Combining Spaceships and GURPS Space Catapult Launch

[Riandor Na'Eris]

First and foremost my English Written level is far from Native so forgive me.
I’m trying to convert a specific Sci-Fi setting to GURPS. Now, this setting is a bit tricky when it comes on how it handles Space Travel.
Travel between different Star systems is possible thought stabilized Wormhole but only specially equip ships can open such gates, most spaceships literally hitch a ride on some gigantic Ferry Boat Spaceships that carry them across fixed routes across the colonized space.
This is mostly a feature of the setting, some highly classified Military or Government ships can open the gate but those are currently out of the scope of my PCs.
What is paining me to adapt using Spaceships is how most Spaceships travels inside a system.
Basically every colonized star has some kind of Mass Drivers built to accelerate and decelerate ships while they are in the space (most ships are built for space travel only and they access planetary surface using shuttles or Orbital Lifter) yet they have propulsion on their own (mostly Vasimir/Plasma Thruster with some High-Class ships being able to use Antimatters) and the Mass Drivers allow them to reduce the need for massive fuels tanks.
GURPS Space do consider this kind of external propulsion system but I don’t know how to combine it with Spaceships and it’s math since the ships propulsion is somewhat external to it.
Can someone help me?

[Ulzgoroth]

Originally Posted by Riandor Na'Eris

First and foremost my English Written level is far from Native so forgive me.

Not bad at all, though I'd suggest using blank lines more - paragraphs back to back with no blank lines in between wind up looking like a nearly continuous wall of text here.

Originally Posted by Riandor Na'Eris

Travel between different Star systems is possible thought stabilized Wormhole but only specially equip ships can open such gates, most spaceships literally hitch a ride on some gigantic Ferry Boat Spaceships that carry them across fixed routes across the colonized space.
This is mostly a feature of the setting, some highly classified Military or Government ships can open the gate but those are currently out of the scope of my PCs.

Picking at a nit here, but what makes those highly classified ships distinct from the non-classified gate-opening ships?

Originally Posted by Riandor Na'Eris

What is paining me to adapt using Spaceships is how most Spaceships travels inside a system.
Basically every colonized star has some kind of Mass Drivers built to accelerate and decelerate ships while they are in the space (most ships are built for space travel only and they access planetary surface using shuttles or Orbital Lifter) yet they have propulsion on their own (mostly Vasimir/Plasma Thruster with some High-Class ships being able to use Antimatters) and the Mass Drivers allow them to reduce the need for massive fuels tanks.
GURPS Space do consider this kind of external propulsion system but I don’t know how to combine it with Spaceships and it’s math since the ships propulsion is somewhat external to it.
Can someone help me?

This is probably easy, but it depends a little on how you're using the mass drivers. Fundamentally, this probably makes no difference to the spaceships delta-V math.

If you're literally shooting the ships out of and into 'cannons', then the effect is just that they have the mass driver velocity added on at no delta-V cost. (Though they'd have to use thrust to decelerate if they're going from a driver to a place without a driver.)

If you're shooting some kind of stream of material that the ships deflect for thrust throughout the flight, they effectively gain a 'reactionless' acceleration as long as they're able to use the stream.

Which math are you wanting help with?

[Riandor Na'Eris]

Thank you for your answer.

Originally Posted by Ulzgoroth

Picking at a nit here, but what makes those highly classified ships distinct from the non-classified gate-opening ships?

In this setting, the Gate built around the Wormhole stabilize it but the Wormhole is not ALWAYS OPEN but you need a specific kind of Engine to 'OPEN' it, like a key.

According to the material I've, it's costly and requires power and other stuff that can't be made easily available on normal ships safe for the most advanced and powerful one. Everyone else needs to hitch a ride if they want to move out of a Solar system. It's a setting feature more or less.

Originally Posted by Ulzgoroth

This is probably easy, but it depends a little on how you're using the mass drivers. Fundamentally, this probably makes no difference to the spaceships delta-V math.

Again they are described as a set of electromagnetic tunnels used to accelerate and decelerate the ships while they are in space. Sadly at which speed is not given since the whole setting doesn't go too much hard on math. Which kind of Delta-V and G could be appropriate for this kind of external propulsion?

[Ulzgoroth]

Originally Posted by Riandor Na'Eris

Again they are described as a set of electromagnetic tunnels used to accelerate and decelerate the ships while they are in space. Sadly at which speed is not given since the whole setting doesn't go too much hard on math. Which kind of Delta-V and G could be appropriate for this kind of external propulsion?

Probably not much realistically. Even if you could produce it with what sounds like a very wide coil-gun, ships probably couldn't tolerate a very high acceleration. And you can only make the barrel so long. And, frankly, it's pretty fuzzy what you're supposed to be gaining by this considering that the launcher is in space and thus winds up recoiling from whatever impulse it delivers. I suspect math isn't the only place the setting isn't too hard! But we can work with that.

Do you have any numbers for the setting's travel times? We might be able to back-solve the performance of the tunnels from there.

[Riandor Na'Eris]

Yes, the setting isn't exactly Hard-SciFi or too reliant on math.

Originally Posted by Ulzgoroth

Do you have any numbers for the setting's travel times? We might be able to back-solve the performance of the tunnels from there.

Not in what's has been produced so far, for what I got some Gates are placed even far than Pluto is from Sol while some are a bit closer.

When time is an issue the Antimatter Drives are used so I suppose I need to figure a value that makes a normal ship journey inside the system long enough to be a factor but not too long enough.

Hence my issues.

[Ulzgoroth]

...Okay, if the setting material is completely blank here, how long do you want trips to take? On a very loose scale. Days, weeks, months, years?

I'm gathering that 'normal' in-system ships are capable of making the trip out to the gates. That could be useful for figuring out some minimums. Any feeling about how long that should take?