TLDR; Long boring RP explanation how the "science" of FSD drives causes top speed limitation.
Early in human space flight and when humans still had no idea what dark matter was, humans accidentally discovered how to interact with dark matter, setting the foundations for the Frame Shift Drive.
See ancient archives at : https://en.wikipedia.org/wiki/RF_resonant_cavity_thruster
At the time, the EM drive seemed to violate the laws of physics as it generated thrust without seemingly interacting with any matter.
What it did interact with, was Dark Matter Quantum Foam (DMQF). We still don't exactly understand how this interaction work to this day, but we do understand the effects of the interaction really well and can control it fairly presicely.
The Reactor core, thrusters and FSD are an integrated system that interacts with the DMQF to provide all modes of travel. The reactor rips the Hydrogen apart sub-atomically and generates a lot of power and a field that interacts with the DMQF:
During FTL travel the FSD interacts with DMQF with the reactor field to stretch time space in front of us and collapse if back behind us in order to make us travel apparently faster than the speed of light to observers outside of our reference frame. To jump long distances, the FSD in effect stretches out space time in all directions and then collapses the one side of it all in one go, in effect catapulting the ship in a direction with the DMQF acting like an elastic band. The detailed working of this is a topic for another day.
The thrusters system "pushes" against the DMQF by using taking the reactor field and directing it out in a direction through "nozzles". The nozzles can precisely direct the DMQF stretching and what is left of the Hydrogen is ejected out of the nozzles at relativistic speeds. Thus these thrusters can generate tons of thrust while only consuming very little fuel in the process (and while being fairly small). Movement here is created in part by time space streching and in part by thrust from the thrusters.
The one disadvantage of this is, that the central "bubble" of DMQF compression (that is directed by the nozzles) is a source of drag to the surrounding non-compressed DMQF.
So, in normal travel mode the interactions with the DMQF is analogous to a rocket engine moving through air, with the body causing drag, and the nozzle end giving thrust. As long as the DMQF compression bubble is active, you can generate lots of thrust in a direction, but the faster you move through the DMQF field, the more drag you will encounter.
DMQF interacts with gravity and is in effect "swept along" by large masses. Thus, the DMQF will always seem to move along with a heavy body. That is why drag is always relative to a local gravity well and thus, the "top speed" is relative to that local gravity well (that is also why speeds vary wildly when frame shifting past heavy bodies). This also explains why heavier ships tend to be slower as their own hull mass causes the compressed DMQF bubble to have even more drag with the surrounding DMQF. Some of this can be overcome with better compression and direction, but it's a diminishing returns problem which means that it becomes really hard to go much faster than about 500m/s. Faster speeds are possible, but then it becomes a serious tradeoff between the mass of the thing you want to move and the size of it's FSD core.
The interaction with gravity wells is also the reason why commercial drives jump from star to star - the ship is "thrown" in the direction of a star (gravity well) where the gravity well will naturally pull it out of jump speeds to normal FSD speeds).
When you disable a ship's flight assist, you also disable the DMQF compression and the ship can drift freely under regular newtonian physics. If a ship had ancient chemical rocket thrusters, you would have been able to accelerate it to higher speeds than the "top speed". The problem is that regular thrusters EAT fuel. The thrust needed to accelerate a 100t ship significantly would eat through tons of fuel in a manner of seconds.
(a 300t cobra burning through it's 16t of hydrogen fuel and 2t of oxygen in the cargo will only gain a few tens of m/s before running out of fuel).
For typical ship design it is just not seen as worth it and the speed limit is accepted as you have regular frame shift travel if you need to go further or faster.
This is my attempt at trying to explain in layman terms why ships have a "top speed". There are of course much brighter commanders under us which may be able to point out some flaws in my explanations and any comments are welcome.
EDIT : clarified the interaction between reactor, thrusters and FSD and that it is an intergrated system.
Early in human space flight and when humans still had no idea what dark matter was, humans accidentally discovered how to interact with dark matter, setting the foundations for the Frame Shift Drive.
See ancient archives at : https://en.wikipedia.org/wiki/RF_resonant_cavity_thruster
At the time, the EM drive seemed to violate the laws of physics as it generated thrust without seemingly interacting with any matter.
What it did interact with, was Dark Matter Quantum Foam (DMQF). We still don't exactly understand how this interaction work to this day, but we do understand the effects of the interaction really well and can control it fairly presicely.
The Reactor core, thrusters and FSD are an integrated system that interacts with the DMQF to provide all modes of travel. The reactor rips the Hydrogen apart sub-atomically and generates a lot of power and a field that interacts with the DMQF:
During FTL travel the FSD interacts with DMQF with the reactor field to stretch time space in front of us and collapse if back behind us in order to make us travel apparently faster than the speed of light to observers outside of our reference frame. To jump long distances, the FSD in effect stretches out space time in all directions and then collapses the one side of it all in one go, in effect catapulting the ship in a direction with the DMQF acting like an elastic band. The detailed working of this is a topic for another day.
The thrusters system "pushes" against the DMQF by using taking the reactor field and directing it out in a direction through "nozzles". The nozzles can precisely direct the DMQF stretching and what is left of the Hydrogen is ejected out of the nozzles at relativistic speeds. Thus these thrusters can generate tons of thrust while only consuming very little fuel in the process (and while being fairly small). Movement here is created in part by time space streching and in part by thrust from the thrusters.
The one disadvantage of this is, that the central "bubble" of DMQF compression (that is directed by the nozzles) is a source of drag to the surrounding non-compressed DMQF.
So, in normal travel mode the interactions with the DMQF is analogous to a rocket engine moving through air, with the body causing drag, and the nozzle end giving thrust. As long as the DMQF compression bubble is active, you can generate lots of thrust in a direction, but the faster you move through the DMQF field, the more drag you will encounter.
DMQF interacts with gravity and is in effect "swept along" by large masses. Thus, the DMQF will always seem to move along with a heavy body. That is why drag is always relative to a local gravity well and thus, the "top speed" is relative to that local gravity well (that is also why speeds vary wildly when frame shifting past heavy bodies). This also explains why heavier ships tend to be slower as their own hull mass causes the compressed DMQF bubble to have even more drag with the surrounding DMQF. Some of this can be overcome with better compression and direction, but it's a diminishing returns problem which means that it becomes really hard to go much faster than about 500m/s. Faster speeds are possible, but then it becomes a serious tradeoff between the mass of the thing you want to move and the size of it's FSD core.
The interaction with gravity wells is also the reason why commercial drives jump from star to star - the ship is "thrown" in the direction of a star (gravity well) where the gravity well will naturally pull it out of jump speeds to normal FSD speeds).
When you disable a ship's flight assist, you also disable the DMQF compression and the ship can drift freely under regular newtonian physics. If a ship had ancient chemical rocket thrusters, you would have been able to accelerate it to higher speeds than the "top speed". The problem is that regular thrusters EAT fuel. The thrust needed to accelerate a 100t ship significantly would eat through tons of fuel in a manner of seconds.
(a 300t cobra burning through it's 16t of hydrogen fuel and 2t of oxygen in the cargo will only gain a few tens of m/s before running out of fuel).
For typical ship design it is just not seen as worth it and the speed limit is accepted as you have regular frame shift travel if you need to go further or faster.
This is my attempt at trying to explain in layman terms why ships have a "top speed". There are of course much brighter commanders under us which may be able to point out some flaws in my explanations and any comments are welcome.
EDIT : clarified the interaction between reactor, thrusters and FSD and that it is an intergrated system.
Last edited:
