02-04-2016, 01:16 AM | #11 |
Join Date: Feb 2005
Location: Doncaster, UK
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Re: Empty Cargo Holds
What about the mass driver/powered rock example, in which fuel tanks and cargo holds are one and the same? The rocket equation surely wouldn't care if it's a fuel tank being emptied of fuel, or a cargo hold being emptied of fuel, its still a reduction in mass?
Related question: Does the dV multiplier hold true when looking at partially full tanks? e.g. If I have 6 fuel tanks in total, but only one is full (e.g. 3 mps of argon), do I still get the x1.2 multiplier (I get 3.6 mps)? Sorry for being dumb. Last edited by Marasmusine; 02-04-2016 at 01:42 AM. |
02-04-2016, 02:05 AM | #12 |
Join Date: Oct 2004
Location: Yorkshire, UK
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Re: Empty Cargo Holds
Spaceships is an intentionally simplified system, and the dV multiplier table is a simplification of what the rocket equation would give for reduced mass from empty fuel tanks if you did the calculation.
If you really wanted to be accurate, you would need to be recalculating the delta-v per mass of fuel every time the mass of the spaceship change - from burning fuel, firing missiles, taking damage, jettisoning cargo, being boarded, launching vessels from hangers, etc. - which would be no fun (for most people). For quick play at the table, treating empty cargo holds as empty fuel tanks for the dV multiplier is going to be close enough for game purposes and most people. |
02-04-2016, 02:16 AM | #13 |
Join Date: Feb 2005
Location: Doncaster, UK
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Re: Empty Cargo Holds
Yeah... I am wanting to keep it abstract.
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02-04-2016, 02:39 AM | #14 | ||
Join Date: Jul 2008
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Re: Empty Cargo Holds
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As seen before, what empty tanks are equivalent to is making your ship less massive. So with 1 full tank and 5 empty tanks, your ship is only 3/4s its rated mass. So your one tank is equivalent to 4/3s of a tank, and should provide delta-V according to that. (Which is slightly better than 1.2x one tank, again. Because the last bit of reaction mass you use is the most effective.)
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I don't know any 3e, so there is no chance that I am talking about 3e rules by accident. |
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02-04-2016, 03:03 AM | #15 | |
Join Date: Mar 2013
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Re: Empty Cargo Holds
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02-04-2016, 03:13 AM | #16 | |
Join Date: Jul 2008
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Re: Empty Cargo Holds
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Also, how would you ever leave port with 6 full tanks and have 1 left? You can't tell when you've spent 5 tanks of reaction mass.
__________________
I don't know any 3e, so there is no chance that I am talking about 3e rules by accident. |
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02-04-2016, 03:27 AM | #17 | |
Join Date: Mar 2013
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Re: Empty Cargo Holds
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I'm pointing out how things are wrongly applied in Spaceships |
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02-04-2016, 03:57 AM | #18 | |
Join Date: Jul 2008
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Re: Empty Cargo Holds
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Do you have a cite for where Spaceships actually does this wrong application? I didn't think it addressed the situation, rightly or wrongly.
__________________
I don't know any 3e, so there is no chance that I am talking about 3e rules by accident. |
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02-04-2016, 05:22 AM | #19 |
Join Date: Aug 2007
Location: Vermont, USA
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Re: Empty Cargo Holds
A (naive) application of the rocket equation says that:
delta-V'/delta-V = ln(m0'/mf')/ln(m0/mf)Empty cargo holds reduce both m0' and mf', but reducing them by the same amount causes m0'/mf' to increase, increasing delta-V'. Increasing the number of fuel tanks will cause the empty cargo holds to have a greater impact on the change in delta-V. Plugging that into a spreadsheet with a variety of fuel tank and empty cargo hold counts results in delta-V increasing by 6-9% for each empty cargo hold at the beginning of the trip. Code:
delta-V'/delta-V fuel\holds 1 2 3 4 5 6 1 1.054 1.114 1.182 1.258 1.345 1.445 2 1.056 1.118 1.188 1.267 1.358 1.463 3 1.057 1.122 1.195 1.278 1.373 1.484 4 1.059 1.126 1.202 1.289 1.390 1.508 5 1.062 1.131 1.211 1.302 1.409 1.536 6 1.064 1.137 1.220 1.318 1.432 1.569 |
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