Technical Journal: Chemical Drives

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by Richard “Shadow Shack” Rose
Artwork by GJD

Chemical drives burn solid oxygen, available at any docking station or SCC at the cost of 10Cr per unit. Fuel cost is doubled when taking off from a planetary atmosphere, and external tanks must be purchased for such duty. One external tank is required per drive in order to double the fuel capacity; price of the external tank is 10Cr per unit plus fuel. Tanks can be retained and refilled rather than disposed with no penalty, or removed and stored once docked at a space station.

As such, a ship equipped with chemical drives will have a maximum safe velocity, which can be calculated by figuring half the total fuel capacity divided by the number of drives, and divided again by half. That number will be divided again by the fuel consumption rate. This figure represents the number of 10,000km hexes the ship may travel per turn when using the fold out map from the KH boxed set.

Note that if a ship accelerates beyond this maximum safe velocity, it will not have enough fuel to decelerate at its destination...hence the term “maximum safe velocity”.

Note that the ADF for a ship equipped with the specified amount and size drives will be 1. This can be increased by a factor of 1 by doubling the number of drives when applicable (no more than eight drives of any type are permitted, so in cases where doubling the number of drives exceeds eight this increase is not possible), which increases fuel capacity and consumption. Also, supercharged chemical drives have been recently made available which increase ADF by a factor of 1, which can be consecutively figured in (re: a ship that requires two A drives can have four SC drives with an ADF of 3). SC Chemical drives are only available through a military contractor and are double the standard price. Note that doubling the number of drives can only be performed once for increased acceleration by a civilian contractor, further doubling will have no effect unless performed by a military contractor. Again total number of drives must be observed for such increases.

Also noteworthy is the deck arrangement of system ships. Streamlined craft (available for system ships up to HS:5) will typically have their decks parallel to the main axis so as to permit movement when on the surface. Larger craft will typically (but not always) have the decks arranged perpendicular to the main axis. The bulk of a system ship’s travel time will be spent coasting at zero G, as it will spend considerably less time accelerating to the maximum safe velocity (or any other desired travel speed) than it will coasting along to its destination. Larger craft boasting higher fuel capacities will spend a little more time accelerating than their smaller counterparts, and as such at ADF:1 (1G) the crew can travel about the craft under such conditions...but once the desired travel speed is reached it will spend the bulk of the trip coasting along at zero-G.

Also note that if a ship accelerates past 200 hexes per turn, it will enter the void...but this is unlikely to happen on most system ship designs considering fuel capacities and consumption rates. However, assuming if extensive fuel capacity modifications can be made, it is possible to convert a system ship into a starship. Also note that it is much more cost efficient to use the Ion or Atomic drives for such duty...

Engine SizeFuel Capacity*Consumption Rate**Cost (Cr)
A 12u 1 50,000
B 16u 2 100,000
C 20u 4 200,000
* Multiply fuel capacity x HS for each engine
** This is for each ADF point expended per dive
Note: Prices are the same regardless of SCC.