I'm going to run a campaign that spends a significant time in a system with no jump capability. The players will be similarly limited.
This means that for most of the time they are going to travel between celestial objects in this one system. In system travel seems to be covered rather briefly by the core books. It seems to me that the idea is that you arrive 100D from where you want to be and travel in a direct line with a flip and burn strategy.
Since the focus for several sessions will be this system, I'm looking to give it a more realistic feeling of having celestial objects actually orbiting the star, which in turn should make objects change position relative to each other. And I would like to be able to have travel not be a matter of pointing the nose of the ship in the direction of where you want to be and hitting the throttle. As I understand it, in space you would increase your orbit until you reached escape velocity and then maybe do a braking burn to enter the new orbit around a different object.
The perfect answer is a reference to a book or text that provide a RPG system that solves this, but it is also an acceptable answer to explain how you have handled this in the past and/or what is the Traveller tradition of handling this.
Best Answer
An excellent way to learn about real orbital mechanics (and a lot of fun, if a terrible time sink) is to get a copy of Kerbal Space Program.
By the time it's eaten all your RP gaming time for a few weeks, you'll know all you want to know about what's involved in getting from planet to planet the real world way -- right down to how much more fuel it takes to get somewhere fast compared to the minimum-fuel Hohmann transfer, waiting for a transfer window, and sitting in your spaceship while you wait through half an orbit (which can be decades for, say, a trip from Earth to Saturn).
Canonically, the maneuver drive in Traveller was a constant-boost type, and even at a "mere" 1G, such a drive can take you anywhere in our solar system in a matter of weeks (Neptune is six or seven weeks at 1G -- and it doesn't make much difference which side of the Sun the Earth is on relative to Neptune). A faster drive gets you there proportionally faster.
Therefore, there's no sense, if you have Traveller maneuver drives, in trying deal with Hohmann transfers or even cometary orbits, unless you have a fuel limitation (ships built with tiny tanks, so they can't operate the maneuver drive continuously -- a possible optimization for cost/profit) or something like system laws against using fusion drives near planets, where they do the most good. Failing limitations of that sort, anyone who has access to a constant-boost drive, even one good for a small fraction of a G, ought to use it, and if it's better than about a quarter G, point-and-burn, flip-and-brake is the most effective way to use such a drive.
BTW, this was known as long ago as the 1950s, at least. E.E. "Doc" Smith used this kind of travel model in Spacehounds of IPC, originally published in 1947.
Now, original Traveller had (as I recall) an orbital movement system for intership combat with miniatures or counters, but that's most likely more detailed than you want. It should be sufficient to say "It'll take you 374 days to get from Systema to the fourth moon of Gigantor -- fill out your time use cards." The problem with that is that few if any starships have that level of life support endurance and nobody in their right mind, in possession of a working jump drive, would spend that kind of time as opposed to making an intrasystem jump and getting there in one week, or using a constant-boost drive and getting there in three or four weeks (if jumps are impossible inside the system for some reason).
Even with a constant-boost drive in the 1G range, orbits will affect travel time a bit -- it's close to a week to travel from Earth to Mars, on average, but that figure varies by several days depending on relative positions -- nearest approach is less than a quarter what it is when the Sun is between. The only practical way to track this is by knowing the orbital distances and periods, and using geometry and trigonometry to keep track of distances. Not my idea of fun, but should be possible with a spreadsheet...