that it takes less energy to launch something out of the solar system than directly into the sun. Apparently its because the massive gravity of the Sun causes objects to orbit instead of pulling objects into itself. Why?

Question

TIL that it takes less energy to launch something out of the solar system than directly into the sun. Apparently its because the massive gravity of the Sun causes objects to orbit instead of pulling objects into itself. Why?

In: Physics

Answer 1

It is because you are not starting from nothing.

You are starting from earth which is in orbit around the sun.

If you had an object that was as far away from the sun as Earth is but not moving around and you let it go, it would more or less drop straight down without any effort on your part.

However since you are starting from Earth, you are starting with all that orbital speed that Earth has in respect to the sun.

To get down to the sun you need to slow down from that enormous speed. (something like 100,000 Km/h).

It takes as much energy to slow down from going that fast as it would to speed up to that speed from nothing. Escape velocity is less than two thirds of the velocity needed to fall into the sun.

We would have a similar problem when deorbiting for earth orbit back to earth, but we cheat there by using the earth’s atmosphere to slow down returning spacecraft. That is unfortunately not an option for trying to fall down into the sun.