[Spaceships] Is This Legal?

[Phantasm]

Originally Posted by Fred Brackin

I not only wouldn't allow it I don't think it's legal either. "Fuel Tank" as a larger system doesn't even make sense. A larger system should stuill only be 15% of your mass or the same as the 3 regular systems it replaces.

In particular it screws the calculation of "miles per second per tank of fuel". Fuel is never measured in Spaceships as anything other than "tanks" or miles per second". Never convert fuel tanks to tons, lbs, gallons or hogsheads of fuel when calculating performance.

It also screws up the bonus you get for having many tanks of fuel. See "Delta-V increase" on p.17 of Spaceships I.

This. Also note that engine performance in G and dV is constant regardless of whether the ship is SM +4 or SM +44; a larger engine requires larger fuel tanks, but the net performance is the same.

[MatthewVilter]

Originally Posted by Fred Brackin

Fuel is never measured in Spaceships as anything other than "tanks" or miles per second". Never convert fuel tanks to tons, lbs, gallons or hogsheads of fuel when calculating performance.

That is a good point! If you are going to start doing that (which you would need to do to get any benefit from this trick) you are doing math that Spaceships never intended and should not complain if your GM asks you to do a bit more to work out the negative consequences as well.

[scc]

Originally Posted by tbrock1031

This. Also note that engine performance in G and dV is constant regardless of whether the ship is SM +4 or SM +44; a larger engine requires larger fuel tanks, but the net performance is the same.

No it isn't, this is from Spaceships 7 on the subject of smallar systems:

Originally Posted by Spaceships 7 - Divergent and Paranormal Tech, page 4

Fuel Tanks, Sails, Drives, or Engines: Use 1/3 the delta-V reserve of a smaller fuel tank and 1/3 the acceleration of a smaller engine or sail.

[ericbsmith]

Let me start out prefacing that I feel I know more about the Spaceships Design System than anyone else (excepting, possibly, Mr. Pulver). I've ripped it apart, put it back together, coded it, input the statistics for *EVERY* official ship into my Spaceship Design Spreadsheet (all 250+ of them), built dozens and dozens of other ships, found more errata in the Spaceships designs than I can remember, etc. etc. etc.


All that said, it absolutely is *NOT* kosher to use Larger Systems as you did. The Larger Systems rules are present to allow the ship to install "a device that isn’t normally available at its size" - examples of this include systems which have a minimum SM requirement such as Habitats, Open Spaces, Major Batteries that are one SM larger than the ship itself, or systems that have increased effects at larger SM such as Force Screens or Sensor Arrays. The rule specifically states that other systems are "best handled as three normal-sized components, since scaling has already been determined." I can also safely say that in no official ship was a "Larger Cargo Bay" or "Larger Fuel Tank" ever used - because those two systems are precisely the type of system that the rule is talking about when it states "scaling has already been determined."

Originally Posted by scc

No it isn't, this is from Spaceships 7 on the subject of smallar systems:

Smaller Systems are a special case, and really you are not installing a "SM+6 Engine into a SM+7 ship" but rather you are installing "1/3 of a SM+7 Engine into a SM+7 ship" and using some of the statistics of the SM+6 listing such as cost. This is why it gets 1/3 of it's thrust and delta-V, because you're really installing 1/3 of a system.

There are lots of odd breakpoints and cheats in the Spaceships system because of the choice of scaling - having the scaling go x3/x3.33/x3/x3.33 is necessarily going to include some weird breakpoints. There's an even stupider such breakpoint involving Habitats and Smaller SM systems because of the way they chose to round the number of Habitat cabins available at one particular SM. However, that doesn't mean that it's kosher to exploit those breakpoints. As a GM if I saw someone trying to do so I would slap them with a silly hammer and tell them to abide by the spirit of the rules.

[MatthewVilter]

Originally Posted by ericbsmith

The Larger Systems rules are present to allow the ship to install "a device that isn’t normally available at its size"

OH! For some reason I was struggling to understand that paragraph. So yes, what scc is trying to do is not even in line the RAW...

Originally Posted by ericbsmith

Let me start out prefacing that I feel I know more about the Spaceships Design System than anyone else (excepting, possibly, Mr. Pulver).

While you are here can you give me your understanding of the delta-V provided by one tank of hydrogen for a NTR at TL 8?

[ericbsmith]

Originally Posted by MatthewVilter

While you are here can you give me your understanding of the delta-V provided by one tank of hydrogen for a NTR at TL 8?

I don't know enough about NTRs to say much. While I know the design system inside and out, that doesn't necessarily mean I know all of the underlying assumptions (or physics, or whatever else) as intimately. What is the issue you're referring to?

[Ulzgoroth]

Originally Posted by scc

No it isn't, this is from Spaceships 7 on the subject of smallar systems:

Are you serious?

That is the same performance. One SM up means 3x the mass. The smaller engine provides the same performance as ever, but it's pushing 3 times as much ship so its thrust only gives 1/3 as much acceleration.

Similarly, the smaller fuel tank contains the same amount of fuel as ever, but delta-V relates to the fraction of the ship that is fuel...so naturally, on 3 times as much ship...

EDIT: Note that the fact that one SM is sometimes not the same as x3 mass is beneath Spaceships notice. It's not exactly a high-precision system.

[MatthewVilter]

Originally Posted by ericbsmith

I don't know enough about NTRs to say much. While I know the design system inside and out, that doesn't necessarily mean I know all of the underlying assumptions (or physics, or whatever else) as intimately. What is the issue you're referring to?

"Each fuel tank of hydrogen gives a delta- V of 0.3 mps (TL7-8) or 0.45 mps (TL8)." - Spaceships p. 22

At TL 8 we are "TL7-8" and "TL8"...

[vierasmarius]

Originally Posted by MatthewVilter

"Each fuel tank of hydrogen gives a delta- V of 0.3 mps (TL7-8) or 0.45 mps (TL8)." - Spaceships p. 22

At TL 8 we are "TL7-8" and "TL8"...

That second entry should read "0.45 mps (TL9)". Must be errata in your copy. You should re-download the pdf from e23.

[MatthewVilter]

Originally Posted by vierasmarius

That second entry should read "0.45 mps (TL9)".

That makes sense. Thank you.

Originally Posted by vierasmarius

Must be errata in your copy. You should re-download the pdf from e23.

Hum I have "Version 1.31 – April 2009" and just redownloaded it and got the same "Version 1.31 – April 2009".

Neither of the errata pages (First Printing or PDF Edition) lists anything about the NTR...

EDIT: What version do you have?