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Old 02-20-2019, 06:01 AM   #11
Rupert
 
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Default Re: FTL rate of movement for GURPS SPACESHIPS

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Originally Posted by ericbsmith View Post
I disagree. Modern day carriers are lumbering hulks compared to jet planes. However, modern day carriers are not meant to be front line vessels, they are meant to serve as a base of operation for the much faster fighters, a place where the pilots can take their fighters to rest, refuel, rearm, and repair.
A modern carrier is as frontline as any ship in a carrier group. Either the whole group is out of reach of the enemy, or it is not.
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I see nothing about the proposed setup that would change that, though it does open the door for a different class of medium-occupancy "corsair" fighter which has limited fuel, repair/maintenance capabilities, and extremely cramped living space but is based out of a carrier allowing the crew to rotate and any necessary repair/maintenance to be done back on board the carrier. These would be larger than your typical fighter, capable of operating on their own for a few weeks, but smaller than your typical independent ship. Given the background description such vessels could dart around ahead of the larger fleet, performing reconnaissance or hit-and-run operations.
The OP is proposing an FTL system that makes large ships noticeably slower in FTL than small ships. Thus a carrier with a fighter wing is slower strategically than a fleet of FTL gunships. As missiles tend to make large ships a liability anyway, it works against carriers quite strongly, because they have to carry the fighters right into any system there's combat in (and may have to recover them directly from combat). A gunship fleet's support vessels, if they're operating very far from a base, may be no faster than a carrier, but they don't have to come into a hostile system - they can be non-combat vessels in a way that a carrier can't.
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Old 02-20-2019, 06:05 AM   #12
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Default Re: FTL rate of movement for GURPS SPACESHIPS

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Originally Posted by AlexanderHowl View Post
What would happen if you flipped the assumption? For example, that spacecraft possessed a speed equal to ((mass^0.5) × (FTL engines^0.5))c? In that case, a 100 metric ton smallcraft with four FTL engines would have a maximum velocity of 20c while a 10 million metric ton capital ship with one FTL engine would have a maximum velocity of 3,160c. It would give a military reason for large ships and a logical reason for carrers.
Bulk freighters dominate interstellar shipping and small tramp cargo vessels don't exist except in really marginal areas that simply don't have the volume of trade to fill large vessels, even when you run the large vessels in a long circuit to give the cargo plenty of time to pile up. The small vessels not only can't carry much, they do slow slowly.

For long distances you'll have your small FTL scout or yacht carried by a larger vessel, and if this is at all common it'll be a standard procedure.
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Old 02-20-2019, 06:13 AM   #13
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Default Re: FTL rate of movement for GURPS SPACESHIPS

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Originally Posted by David Johnston2 View Post
Assuming that you include the defense favouring switches then it creates the early 20th century paradigm of battleships for heavy firepower, destroyers for speed and cruisers to catch destroyers.
While these classes had differing tactical speeds, where their strategic speed varied it did in ways you might not expect - for long distance movement destroyers were often quite slow because they were small (making them uneconomical at quite quickly as their speed rose, and they lost speed in bad weather) and carried little fuel (so they had to travel slowly to conserve fuel if they were moving long distances between bases). Cruisers were only faster than battleships if they had reasonably close bases for the same reason. However, these things varied a lot depending on the exact time - before reduction gearing was used the only steam turbine ships with good range were ones with 'cruising' turbines, and that limited them all to quite slow cruising speeds.

Also, if you're using that naval model, destroyers are fleet boats and FTL that's faster than that of the battleships is wasted, as they'll be moving as a group. Cruisers are the scouts and would need fast FTL speeds, but destroyers wouldn't.
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Old 02-20-2019, 06:20 AM   #14
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Default Re: FTL rate of movement for GURPS SPACESHIPS

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Originally Posted by Agemegos View Post
On the other hand, the larger ships don't need engine rooms and can be automated more cheaply. I recently did a cost study for a particular set of assumptions, and found that a highly-automated SM+12 ship came in 30% cheaper per ton-lightyear than an SM+9 ship with an engine room.
I assume that's including crew salaries and life support costs, etc. Did you try a SM9- ship with Total Automation of the Engine Room?

I'm curious as to whether the high cost of total automation would be worthwhile in this case.
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Old 02-20-2019, 06:45 AM   #15
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Default Re: FTL rate of movement for GURPS SPACESHIPS

I suspect you get better results if you cap the speed gain from size at some point. That sort of thing happens all the time, as different limiting factors take over.



If you want to create a fighter and carrier paradigm, increasing the FTL speed of the fighters is a little odd, unless you intend for battles to be fought with carriers parked in different systems sending fighters back and forth to each other. Also, with many paradigms you end up with the "Carriers" being nothing more than fuel tankers and cargo ships, so watch out for that.
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Old 02-20-2019, 11:08 AM   #16
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Default Re: FTL rate of movement for GURPS SPACESHIPS

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Originally Posted by AlexanderHowl View Post
What would happen if you flipped the assumption? .
You'd get the Alternity Star*Drive setting.

The purpose there was to isolate small PC ships in a frontier sub-setting. The mostly barren area between the Core and the frontier (or whatever it was called) would have been more than year's trip for PC ships and they couldn't carry enough food and would have broken down without their yearly maintenance. Gigantic ships could jump 10x as far per week and thus link the Core and the Frontier together.

It worked to produce the isolation that TSR wanted but put a pretty sharp damper on PC importance generally. Want to warn your homeworld that the Evil Corporate Cruiser is coming? You can't get there before it does.
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Old 02-20-2019, 12:49 PM   #17
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Default Re: FTL rate of movement for GURPS SPACESHIPS

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Originally Posted by Rupert View Post
I assume that's including crew salaries and life support costs, etc.
Yes, and propellant, insurance, amortisation, depreciation. Also maintenance, repairs, and overhauls of the reaction and FTL engines based on engine hours.

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Did you try a SM9- ship with Total Automation of the Engine Room?
No. It seemed to me that total automation is so expensive that you would need really, really low interest rates, insurance rates, and depreciation to let it compete with crew salaries, quarters, and life support.

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I'm curious as to whether the high cost of total automation would be worthwhile in this case.
At 8% interest, insurance, & depreciation (which was as low as I dared to go) each workspace totally automated costs G$400,000 per year. Spaceships 2 suggests a crew employment cost of $67,200 per year for base-level crew, plus which it costs G$150,000 (G$12,000 per year) to give them a cabin, $75,000 to give them a shared stateroom or couchette, or $37,500 a bunk in a bunkroom. And $730 per year for consumables. High automation is really marginal at 8%, even with comfortable long-occupancy crew quarters. Only adding foremen to large crews puts it firmly over the top.

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.
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Old 02-20-2019, 01:19 PM   #18
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Default Re: FTL rate of movement for GURPS SPACESHIPS

I would expect a couple of interesting results:

1: Carriers would become a real big deal.

2: Ships would have some kind of connection device or coupling connection.

For some applications, staying together is much more important than speed. You don't want your big ship to jump in-system with no support, so attach a few (dozen) small ships to it's hull and have them ready to detach. This is not necessarily a military application, but for an exploratory mission, everybody may want to arrive together and not 3 days ahead of the supply cruiser.

Similarly, having all the ships show up at the same time may be better than being fast. Even with an exponential slow-down, having all 30 invading ships show up at the SAME time instead of over the 5-minute span which is the closest you can get with careful weighing may be worth a full 2-day delay in the plans. Even with careful weighing and math, it may be impossible to time things better than a few hours when systems are days apart. And that can be an eternity in battles.

If these connections double as some kind of emergency towing and/or rescue attachment and are standardized, that's a bonus.
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Old 02-20-2019, 01:22 PM   #19
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Default Re: FTL rate of movement for GURPS SPACESHIPS

My small freighter cost G$207,307.69 per "compartment" of cargo space, and the large freighter G$189,233.33 per "compartment"; the passenger ships cost G$368.846.15 per passenger compartment and G$358,677.78 per passenger compartment. So total automation is more expensive than more/bigger ships as a way of increasing payload, in the situation I modelled.
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Old 02-20-2019, 03:26 PM   #20
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Default Re: FTL rate of movement for GURPS SPACESHIPS

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Originally Posted by Rupert View Post
The OP is proposing an FTL system that makes large ships noticeably slower in FTL than small ships.
And in which even 30-ton "fighters" take a couple of days to travel one light-year and a month or so to travel the typical distance between a habitable planet and its nearest neighbour among habitable planets.
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