FTL rate of movement for GURPS SPACESHIPS

[AlexanderHowl]

Which is rather slow. Slower universal FTL speeds usually mean that larger ships are more effective and efficient, as they are capable of doing more stuff, but a difference in FTL speeds that favors smaller ships changes generally messes everything up. When it gets that slow though, it really means for combat is that interstellar wars will be fought with waves of automated SM+4 fighters equipped with missiles with antimatter warheads.

[munin]

Originally Posted by hal

Hello Folks,
… the rate a ship travels is equal to its mass^.2 such that a 1000 ton ship would 3.98 days to travel 1 light year. A 1,000,000 ton ship would take 15.85 days per light year to travel. …

If you don't like the fifth root of mass, then use some other value such as cube root or log of, etc. …

For easier math, you can get something similar by saying a ship takes its dST in hours to travel one lightyear (or parsec, or 10 ly, or whatever). That 1000-ton ship (dST 70) would take 70 hours (2.9 days) per lightyear, while a 1,000,000-ton ship (dST 700) would require 29 days per lightyear.

[Rupert]

Originally Posted by Agemegos

If I had ships with very small payload fractions it might be different: total automation of all workspaces and NAI "officers" might mean having no crew habitat at all. But I was at a payload mass fraction of 70% or better, so it obviously wasn't going to work.

I'll take a look after breakfast and get back to you.

I had a feeling it probably wouldn't be worthwhile. I do wonder how removing the engine room entirely changes things - it reduces crew requirements, and frees up space for more payload. The question is how much the -1 HT and the annoyance of having to do maintenance from outside the ship costs compared to the savings, and I have no idea how best to assess that.

[Agemegos]

Originally Posted by Rupert

I had a feeling it probably wouldn't be worthwhile. I do wonder how removing the engine room entirely changes things - it reduces crew requirements, and frees up space for more payload. The question is how much the -1 HT and the annoyance of having to do maintenance from outside the ship costs compared to the savings, and I have no idea how best to assess that.

You would need to make assumptions about the amount of extra hangar time needed for the maintenance and the increased rate of depreciation. I'd start with the number of staff-hours that the crew in the workstations put in for the amount of extra MRO, and I might start on the costs of lower HT by looking at the rules for extra maintenance costs of Cheap and Used Ships at the top of Spaceship 2 p.28. You could interpret -2 to HT as costing 1% per month in extra maintenance, and -4 to HT as costing 4% per month in extra maintenance, extrapolate a value for -1, and apply it only to the price of systems that would have a workstation requirement if the ship were large.

[Rupert]

I notice that Cargo Holds, even refrigerated ones, do not require any workstations, and thus a ship that is largely cargo spaces will have little increased maintenance with your suggestion. I think both this effect and your suggestion make sense.

As for the OP's thought on making smaller ships faster, how about simply having a cap on speed that varies depending on ship size? If each stardrive/super stardrive produces 5LY per day for each point of power, and the maximum FTL speed is set at something like: 80 - (SM x 5) LY/day, then a SM+6 ship (a little 100 ton scout, FTL shuttle, or heavy fighter) can do a maximum of 50LY/day, and so can't utilise the output of more than five Super Stardrives. A SM+13 ship (a 300,000 ton freighter or major warship, say) can do no better than 15LY/day, and shouldn't mount more than three standard Stardrives or one Super and one standard Stardrive.

This means that for the same speed a large ship is no less mass efficient than a small one, they just can't go as fast.

[AlexanderHowl]

While it lends itself to certain types of adventures, a faster FTL speed for smaller spacecraft distorts everything. Why have capital ships when you can use the same tonnage in automated bombers to accomplish the same military goals faster? Why have merchant haulers when you when you can use the same tonnage in automated cargo pods to accomplish the same commercial goals?

By having smaller spacecraft go faster, you remove any economic or military reasons for humans to be in space. Now, if your group wants to play AIs, that is fine, but I think that would get boring after a while, as there would be no particular reason to allow robotic bodies on the drone. After all, a robotic body would count against the cargo/weapons available to the drone...

[Rupert]

Originally Posted by AlexanderHowl

While it lends itself to certain types of adventures, a faster FTL speed for smaller spacecraft distorts everything. Why have capital ships when you can use the same tonnage in automated bombers to accomplish the same military goals faster? Why have merchant haulers when you when you can use the same tonnage in automated cargo pods to accomplish the same commercial goals?

By having smaller spacecraft go faster, you remove any economic or military reasons for humans to be in space. Now, if your group wants to play AIs, that is fine, but I think that would get boring after a while, as there would be no particular reason to allow robotic bodies on the drone. After all, a robotic body would count against the cargo/weapons available to the drone...

Umm. Why do you assume automation is related to size? Why would robots/AIs not invalidate humans on large ships just as well as small?

Actually, it's easier to do this on large ships, because of the automation rules.

[AlexanderHowl]

Automation is not mandatory on capital ships. When it comes to long distance SM+4 or SM+5 spacecraft though, automation is mandatory because they cannot have habitats. In addition, smaller spacecraft only need to pay for automation if they have an Engine Room. If their designers are willing to accept a -1 HT (after all, who cares in the case of a drone), they do not need to pay for automation.

Since you automatically have automation for long distance SM+4 spacecraft and since SM+4 spacecraft are the fastest spacecraf in this scenario, conflicts end up being decided by whom can send the most antimatter warhead equipped drones against the other side. It would not be unreasonable for a TL10 developed planet to be capable of fielding multiple wings of ten thousand such drones, which would mean 250,000 16cm missiles with 25 kiloton antimatter warheads of each. Since they would travel faster than larger spacecraft, such a world could torch the worlds of their enemies and have their drones return for resupply long before the capital ships of their enemies reached their systems.

[hal]

In light of automated drones being the ultimate system, might it not be best to limit FTL capabilities to hulls of a given size?

Some of the issue being discussed in the previous post apply to autonomous units regardless of whether one uses a uniform speed for FTL travel or not. One could use the same "wave" tactic using automated drones regardless. If, as in Traveller, FTL is limited to size modifier +7 or +8 hulls, that might help (not really in my opinion).

In the end, it seems to be an issue where GURPS ULTRATECH plus assumptions about SAIs etc, make human crewing illogical and inefficient. My suggestion is to revisit the assumptions inherent in artificial intelligences. But, that is a topic for another thread - one that will likely have some major ramifications not only on an adventuring level, but also cultural level. If AI labor is superior than flesh labor, then AI labor will supplant human labor, interfering with a human's ability to compete in the current economic model of exchanging labor (time) for finished goods/services produced more cheaply elsewhere via robotics coupled with computers.

In the end? The suggested route of autonomous robotic fighting spacecraft will result in BERSERKER style stories (see Fred Saberhagen). From there, it makes more sense to have robotic tanks, or robotic soldiers.
Your miles may vary.

[Fred Brackin]

Originally Posted by hal

In light of automated drones being the ultimate system, might it not be best to limit FTL capabilities to hulls of a given size?

If you're looking to chnge the balance of combat you want to diddle with non-ftl propulsion.

For example if you have sub-warp drives but limit those to SM+4 hulls you have no super-missiles. You could have SM+4 robo-kamikazes but those would be orders of magnitudes more expensive to do massive strikes with.

Small ships would have to fight other small ships with beam weapons and armoring big ships so small ship beams can't damage them requires only that you edit out those beams with the highest armor divisors.