Examine my proposed FTL travel mechanics

[Minuteman37]

I'm putting together a sci-fi setting and could use help with the FTL.

My idea is that FTL travel is achieved by installing Warp bubble generators and warp sensors created by a Forerunner civilization onto ships that scan frequencies generated by warp buoys, lock on and plunge into subspace where the warp drive "pulls" them to the buoy eventually arriving before the light does.

I'm wanting fighters and small Millennium Falcon style cargo ships to be viable within setting, so I'm planning on having a ships ftl speed be inversely related with the size of the ship, and the Power requirements needed to activate the drive to increase exponentially with the size of the ship. Meaning larger ships need to devote more mass to Power generation and can't travel as fast.

Here are my initial alpha test rules.

• Your warp generator requires power points equal to your ships SM to function.
• You're ship can traverse 1 light year in a number of days equal to your ships SM squared.
• Your ships warp sensor range scales up with the size of the sensor, bigger ships can mount bigger sensors and take more direct routs to their final destination.

[Stormcrow]

Originally Posted by Minuteman37

Your warp generator requires power points equal to your ships SM to function.

This means that larger ships have to devote larger percentages of their mass to power generation. I dunno the assumptions of your setting's physics and technology; let's suppose you're using Total Conversion Power Plant, the best you can get in Spaceships 1, not counting cosmic options. One such plant gives you 5 Power Points no matter what size your ship is. To keep up with SM, you'd need a number of systems of power plants:

SM +5: 1 system
SM +6 to +10: 2 systems
SM +11 to +15: 3 systems

And that's just to drive a single engine. If you want multiple engines, or to power anything else while using the engine, you'd need even more power plant systems.

Power Points already scale with ship size, since a Power Plant system will produce the same number of Power Points regardless of ship size. The Power Plant gets bigger as the ship itself gets bigger.

You might instead impose an arbitrary number of normal engines per SM, saying that a single engine produces FTL thrust X, and ships above SM +A require 2X thrust to achieve FTL and ships above SM +B require 3X thrust.

[Flyndaran]

That would make small merchant ships more reasonable, but also make giant tanker like cargo ships less reasonable.

[Minuteman37]

Originally Posted by Flyndaran

That would make small merchant ships more reasonable, but also make giant tanker like cargo ships less reasonable.

I hope so but my napkin math is ambiguous.

Assuming TL 9 power generation and that a dedicated tradeship will need the following 10 systems regardless of size.
Armor
Armor
Armor
Open space for food growth
Control room
Fual tank
Sublight engine
At least one habitat
Warp bubble generator
Warp sensors

A SM 8 ship the smallest one that can be relatively self-sufficient for long voyages would need 8 nuclear fission planets in addition to the above allowing two systems for cargo. A capacity of 100 tons and can travel at 6*C.

An SM+15 ship would also need 8 reactor systems becouse it can use nuclear fusion instead. With it's 2 cargo holds it can carry 300k tons of cargo but only travels at 1.5*C.


A SM+10 ship is a third option becouse it's as small as you can go and still use the two power point fusion reactors. You'd have five fusion reactors that would allow for five cargo holds giving a total capacity of 2.5k tons and a ftl speed of 3.5*C

[RyanW]

Originally Posted by Minuteman37

A SM+10 ship is a third option becouse it's as small as you can go and still use the two power point fusion reactors. You'd have five fusion reactors that would allow for five cargo holds giving a total capacity of 2.5k tons and a ftl speed of 3.5*C

A SM+9 ship ought to be able to use fusion plants as well, provided it has at least three of them.

[Minuteman37]

Originally Posted by Stormcrow

This means that larger ships have to devote larger percentages of their mass to power generation. I dunno the assumptions of your setting's physics and technology; let's suppose you're using Total Conversion Power Plant, the best you can get in Spaceships 1, not counting cosmic options. One such plant gives you 5 Power Points no matter what size your ship is. To keep up with SM, you'd need a number of systems of power plants:

SM +5: 1 system
SM +6 to +10: 2 systems
SM +11 to +15: 3 systems

And that's just to drive a single engine. If you want multiple engines, or to power anything else while using the engine, you'd need even more power plant systems.

Power Points already scale with ship size, since a Power Plant system will produce the same number of Power Points regardless of ship size. The Power Plant gets bigger as the ship itself gets bigger.

You might instead impose an arbitrary number of normal engines per SM, saying that a single engine produces FTL thrust X, and ships above SM +A require 2X thrust to achieve FTL and ships above SM +B require 3X thrust.

I'm aware that one power point represents different levels of energy depending on your ships size, regardless though the default assumption is that it takes the same number of power points to power a system on any give size ship. I'm adding another layer of exponential power consumption on becouse larger ships have more carrying capacity.

[ericbsmith]

The biggest issue I see with the power issue is that it will seriously hamper commercial travel, since it becomes exponentially more expensive to build larger ships. This will help support a "tramp freighter" economy. OTOH, it will barely affect military vessels, especially with lots of higher TL and TL^ ship systems. Military vessels already need a robust power supply to power their engines, weapons, shields, and other equipment. They will simply need to turn some of that equipment off in order to enter Warp, and at worst may have some extra Power Points available during combat giving some redundancy.

So the universe based on these assumptions is likely to have lots of Tramp Freighters being pushed around by some seriously large military and/or pirate vessels.

[ericthered]

What is there to keep from one crew running a swarm of ships from a command vessel? That would be my first idea to achieve economies of scale in such a system.

[Minuteman37]

Originally Posted by ericthered

What is there to keep from one crew running a swarm of ships from a command vessel? That would be my first idea to achieve economies of scale in such a system.

You can't communicate in subspace, you're in an entirely separate dimension with fluid geometry your warp bubble is the only thing keeping your ship from just crumbling under the weight of different physical laws and you'll be in this silent vacuum of death for months or years at a time. At TL9 you can't guarantee those ships will make it to your destination and if they don't you certainly can't figure out what happened to them in the absurd vastness of space.

Feel free to poke holes in this justification though, I hadn't considered that idea yet and this is off the cuff so to speak.