>The fastest man-made object (spacecraft) was the NASA-German joint ventures Helios 1 and 2. They reached speeds up to 156,000 mi/hr. That may have been helped along by their proximity to the Sun; I don't know.
In general, the fastest man-made objects obtain part of their final speed by a "gravitational sling", in which the sun and planets intervene. The basic idea is that a craft approaches, say, Jupiter, and leaves at a different angle. The object is accelerated when it approaches the planet, and decelerates again when it leaves the planet. The speed (scalar) is the same when it approaches the planet than when it leaves; the velocity (vector) obviously is not, since the direction changed. Therefore, the speed (relative to the sun) will also be different, since the planet moves (relative to the sun).
Hilmar.
Difference in opinions hath cost many millions of lives: for instance, whether flesh be bread, or bread be flesh; whether whistling be a vice or a virtue; whether it be better to kiss a post, or throw it into the fire... (from Gulliver's Travels)
