Hyperspace

Hyperspace is actually a misnomer. While it appears from the inside that a jump via hyperspace causes the ship to enter a swirling tunnel of glowing energy that it speeds through, in actuality a hyperspace jump compresses the entire ship and all its contents into a single tachyonic particle which hurtles through the universe at many times the speed of light.

Jumping

Calculation

Planning a hyperspace jump is generally a matter of comparing with star charts (which are generally widely available and mostly accurate) and finding a sine wave that gets to the destination without passing through any planets or stars or dense nebulae. Aside from the use of devices such as a jump calculator, this can be done with a DC 5 Items check and ten minutes, or eyeballed as a lesser action with a DC 10 Items check. The check is rolled secretly, trying an unsuccessfully plotted jump results in finding your ship deep within the mass of something very large. If there's clear line of sight to the destination and it's less than 10 light minutes away (180,000,000 kilometers), no calculation is needed.

As things shift around in space, a calculation is only good for ten hours before it becomes out of date, but you can plan in advance which ten hour period you calculate it for. You also need to be in roughly the right position in space for the calculation to be accurate, within 10 kilometers of where you planned to be.

A normal jump has an inaccuracy of 2d6 kilometers forward or backward from the desired destination. By spending 5 times as long calculating the jump, and increasing the DC by 3, you may entirely remove the inaccuracy of the jump. Failing on this increased DC but succeeding on the normal one results in merely having the regular amount of inaccuracy, not ending up in a planet along the way.

Returning to Realspace

When a ship reappears, it rapidly expands into its full size, potentially ripping apart whatever it collides with. If it collides with solid ground, the ship and the ground take 1d6+4 Noise damage with 5 demolition. If it collides with loose matter such as pieces of shrapnel of 1 kilogram or more, or gas like an atmosphere, the ship and the shrapnel take 1d6+2 Noise damage with 2 demolition. When the ship reappears, its velocity matches the velocity of nearby large bodies of matter: appearing near a planet, it moves with the planet (not in orbit, leading to it plummeting towards the surface); appearing in space in a solar system, it moves with the solar system (taking on some of the orbital velocity of the planets, but most likely leading to it plummeting towards or at least past the star); appearing in deep space, it moves with the rotation of the nearest galaxy (possibly leading to it orbiting the galactic core).

Planned: The tachyonic particle form that a ship is transformed into has a limited duration before it turns back into a full ship. In normal use, the hyperspace jump is charged with a very specific amount of energy to make it turn back after traveling exactly the distance to the destination.

Inhibition: If the particle passes into an inhibition area, such as from a hyperspace inhibitor, it immediately turns back into a full size spacecraft.

Physical Objects: If the particle collides with a neutron, it immediately turns back into a full-size spacecraft. The odds of this are negligible in deep space, but as high as 1 in 6 for every 100 kilometers of matter with the density of water.

Hyper Drive Statistics

Hyperspace jumps are very fast, but have only mild relativistic effects. Each hyperdrive lists its jump capabilities in the format "10000c/2/10ly", where the first number is its speed in multiples of the speed of light, the second number is how much times less time the ship experiences than the outside world does, and the third number is the maximum range of a jump.