It appears the Non-Biological Entities powering human spacecraft can be categorized according to their habits. Don't call them ghosts please.
The three classifications of NBEs are
Haunts- Haunts are the equivalent of herbivores usually feeding on heat or electrical energy in machinery and electronics and causing occasional malfunctions, They are the most common NBE. They can sustain accelerations of 2gees or less and Jump-1 or 2.
Overts- Overt NBEs make themselves known more often than haunts and may even try to communicate occasionally. They will feed on energy in the environment or that of living beings. they elicit a fear response in sentient life to make their brains generate more energy. They can sustain accelerations of 4 gees or less and Jump-3 or 4.
Poltergeists- Poltergeists are the most powerful NBEs. They prefer to feed from living creatures and often have negative side effects on them. They are the most intelligent of the NBEs and the most dangerous. Some are capable of psionic assault. They are also the most hostile entities often causing damage to ships and structures or harassing occupants to the point of madness.
The categories of 'feeding' may be innate or preferences. A NBE's energy needs are easy to satisfy with ship power and will usually keep them quiet and content. Using too much power in too short a time has side effects on the entities. For example if you run your thrusters too long to get a very high delta-vee or make a series of jumps as fast as possible instead of waiting the usual week NBE's can move up the food chain, from Haunt to Overt to Poltergeist. Power plants are rated for the highest order of entity they can contain. This is not hard and fast. Containment has to be checked weekly at least, preferably day by day by a psionic.
Scout ships and long range vessels typically have rocket drives to fall back on if they aren't in a hurry or solar power systems to shut down the main reactor and starve the ghost crew into submission.
Using your NBEs for too long without a break is the surest way to find out about the classification beyond Poltergeist. No one wants that.