[Spaceships] Using two smaller ships to simulate a larger ones

[Krinberry]

Heyas! Okay, this is another in my series of Dumb Questions Based Off Of What Are Probably Bad Variant Designs To Begin With, but in my various mucking around with things, I was curious if anyone had any thoughts (official or otherwise) on doing things like using two 'ships' to construct was is in essence a single larger vessel. From the design standpoint it seems technically pretty easy (for engines you'd just add up the total thrust and dV for both and divide by 2, power points could be shared, armor would be as per normal and in combat they could be treated as two ships flying in close formation for attacking etc).

That said, I know it's still probably a bad idea for reasons I can't immediately see myself, so I thought I'd ask folks what they thought, or if they had a better way to deal with it (I know that there's the SM X.5 rules for example which keeps it all treated as a single vessel).

[Ulzgoroth]

Assuming they're both the same size, it's probably not too hard to deal with. It does complicate things in some strange ways, though. For instance, you could have one of the two sections destroyed or at negative HP while the other is not. And treating it as two ships creates a kind of damage blowthrough cap, and raises questions about targeting of incoming attacks.

I wouldn't recommend it, but I imagine you could do it successfully. I would recommend making the two halves as symmetric as possible...


EDIT: Your note on what to do with delta-V is not right. The delta-V of two equal-mass ships together is not necessarily the average of the delta-V of each separately.

Assuming both ships use the same type of engine (highly recommended), what you should do instead is average the number of tanks of reaction mass between the two, and then calculate the delta-V for that average. This is not the same as what you said, because for high fuel fractions delta-V is not linear in number of tanks of reaction mass.

[Krinberry]

Originally Posted by Ulzgoroth

Assuming both ships use the same type of engine (highly recommended), what you should do instead is average the number of tanks of reaction mass between the two, and then calculate the delta-V for that average. This is not the same as what you said, because for high fuel fractions delta-V is not linear in number of tanks of reaction mass.

Woops, yeah that's what I meant, just poorly explained. :) Definitely agree about the same engine types etc too.

The blowthrough thing is a problem I definitely hadn't thought of... gonna have to think about that one.

Thanks!

[weby]

If I wanted a "in between" ship size I would just interpolate the values. That would work much better with no(or less) weird effects.

[ericbsmith]

Originally Posted by weby

If I wanted a "in between" ship size I would just interpolate the values. That would work much better with no(or less) weird effects.

That's exactly what I did in my GURPS Spaceships Design Spreadsheet to create intermediate SM systems. Most systems scale at either a 1/3/10 or 2/3/5/7/10/15/20 pattern, making intermediate SM's pretty easy: 1/2/3/6/10 for the former and 2/2.5/3/4/5/6/7/8.5/10/12.5/15/17.5/20. For weapon damage I just used a value half-way between the two, so for the dDam2 listing where it goes 2d/3d/4d/6d/8d I used 2d/2d+2/3d/3d+2/4d/5d/6d/7d/8d.

I think that the biggest advantage of using the extrapolation method is that all ship designs still look the same - they all have exactly 20 systems.