* No vessel may travel in excess of warp factor 5 unless special modifications have been made to ensure the fabric of space is not disturbed (such as the Royal Sovereign class starship).
* Every starship or starcraft can't be the fastest, however extraordinary sim conditions may allow for speed records to be broken by any craft upon rare occasion (Hosts's prerogative).
* Federation Warp Drives are powered by a Matter/Antimatter Reactor. One part Deuterium plasma (Matter) added to one part Anti-Matter plasma via a magnetic containment field conduit into the dilithium crystal of the Reaction Chamber (Warp Core) where it annihilates each other into pure energy, and is focused for shipboard power.
* This pure energy is routed to the warp coils (engines) which create a subspace field around the vessel (Static Subspace Bubble).
* Mass and bulk of a starcraft affects warp speeds. The more mass & bulk, the more energy required to warp it into subspace (It's not really a gravity versus acceleration thing, it's mainly a dimensional thing).
* Once in subspace, the hi-tech warp engine causes the interlaced warp coil fields to actuate against each other at an ultrahigh frequency, moving the ship through subspace very fast at a controlled rate.
* The faster you go, the more energy you need... the more anti-matter, and deuterium you burn... the more wear and tear on your dilithium crystal (24th Century technology allows for Dilithium Crystals to be regenerated by the ship's Theta-matrix Compositing System. Be sure and carry spare crystals anyway).
* Warp 9.985 is as fast as we should risk for an ultrahigh tech starship's (see your specs for Maximum Safe Speeds) quasi-safe maximum upper limits. Beyond that threatens various destructive effects to the ship as determined by the Sim Master.
* The difference between Warp 9.9 and Warp 9.975 appears only in fractions, but in actuality 9.975 is over three times as fast as 9.9. This is because the speed increases geometrically (as well as the energy requirement).
* Warp 9.99 is unattainable by any object with significant mass, due that it would require nearly infinite energy.
* Warp 9.9999 is the maximum speed that can be attained by subatomic particles when warped through subspace. This is the maximum speed of subspace messages, long range sensors, and the like (Subspace Transporter beams, Warp Phaser Canon beams).
* Warp 10 is not attainable and would require infinite energy (USS VOYAGER may have been mistaken in it's testing of the experimental shuttle, since its sensors can't travel that fast. :^) Besides, their Sim Master made the passengers suffer terrible side effects. LOL).
Based on the Star Trek Technical Manual, and Voyager Technical Guide.