02-03-2016, 04:02 AM | #1 |
Join Date: Feb 2005
Location: Doncaster, UK
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Empty Cargo Holds
Hello, this has probably already been answered somewhere but I can't find anything related through Search. Maybe there's a FAQ I don't know about?
In Spaceships, if I have empty cargo holds, my ship has less mass. Is it reasonable to have each empty cargo hold "count as" a fuel tank for the purposes of delta-V increase (GURPS Spaceships p. 17) ? |
02-03-2016, 07:09 AM | #2 |
Join Date: Jun 2006
Location: On the road again...
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Re: Empty Cargo Holds
I believe your logic is sound, but I'm not entirely sure treating an empty cargo hold as a fuel tank is the right way to go about it. Isn't there something in a later chapter for when fuel tanks start to get empty?
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02-03-2016, 07:29 AM | #4 | |
Join Date: Oct 2004
Location: Yorkshire, UK
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Re: Empty Cargo Holds
Quote:
SM+8/TL10: Fusion Torch (15mps on Hydrogen), 5 Fuel Tanks (250 tons of fuel, 75mps Total); 4 Cargo Bays - where 2 are empty. Treating the empty cargo bays as empty fuel tanks raises the Delta-V by 1.2 to 90mps. This would be the same calculation for if you had 7 fuels tanks giving 126mps; If you burn 36mps of fuel, you've emptied 2 fuel tanks, and have 5 fuel tanks of hydrogen left. i.e. 2 empty fuel tanks has the same state as 2 empty cargo bays - just without that initial 36mps of fuel! Calculating the actual effect requires the rocket formula which is somewhere here on the forums, but it does not seem necessary. |
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02-03-2016, 09:46 AM | #5 | |
Join Date: Apr 2011
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Re: Empty Cargo Holds
Quote:
That should only count for Cargo Hold modules, and a damaged cargo hold won't count until you've actually taken the time to empty the ruined cargo from it. Empty Hangars... well, I suppose you could say that every 2 empty Hangars could count as one empty fuel tank for delta V purposes. But that's starting to get fiddly. I'd absolutely not allow that for steerage cargo you get from a habitat module. |
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02-03-2016, 09:53 AM | #6 |
Join Date: May 2015
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Re: Empty Cargo Holds
You could also have jettisonable modules for passengers and non-essential crew.
(Alert lighting comes on. Internal blast doors seal.) "This is the captain speaking. We are being pursued and will not escape unless we can increase our acceleration now. Therefore I regret to inform you that we are about to jettison non-essential personnel. You have five minutes to make your final prayers, or put on a vacc suit. Sorry. We have no other option. Captain out." ;-> |
02-03-2016, 09:54 AM | #7 |
Join Date: Jul 2008
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Re: Empty Cargo Holds
'Count as an empty fuel tank' isn't particularly simple. If you've got 15 'fuel tanks' but 9 tanks full of reaction mass, you do not have 9/15ths of the delta-V you'd have at 15 tanks. You have more than that, because the last few drops are the ones that do the most.
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I don't know any 3e, so there is no chance that I am talking about 3e rules by accident. |
02-03-2016, 02:16 PM | #8 |
Join Date: Feb 2005
Location: Doncaster, UK
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Re: Empty Cargo Holds
Thank-you for your answers.
I've also noticed that fuel for the mass driver (e.g. "powdered rock") can be stored in cargo holds or fuel tanks, so there's that too. |
02-03-2016, 02:34 PM | #9 | |
Join Date: Feb 2005
Location: Doncaster, UK
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Re: Empty Cargo Holds
Quote:
I'm wondering if the math is correct If we say, well I have 8 fuel tanks and two full cargo holds, my effective dV is x1.2. On the return trip I have two empty cargo holds, my effective dV is x1.4 (the next step on that table, 10 tanks). Writing it out now, I have a feeling it's not correct. Per what Ulzgoroth said. |
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02-03-2016, 03:59 PM | #10 | |
Join Date: Jul 2008
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Re: Empty Cargo Holds
Quote:
Which, um. Should give a better number than your way, but doesn't. (It gives one-tank delta-V x 8*10/9*1.2 = 8*1.33..., if one applies the rules.) Probably to do with multiplier table breakpoints, I can check the rocket equation math later.
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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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