Approximating High-Tech and Ultra-Tech with Spaceships

[ericthered]

With the sedan, you should probably have another two seats: one for the center back, and one for the driver: the steering wheel, dashboard, and cars electronics probably are taking up all of the chair's space and weight.

I'd also add more engine for even the most basic vehicles.

I'd say streamlining starts at TL 7, yeah.

Isn't there a way to do half sizes with spaceships?

[Anthony]

Originally Posted by ericthered

Isn't there a way to do half sizes with spaceships?

Not per RAW, but Spaceships scaling is actually super-simple: just pick a scaling factor, F, and then:
Multiply weight, cost, crew, freight, etc, by F^3
Multiply DR, HP, damage by F.

A half-size down is about F = 0.83, a half-size up is about F = 1.2; if you want F < 0.7 or F > 1.5 you should probably design at a larger SM, though it won't make a lot of difference.

[Michael Thayne]

One major inconsistency between Spaceships and other sources that hasn't been covered yet: Spaceships HP and ST are too high. I've tried to look to see if anyone else has caught this, and all I can find is someone mentioning "generous rounding". But it's really more like 1 step to high on the speed/range table. Mostly it's not noticeable, but it's really painful if you extrapolate to an SM +1 mecha and it has 50 ST, regardless of TL.

[ericbsmith]

Originally Posted by ericthered

Isn't there a way to do half sizes with spaceships?

My spreadsheet fully supports it, and I've been working on more explanative rules for scaling Intermediate SM spaceships. Mostly, though, it's just finding a good midpoint value for the stats of each system. I start out with the basic assumption from my Optional Rules (PDF) I use for my spreadsheet, where an intermediate SM ship is twice the mass of the next lower SM and extrapolate from there. There are only a few scaling progressions used in the tables, which makes it much easier to scale everything. The biggest problem is extrapolating weapon damage properly.

[ericthered]

I'm guessing a sedan is best built at 2.5 (it rounds up to 3 for in-play stats, but we'll price and build it like its its 2.5 in spaceships)

Counting seats get a little weird: you divide the seats by F^3 (.57). I'm counting 4 seats for this little car: the fifth comes a little out of the control "room" and a little out of the fact the back seat doesn't really sit 3 adults. That gives us 4/.57 = ~ 7 seats.

I realized something else: Modern cars probably have a unit of open frame armor -- but it only protects the back and center parts of the car. So we put in four armor systems. Someone argue me down if that's a bad build

Steel Armor x3
Steel Armor (open Frame)
Control Room
Internal Combustion Engine x2
Wheeled Drive Train
Maneuver Enhancement
Cargo x2
Passenger Seat x7 (No Life Support)

Still missing two slots, but its looking fair at this point. Part of me wants to add a second drive train, but there really isn't a lot of incentive there. another engine slot is only necessary if we want this thing to go 120 mph.

Of course, instead of solving for how many seats we need at a given scale factor, we could figure out how far we can scale it down and have enough seats. We have 9 empty slots, and we need it to equal 4 seats.

9*F^3 = 4 => F = (4/9)^1/3 = .76

Base cost as SM 3 is $25,000, cost at reduced size is 4/9ths of that, so it costs $11,200, weighs a little over a ton when loaded, and has a 7 gallon tank that will last for 8 hours. Move is 4/52 (ie, can reach 104 mph and gets to 60 mph in 8 seconds). fuel costs $6 a gallon, but I get over 100 mpg, so I'm not too disapointed. In all this seems a little too good to be true, but its not bad.

[The_Ryujin]

Originally Posted by Michael Thayne

How did you get that volume figure? It looks like you're assuming a density of 20 lbs. per cubic foot. However, that 30 ton weight statistic is loaded weight. Water is about 60 lbs. per cubic foot. Few common materials are 1/3 the density of water, 40% to 120% is more common for hydrocarbons and organic matter. And an ore hauler will be hauling cargo significantly more dense than water—silica is 2.65x as dense as water, metals can be 8x as dense as water or more. So if you're looking to make an assumption about spaceship density, assuming 60 lbs. per cubic foot is probably better as a simplified approximation.

(In the end, though, you seem to have reached a similar conclusion to what I did about Spaceship armor WM. Probably a good mathematical reason for this that I'm too lazy to figure out right now.)

100 cubit feet/ton is the definition of a shipping ton and is what David based his assumptions on. Keep in mind that most vehicles are mostly empty air aren't as dense as they seem, after all a 100,000 ton super carrier can float after all!

As for using the loaded weight, the loaded weight is what David used for his calculations, even for HP even though GURPS uses unloaded weight (though in this case I think using loaded weight for large structure like ships makes sense, cargo can eat up energy just as well as hull can).

So yeah, if you want more detail in how much your ship weighs then calculate their area as a cylinder first and then go to town. Just keep in mind that your numbers aren't going to 100% line up.

[ericbsmith]

Originally Posted by ericthered

Maneuver Enhancement

Technically, Maneuver Enhancement is only available for Air; it's available for Ground and Water vehicles at Superscience TL's.

[ericthered]

Originally Posted by ericbsmith

Technically, Maneuver Enhancement is only available for Air; it's available for Ground and Water vehicles at Superscience TL's.

Oh! I was just taking Michael Thayne's suggestion as a baseline. Where are the rules on those things anyways? I'm not finding them...

As a note, is there a way to do custom sizes on the spaceships spreadsheet? Or could you add 2.5 as a valid size?

[ericbsmith]

Originally Posted by ericthered

Oh! I was just taking Michael Thayne's suggestion as a baseline. Where are the rules on those things anyways? I'm not finding them...

Maneuver Enhancement is in Spaceships 7 p. 11, the extra rules for Land/Water are in Pyramid 3/64 p. 32.

Originally Posted by ericthered

As a note, is there a way to do custom sizes on the spaceships spreadsheet? Or could you add 2.5 as a valid size?

No, there's not a way to do custom sizes. There's no way I could add it without a significant redesign (and, frankly, the Spaceships rules aren't fine-grained enough to really support that kind of finickiness). I did include half SM vehicles, but below SM+4 things get weird with some of the rules so I limited it to SM+3. I could, and may, expand that down a bit more but that's going to take a little bit of work so is going to have to wait as I have more pressing concerns with the sheet.