I decided to take a look at the example I posted last night with the flight from Home to Hot chi by 9.81 m/s^2 ship.

Interesting factoids:
If you compute flight time directly by their immediate distances the time of flight result is 780414 seconds.

If you then compute where Hot chi will be in 780414 seconds and then compute the time of flight from start point to that and continue to iterate until you get the flight time with the minimum position error you end up with 780366 seconds. I think it's very close to the naïve estimate by luck - as the distance increases the average velocity of the Hamiltonian over the course of the trip increases as well. There's probably a theorem out there somewhere about this.

The trick is in the trajectory, the players need to aim about 0.268 degrees off of direct line-of-sight (not taking account observation lightspeed delay).

The most difficult part though, is that the difference of initial velocity of the Hamiltonian with the expected final velocity (that of Hot chi in 780366 seconds) is 22730.9 meters/second, requiring an additional 38m37s worth of thrust, and somewhat screwing up all previous calculations. Obviously this can be ignored for all but the most technical of games.

Hopefully drive systems don't fail often. In the flight example from last night, system escape velocity was attained after slightly more than 55m15s of flight (and planetary escape after only 17m30s - and that in part because line of sight to Hot chi was not directly against the local gravity gradient). After 12-14 hours, they've got the velocity for galactic escape. I wonder how many derelict spacecraft there are out there in the traveller universe, drive systems failed, drifting at >0.01c, doomed to wander the universe with the unfortunate player characters forever. It's one way to end a campaign.

-------- Original Message --------
 On January 23, 2018 7:07 PM, shadow at shadowgard.com (via tml list) <xxxxxx@simplelists.com> wrote:
> If you are using computer support, just use orbital period data for
> the planets, and pick some point in the past where all of them were
> at a starting point (say, the most coreward part of their orbit).
>
> Then the computer can just run that forward to determine the
> positions when the players visit.
>
> Given that interplanetary travel is pretty much "point and shoot"
> with multi gee constant acceleration drives, all you need to do is
> figure out the positions to get the distance, which won't change
> significantly during the trip.