[Spaceships] Gasbag system - size modifier?
 

Greetings, all!

Spaceships #7 has stats for gasbags, and RPK mentioned that (for example) an SM+10 craft with appropriate-sized gasbags is the SM of folded, deflated state. So . . . what is the necessary SM adjustment for craft featuring gasbags?

Thanks in advance!

Re: [Spaceships] Gasbag system - size modifier?
 

Assuming the rest of the craft is "typical", you could use the relative static lift of the contents of the gas bag and the craft's (full) mass to determine the volume of the gas bag; then… Well, that's probably going to dwarf the rest of the craft, so you could take that volume to the equation in VE, or figure some proportions and use the table in Basic.



But Spaceships does not adjust for volume; its SMs are determined by mass. Consider these two craft:

SM: +8 Ballistic Escape Pod, 1 core Habitat, 19 Exotic Laminate Armor systems

SM: +8 Park Trailer, 1 core Engineering Room, 19 Open Space systems

Those should not have the same SM for targeting purposes.

Now, somebody could make a list of systems and the volume they come out to under VE(which would require some extrapolation and interpolation), and you could then add up volumes and use the equation in VE to find the SM. But that's a bit too complex for Spaceships.

Re: [Spaceships] Gasbag system - size modifier?
 

Well, that 60 is 60cf/lb. The rest of the ship isn't 1cf/pd; the spaceship in VE has a density of 11.93463pd/cf.

So, let's see… a 300T ship, as in, with the gasbag deflated, requires 600 000lb of lift in 1G. At 60cf/lb, that requires 36 000 000cf. Using the spaceship in VE as "typical" density, the volume of a 300T non-gasbag ship would be about 50 274cf. The non-gasbag portion of the ship with a gasbag is about 40 219cf. So about ×717 volume, or +6 SM by the table in VE. (+5.7 SM by the equation, which I guess I derived from the table.) The same with lifting gas is about ×180 volume, or +5/+4.5 SM.

Re: [Spaceships] Gasbag system - size modifier?
 

Yes, ever so slightly failed to read...
Would 300 tons @ 1 ton per cubic metre be about 11,000cf?
If so, I get lifting gas +6SM and hot air +7SM? Probably wrong again.
Funniest thing is, the first time I worked it out, I used the wrong scaling (read linear for volume) which gave the sort of numbers I just got...

But, Wow, an increase by a factor of 1,000? And that's just for enough gas to lift the ship.
And a zeppelin would be SM+11 (30ton? They had about a 9 ton cargo capacity...)

Re: [Spaceships] Gasbag system - size modifier?
 

It must be possible to make a quick-and-dirty solution that's better than the RAW, at handling these kinds of "edge cases".

Re: [Spaceships] Gasbag system - size modifier?
 

+5 to +6 (x300-x1,000 volume); the assumed density of normal craft is on the order of 320 kg/m^3 (20 lb/cf), the density difference between a gasbag and the surrounding air is on the order of 0.5-1 kg/m^3 depending on what the gasbag is filled with, so the gasbag needs to be 320-640x the volume of the craft.

Re: [Spaceships] Gasbag system - size modifier?
 

You could just treat them as Exposed Systems (p. SS66), targeted at the spacecraft's SM +3.

Re: [Spaceships] Gasbag system - size modifier?
 

Ish, yeah. Try Google Calculator :J

Pretty close; I just double-checked my numbers above, and so long as my assumptions are valid, it holds. (Note that among those assumptions are operation in 1G and 1atm.)

Sounds about right. Pick a hot air balloon, note that the balloon is thicker in Z than the gondola, and compare the total volume to the gondola volume.

Plural? Doubt it. This particular edge case is so extreme that it dwarfs any normal variation, but what happens if you add radiator fins to the Ballistic Escape Pod?

Also, I suspect something like the volume-adding system would probably be needed as a stepping stone to such a system.