On 26 Jun 2015 at 11:15, Knapp wrote:

> I would think predicted position would be a cone for a ship with a
> fast vector and a sphere for one sitting, "still". The cone might
> bend or even split (more like a hole in the cone), if it is
> interacting with a gravity well.

If it's not being affected by a gravity well, future posituion f it
*doesn't* accelerate is a straight line. But due to relativity (the
non-near-c version) you can treat the "not accelerating" path as a
*fixed* point.

It's just fixed in a reference frame that's moving at X km/sec onlong
vector Y. :-)

Once you realize *that* then the future position *in that frame* is a
sphere whose diameter is set by the max accel of the ship, and the
time in the future you are predicting for.

Limitations on how fast the ship can change "facing" (ie the
direction it is *pointing*, as opposed to the direction it is
*moving*) will distort the sphere. (the longer it takes to rotate to
a given facing, the smaller the radius of the "sphere" in that
direction).

--
Leonard Erickson (aka shadow)
shadow at shadowgard dot com