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Date: Fri, 17 Jul 1998 02:24:20 PDT

Subject: So How Big is a Starship?

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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
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