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Hyperspace Physics
Thanks to
http://www.theforce.net/swtc/hyperspace.html#introduction
How Hyperspace Works
1. Light is not the only entity which can propagate at lightspeed. Gravitational influences do also. All entities travelling at lightspeed must have zero mass and can never travel at any other speed. They are collectively called luxons.
2. Particles which bear mass can be either below or above lightspeed. The former are called bradyons and the latter are tachyons.
3. For the purpose of superluminal travel in STAR WARS it is sufficient to choose the viewpoint of the galaxy at rest as realspace, and anything which is tachyonic relative to the collective of star systems is considered to be in a realm called hyperspace.
During the Palpatine Era it was fashionable for starships to carry navicomputers, astrogation aids which greatly simplify the process of calculating a jump through hyperspace. Navicomputers contain at least a rudimentary database of navigational obstacles and destinations within the galaxy. Their primary value is that they enable ships to choose their own courses through interstellar space, rather than being restricted to common trade routes. For smugglers, rebels and other dubious individuals the independence provided by a navicomputer is extremely valuable. Of course the same is true of the Imperial warships and the bounty hunters who must pursue the renegades.
Desperate for resources and dependent on hit-and-run tactics, the Rebel Alliance installed rudimentary hyperdrive systems into many of its starfighter designs. The jump capabilities of these ships were limited. In most cases there was no onboard navicomputer and the only possible destinations were a small handful of pre-calculated jumps loaded into the memory of an astromech droid mounted behind the pilot. Consumables including air and fuel are extremely limited for these vessels, so only short hyperspace hops are possible in a starfighter without resort to hibernation, Jedi trances or other unorthodox and uncomfortable measures.
Hyperspace routes are either:
Safe; a standard jump through safe space. These areas of space have very little interference from natural or artificial forces such as asteroids, planets, nebulas and the like.
Murky; standard jumps through space that have lots of natural interference, meaning that the navicomputer would have to constantly adjust the jump, but that the jump is safe
Uncharted; Jumps made through unknown space. These jumps are dangerous. Plotting a safe short jump requires 1d6 x 100 minutes. If the roll fails, there is a 50% chance the astrogation appears safe - the math is difficult even for intelligent computers. Making a jump into unsafe hyperspace requires that the navigator make a resisted and compared Astrogation roll (see compendium 2) against a "resisted skill" of 18, and the modified skill can never be above 15. Failure indicates a 30% chance that the ship is lost, and a 70% chance that it is destroyed/lost in hyperspace forever. Needless to say, probe droids are the standard explorers, although the most famous explorers (and the most successful, strangely enough) have been human.
It takes 1d6 minutes to plot a Safe hyperspace jump. Murky jumps require 1d6 x 10 minutes. Uncharted jumps require 1d6 x 100 minutes and rolls (see above).
Hyperspace trips run about 1 hour per sector on the average. If the jump is not "safe" (also called a "murky" jump; the navicomputer must constantly adjust the jump in hyperspace), the jump will take 1d10 x 10% longer. For example, a roll of 3 indicates that the trip takes 30% longer than usual.
Further GURPS game facts about hyperspace:
1. Straight jump lines on the map are safe and require 1d6 minutes to prepare the jump
2. Dotted lines are murky and require 1d6x10 minutes. The jump will also require 1d10x10% longer.
3. If the characters are jumping where there is no line on the map, follow the instructions above.
4. Force Astrogation can be used to plot hyperspace jumps without a navicomputer in the standard amount of time.
5. Plotting a course without a navicomputer requires 1d6x17 hours, regardless of the type of jump.
Tracking Hyperspace Jumps
There will be times when characters, including players, would like to track hyperspace jumps. This raises many questions. Can they be tracked? For how long? How percise? The following section will be used to answer such questions.
Can hyperspace jumps be tracked?
The short answer is yes. However, it is not easy to do so. Ships that have entered hyperspce look to most computers to be lost. Entering hyperspace reads as all points in space at once, although it is not. Hyperspace uses unknown technology in the Star Wars universe (characters can build and use them, but don't really know how they work).
How can ships be tracked then?
Sensetive computers don't actually read the energies used in the jump, but rather read the direction other energies were going before they disappeared in the jump. Therefore, a computer can tell the direction a ship was going before a jump, which indicates it's destination, if the ship continues in a straight line. This is most useful when a ship does not know it's being tracked. Other energies can interfere with this tracking, so areas around busy planets, nebulas and other high-energy areas almost insure failure.
How long can a ship be tracked?
Larger ships leave "tracks" for longer periods of time. In game terms, ships leave a trail for a time equal to space used for the engines in minutes.
In game terms, a ship must have Advanced Sensors and a hyperdrive (the character needs a navicomputer to aid him) to be able to track hyperspace jumps. This requires a Computer Operation (sensors) and Intelligence Analysis roll to be successful, both compared against a skill of 20 (see comparative rolls, GURPS Compendium II). If successful, the operator knows the direction of the jump and could conclude the destination in a straight line.
A critical success can track a ship that has had a hyperspace malfunction, and, if the ship was not destroyed, track it to within one sector of space (one square on the map) of where it might have come out of hyperspace. Following this path in a straight line might also indicate where a large body of gravity would have pulled the ship from hyperspace.
Sublight Travel
Traveling without hyperspace can be accomplished, but is very slow (the Millineum Falcon limped to Cloud City after escaping the Imperial Fleet in The Empire Strikes Back). Ships without a hyperdrive can accelerate to near light speeds and travel very quickly. In game terms, this means that a ship can travel across a sector at 1/100 normal time. A 1-hour jump out of hyperspace requires 100 hours to travel, for example. Time is calculated without hyperdrive modifiers. Just because you have a x4 hyperdrive means little if you are not using it.
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