Engines fall into two basic categories: those designed for space travel and those designed for atmospheric conditions. Both kinds already exist, but it is mostly engines intended for space travel which get mentioned in our work. There appears to be a correlation between how often an engine’s functionality is explained and how fictional it is; the more fictional, the more explanations are given. Writers have as little interest in learning and explaining actual technology as the audience, who typically understands it to some degree. But fictional tech? We’re all ears.
Air Breathing Engines
Engines for atmospheric conditions are the sorts of engines currently in use by planes on Earth. We don’t need to invent anything or get into details of whether it’s a rocket or turbine engine unless we desire to. We should just be aware that characters may need to remark that they’re switching to “so-and-so power” as they enter a planet’s atmosphere because the space engines they were using might not be suitable. This minor touch adds realism. Slower-than-light (STL) engines might also be used here and it’s up to us to decide a given ship can use such engines both in space and in an atmosphere. This is one way to distinguish between ship types: some vessels might have engines that can be used anywhere and be considered more advantageous than ships that must change propulsion.
Space engines can be divided into two categories: those that allow faster-than-light (FTL) speeds and those that do not. For STL engines, propulsion is similar to atmospheric engines in that matter is ejected, usually from the rear, to propel the ship forward through normal space. This is one reason slower-than-light engines could be used in an atmosphere. STL drives propelling a ship at high velocities can cause time dilation, which is when two observers experience a difference in how much time has passed. Some stories discuss a captain not letting the ship go too fast using those engines, generally, to avoid this problem.
Some FTL engines are discussed next and are all public domain ideas anyone can use.
As the name implies, a ship with jump drive essentially teleports between two locations in an instant. This may be safely called a “jump drive” or something else. The main problem with such technology is that it eliminates all conflict involving travel and not having enough time to reach a destination by an important date. Consider using this sparingly or placing severe limits on how often such a drive can be used, such as it uses too much power, relies on a rare fuel source, is expensive to manufacture, or is too large for ordinary ships. Ships equipped with jump drive do not experience time dilation.
A hyper drive moves a ship into hyperspace, a fictional, separate dimension adjacent to normal space. As a result, ships in hyperspace are often depicted as being unable to communicate with those in normal space. Normal physics, such as the barrier to FTL travel, may not exist in hyperspace, allowing the ship to traverse great distances quickly. It takes time to travel in hyperspace but those traveling this way experience time normally and experience no time dilation upon returning to normal space.
Warp drive is a conceptual FTL drive that is public domain despite being heavily associated with Star Trek. The idea includes multiple velocities of warp, such as warp one being far slower than warp ten. Instantaneous travel is not possible with warp drive. The ship suffers no time dilation and remains in normal space. Despite our use of the term “space”, there are plenty of objects with which a ship could collide, which begs the question of how deadly such an impact would be. Without high-speed automated navigation systems and equally impressive shields, warp speed is unwise.