James once used that phrase for describing the process of designing ships
for MegaT.
Here are some small notes that I'll hope will help people with their dental
work :-)
The dividing of starship components in %-components and tonnage-components
is old and have been rehashed many times in JTAS and TD.
In essence it is an observation that certain components always take up an
certain % of the ship for a given performance. For example: A jump4 drive
always need 5% of the ship's volume (excluding fuel) regardless of the ships
volume.
The tonnage components is the components that have a fixed size (like
staterooms and turrets). A tripple Beamlaser turret at TL13 will always have
an volume of 13.5kl regardless of if the ship is an Type S scout or an
1,000,000 ton Experimental Battle Intruder
The main %-components is the Jumpdrive, the Manueverdrive, the Lifesupport, and
to some extent, the Agility. (The agility is really shakey, see below)
In the data below, the volume of an component, the powerplant required to
power it and the fuel required to keep the plant happy for 30 days is added
to obtain a % of the ships volume that have to be dedicated to obtain the
stated performance in a certain area.
For calculation purposes the powerplant is divided into parts grouped with the
equippment the part powers. In the final design the powerplant is placed as a
unit, of course.
These examples is only correct for TL15 and for ships with total powerplants
over 14kl (and of course for MegaT). Inconsistencies between the components
and the "Total:" line comes from rounding errors.
Jump:
(the % includes the drive and the fuel required for one jump at max performance)
Jump: 1 2 3 4 5 6
-----------------------------------
Drive: 2% 3% 4% 5% 6% 7%
Fuel: 10% 15% 20% 25% 30% 35%
Total: 12% 18% 24% 30% 36% 42%
>From this table one might learn that a Jump 6+6 ship is a distinct possibility.
It would need 7% for the drive and 70% for the fuel, and that would leave 23%
for everything else. Riftbreakers anyone?
Manuever:
(The % includes the drive, the part of the powerplant that's needed to power
the drive and the fuel needed to fuel that part of the powerplant for 30 days.
Manuever: 1 2 3 4 5 6
-------------------------------------------------
Drive: 2.0% 5.0% 8.0% 11.0% 14.0% 17.0%
Powerplant: 0.6% 1.4% 2.3% 3.2% 4.0% 4.9%
Fuel: 3.7% 9.3% 14.9% 20.5% 26.1% 31.7%
Total: 6.3% 15.8% 25.2% 34.7% 44.2% 53.6%
Note that if you want a Jump6 6Gee ship with 30 days endurance you need to
dedicate 95.6% of the hull to plants, drives and fuel!!
Environment:
(The % includes basic env, basic life-support, extended life-support, grav
plates, inertial compensators, the part of the powerplant that's required
to power it and fuel to fuel that part of the powerplant for 30 days)
Components: 3.3%
Powerplant: 0.4%
Fuel: 2.7%
Total: 6.4%
This means that for a given hull you can only use 95.6% for useful components
(useful for other things that keeping the crew alive, that is). The environent
% can be reduced by various strategies, such as not installing grav and inertial
compensators for the fueltanks. That will lead to problems with getting a smooth
feed from the tanks to the jumpdrive if you have engaged in any acrobatics
(used agility, turned the ship etc) during the rounds before the jump.
(The fuel will be sloshing around like nuts, and baffles is only effective to
a certain degree.)
Agility:
(The % includes the part of the powerplant that's neccesary to obtain the
required extra power to achieve the given agility and the fuel to fuel that
powerplant for 30 days).
The Agility is the most unpredictable characteristic of a ship. It is dependent
on the ships unloaded weight and the excess powerplant output.
The data below assumes that the ship has an average density of 1 ton/kl.
The density of ships varies from around 0.5 for a bulk cargo ship to around 2
for a heavily armored SDB. Large drives, powerplant, or any amount of armour
tend to raise the density and large cargoholds or fueltanks tend to lower it.
The Density for unarmored combatships is around 0.9 to 1.2
This table will give atleast an approximation of the investment in volume needed
to achieve a certain given agility.
Agility: 1 2 3 4 5 6
-------------------------------------------------
Powerplant: 1.0% 2.1% 3.1% 4.1% 5.1% 6.2%
Fuel: 6.7% 13.3% 20.0% 26.7% 33.3% 40.0%
Total: 7.7% 15.4% 23.1% 30.8% 38.4% 46.2%
Well then: How is all this data used?
You add together all the tonnage-components (weapons, cargo, subcrafts, state-
rooms and computer etc and the powerplant and fuel for all of this). Then
you compute how much % of the hull is needed to achieve the needed performace.
Divide the tonnage of the tonnage components by this percentage to get the
hullsize. Choose the next larger hull to ensure place for electronics, crew,
sensors, and controls. Design and adjust until it works.
Lets say that you want to design a longhaul cargoship that can transport
20,000 kl of cargo and performs at jump4 and 1Gee (no agility).
The Environment requires 6.4%, Jump4 needs 30%, 1Gee needs 6.3% for a
total of 42.7%.
We guess that the crew will be around 10 persons, 10*54=540kl, no weapons,
no subcrafts, Model4 computer: 33kl for a total of 20573kl.
20573/0.427=48180 kl total volume. A 4000 hull (54000kl) seems about right
and also leaves extra room for electronics, crew, sensors and controls.
- -bertil-
- --
Bertil K K Jonell @ Chalmers University of Technology, Gothenburg
NET: [email removed]
VOICE: [phone removed] / +46 300 61004 "Don't worry,I've got Pilot-7"
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"There's a sucker born every month, except february, which have 28!" Alf Tanner
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