Starships use Void engines to travel both interplanetary and interstellar distances.
Void engines come in two designs:
The first Void engines developed, nuclear engines use an explosive thermonuclear reaction to generate power and thrust. Plutonium pellets are continously accelerated into one another inside the fisson chamber at relativistic speeds-allowing for critical-mass reactions with smaller minimum sub-critical masses-the resulting fission explosion then detonating tritium inside the bomb chamber-lined with x-ray containment mirrors-creating a powerful thermonuclear explosion, energizing thermopiles in the bomb chamber and the exhaust chamber, the blast plasma being directed out of the exhaust chamber to drive the ship through space.
Developed by the Mhneme during the Second Sathar War, antimatter pion engines generate power and thrust through a matter/antimatter reaction.
A pion engine uses liquid hydrogen fuel, subjected to X-ray bombardement in the bombardement chamber, the resulting liquid antihydrogen fuel being siphoned off and injected into the primary reaction chamber along with the remaining liquid hydrogen fuel, the resulting explosion energizing thermopiles lining the chamber, with the pions generated from the matter/antimatter reaction directed through the exhaust chamber by magnetic coils which compress the pion stream to generate a higher specific impulse than would be possible with the nuclear engine design.
The Drivefield Generator
By the time a ship accelerates to Void speed—3,000 km/s(.01 c) for a nuclear engine design, 1,500 km/s(.005 c) for a pion engine design—its Void engines have generated enough power to engage their drivefield generators. The generators energize lathanide thermopiles embedded into the skin of the ship to create a series of overlapping fields which warp spacetime around a ship at a frequency which creates a pocket continuum where the ship's relativistic mass is reduced to zero, after which any amount of thrust is sufficent to give the ship imaginary mass, allowing for FTL travel.
When the generators come online, the ship disappears in a pulse of heat and radiation-harmless in space, but making for a pretty light show-the alternate spacetime created by the drivefields being called drivespace, subpsace, or more commonly, the Void, hence the name Void engines.
The largest nuclear engines manufactured generate 12,000,000 Standard Energy Units(SEU), while the largest manufactured pion engines generate 18,500,000 SEU. In both cases, 90% of the power generated goes to thrust and the creation of the drivefield, the remaining ten percent going to power the ship's beam weapons, defenses and other systems.
Time-Dialation & the Void
A ship travelling through the Void expiriences an accelerated sense of time, travelling at one light-year per day as measured by observers in the outside Universe, but expiriencing only 15 seconds of elapsed time per light year travelled.
EXAMPLE: The Triad refugees took 1,600 Galactic Standard Years to travel from the Triad system to the White Light system. From their perspective, however, the trip only took a little over six months, with the actual passage through the Void taking three months from their point of view(the other three spent in normal space for servicing, refuelling, resupplying and fighting the Corpses).
Hazards Of Void Travel
Aside from the consequences of misjumping(covered in the Knight Hawks rules), there are other hazards to travelling through the Void.
The drivefield still interacts with normal space, meaning that solid objects of sufficent density(including other drivefields) impacting with the field can disrupt it and destroy the ship completely.
In particular, ships must drop to sublight speeds when passing through nebulae, as the density of the ionized particles is sufficent to disrupt drivefields. Ships in the Void can only cross nebulae along paths relatively clear of interstellar matter.
Also, ships cannot use weapons, subspace radio or radar while in the Void, since solid objects striking the inside of the drivefield will also disrupt it and destroy the ship.
These paths, as well as any known interstellar route, can be successfully mined, the mines in question having proximity fuses which detonate upon detection of the heat and radiation pulse resulting from ships in the Void changing the density of local space-time as their drivefields interact with normal space.
Even if the ship manages to use its cameras and passive sensors to detect the mines in time and drop back into normal space, it is still vunerable to ambush.
Void engines come in three sizes:
Size A engines are the minimum size required for HS 1-4 starship designs.
Size A engines take up a space equal to two percent of the ship's total volume per point of ADF/MR per engine, with a total cost of two percent of the ship's total volume per point of ADF/MR per engine.
Size B engines are the minimum size required for HS 5-14 starship designs.
A size B engines occupies a space equal to four percent of the ship's total volume per point of ADF/MR per engine, with a total cost of four percent of the ship's total volume per point of ADF/MR per engine.
Size C engines are the minimum size required for HS 14+ starship designs.
A size C engine occupies a space equal to six percent of the ship's total volume per point of ADF/MR per engine, with a total cost of six percent of the ship's total volume per point of ADF/MR per engine.
Pion Engines cost twice as much as listed above and have one extra point of ADF for their size.
EXAMPLE: A size A nuclear engine with an ADF/MR of six takes up twelve percent of the ship's total volume and costs twelve percent of the ship's total volume.
Should the designer use pion engines instead, each size A pion engine will cost 24% of the ship's total volume, while the volume each pion engine occupies remains the same.
Instead of ADF 6, however, the size A pion engine discussed above will have an ADF of 7, while its maneuver rating remains 6.
Bigger Engines For Smaller
Two engines can be switched out for a single engine of the next larger size.
EXAMPLE: A HS 4 starship design normally requires two size A engines. The designer can, if he so chooses, substitute a single size B engine for the two size As.
(source - House Rules WIKI)