Rating The Design

Signature

There is no mention of how the signature in 2300AD is calculated other than a man sized object has a typical signature of 0. However, the Ground Vehicle Guide lists a number of vehicles with their signatures, and so we can make a few rough calculations.

I assumed that the basic 2300AD signature was derived from the volume of the vehicle ( remember, 0 is "man-sized" ). I then made some rough estimations of the dimensions of some vehicles and approximated their volume. For example, consider the Henderson Industries Explorer in the Ground Vehicle Guide. The illustration shows a hatch / airlock on the side which I assume be about 2 metres tall. That means the Explorer is about 6m tall, 14m long and 8m wide, which gives a volume of about 672 cubic metres. The signature of the explorer is +8. If signature is some form of exponential value based on volume, then this could be expressed as -

log₁₀( 672 ) / constant = 8

Now this means that constant is about 0.353 in this case. If we rearrange this equation, we can derive that

log₁₀( 672 ) / log₁₀( 2.256 ) = 8 , or log_2.256( 672 ) = 8 , i.e. 2.256⁸ is 672

Based on the powers of 2.25, I came up with a simple table that linked signature with volume -

The above is the basic signature for Active sensors, especially radar and other sensors which are dependent on the presented surface area and object profile. You can use this as the Signature for all sensors if desired, for simplicity's sake. If you are interested in a little more realism, you might want to try the following rule.

Passive sensors generally work off emissions from the vehicle, and volume is less of a factor in the signature. I suggest that the above scale is used for Passive scanners, but instead of comparing the vehicle volume with the first column, look up the vehicle power plant output in megawatts. Thus a 1 MW power plant has a signature of +0. You can extend this still further if desired - for example a passive radio locator would only detect the transmitted signal, and should really use the signature of the transmitter output power rather than the whole vehicle power plant. A 0.1 MW transmitter would have a signature of -3 on this scale.

Stealth Effects On Signatures

Star Cruiser Radiated Signature

Star Cruiser Reflected Signature
There is no simple conversion scale between Star Cruiser Reflected Signature and the signature given above. This is because the above system relies on volume to given a single unified signature rating, while Star Cruiser splits the signature in lateral and radial quantities, dependent on the sensor cross-sectional area. It is suggested that you use Star Cruiser's system ( given in the Naval Architect's Manual ) for signature if you intend to use the vessel in space combat etc. You may want to calculate the signature using the volume based method for starships when they are involved in planetary operations. You should use the volume based method for all craft which are not used in Star Cruiser.

Ground Vehicle Movement

Power To Weight Ratio
For a vehicle on an even surface, the maximum velocity is given approximately by the following procedure -

• Determine the vehicle power to weight ratio ( henceforth "PWR" ) as the result of dividing the power in megawatts dedicated to vehicle movement by the vehicle weight in kg. It is suggested that this be calculated for unloaded, half loaded and fully loaded weight.
• Take the cube root of the PWR and multiply the result by 2123. This gives the maximum speed in kilometres per hour. This is referred to as V_max in the tables below.

As an example, a vehicle with a engine power of 0.08 MW and and a weight of 800 kg has a PWR of 0.0001 and a top speed of 98.5 kph or about 65 mph.

( The above method is derived from the formulae that associate motive horsepower with speed. It serves as an approximation only and neglects air resistance and other factors ).

Now the actual maximum speed depends on aerodynamic drag and the transmission involved.

Walkers have motion rates proportional to the length of their legs in metres. Consider the Kz-7 is about 3 metres tall, and has a leg height of about 2m including the hips. Crawl is this x1, Walk x7.5, Trot x15 and Run x25.

Watercraft Movement

Aircraft Movement

Spacecraft Movement

Stutterwarp Drive Efficiency
Calculate the Warp Efficiency of a stutterwarp drive using the standard formula given in the Naval Architect's Manual. Then -

• Interstellar movement is Warp Efficiency in light years per day.
• Interplanetary movement is 6.324 * Warp Efficiency AU per day. ( Note that the 2300AD movement rate in the Director's Guide is incorrectly listed as 0.645 AU per day - there was a long argument about this on the 2300AD mailing list, and the majority voted in favour of accepting 6.45 AU per day as being closer to the GDW 1/10,000^th rule ).
• An interesting fact is that Stutterwarp drives can function within a 0.1g and higher gravitational field, just not fast enough to achieve escape velocity. If stutterwarp performance drops off by a factor of 10,000 in a 0.1g+ field ( like the 10,000 factor at 0.0001G ) then the pseudovelocity of a stutterwarp drive is 4020 * Warp Efficiency in kilometres per hour, or about Mach 3.35 * Warp Efficiency. This is somewhat short of the Escape Velocity of Terra ( which is about 11 kps or 40,000 kph ) but still quite a respectable performance. However, I would suspect that few ships could withstand the effects of superheated displaced gas in an atmosphere on the hull, and a collision with a small mass such as a bird could cause big problems.

Combat Move

Evasion Rating

Drawing Deck Plans

Rather than go into great detail on the subject of drawing deck plans for vehicles and spacecraft, here are a few guidelines that may be of use.

• If we assume that a deck plan grid square is 1.5 m by 1.5 m ( the "de facto" standard used in Traveller and a number of other SF-RPGs ) and that the height between decks is 2.5 m then one grid square is equivalent to 5.625 cubic metres of volume.
• That 2.5m figure is for starships and very large vehicles and represents a bulkhead between decks. For single deck vessels, you can reduce this to 2.0 m if desired ( and hence 4.5 cubic metres of volume ).
• So, prepare a worksheet that lists the volumes of all components to be displayed on the deckplans. For each component, divide the volume by 5.625 ( or 4.5 ) to get the number of grid squares on the deckplan. Round .5 and above up, otherwise round down. Remember the hull configuration determined in Step 3 and use the dimensions there to calculate the maximum extent of the deck plans.
• Remember also that some components have fixed dimensions - specifically wings, some accommodations ( especially spin-simulated gravity sections ) and subcraft hangars / missile tubes. Other components have a fixed surface area on the hull, which may affect the size of certain features on the deck plans.
• All extended accommodations have a 25% volume overhead which allows for connecting corridors and common areas. For all other components, assume a 10% overhead for the same features. The average cramped quarters are 45 cubic metres, which is 8 * 5.625 or 8 squares, so 6 squares are actual quarters and 2 squares are available for common areas. A stutterwarp drive with a volume of 100 cubic metres is actually 90 cubic metres of drive ( 16 squares ) and 10 cubic metres of access ( 2 squares ).
• You may have to spread some components out over two or more decks to fit them into the hull dimensions. Any deck plans that come within 5% to 10% of the total volume of the ship are "acceptable".
• If you want to draw deck plans for use with miniatures, you need to draw them to the correct scale to start with. There are two common scale heights for miniatures : 15mm and 25mm. Assuming that the average adult is 1.8 m tall, 15mm is 1/120th scale and 25mm is 1/72nd scale. At 1/120th scale 1.5m is 1.25cm, while at 1/72nd scale, 1.5m is a little over 2 cm.

This page was last updated on the 10^th July 1997.

This page is © 1997 Andy Brick except where components are already copyright / trademarked by others in which case their use is not intended as a challenge to such ownership.