Shut Up and Drive
OK, here’s how space travel works in the TMIverse.
There is no doubt that reaction mass and energy are the two greatest concerns when it comes to space travel. Or so it seems at present levels of Terran technology and theoretical physics.
A star ship needs to be able to do three things; maneuver within solar system and planetary gravity wells, get to and from the inner system to outside a system's Oort Cloud, and cross the gulf between star systems. All in a practical, safe and timely manner.
When Dilmun abandoned the Solar System millions of years ago, they relied upon fusion drives. Even so, the majority of travel time was spent drifting between star systems; usually brown dwarfs. Most of the fleet has never entered a star system since the diaspora.
It is only within the last 100,000 cycles that Dilmun developed FTL travel (hyperspace transition) at all. It turns out that entering and leaving hyperspace is ridiculously easy and requires relatively little power (compared to making the trip in real space-time). The greatest impediment to the development of hyperspace travel is that most mathematicians and researchers look at their findings, decide that it can't be that easy, and throw out their data; frequently taking up a more challenging fields such as knitting or gardening (both considered to be excellent therapy in Dilmun sanitariums). The “hyper drive” used by Dilmun was actually invented by a K'Sel male who was considered to be their equivalent of a crackpot inventor with a garage workshop.
A hyper drive is not an actual drive, per say, but opens a window between real space-time, and a condensed space-time (hyperspace). The amount of energy needed to open an H-space window varies with the “density” of H-space desired and to a lesser degree the mass of the ship. As a general rule, larger ships can employ more energy relative to their mass to open an H-space window. The OIS Rod Serling can make the trip between Earth and the Orion Nebula in under 4 deci-cycles, where Ruby would need 12. The “density” of an H-space transit is usually expressed as a ratio between real space distance and the apparent distance. At a 1:100 H-density, a ship in hyper would travel 100,000 kilometers in the same time that a ship in similar conditions would cross 1,000.
There are several issues that do make H-space travel difficult.
The Sub-Space Traction Drive (which also turned many mathematicians and researches into accomplished gardeners and knitters) is the other element that makes space travel potentially practical. S-space is, in a way, denser than real space, and is much like the aether proposed by medieval science. It ebbs and flows. It swirls about mass in real-space and streams away. Even super massive black holes can't hold a sub-space current. It may be that the energy found in sub-space has been stripped from singularities, leading to their eventual "evaporation" and that energy drawn from sub-space is not being created, but instead is being returned to real space-time.
Ghost Drive is actually a combined mode for hyper and traction drives. “Ghost Space” is most simply explained as hyper space at 1:1 density (up to 1:1.02 in some cases). Like hyper space there is no interaction with mass in real-space and ships leave ghost space at the same velocity as they entered. It varies from higher densities in that Traction Drive can be used for acceleration, deceleration and maneuvering. Also sensors can detect most objects large enough to be a navigation hazard. Under Ghost Drive, the time and energy necessary to transit nebula and star systems is usually less than 10% of what would be required making the same passage in real-space. The concept was first proposed by Just Ace Gina-scion and developed by Princess Sky Peach-scion Galadriel-scion in Heir Standing, and her bond-parent Commander X Racer-scion.