The cover for Squadron Strike: Traveller
I get asked "Why are you doing Squadron Strike: Traveller when Power Projection: Fleet already exists?" I publish both games, and while you never really want to get into these kinds of discussions on the Internet, because they quickly devolve into "System A is better than System B, well, I like System B, and must defend it!", discussing what the games do differently is important.
So, with the caveat that I publish both rules sets, and am trying not to say Power Projection or Full Thrust is worse, here goes:
Squadron Strike is hex based, and ships have faced defenses - the armor on the Nose may (and often does) differ from the armor on the Aft of the ship; Left, Right, Top and Bottom are distinct facings. Power Projection doesn't have faced defenses. Armor in Squadron Strike is reductive - if you fire at a ship with armor 7 with a 6 damage weapon, you're not going to get any effect whatsoever. Armor in Power Projection is, like Full Thrust, ablative. It's extra hit points, basically.
In Power Projection, Andy Lilly and Dom Mooney pretty much renamed the Full Thrust weapons. This is great for simplicity, which is one of the strengths of Full Thrust...but a lot of Travellerisms kind of vanished in the conversion. For example, I'm not terribly fond of their Meson Gun rule - it just doesn't have the same pucker-factor that it should from Traveller.
In Squadron Strike, weapons are player-designable. I'm not trying to make something work out of a half-dozen pre-built weapons, I'm able to specify range, accuracy, damage, variable damage and special weapon abilities on a per-weapon basis. The same weapon in High Guard may have slight regional differences in SS Traveller, for example.
Coming back around to the Meson Gun, the Meson Gun has a high base damage, a high variable damage component, and two special weapon traits.
One is "High Impact," which adds a point of damage to the base damage for every pip you beat the Accuracy number by - if it's got an Accuracy of 4+ on a d10, and you roll a 7, High Impact would add 3 additional damage.
The other is "Ignores Armor," typically at 8+, though earlier models have it at higher target numbers. If your Accuracy die roll is an 8 or higher, ignore the target's armor when the damage is allocated.
Both these traits benefit from high die rolls. While it doesn't happen all the time, I've had a a ship I've been flying take an appropriately "Traveller-esque Meson Gun" hit and go from "Unhurt, unhurt, un..." to "Ooh, pretty explosion..."
The other big difference is 3D movement, and an easier to use vector movement system than Full Thrust uses. Maneuver is important in SS Traveller, and it's a lot of fun.