[Spaceships] balance with a) interstellar wars, b) super-science and c) size mods

[muduri]

Still haven't managed to break the Spaceships addiction - particularly propulsion systems. So I'm curious about the balancing act between some different publications and systems.

a) I've tried building some sample vehicles from Spaceships but have only skimmed the Interstellar Wars rules. So I'd like to ask - let's say you started with a similar concept (and presumably setting, budget, TL and SM) - would a spacecraft built with the ISW rules come out similar to Spaceships? Or has anyone found significant break points worth keeping in mind?

b) This one's a bit trickier. Given the addiction to propulsion, I'd like to keep both the normal and super-science drives both available and locally optimal. But right now the super-science engines seem like game-changers - there's not much reason to use a nuclear thermal rocket if a fusion torch or a reactionless drive are available. I was thinking of some kind of GM fiat - maybe "super-science is available, but only TL10^ in a TL11 world, and at 10x cost." It seems like then the torches only go to the richest, and the PCs might have to start with NTR or fusion pulse drives as they work their way up. Am I understating the cost differences that already exist, or risking unbalancing the game for other reasons, or is this something that people have already thought about tweaking?

c) Obviously the atmospheric scaling principles that cause a massive cargo aircraft < a bomber < fighter for speed don't apply for the same reasons in space. But could something be justified? I don't know, limited surface area means that only so much reaction mass can be tossed out at a time per engine? Really it's just the instinct to stop carriers and battleships from buying double-hot-reactionless drives and keeping up with the fighters. But, assuming it could be tweaked out, is there any way to justify this or would it just be fiat?

Many thanks for your thoughts on any or all three of these!

[weby]

Originally Posted by muduri

Still haven't managed to break the Spaceships addiction - particularly propulsion systems. So I'm curious about the balancing act between some different publications and systems.

a) I've tried building some sample vehicles from Spaceships but have only skimmed the Interstellar Wars rules. So I'd like to ask - let's say you started with a similar concept (and presumably setting, budget, TL and SM) - would a spacecraft built with the ISW rules come out similar to Spaceships? Or has anyone found significant break points worth keeping in mind?

For smallcraft, if you use reactionless thrusters they come to similar things though thusters in ISV are better than the normal reactionless drives in SS and way less than super reactionless.

For starhips, the base feel of the ships is very different. In general for ISV ships you are volume limited more often than weight limited, but SS ships ignore volume. You will find that ISW ships with higher jump ratings are seriously cramped for space due to all the jump fuel they have to carry, there is no similar feel in SS, even if you add the requirement of fuel to jump drives.

So if you are trying to build Traveller ships in SS you will need to be careful or they will not seem like Traveller.

As a example:
There is very little need for things like battle riders in the base SS system as a FTL engine only uses 5% of your limited resource(mass), so the increased utility is usually worth it.

But in Traveller battleriders are definitely worth it at higher TLs. A basic jump 4(Third imperium "fleet standard") warship will be using 5% of it's volume for the drive and 40% for fuel. A battlerider can cram more weapons, powerplants and drives in that volume, basically doubling the combat effectiveness for the same tonnage. (Note: tonnage=volume measurement in Traveller)

b) This one's a bit trickier. Given the addiction to propulsion, I'd like to keep both the normal and super-science drives both available and locally optimal. But right now the super-science engines seem like game-changers - there's not much reason to use a nuclear thermal rocket if a fusion torch or a reactionless drive are available. I was thinking of some kind of GM fiat - maybe "super-science is available, but only TL10^ in a TL11 world, and at 10x cost." It seems like then the torches only go to the richest, and the PCs might have to start with NTR or fusion pulse drives as they work their way up. Am I understating the cost differences that already exist, or risking unbalancing the game for other reasons, or is this something that people have already thought about tweaking?

Basically super science drives come in two general lines: Reactionless and higher output.

Balancing higher output reaction drives vs low is likely indeed as easy as cost. The cost difference should be greater than the effect multiplier, likely it raised to 1.5 to 2 power.

If a super science drive is *10 as effective it should cost *30-100, The reason being that a *10 price would just have people buy the more effective drive but 1/10th the volume. at *30 cost you would likely see some use of the less effective, but many would still prefer to use the smaller drive to get in more payload, at *100 cost only the most demanding applications would likely use the more effective drive.

Balancing reaction and reactionless drives is trickier as the reactionless drives are "always" better at longer distances as the reaction drive will need more and more fuel to match to d-v.

If you want to have both, then one option is to make the reactionless drives really low thrust compared to reaction drives. Thus civilian system ships would likely have reactionless drives, thugs and local space craft would likely use reaction drives. Warhips would likely have reactionless "cruise engines" and reaction "sprint engines" with fairly small fuel tanks. Fighters would likely have only reaction engines. Starships would depend on how far they have to travel before they have can go FTL.

c) Obviously the atmospheric scaling principles that cause a massive cargo aircraft < a bomber < fighter for speed don't apply for the same reasons in space. But could something be justified? I don't know, limited surface area means that only so much reaction mass can be tossed out at a time per engine? Really it's just the instinct to stop carriers and battleships from buying double-hot-reactionless drives and keeping up with the fighters. But, assuming it could be tweaked out, is there any way to justify this or would it just be fiat?

Many thanks for your thoughts on any or all three of these!

In fact many of the reasons why aircraft are superior to ships in todays word do not apply to space, a space fighter is more like a torpedo boat vs the battleship.

A fighter as single purpose lightly armored,short duration craft can likely devote more of it's mass to propulsion than a warship, but the difference may not be that big.

If you want there to be a big difference then you have to invent a reason. In my star wars campaign I decided that there were two technologies of reactionless drives(called ion drives for lore reasons, but really they are reactionless drives....)

The small version was equivalent to a hot reactionless drive: 1g acc/5% mass. The large version was equivalent to the rotary reactionless drive: 0.1g acc/5% mass.

The small drive had a minimum mass of is 1.5 tons. (30 tons thrust) and maximum total mass of 16.67 tons. (333.33 tons thrust and you could only have normally maximally two of those before they started interfering with each other

The large drive did not have a maximum, but had a 10 ton minimum mass(20 tons thrust)

This in effect created three classes of vehicles,
The smallcraft like fighters could have high G drives, typical having 5-8g.
The smallest practical starships at 300 tons could have 2.2g acceleration, 1000 ton ships 0.67g (Though many people said their knew this someone, usually an acquaintance of an acquaintance who had successfully mounted a third drive in a 1000 ton class ship and got 1g...), a 3000 ton ship could stll use such a drive to get 0.2g
Larger ships would use the other drive and thus have normally 0.1 to 0.4g acceleration.

This resulted in the the star wars feel where while Millenium Falcon could behave like fighter against star destroyers, actual fighters could out maneuver it easily.

Thus setting some limits on drives to suitable places could be one way to achieve such.

Edit: and a final note: A g is a unit of speed, not acceleration in starwars universe as the space is filled with a fluidlike substance that you have to push against and thay you can use to maneuver... :)

[muduri]

Weby, your clearly thought-out-in-detail answers to all three of those are much apprecated - particularly a) the battle-rider example and b) the 1.5-to-2nd-power cost factor on superscience drives. Will look into those and mass gradients for drives in more detail - many thanks!

[Ulzgoroth]

Interestingly, it's much easier to justify a rider-and-carrier model with reaction engines than with reactionless.

A carrier, as a long-range vessel, needs to pack long-term accommodation and high-delta-V drives, plus possibly FTL drives and big reaction mass tanks. A rider wants higher-thrust drives, and by off-loading the long-range drive and support elements to the carrier it gets to reduce the mass it has to push around with its much more expensive engines.

If the rider engines are rockets, that basically falls out directly. If the rider engines are reactionless, you've got to go out of your way with something like weby's system to explain why the carriers don't use those same engines. (Riders with the same core thrusters as their carriers are justifiable, but have a lot less going for them.)

[Varyon]

My own approach is a bit complicated and is outlined here. Of course, most of the complication is because I want battles to work out more like those of WWII.

Ignoring the complicated interdiction bit, I paralleled the real-world comparison of aircraft vs watercraft (namely, the latter being far more efficient) by having two different types of drives - fully reactionless and semi-reactionless (basically, reaction drives with impossible efficiencies). The fully reactionless versions have such atrocious power requirements that you cannot use a proper power plant for them - rather, you need some high-output, low-efficiency power supply. The semi-reactionless ones require very little energy and reaction mass, but give much worse performance.

The result is that vessels with reactionless drives are incredibly maneuverable and have excellent acceleration/velocity, but are rather short-ranged. Vessels using semi-reactionless drives are more ponderous, but they have incredible range. This gives a good split between fighters (small craft using reactionless drives) and capital ships (larger craft using semi-reactionless drives).

This scheme does allow for a massive SM+15 behemoth that nonetheless handles similarly to a much smaller fighter. It would probably be limited to planetary defense, or need to be hauled to the battlefield. If this is problematic, you could go with weby's suggestion of the high-acceleration drives having a maximum size limitation. One good justification for that is stress - a higher mass vessel is going to suffer far greater stresses during high-G maneuvers, so you might have a size-based limit on how quickly a vessel of a given size can go before it risks tearing itself apart.

[Ulzgoroth]

Originally Posted by Varyon

The fully reactionless versions have such atrocious power requirements that you cannot use a proper power plant for them - rather, you need some high-output, low-efficiency power supply.

What's the motivation for filling this niche with a short-endurance reactionless drive rather than a high-thrust reaction drive?

[Varyon]

Originally Posted by Ulzgoroth

What's the motivation for filling this niche with a short-endurance reactionless drive rather than a high-thrust reaction drive?

The fighter drives are meant to function differently, not just in terms of efficiency but also in terms of how the vessels behave - they function with pseudoatmospheric maneuvering. To this end, it seemed appropriate to have them function outright differently. This isn't strictly necessary for a similar scheme, of course.