From: Michael Blair <amfortas@h...>
Date: Fri, 17 Jul 1998 02:24:20 PDT
Subject: So How Big is a Starship?
So How Big is a Starship? The Fleet Book changes the basic assumptions on which ships are designed, the value of the units of MASS have decreased by about 2.5 as ships now have about 2.5 times the MASS they had under the second edition rules. I was thinking about the design of assault ships for invading planets when I realised that the figures given in More Thrust were not applicable for ships designed using the Fleet Book. The following is an attempt to show the workings and the conclusions that resulted from this. For those who do not want to work through this mess the results are tabulated at the end. What is a MASS? The Fleet Book gives us some hard numbers to work with. 1 Mass represents a displacement of 10 tonnes. Now displacement in wet navies and Traveller [1] is a measure of volume worth 1 and 14 cubic metres respectively. The first for the amount of water displaced and the latter for liquid hydrogen. These give us two possible values for one mass, 10 or 140 cubic metres. We will use the latter as: i. It gives us a larger volume to play with. ii. Hydrogen is more applicable in a Science Fiction setting. iii. If you don't use 140 cubic metres the following is bunk. The mathematicians among you are probably screaming already at the careless transposition of volume and mass but if you assume that the design unit known as a MASS is a measurement of volume and not mass then you should be able to choke this down. Transporting Vehicles An M1A1 Abrams tank occupies a volume of roughly 10 x 4 x 2.5 metres [2] giving a volume of 100 cubic metres and a mass of 60 tonnes. If we assume that the M1A1 is a size 3 vehicle then according to More Thrust it would occupy a volume of 12 CS or 12/50 MASS (FT II). Now that ships have increased in size this is equivalent to 12/50 × 2.5=0.6 MASS (FT III). This approximates to ½ MASS per vehicle size. This is reasonably in accord with the real volume of an M1A1 as there will be wasted space, particularly if the ship is combat loaded [3]. Transporting People According to the Fleet Book one MASS gives one passenger space. Does this mean that one passenger occupies one MASS? For commercial passengers travelling in luxury the answer is yes, for grunts, no. > From Traveller we have the following figures (cubic metres): Small Stateroom 28 One man Large Stateroom 56 One in comfort or two normally. Low Berth 14 Emergency Low Berth 28 Originally for transporting animals. Applying these to our 140 m^3 MASS gives the following figures per MASS: One Man Standard 5 Comfortable 2.5 Cryosleep 10 One Horse 5 Now 14m^3 per cryoberth seems very roomy, going down to 7 m^3 feels right and appears to be the FT III volume. More Thrust gives the following values in cargo spaces (CS). 1 Man 4 CS Cryoberth 1 CS Now 1 CS is 1/50 of a MASS (FT II) but with the Fleet Book ships are about 2.5 times larger, so one FT II MASS is equivalent to 2.5 FT III MASS. Unit Volume CS MASS (FT II) MASS (FT III) # per MASS (FT III) 1 Man 4 CS .08 .2 5 Cryoberth 1 CS .02 .05 20 These match the Traveller derived figures given above (post tweaking for the cryoberth). When FT III finally comes out we will probably not see the Cargo Space, as the FT III MASS has a smaller value there is no need to subdivide it further. ½ MASS per man is a workable figure, matching the ½ MASS volume for a size one vehicle. Cost The Fleet Book does not charge anything for cargo or passenger spaces. Though in principle I do not agree with the cost of passenger space would be so low (one point is worth 10 million!) as to be not worth bothering about, so assume that the hull cost pays for it. Only cryoberths are going to cost 'extra'. in FT II they cost 10 points/MASS or .1 per man. In FT III this translates to 2 per MASS. Finally we have the FT III volumes: Object MASS # per MASS Cost per MASS Passenger, Grunt 0.2 5 0 Passenger, Luxury 1 1 0 Straight from the book. Size 1 Vehicle 0.5 2 0 Size 2 Vehicle 1 1 0 Size 3 Vehicle 1.5 - 0 Size 4 Vehicle 2 - 0 And so on Cryoberth 1/20 20 2 Horse (Frozen) 0.2 5 2 Notes 1. All references to Traveller are to Frank Chadwick and Dave Nilsen's Fire Fusion and Steel (GDW, Bloomington, IL, 1993). 2. Peter Gudgin in Armour 2000 (Arms & Armour Press, London, 1990) gives dimensions of 9.8 x 3.65 x 2.44m for the M1A1. 3. Combat Loading is loading a ship so that its cargo can be unloaded quickly and in the order that it will be required. This is very a very inefficient use of the available volume. As an example of what not to do: apparently at Suez the first lorry ashore carried regimental silver. MRB