Step 2 - Materials

Generic Materials 

The following is a list of generic materials used in craft construction in 2300AD. These materials are derived from the Armour Value table in the Director's Guide and the Materials table in the Naval Architects Manual.

For the purposes of this design sequence, two assumptions have been made -

1. That the armour value of a material, listed in the Director's Guide, is per centimetre of that material.

This means that 2 cm of Aligned Crystal Steel would have an Armour Value of ( AV 1.5 x 2.0cm = ) 3.

Note that for the purposes of explosive penetration and breaching charges only, the material armour value used is unmodified by thickness. Thus, an EP 4 explosive would penetrate ( EP 4 / AV 1.5 = ) 2.67 cm of the same 2 cm thick Aligned Crystal Steel and make a hole 1.17 cm across.

This document uses the acronym MAV for the Material Armour Value ( i.e. AV per cm ) and the acronym CAV for the Combat Armour Value ( i.e. MAV x thickness in cm ).

( Note that in reality armour toughness does not increase linearly with thickness. However, the above is a reasonable approximation, and will do for the purposes of this design sequence. )

2. That the material listed as "Metallics" in Star Cruiser is equivalent to "Aligned Crystal Steel" in the Director's Guide.

There are two reasons why I chose Aligned Crystal Steel as my common ground between both Star Cruiser and 2300AD. The first is that the 2300AD technological base assumes great advances in material technology according to the Director's Guide. If this is the case then I do not believe that Starships would be constructed out of inferior hardened steel, especially since most Starships will be constructed in orbital facilities, where Aligned Crystal Steel is manufactured. Secondly, the choice of Aligned Crystal Steel as a baseline also produces a nice correlation between SC Composites and DG Composite Matrix Armour.

Based on these two assumptions, the materials table looks as follows -

The Signature table lists two values - the first is the signature modifier used by this system, the second ( in parentheses ) is the Naval Architects' Manual modifier for the material.

The Star Cruiser Armour Multiplier is provided so that the above table can be used with an otherwise unchanged Naval Architects' Manual if desired. It is not used for this design sequence, however - see below for the conversions between Star Cruiser and 2300AD. Note that the product of multiplying the Material Armour Value by the SC Multiplier should always equal 6 exactly - this should aid the Director in designing new materials to extend the above table.

Material Definitions

• Soft Steel is ordinary unhardened steel.
• Hardened Steel is an alloy of Steel and another metal, usually Titanium.
• Aligned CrystalSteel is steel that has been produced in a zero-g environment, and thus has a structure which is undistorted by heat convection and so forth. It is not usually alloyed.
• Synthetics is a broad term that covers most molecular-engineered "designer" polymers.
• Low Profile Synthetics are as per Synthetics but have electromagnetic radiation absorption properties.
• Advanced Synthetics are either polymers with reinforced covalent bonds, or electropolymorphic polymers whose integrity is increased with the application of electrical energy ( 1 MW per m³ quadruples material armour value ). The latter cost 4 times as much as ordinary Advanced Synthetics and have the same MAV rating when not powered.
• Construction Composites are not normally used in vehicle construction. They are materials used to construct buildings and other immobile structures. They are listed here for completeness.
• Composites / Composite Matrix Armour includes such multi-layer armours as boron reinforced, depleted uranium backed with titanium backing, and so forth.
• Advanced Composites are a "catch-all" for advanced metallic-ceramic laminates.
• Herculanium is an invention from my own campaign. Here I use it as the name for alloys with element number 114 which does not occur in nature but which must be made artificially. Atomic Theory predicts an island of stability around Atomic Number 114, with super-heavy elements that do not decay radioactively. Since the 1960s, people have been trying to make such elements. Since element 112 is the heaviest so far to be synthesised, ( a few atoms that lasted for millionths of a second ), no one really knows the physical properties of these metals. The proper name for element 114 is ununquadrium.

Transparent Materials

Viewports and so on are usually constructed from Optically Enhanced Synthetic Diamond. This is artificially created diamond, grown in slab shaped crystals and then shaped with lasers to reduce optical distortion. An special chemical layer is then deposited on the surface to reduce glare and UV radiation. The same chemical layer is rendered opaque in thousandths of a second by sudden high energy flashes to protect eyesight.

Synthetic Diamond can only be machined with diamond tipped tools or lasers.

Viewports are not calculated as a distinct cost or mass, since it is assumed that any hull makes provision for such things. However, a situation could arise where a character shoots through a view port, or statistics are needed for repairs. To this end, here are the properties of Synthetic Diamond -

The minimum thickness of a viewport on a starship is thus about 0.27 cm to provide an armour level of 2.70 ( see below ).

Someone suggested to me that an entire ship hull could be made out of this material. I decided to rule that Synthetic Diamond could not yet be made in such quantities cheaply. Nice idea, though.

Asteroid Hulls 

Some space / star ships may be fashioned from small, hollowed out asteroids. This is a relatively cheap method of making a ship - just find a suitable small rock, hollow out compartments within it, spray deposit airtight sealing material, pressurise and you have a basic hull.

No more than 35% of the interior of an asteroid can be hollowed out, however. The reason for this is that even with structural bracing and support, asteroids tend to start to crack and break up if too much mass is removed. The remaining 65% is waste space and dedicated to "hull" material.

The finding fee for an asteroid is fixed at Lv250. Each cubic metre of material removed from the asteroid costs Lv45. Pressurisation preparation and treatment costs Lv5 per cubic metre of hollowed out volume.

The simple method of calculation for asteroid hulls is as follows -

• Determine useful interior volume desired in cubic metres. Call this "X".
• Total hull cost is ( Lv50 * X ) + Lv250 ( i.e. the total of the preparation cost and the finding fee ).
• Total hull volume is X * 2.8571 in cubic metres.
• Material volume is X * 1.8571 in cubic metres. Average density for an asteroid is 2.5 tons per m³ of material. I suggest rolling ( 0.2 * 3d6 ) + 0.5 tons per m³ to represent variations in composition and structure. This yields a range of 1.1 to 4.1 tons per m³.
• To determine hull dimensions and hence surface area it is easier to assume that the asteroid is a simple, regular shape and then reverse engineer a standard volume equation.
• As a rule of thumb, assume that the average Combat Armour Value of an asteroid hull is 0.01 * the material mass in tons.

Asteroid hulls are obviously not capable of re-entry or atmospheric operations. If you wish to use Classic Star Cruiser, then they have a signature material multiplier of one tenth of their density, although never less than 0.2 and never more than 1.

Example

If we want a 1000 m³ compartment, then it will cost Lv50,250 and be contained in an asteroid with a total volume of at least 2857 m³. The material volume will be at least 1857 m³ and mass a little under 4643 tons with an average density of 2.5 tons per m³. If the asteroid was roughly spherical, it would have a radius of about 8.8 m and a surface area of 973.1 m². The CAV is calculated to be 46.43 for this hull. The Classic Star Cruiser signature multiplier is 0.25 ( one tenth of 2.5 tons per m³ ).

Mass Limit For Asteroid Starships

For asteroid ships equipped with a stutterwarp drive, there is a definite limit to the mass of the asteroid. Stutterwarp drives are unable to perform at FTL velocities in the presence of a 0.0001 g gravitational field. As a result, the asteroid may not have an intrinsic gravitational field equal to or in excess of this limit if you want the ship to go faster than light.
Assuming a density the same as the earth of 5.52 grams per cubic centrimetre, this is a solid sphere 635 metres across with a mass of about 5,927,270,400 tons. It would take a million million such masses to make just one Earth.
This is a warp efficiency of 17.50 * ( 300 / 5,927,270,400 )^0.33 or about 0.065. That's not too bad - it's a light year in 15.4 days or so. You could make some pretty impressive asteroid "generation" ships with tricks like this. Lower the density and you can come up with some very big ships ...

Star Cruiser Armour Rating

Given the above assumptions it is possible to derive a conversion scale between the Star Cruiser Armour Rating ( SCAR ) and the Director's Guide Armour Value ( DGAV ). This is useful not only in this design system, but for situations where starships come under direct fire from small arms or when attempting to breach a starship hull using explosive charges.

Given that we have an Aligned Crystal Steel hull, and that the hull is a standard 3 m diameter x 10 m long cylindrical section, we know that the material volume required for SCAR level 0 is 2m³. This equates to a layer 1.83 cm thick external to our 3m diameter. We can then calculate the DGAV for this thickness, using Assumption #1, above. Here are the results of that calculation for all armour ratings to level 10 -

Unfortunately, if the above table is derived using Advanced Composite and not Aligned Crystal Steel, we get the following -

You can see that the "fixed" material volume rule in Star Cruiser generates different results depending on the material involved. SCAR 10 is DGAV 86.13 using Aligned Crystal Steel, yet DGAV 102.43 using Advanced Composites. In other words, the "fixed" material volume method is internally inconsistent. You would expect SCAR 10 to be the same DGAV in both materials, yet for there to be a difference in thickness. It does not matter what conversion scale you use, incidentally - if instead of Aligned Crystal Steel you used Hardened Steel as the equivalent to SC Metallics, the results would still be different.

In order to resolve this conflict, I have decided to move away from the Star Cruiser "fixed" material volume and towards a fixed DGAV value for each SCAR level. This does affect Starship design as the mass of the hull / armour for a Starship will, on average, decrease for Synthetic and Composite materials.

Starships designed using these design sequences will therefore have less mass and move faster.

Using Aligned Crystal Steel as our baseline again means using the first table for conversion purposes. Therefore, the final table looks like this -

This provides us with a conversion scale which we can now use to determine the thickness of material required to achieve a particular Star Cruiser Armour Rating. For example, we know that Advanced Composite has an DGAV of 6 per centimetre. We would need a layer at least 14.355 cm thick to get Star Cruiser Armour factor 10.

Notice that I do not state that SCAR 0 is equivalent to DGAV 0.00 to 10.70 ; that is because I also make the following assumption, based on the minimum possible material volume and smallest hull size in the Naval Architects' Manual.

3. That a minimum AV of at least 2.70 is required for space vessels to protect against micro-meteorites and radiation.

Sloped Armour Effects

The following is an optional rule and applies mainly to Surface Vehicles.

If an armoured plate is inclined or "sloped" then the effective thickness of the armour is increased against rounds fired horizontally against the armour ( i.e. against rounds that do not have an overhead attack angle ).

This increase can be calculated as follows -

s = t / cos ( 90 - )

where s is the new effective armour thickness, t is the old armour thickness and is the angle of slope, measured between the base of the vehicle and the sloped face - 90 degrees is thus vertical, 0 degrees is horizontal.

As an example, consider a hull 1 cm thick and inclined with a slope of 30 degrees. The effective armour against lateral attacks is 1 / cos ( 90 - 30 ) = 1 / 0.5 = 2 cm. The formula will also work if CAV is used instead of thickness.

This page was last updated on the 1^st September 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.