simplified starship travel

One of the dissonant things, for me, about space games is that we've learned a lot about space and the nature of space travel in the last fifteen years and all of it contradicts or deflates many of the old science fiction tropes about charting courses around stars and engaging with other starships that just suddenly appear out of nowhere. The former would be an easy task and the latter would never feasibly happen just with the level of technology we have for spaceships today. A more realistic approach would be that a ship's sensor array could be advanced enough to chart the stars.

The way that Stars Without Number currently works a character must make a successful Navigation/Intelligence roll on 2d6 against a base difficulty of 7. Navigators can attempt to “trim the course” by increasing the difficulty by +2 in exchange for increasing the effective spike drive rating of the ship by +1, but a navigator cannot trim a course by more levels than their Navigation rating. Travelling within a solar system requires Navigation-0 skill, but doesn't require a skill check unless some special hazard is involved or the navigator attempts to trim the course (difficulty 6, +1 for each level of course trimming). This skill check difficulty is increased even more based on the age of navigational charts that the Navigator uses to chart their course, and if they are charting a course into unknown territory the difficulty jumps by +4.

That's the rules as written.
Rather than fiddle with a bunch of difficulty ratings and modifiers, a simpler approach would be:

If a pilot is flying under the spike drive parameters (e.g. flying 1 hex with a drive-2 engine) and not attempting to trim the course then there is no need to roll. Trimming a course means shortening the time in hyperspace by one day. Default is 5 days (my game, it's 6 days by the rulebook).
Navigation+Intelligence, base difficulty 7, difficulty increases by +1 for every level of course trimming.
With no limits placed on the amount of course trimming a player might attempt.
Succeed at the roll and you arrive safely.
Fail the roll, and the player must select two.
Fail the roll by a margin of 4+, the player must select three:

• drive down, ship cannot be operated until repaired
  
• computers down, piloting at -1ongoing until repaired
  
• navigation systems down, courses cannot be plotted until repaired
  
• off course, GM randomly determines current location
  
• travel time is twice as long

Roll snake eyes and all of the above are true, plus the following:

• life support systems down, crew will die if it is not repaired immediately