A few years ago, I ran several Mongoose Traveller adventures at Gen Con. The beauty of the system was that I could provide a character in a very small stat block, leaving the rest of the page for a brief synopsis of the task resolution rules, as well as some basic combat tables to hit minimize rule lookup during the game.
Below is the brief overview of task resolution that I provided my players at those games. I believe it helped significantly with moving things along. So it occurs to me that perhaps others might benefit from using this or a similar presentation of the rules for their own Traveller One Shots.
The core mechanic of Traveller is very similar to other popular roleplaying
Roll 2d6, add your modifiers to the roll, and the result should equal or exceed 8 in order to succeed.
Die Roll Modifiers (DMs)
There are three primary modifiers that are applied to each die roll.
1. Ability Score DM: Each die roll is typically modified by a specific ability score.
Ability Score DM 1-2 -2 3-5 -1 6-8 +0 9-11 +1 12-14 +2 15-17 +3 etc. etc.
2. Skill Level DM: Each die roll is modified by a specific skill level.
3. Difficulty Level DM: Each die roll is modified by the difficulty level of the task as set forth by the Referee (another name for the Gamemaster). Difficulty level is often set by the current circumstances surrounding the attempted action.
Difficulty Level DM Simple +6 Easy +4 Routine +2 Average +0 Difficult -2 Very Difficult -4 Formidable -6
If a difficulty is not stated, assume that the action is of Average difficulty
(which means there is no modifier to the die roll based on difficulty level).
There are several special circumstances that should be mentioned: Unskilled
Tasks, Hasty Tasks and Cautious Tasks.
1. Unskilled Tasks: If you are attempting a task that requires a skill you do not have, then you suffer a -3 penalty on your skill check.
2. Hasty Tasks: For each step on the time frame table faster, you suffer a -1 DM on your skill check.
3. Cautious Tasks: For each step on the time frame table slower, you gain a +1 DM on your skill check.
4. Multiple Actions: For each additional action in a single round, you
take a -2 DM to all skill checks.
Effect: The Degree of Success or Failure
The Effect, or the degree of success or failure, is determined by the amount
of your die roll total above or below the target number of 8. In combat, you may add your Effect to your damage on a successful attack.