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Mass Values for Ships & Vehicles
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CRMcNeill
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Joined: 05 Apr 2010
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Location: Redding System, California Sector, on the I-5 Hyperspace Route.

PostPosted: Mon Jul 17, 2017 8:52 pm    Post subject: Mass Values for Ships & Vehicles Reply with quote

So, in another topic, I mentioned it would be nice if WEG had included Mass values for starships, as it would help with calculating how a given starship drive would perform when installed of ships of different sizes.

I know other games have used mass values as a measurement of relative size instead of length; the Serenity RPG was one that I know for sure.

Is this something anyone else has used? If so, how did you calculate, and what standards did you use to generate the mass values, not just for ships, but for speeders and other vehicles, too?

EDIT: Specifically, have you used it IN STAR WARS D6, and how? I'm aware other systems use this rule, so I want to see how it could be adapted to SWD6.
_________________
"No set of rules can cover every situation. It's expected that you will make up new rules to suit the needs of your game." - The Star Wars Roleplaying Game, 2R&E, pg. 69, WEG, 1996.

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Last edited by CRMcNeill on Mon Jul 17, 2017 9:26 pm; edited 1 time in total
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Wajeb Deb Kaadeb
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PostPosted: Mon Jul 17, 2017 9:15 pm    Post subject: Reply with quote

In Traveller. Classic Traveller. Not in Star Wars.
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Zarn
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PostPosted: Tue Jul 18, 2017 3:02 am    Post subject: Reply with quote

I didn't use mass, I used volume. I just said that metric tons were metric tons with water, so 1 metric ton = 1000 kg = 1000 l. I assumed that the inertial compensation made density irrelevant.
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Ray
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Location: Winnipeg, Manitoba, Canada, North America, Western Hemisphere, Earth, Sol, Western Arm, Milky Way

PostPosted: Wed Jul 19, 2017 5:01 pm    Post subject: Reply with quote

Zarn wrote:
I didn't use mass, I used volume. I just said that metric tons were metric tons with water, so 1 metric ton = 1000 kg = 1000 l. I assumed that the inertial compensation made density irrelevant.
I approve of this, as pure water is pure water no matter which species you are.

Of course, some backwards species that uses a different measurement system would throw off a bunch of stuff with freighters, which is why there are different types of tie-downs and securing straps.

In the old Han Solo books, Han complains mentally about the weird measurements used for parts on one planet being based on a local bean (a reference to inches and barleycorn.).
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Naaman
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PostPosted: Wed Jul 19, 2017 8:26 pm    Post subject: Reply with quote

In all honesty, the relative mass of the ship is only relevant if the different drives also have power ratings.

Accelleration equals force over mass, so we would also need a power or force rating for the various types and degrees of drives.

This would then require us to make a few different drives or enngines, and give them power ratings. But then we divide those numbers by the ship's mass, and we get its maximum speed....

So its the combination of engine and ship that results in the ultimate "space move" stat.

So the mass rating would only matter if we wanted to spec out a limited number of engines to be used in the galaxy.

Alternatively, you could spec out engines according to their general purposes or accordingto performance category.

For example, you could have the different degrees of "V8," (300 horsepower, 400, and 500), and three degrees of "Inline 6," (200, 275, and 350 horsepower), etc...
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Zarn
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PostPosted: Thu Jul 20, 2017 8:59 am    Post subject: Reply with quote

Or, you know, perhaps not - because you'll then also implicitly start worrying about acceleration and stuff, and then we're deep in delta V and Tsiolkovsky territory.

I usually run loosely with the following rules - inertial dampers make, for the most part, the physics internally irrelevant. There'll be shaking and sparky control boards, but you don't have to worry about turning too hard and making yourself a half-inch thick smear over the internal walls. If the inertial dampeners are damaged or otherwise disabled, everything shuts down hard - you're drifting in space.

However, physically fitting stuff inside a ship is still a problem - which is why I consider the 'metric tons' not a measure of mass, but a measure of volume. If it fits, unless there's story factors saying something else, the ship will take off and not have a measurable decline in its performance no matter what the density of the cargo is.

Which means that there's no problem having a big bulk freighter with an insane top speed. You might have some handwavy square cube thing going on with the inertial dampeners if you don't like that idea and want to keep your bulk freighters ponderous and slow - perhaps they don't scale particularly well with volume - but for me, I'm just saying that slower drives are 'more efficient' and therefore bulk freighters are slow.

Basically, I don't want to start doing numbercrunching to find a Hohmann transfer for my ship in Star Wars - Star Wars is firmly in the 'push the button and it goes' category for me. Unless, of course, there's some story reason why something's more difficult than it usually is.
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CRMcNeill
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Location: Redding System, California Sector, on the I-5 Hyperspace Route.

PostPosted: Thu Jul 20, 2017 10:06 am    Post subject: Reply with quote

Zarn wrote:
I didn't use mass, I used volume. I just said that metric tons were metric tons with water, so 1 metric ton = 1000 kg = 1000 l. I assumed that the inertial compensation made density irrelevant.

The problem is that using volume doesn't work when trying to calculate drive performance. A ship with a high relative volume (a freighter built around a large cargo hold) will have a low relative mass, and mass is what matters in the physical calculation of movement.
_________________
"No set of rules can cover every situation. It's expected that you will make up new rules to suit the needs of your game." - The Star Wars Roleplaying Game, 2R&E, pg. 69, WEG, 1996.

The CRMcNeill Stat/Rule Index
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CRMcNeill
Director of Engineering
Director of Engineering


Joined: 05 Apr 2010
Posts: 16163
Location: Redding System, California Sector, on the I-5 Hyperspace Route.

PostPosted: Thu Jul 20, 2017 11:01 am    Post subject: Reply with quote

Naaman wrote:
In all honesty, the relative mass of the ship is only relevant if the different drives also have power ratings.

Acceleration equals force over mass, so we would also need a power or force rating for the various types and degrees of drives.

This would then require us to make a few different drives or engines, and give them power ratings. But then we divide those numbers by the ship's mass, and we get its maximum speed....

The 1E version of Tramp Freighters had an Improved Thrust rule for engine modification, allowing the character, at the time of the install, to sacrifice Speed for improved Cargo Capacity (the ratio was 20 tons per D in 1E rules, which translates over to 10 tons per SU in 2E terms).

Quote:
So its the combination of engine and ship that results in the ultimate "space move" stat.

So the mass rating would only matter if we wanted to spec out a limited number of engines to be used in the galaxy.

Alternatively, you could spec out engines according to their general purposes or according to performance category.

For example, you could have the different degrees of "V8," (300 horsepower, 400, and 500), and three degrees of "Inline 6," (200, 275, and 350 horsepower), etc...

That's sort of what I was thinking. If we can come up with a baseline (the YT-1300 is an obvious choice) for a ship's mass, we can use that as a rule of thumb to give the different drives in Tramp Freighters Mass ratings to go with their speed. Then, if we can generate some usable relative Mass ratings for other ships, it'd give the ship modification rules some indicator as to how an engine that gives a YT-1300 a Space of 4 with the ability to haul 100 metric tons of cargo would perform when installed in, say, a Ghtroc 720.

For instance, if a YT-1300 has a Mass of 100 metric tons, its Space 4 drive would have a Mass rating of 200 metric tons (the ship plus the cargo capacity). If you install that same drive in a ship with a Mass of 120 metric tons, that tells you the Cargo Capacity is 80 metric tons. However, the designer / installer can choose to shift power from the engine to Cargo Capacity (using the 1E conversion from above), resulting in a Space of 2 with 100 metric tons Cargo Capacity.

The closest real world analogy would be the difference between horsepower and torque...
_________________
"No set of rules can cover every situation. It's expected that you will make up new rules to suit the needs of your game." - The Star Wars Roleplaying Game, 2R&E, pg. 69, WEG, 1996.

The CRMcNeill Stat/Rule Index
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