OrlandoNative wrote:Keith_w wrote:Would you mind explaining WHY I couldn't get a KEW to another planet? I am glad that you are a planetary scientist, which I am not, so you should be aware that Safehold is a planet, which could be used to provide the initial gravity boost. We don't even know if there are other celestial objects in the solar system. There has been AFAIK no mention of astronomy on Safehold.
As for the rest, I didn't say that it would be particularly effective, just that it could be done. As it was pointed out in OAR, coasting missiles are easy to avoid for spaceships, but not for planets.
It's not so much that you possibly couldn't get a KEW to another planet, it's that a orbital bombardment system wouldn't be the *kind* of KEW one would use to do so. Such a system has minimal capabilities for flight. Basically a way to slow down (so the projectile falls from orbit) and possibly some steering capability while still in space.
For a projectile to travel to another planet, it would need the capability to boost itself out of the gravity field of the planet it's orbiting. That would require significant thrust. For example, the moon trips couldn't just "slingshot" themselves from Earth to Moon, though they could from Moon to Earth if they needed to; due to the Moon as a starting point being "higher" in the gravity well than low Earth orbit was.
"Slingshot" maneuvers require either (1) the projectile *not* being part of the planetary "system" being used for the slingshot (ie, having more than escape velocity to begin with) or (2) significant propulsive assist at some point during the trajectory. Otherwise, the velocity gained diving into the gravity well is lost again as the projectile climbs back out. Conservation of energy - you can't get something for nothing. It's really more of a course *correction* implementation; where one can alter course with minimal fuel usage.
It would not need to boost itself. It could be boosted by the launcher, and when it gets to the other planet, it doesn't need to boost itself out of the gravity well, the vector of transit will do that for it. After all, we do that for our planetary probes and they sure don't carry enough fuel to do that - if they did, they could boost themselves to decent speeds and not worry about slingshotting.