some runner wrote:
Oh goddammit! The force of the sun's gravity is immaterial here. the missile, once free of the earth's gravity and on the right trajectory, would travel to where the sun is, even if the sun was not there or if the sun had no gravity. don't you get it? The missile would only require the amount of fuel necessary to get away from the earth in order to get the 93 millions miles away. it would not NEED the sun's gravity to help it there. The sun's gravity would only make it accelerate along its path.
Wrong. You need more fuel than to just get away from the earth, because once you do that, the missile is still in an orbit about the sun. You need to get it into an orbit that intersects with the sun. This would either take quite a bit of fuel or, if travel time is not an issue, a carefully-plotted trajectory that will use a gravity-assist from a planet, which would still require extra fuel, albeit less. Sending it on a trajectory into the sun from the earth would require not just escaping earth's gravity, but also accelerating to counter most of the earth's 30km/s orbital velocity to allow the missile to fall more-or-less directly into the sun.