Power in Mongoose Traveller/ Traveller:2300

The Problem

In Mongoose Traveller 2nd edition, rather than real measures of energy, an abstract system of power points (or just "power") is used. There is speculation that each unit is many MW. However, from the general size of reactors, by comparing them to real reactors we can tell this isn't true. In the Aerospace Engineers Handbook, Colin went with the round 0.1 MW per power. This is far too high still.

(Note: none of this applies to 1st edition Mong 2k3 as far as I can tell, the original system I wrote was a straight conversion, and system used in 2320/1st Mong was at least inspired by it.) 

GDW nuclear reactors are the right size. They fit with modern reactors, and there isn't much improvement that can be made. Ergo to get 1 MW, you need 4.8 dTons of fission reactor. Assuming the real reactors map to advanced fission reactors in the AEH, 4.8 dTons is 38.4 power, and so 1 power resolves as 1/38.4th of a MW, or 25 kW to a reasonable rounding.

Reactor sizes are allowed to be much smaller in the AEH, with fission being allowed to be 20 dTons and fusion 60 dTons. This is apparently simply because the minimum power was kept constant, and hence everything moves around it.

In mathematical terms, the conversion of MW to power resolves into two simple arithmetical equations, one of which can be substituted into the other to give the correct result.

In short:

1 power = 25 kW

40 power = 1 MW

This is a general result for the whole of the Mongoose Traveller line.

 

An Aside: A GDW Mistake

GDW made a mistake in the density of H2/O2 fuel. To get a density of 0.6, 1 molar equivalent of hydrogen is reacting with 1 molar equivalent of oxygen. This is stoichiometrically incorrect, and 2 equivalents of H2 are needed per mole of O2, giving a density of 0.43. GDW engines run very oxygen rich. This is the opposite of the real world, where an excess of H2 is used (33% excess) to assure the use of all the liquid O2 (the heavier component).

Hydrogen produces 120 MJ/kg of usable energy when burned. We ignore the O2, as long is it sufficient to burn the fuel. Converted into Mongoose Traveller, 1 dTon of H2/O2 contains 205.9 kg of H2 assuming exact 2:1 stoichiometry (i.e. all the H2 is burnt with no leftover O2). The energy content of 1 dTon of fuel is thus 24,706 MJ or 6.863 MWh. 

I should also note that GDW got the efficiencies of fuel cells and MHD turbines correct in the boxed set, but reversed in Star Cruiser, and corrected this in errata. An MHD needed 75 metric tons of H2/O2 for 1 MW-week by the rules, but most were made with the 100 ton superceded rule.

Using the real world moderate excess of hydrogen (which gives 4.5 kps exhausts), I can keep the volume of H2/O2 the same at 165 m3/MW-week, but the mass is reduced to 60 tons from 75 or 100. This gives a moderate boost to conventionally powered ships. An Aconit now has 840 metric tons of fuel instead of 1,400/1,050 tons and is warp 1.67 fully fueled.

The Aerospace Engineers Handbook

The stutterwarp equation is broken in several ways, meaning it doesn't produce similar results to the original. This creates a problem wherein designers using it have to make a conscious effort not to break the game.

There were so many problems with the stutterwarp, that this one is broken out to a separate post. To fix the problem, multiply all power requirements of all systems in the AEH by 4, to reflect the "true" value of a power.

This also fixes the MHD turbine issue, wherein the turbines were several hundred percent efficient. In fact, this simple rescale fixes prettymuch everything:

1. Nuclear and fusion plants scale as per reality
2. MHD Turbines and Fuel Cells now have ca. 60% rather than > 200% efficiency
3. Solar panels have realistic efficiencies of ca. 37-50% rather than 180-270% as in the AEH

On the solar panel point, the intensity of sunlight in Earth orbit is 1.36 kW/m2. So 272 kW falls on a standard solar panel. For 4 power (100 kW in the revised scale), a basic solar panel is 37% efficient, which just under the theoretical efficiency we're striving for (good panels are ca. 15-20% efficient now).

Here I should note that neither Mong 1st edition 2300AD, nor the AEH mention that sunlight intensity depends on the distance to the star. Solar light intensity falls off in proportion to the square of the distance from the star. The standard solar array produces 4 power at 1 AU from Sol, but at 5.2 AU (Jupiter orbit) it would produce 4/(5.2^2) = 0.15 power and roughly 7 standard arrays (1,400 m2) are needed for 1 power (whatever the scaling). To provide meaningful power in the outer systems, solar arrays measured in 10's of square km are needed.

Conclusions

The problems of > 100% efficiency etc. can all be fixed by scaling 1 power at 25 kW. At this scale everything that I've inspected basically is realistic.