GDW's House Rules
Atmospheric
Propulsion
In Space 1889, a speed of 1 indicates a velocity of 5 knots. The nautical mile defined in Ironclads and Ether Flyers is 2000 yards, or 1800 meters. Therefore, a speed of 1 indicates a velocity of 9 kilometers per hour.
The speed formula given in FF&S is Speed (in kph) = (G × 3500) × Efficiency. Early flyer hulls will most likely be the equivalent of simple airframes, so the Efficiency above will be 0.85. Using the above formula, we can determine that an aerial flyer needs to generate about 0.003G to achieve a speed of 1.
G is defined as thrust divided by 10 times hull displacement (which assumes the flyer masses about 10 tonnes per displacement ton). Each hull size in Space 1889 is equal to 100 tonnes, or 10 FF&S displacement tons. It therefore requires 0.3 tonnes of thrust per Space 1889 hull size to achieve a speed of 1.
The formula for speed in Space 1889 is S=6×Es÷HS. A flyer therefore requires 1/6Es per speed number per hull number. As each Es is equal to 125 hp, the flyer needs about 21 hp, or 0.016 MW per hull size per speed number.
So, now we can figure how efficient Victorian propellers were. 0.016 MW generates 0.3 tonnes of thrust, giving us a thrust of 18.75 tonnes per MW of power plant devoted to thrust. This is 37.5 times more efficient than the propellers listed in FF&S for TL 4.
It gets even more interesting when one considers the screw galley. Each turncrank position is equivalent to 21 hp. Now, if one considers that each turncrank position might represent 10 actual turncranks, this drops the output per man to merely 2 hp, but this is still equivalent to the output of 40 real world people. One could conceivably postulate that there is more to the turncrank position than a bench, crank and part of a flywheel.
The following table incorporates these changes. All values are for a Space 1889 engine size of 1, with the exception of the turncrank position, which is per each turncrank. Low Pressure Steam, Forced Draught Steam and the Steam Turbine are the steam engines listed in the basic game. The other steam engines are included for completeness.
|
TL |
Description |
Thrust |
Volume |
Mass |
Price |
Consumption |
Type |
|
2 |
Turncrank |
0.03 |
2.50 |
0.2 |
100 |
— |
— |
|
3 |
Low Pressure Steam |
1.90 |
1.00 |
2.0 |
400 |
0.720 |
Coal |
|
4 |
Forced Draught Steam |
1.90 |
0.80 |
1.6 |
640 |
0.552 |
Coal |
|
4 |
Double-Expansion Steam |
1.90 |
0.60 |
1.2 |
720 |
0.552 |
Coal |
|
4 |
Triple-Expansion Steam |
1.90 |
0.50 |
1.0 |
800 |
0.552 |
Coal |
|
4 |
Quadruple-Expansion Steam |
1.90 |
0.45 |
0.9 |
900 |
0.552 |
Coal |
|
4 |
Sextuple-Expansion Steam |
1.90 |
0.40 |
0.8 |
1120 |
0.552 |
Coal |
|
5 |
Steam Turbine |
1.90 |
0.30 |
0.6 |
600 |
0.720 |
Coal |
|
4 |
Internal Combustion |
1.90 |
0.35 |
0.35 |
350 |
0.480 |
Petrol |
|
5 |
Improved Internal Combustion |
1.90 |
0.25 |
0.25 |
500 |
0.552 |
Petrol |
Note: Fuel consumption above is based upon the volume of the power plant (engine size), not the output.
Campaign Note: Terrestrial steam-driven flyers have dynamos installed to power the few electrical systems on board. These dynamos might act as a primitive æther propeller, increasing the efficiency of the air screw, but not being efficient enough to drive the vehicle through the atmosphere by itself.
Sails mass 1 tonne, have a volume of 1 cubic meter, and cost Cr4800 per displacement ton of flyer.
All kites have a speed of 1 + 1D6 hexes per turn with the wind and 1 + 1D6 ÷ 2 (round down) against the wind.
Kites require one "topman"
(rigging crewman) for every 10 displacement tons of flyer.