PC advancement in a Mercenaries campaign


Banded Mongoose
In normal Traveller, it's heavily implied that PCs spend jump periods in study. How do you handle study periods, etc., when the PCs spend extended amounts of time on-planet? I'm thinking about running a Mercenaries campaign, and one potential issue that occurs to me is that there's no time to get those study periods in. Do you substitute an XP system, handwave it, or something else?
When you can spend eight hours a day of uninterrupted time on study for a week, that is your down time.
The XP system in the Traveller Companion is superb, and builds skills/characteristics at a reasonable rate that is easily controlled by the GM. Takes away any need to track learning and that kind of stuff, although it can run in parallel with that kind of learning if needed. I find my players do the game for exploration and whatnot, not to be in school :p
Though a unit is 3 hours of work per week, it is expected that only one of these hours will be class time. As a general rule of thumb, you should expect to spend two hours studying or working outside of class for every one hour in lecture or discussion. A typical 4-unit course thus will require about 12 hours of work per week: 4 hours of class time and 8 hours of work outside of class.
Start a blank career skills sheet. Fill it in as play progresses. Roll periodically, preferably at major milestones. Scale against the regular charts, so academic skills go on Advanced Education, physical stats used go on Personal Development alongside things like Carouse and Gambling if used. You can take player input on how to split up the career specialties. Service Skills needs watched so it's not just all the most desirable skills, but the basics they'd teach a new guy coming in.

something else

Advancement/"leveling" comes partly through gear. Which you've probably heard before, but it bears being deliberate about. If the party are getting credits make sure they've got periodic opportunities to go shopping. If for some reason you're running a cash poor campaign or arc make sure to place useful gear sometimes. The first grav belt is always fun, and it's funner when they started without one for a few sessions. A merc campaign seems especially suited for this; place a better ground vehicle partway through, place a flamethrower and see if they bite, etc.

Anyway, I've never used the study system as is, in any game. In Classic, skill development was s-l-o-w, which matched character generation. In Mongoose 1e I took it as optional; I liked that it let lower-term characters catch up, I never liked that it didn't scale against character creation. Taken to its extreme it turns every PC into Tony Robbins on ritalin, and the GM's reward for allowing it is characters that break the 2d6 scale and require you to start handing out more modifiers to rolls.