Original Post
I'm wrapping up travel rules for the RPG/empire hybrid I've been working on and would appreciate any thoughts you guys have. Basics The solar systems you play in will be realistically scaled so that planets really are tens of millions or even billions of miles / kilometers away. There are two types of in-system travel: Slower than light (STL) and interplanetary FTL (I-FTL). (Interstellar I'll bring up in another post). STL Flight Flight is pseudo-Newtonian but with a speed cap due to impact from gas, dust and debris. I'm fudging things here, but velocity is capped to around 1000 kilometers a second because of this. Acceleration is unrealistically high to keep manuever playable, but with a small nod to g forces, possible redouts / blackouts and acceleration dampening gear you can buy. For playability, there will also be a "friction" toggle option that causes your ship to drift to a stop when not accelerating. The view is 3rd person behind your ship, but with mouse-look that orbits your craft. This lets you target objects for scanning or combat while you move in a different direction. Under STL, fuel use is neglible compared to the tech level of fusion powerplants. Interplanetary FTL Ships can use I-FTL catapults or buy drives that accelerate them up to 50x light speed. This opens up the star system to real-time travel, making most planets a matter of seconds or minutes to reach. Modules will vary in quality, speed, durability or compatibility with other (alien) systems. Travel is in a straight line for most modules, but a few can accept "planck-space anchors" that allow them to turn and evade. The faster the drive, the more power it will consume, requiring you to tradeoff weapons / cargo with powerplant. Safety causes drives to slow or stop in areas of dense gas and dust, creating nav hazards. Ships can also interdict each other with gas cloud emitting torpedoes. However, a successful gravigation skill check can ignore this. Most I-FTL systems require a fuel resource, which might vary by species manufacturer. While the player can run out of fuel, they are never stuck, as they can always STL back or call for help. In systems with Syscats, they can either pay toll, hack or call in a favor from any contact that might control the catapult. To create a money sink, normal travel does wear and tear on the drive that requires repair, which can be paid for or done by crew. The amount goes up with the mass of the ship, but skills in navigation lessen the decline. This should allow easy advancement in the shuttle and fighter stage, but more challenge in the freighter / cap-ship phase later on. Gravity Whips Fuel concerns under I-FTL make gravity assists desirable because, if done right, a ship can fly around a system nearly for free. In STL, ships use the angular momentum of planets to alter velocity and in FTL use a body's "gravity waves." Storywise, STL assists are so easy that they're automatic. In order to support racing, escape and pursuit and beating competition to market under trade, FTL flybys are much more tricky. Constant skill checks are required, failure of which can result in gravitational shear damage to the ship or even crashlanding. The player can perform a ship task (basically charge up a meter) to boost their chances, and optionally play an orbital mechanics minigame which affects their skills by +/- 50 points. Under FTL, the closer a ship flies to a planet, the more gravity waves it can use. Gameplay wise, you get to risk fuel savings for safety. On critical failure, you deal with a crashland sequence (whose survivability rate is high for your character, but not necessarily so for your ship or crew). Aerobraking Ships can use planetary atmospheres to slow. Again, under STL this is easy, requiring a few nav checks whose worst result is some minor hull damage. Under FTL, the challenge again rises: You select how much you want a planet to slow you down, and this creates a challenge rating based on your speed, mass and the piloting skills of your character and crew. Planets with thicker atmospheres can slow you the most, shedding up to 90% of your speed (in comparison, thinner ones offer only about 15% change per contact). However, denser atmospheres provide a higher challenge rating for every percent you want to slow. Failure again is more severe, ranging from burning extra fuel in course corrections to experiencing thermal and kenetic damage; the worst results range from being deflected off the atmosphere up to 90 degrees, or crashlanding. Orbiting Under STL, you simply "drive" to the planet to orbit. Under FTL, you get similar challenge gameplay as with gravity assists and aerobraking. Success will place you right in front of your target in the orbit you want, failure might place you closer or farther or expose your hull to damaging gravity-wave shear. Quick Map Travel At 1000 kps you can get from the sun to the moon in about 7 minutes, Mars in around 3 days, and Pluto in about 2 months. Once you upgrade your ship with supply generators (advanced air recyclers, protein paste dispenser, etc.) you can travel anywhere in system. In single seat shuttles and fighters, however, your strength and dexterity stats go down every month, reflecting your confined environment. Ships with more floor space, mods for smaller ships like aerobic cabins and items like nano-regen lessen or negate this automatically. Fighters versus Capital Ships The one last mechanism to mention is the "blink module:" It allows a small enough ship (fighter / shuttle) to teleport up to 10 million kilometers. The drive is basically a scaled down interstellar jump drive, and requires special fuel that limits the ships to about 50 million kilometers max. What this should allow for is fighters and shuttles to carry out hit and run attacks from distant carriers or bases. I'm hoping that it keeps small ships relevant even once you've gotten into the big leagues, as being able to jump past defenses or obstacles can make a small shuttle or fighter very useful. As usual, comments welcome...