Homebrew setting

[Old School]

I’ve been kicking around the idea for a homebrew setting. Influenced by Traveller, 2300, and the Expanse, among others. Don’t know if I’ll ever do anything with it, but it’s an entertaining thought exercise at least. Would be interested on anyone’s thoughts on what I might be missing in terms of the implications of this setting.

- Jump drives or something similar, but with a much larger jump shadow. 1,000 diameters or more is my current thought. Jump time greatly reduced, perhaps 2 days to jump.
- I’m uncertain if the jump shadow would limit just the starting and ending point of the jump, or if it is also a barrier a ship can’t travel through while in jump. Leaning towards the former.
- No contra gravity or inertial dampener tech
- Maneuver drives exist in some form. Whatever handwavium is used, M drives will require significantly larger tonnage than in MgT2.
- Cheap fusion power exists. Ships would use MgT2 RAW for power.
- Sensors are powerful: Radar, ladar, and heat sensors can spot drive plumes from millions of km away. Ships without their drives engaged are harder to spot, but even then detection beyond Distant range would be expected for a ship with active sensors. Estimated size and ship details at much longer ranges than in MgT2 sensors.
- Stealth technology exists. Requires both stealth coating and heat sinks to be truly effective, and only with drive system off and running on passive sensors.
- Transponders and active sensors are the norm in heavily populated systems.
- As a general rule, system governments, and perhaps even planetary governments within each system, are independent of each other. No overarching power along the lines of the Imperium or the Hierate.
- Advanced computing and robotics, but no true AI, or at least not readily available. Cybernetics exist but are limited, and come with disadvantages.

Implications for ship traffic:

- Heavily populated systems will have a lot of in system traffic, due to jump shadow. Using Sol as an example, 100D is about 1 au, so 1000D is 10 au, which means our entire solar system out to Saturn would be in the Sun’s jump shadow.
- Fast M Drives (over 1 G) would be limited to military, law enforcement, pirates, privateers, etc. Extended high g runs are too hard on the crew to be commonplace.
- Shorter times for jump limit the need for high jump drives, at least for commercial ships on main routes.
- Everyone can see everyone under normal conditions (but with speed of light delay), so piracy would often involve determining a ship’s route from far away, and positioning to get close enough to strike. Pirates will need stealth coatings, heat sinks and perhaps fake transponders, or will rely on deception to lure targets close.
- Since Pirates need to be invisible before an attack and disappear after, they would run for extended periods on passive sensors. Would sometimes apply to military or patrol vessels as well. Is traveling through space on passive sensors more dangerous?
- A non-government ship with a big drive and stealth looks like a pirate ship, so will be treated with suspicion at best when at port unless the ship is known to authorities. Pirate ships can’t hide in plain sight at a port, so they’ll need their own base of operations. Extreme distances of space combined with ability to disappear make piracy viable, but maintaining a ship will be difficult at best.
- Fast jump times combined with long in system travel distances will affect the nature of both freight and passenger travel. Large ships would often jump in, visit a port near the edge of the jump shadow, take freight / passengers on and off and jump out again, never visiting the main world. Running freight and passengers to their final destination will typically be handled by non-star ships.
- Assuming ships can jump through the jump shadow, just not start or end within it, systems will often have one main starport, at more or less the 1000D limit from the star, to handle intermodal transfers and refueling.
- These starports will be huge strategic assets in times of conflict. Would you want the starport to be a space station on its own orbit of the star so that starships can get to and from it very quickly, or would you put it in a gravity well, say the moon of a gas giant, so that an opposing navy can’t jump in practically on top of it?
- If ships can’t jump through the jump shadow, a highly populated system will likely have several starports, to accommodate traffic coming and going from different directions.
- No FTL communication, but shorter jump time allows information to move much faster between systems.

Any thoughts on the setup? Anything I’m missing in terms of the implications?

 

[AnotherDilbert]

- Jump drives or something similar, but with a much larger jump shadow. 1,000 diameters or more is my current thought. Jump time greatly reduced, perhaps 2 days to jump.

Wouldn't this just lead to interstellar ships stopping by a station outside the 1000D limit, and offloading the cargo to interplanetary ships, at least in civilised systems?

That is a problem for adventurers that will never reach interesting planets? Or are you imagining shipless adventurers that drift around on passenger ships?

 

[Old School]

Yes, that would be the norm for interstellar ships on main shipping routes, although I could see smaller ships being less specialized. If your travellers are the crew of an interstellar freight or passenger vessel, that would be boring. But I’ve always though that type of mercantile campaign is boring anyway, so not concerned with that.

 

[Sigtrygg]

Sounds like a harder science setting - I like it.

Is the m-drive going to be a reaction drive or some sort of 'warp' drive (the 2300 stutterwarp, a ST like warp bubble that is only capable of STL, something else)

Heat management is still magic by the looks of it - have you considered radiators and 'real world physics' heat sinks?

 

[Reynard]

Are you going to finally answer that long time question, are those aft features actually maneuver exhaust ports?

 

[Old School]

Yes. They are exhaust ports. Of course! And thrust can be vectored somewhat to lesson reliance on maneuvering thrusters or reaction wheels, although I would think you’d still need small thrusters for detailed maneuvering work, such as docking.

My physics knowledge probably isn’t good enough for “real world heat sinks”. My expectation would be that heat management technology would continue to improve above our current standard. Radiators, for example have gotten significantly smaller in recent years as efficiency has improved.

I don’t know about the drive technology. This is the part that requires handwavium in any setting. The stutterwarp of 2300 leaves me cold. My least favorite aspect of that setting. I’m leaning towards a reaction drive that manages to overcome the tyranny of the rocket equation, but not convinced on that yet.

 

[Reynard]

Fuelless perpetual reaction system? That's good hard science.

 

[NOLATrav]

IMTU for many years now we’ve declared that the many tons of LHyd required are in effect heat sinks; that is, the hydrogen is used as a coolant for all the various ship systems. Once heated it is vented, mainly thru the “exhaust ports” at the rear of the ship Some amount of the heated, expanded hydrogen is retained for attitude thrusters while in space or oxidized to help with atmospheric operations. Handwavium at its best.

 

[Old School]

Fuelless perpetual reaction system? That's good hard science.

I make no claim to hard science. More focused on the implications to the setting.

 

[Varulv]

...
- Shorter times for jump limit the need for high jump drives, at least for commercial ships on main routes.
...
- Fast jump times combined with long in system travel distances will affect the nature of both freight and passenger travel. Large ships would often jump in, visit a port near the edge of the jump shadow, take freight / passengers on and off and jump out again, never visiting the main world. Running freight and passengers to their final destination will typically be handled by non-star ships.
...

The cost for interstellar freight, planet-to-planet, is changed: The in-system part will become more expensive while the jump-transit part will be cheaper. Long in-system transit times means that non-starships, including smallcraft, will need better crew and passenger facilities.

One possible outcome is that jump traffic is mainly handled by larger vessels operated large corporations, and it is common practice to transport smallcrafts between star systems (just as cars and trucks are transported in ferries on Earth today). Suddenly a 20 dton launch equipped with a couple of stateroom and a small cargo hold is the typical starting ship for a group of Traveller. Not a bad thing in an environment more focused on adventures within a starsystem than on travelleling between multiple starsystems.

 

[paltrysum]

Great ideas, Old School.

I sometimes toy with the idea of a homebrew with no FTL travel. Something like Alistair Reynolds' Revelation Space series. It would put the focus on STL travel within systems. It's easy to scoff at this idea, but it can work. If the travel between neighboring stars takes, say, 20+ years, as long as the relevant parties make the trip as well and there are anti-aging drugs and treatments that have little side effects, all it takes is some story coordination that keeps the characters going to the places where the story is happening. The time gap becomes of little consequence.

The thing that keeps me from doing it? The fact that Traveller – and by extension, Cepheus Engine – are really built to feature FTL travel. I just wonder if another system altogether would be a better fit for such a game.

 

[Old School]

The cost for interstellar freight, planet-to-planet, is changed: The in-system part will become more expensive while the jump-transit part will be cheaper. Long in-system transit times means that non-starships, including smallcraft, will need better crew and passenger facilities.

One possible outcome is that jump traffic is mainly handled by larger vessels operated large corporations, and it is common practice to transport smallcrafts between star systems (just as cars and trucks are transported in ferries on Earth today). Suddenly a 20 dton launch equipped with a couple of stateroom and a small cargo hold is the typical starting ship for a group of Traveller. Not a bad thing in an environment more focused on adventures within a starsystem than on travelleling between multiple starsystems.

I agree with this. Non jump ships may often be freight on large jump freighters, making room for jump drives and fuel is less attractive given the long times of in-system travel. there will always be those smaller ships with both. . .privateers, smugglers, private yachts, etc. Might also still need tramp traders to go to backwater systems. Systems that are off the Main routes may not even have funds or justification for a starport at the 1000D limit.

 

[Old School]

Paltrysum, I think the same thing about a universe in which FTL is accomplished through jump “gates” or wormholes, a la Fading Suns, the Expanse, Coriolis, etc. Ship design is so integral to Traveller. The tradeoff between jump capability and everything else is a big deal. Dropping FTL would probably be suboptimal in the system, even if you can’t put your finger on the actual effects.

 

[locarno24]

Sounds interesting.

Thoughts:

1] Yes, you're essentially going to have big shipping infrastructure at the 1000D orbital limit, and that's going to be a 'gateway' starport (starport - singular - if the 1000D limit can be jumped 'over' even if not 'into' or 'out of', and multiple if it can't be so there is a port on the surface facing you). Assuming you've got a convenient gas/ice giant, you'll potentially see it in very high orbit of that, just so there's some real estate nearby. Taking the example of Neptune, Neso is orbiting at about 1000 times the planet's radius, the planet is well outside the star's radius and Neso has only a 60km diameter itself, so outsystem moons like it are a perfect example.

2] Shipping to and from means you'll get much higher G M-drives on in-system vessels. Any ship which needs to be able to trudge from the jump limit to the mainworld needs to be able to accelerate at quite-a-lot of G. Without artificial gravity you won't want to troll around at 4G on an extended basis, but the option would be good (I imagine high-burn thrusters being fairly common). You might well see unmanned stuff designed to operate at higher G - goods receiving gets it off a jumpship at the transfer station out-system, packs it onto a 'sled' which can accelerate at 6G (or whatever), and 'lobs' it down-system towards a safe downsystem point where a manned ship can collect it. You don't need advanced AI as that's basically no more strenuous a navigation challenge to a modern space probe.

3] Whilst you can be stealthy, if you can only clear an area after doing something nefarious at 1G (give or take), hit and run is going to be hard! A big question is going to be 'jump flash' - is there a big, high energy 'ping' when a ship jumps in? Because a 1000D limit is way too large to patrol effectively, so a carrier can jump in, go dark, and potentially launch silent running gunships, but not if It's going "HEY STUPID! WE'RE OVER HERE!" when it exits jump space...

 

[Old School]

Thanks, locarno. You make a good point about a high enough orbit around a gas giant. Just orbiting the star itself is only convenient close a fuel source (not that this can’t be overcome with enough fuel haulers - similar to the ice hauler Canterbury in The Expanse. My issue with just orbiting out there all alone is that it is very exposed. Meaning that if any conflict st all is anticipated (and what fin would an RapG universe be without it), that gateway starport is going to be extremely well defended. If multiple ports are Required this likely changes things other than in very high traffic systems.

I disagree on the high g aspect. Going from 1G acceleration to 4G only cuts your travel time in half. Most freight isn’t going to be worth it. As for unmanned haulers - this makes perfect sense of course, but one truism of science fiction is that robot ships are boring.

I would expect pirate ships to escape at high G, at least at for short periods. Changing vectors so you can’t be tracked as easily, likely with some sort of maneuvering thrust, would be tricky.

 

[AnotherDilbert]

I disagree on the high g aspect. Going from 1G acceleration to 4G only cuts your travel time in half. Most freight isn’t going to be worth it.

I suspect Locarno is correct. It's not so much a question of the time cost of cargo, but the time cost of ships. If the ships take half the time to perform one trip, it can make twice as many trips per year, hence transport twice as much cargo per year, and we will only need half as many ships.

So, unless 4 G makes the ship twice as expensive, it is likely more profitable.


Take a simple in-system 1 G hauler with 1000 Dt payload:
Assumptions: MgT2 with three times as large M-drives (≈LBB5).

Compare with a 4 G version, still with 1000 Dt payload, so a little bigger:

Under these assumptions the 4 G ship is more than twice as expensive, so 1 G will be cheaper per ton of transported cargo.

 

[Old School]

Even using standard rules, the ship cost per ton of cargo is a wash. Not to mention the difficulty on the crew of a full 4G burn for a couple of weeks at a time. Would be hard on the cargo, as well.

 

[phavoc]

I would expect your stations to be around 999D rather than 1,000D. One reason is safety - ships emerging from jump still have to physically cross the jump shadow line, so it will give time for the station to have both traffic control and be able to dispatch customs ships, etc. The other is going to be from a pure military aspect - ships won't be able to jump into the system and have complete surprise over the defenders. I could see where critical systems and/or those closer to potential conflict zones would move even deeper into the jump shadow to give even more warning.

Where do you plan on placing your stations? Along the plane of the eliptic, or above it?

As far as engines go, I've toyed with separating the Lhyd as both reactor fuel and reaction mass for engines. He-3 is a better fuel source for fusion, and the regular hydrogen is the 'fuel' used for thrusters. And for engines there are ion-engines (low accel rates, good on fuel usage, cheap - merchant engines) and fusion rockets (high accel, gulpers of fuel, more expensive - military and anyone who values speed over economy).

 

[Old School]

Good points, phavoc. Exact station placement would probably vary by system. Farther inside the 1000D limit of anything, the longer it takes to get there, which lessens the efficiency of shipping. But the security aspect could be the larger concern. Far to enough in to bring defenses to bear would be a minimum, I think. In terms of 1000D of a star, that’s not very far in.

Assuming ships can jump through the shadow, just not emerge or depart from within it, is there an advantage to being off the elliptic? Wouldn’t that just put you farther from anywhere on the elliptic you want to go?

Slow but cheap and reliable ion engines? No gravity generators or inertial dampeners? Star Frontiers here we come!

 

[phavoc]

Along the elliptic means it will orbit in roughly the same process as the planets do. Above/below means that travel will, generally, be more efficient (assuming you are above/below the star) to all points in the system. Or at least you start equidistant.

I like the idea of inertial dampeners and gravity fields, so no changes there. Just the power plant being converted to more efficient fuel and using the hydrogen as reaction mass rather than very inefficient fuel. The two engine types follow a pattern used in reality, but also in other gaming systems. merchies will always seek out the lowest cost operations since they care about money.