I remember asking once, we don't we just shoot our surplus trash off into the sun and was told that by the cost of launching it outweighs the benefits. Fair!
But what about all of the old satellites and space stations? Why don't we just send a giant magnet around the earth once or twice and then slingshot all that space junk into the sun and thus giving all science fiction writers (when they return from their strike) a plot point they can no longer use in their film scripts?
Seriously though, without the cost of breaching the atmosphere, this seems really cheap to pull, why don't we do this? Why isn't this a standard thing?
Think of it as a representation of how much energy is needed for orbits. To get to the moon you need about 1.7 km/s of delta v. To get to sun you need 30 km/s of delta v. To escape our solar system you only need 18 km/s of delta v.
Think of it this way. The earth is moving horizontally to the sun at 29.78 km/s (107,200 km/hr). In order to hit the sun you have to cancel all of that movement otherwise You'll miss the sun and enter a new elliptical orbit.
Hmmm, I was thinking we could slingshot our own orbit. Use the centrifugal fly South and use a couple thrusts to point towards the sun. I was clearly over simplifying it.