Traveller: How Big is the Militia of that Mining Colony?

(This is a "thinking out loud / showing my work" post)

Thinking about Boot Hill, Traveller, and (naturally) Starcraft led me to the question - how much military hardware and how many trained men does a backwater mining colony have?

Fortunately, Striker has rules for the GDP of planets based on their population, tech level, and economy tags, and suggestions about what fraction of that GDP is allocated to military spending (and ground vs spacy-navy spending) based on situation.

Let's take, say, the world of Serpentine from HOSTILE (subsector New Concession Zone, UWP D590355-C, Desert).  Population digit 3 means it has a few thousand people; applying Benford's Law and a d% roll, about 3000 people.  Per Striker, a TL12 Desert world has a per-capita GDP of 16kCr, so with 3k people total planetary GDP is 48 MCr.  Assuming 3% of GDP is spent on the military (Striker's baseline), that's 1.44 MCr/year.  60% (864 kCr) goes to the navy and 40% to the army (576kCr) (again, Striker's baseline for a world with an atmosphere).  

One place I'm diverging from Striker's assumptions is that 30% of defense spending goes to the Imperium.

That Navy budget is enough to afford a new police cutter (at MgT1e's prices) every, mmm...  65 years.  Once they have one, maintenance and fuel is about 120kCr/year.  A pilot is 72kCr/year salary, and a gunner is 24kCr/year, so TCO of a crewed cutter is 216 kCr/year.  Assuming the colony has been around a long time, their "navy" might field four such police cutters, and maybe 1-2 are on duty at any given time.  The limiting factor here might be human though - pilots have to sleep, machines don't.  If we went down to three cutters we could pick up an extra two pilots and three gunners (and maybe some admin staff) and that might improve availability somewhat but ultimately "between 1 and 3 police cutters on duty at any given time" is still going to be the right answer.

A solar system is a lot of space to cover with three cutters, at least one of which is probably off duty at any given time.  Pirates take note.

Meanwhile, on the surface, 576 kCr/year in army budget.  Government type 5 is the infamous Feudal Technocracy, which sounds like the sort of government that would field a mix of long-service feudal retainers and militia.  A long-service professional soldier costs 30kCr/year in wages, facilities, support personnel, etc, while a militiaman costs 10kCr/year.  So if we didn't have to buy or maintain any gear and were going just for number of bodies, the upper limit on the size of Serpentine's army would be (drumroll) 57 militia, about two platoons.  Which, to be fair, is about 2% of the population.  In times of crisis, with the military budget jacked up to 15% of GDP, they could support almost 300 militia, about two companies (10% of the population).

What gear do our infantry need?  Atmosphere type is 9, "Dense, Tainted", which means they'll all need filter masks.  Serpentine's temperature isn't listed in HOSTILE, but rolling it gave me Temperate, which is a bit odd for a desert world but whatever I'll allow it.  In any case, it seems like they don't need a great deal of protective equipment just to go outside.  Let's go with something like HOSTILE's ballistic vest (450Cr, 45Cr/year maintenance, AR5, 2kg) for armor.  Probably don't need more than one short-range radio per fireteam (250Cr each in HOSTILE), plus one medium or long-range radio for per platoon (1kCr in HOSTILE).  Assault rifles are on the order of 1-3 kCr each, depending on details.  Machine guns are in the same range.  So with equipment maintenance per year at 10% of its base price, we're looking at about an extra, say, 400 Cr/year in gear maintenance, which is peanuts next to personnel upkeep.

Without going through Striker's design sequences, we could consider picking up a couple of APCs at HOSTILE's prices; 100kCr to buy, 10kCr/year upkeep.  Crew of two, 13 passengers, means that four APCs would definitely cover us for the annual price of four militia.  Sounds like a reasonable deal to me, and helpful for moving them around in an unfriendly (though not outright deadly) environment.

So at the end of the day, neglecting the potential "feudal retainer professionals", we're looking at four APCs, 53 militia.  Eight of our militiamen are vehicle crew (four drivers, four gunners), leaving 49 infantry.  Maybe drop one more of the infantrymen and pick up a couple trucks or something in case one of the APCs is down for maintenance, and that also leaves us some buffer to buy a bit of new gear every year.  It is a little weird to give armored vehicles to militia, but it's a mining colony, they're operating and maintaining dump trucks and excavators daily anyway.

Or we could go up to professionals, and get one APC, 15 guys (two of whom are crew), and have a lot more slack to work with for replacing and upgrading gear (about 100 kCr/year - enough to replace the APC annually if necessary).

But the important thing here - this is a small enough army that PCs could conceivably go up against it, or make a difference against the sort of threats that it could deal with.  15-30 guys with assault rifles and an armored vehicle or two is a scary encounter in Traveller, but not impossible to deal with given command and control, morale, dispersion, defeat in detail, low skill levels on militia, and fighting dirty.  If you get the entire army of 50 militiamen and four APCs shooting at you at once, yeah, you're probably hosed.

But because Traveller's population codes go up exponentially, at Pop 4 we'd expect about 10x the population, 10x the GDP, and consequently 10x the army.  So that would be more like a couple of companies, and a much harder thing for PCs to deal with.  So I guess I got lucky picking the break point as my first testcase.  Meanwhile at population 2, which is 1/10th the GDP of Pop 3, you're looking at an "army" the size of the party.

In conclusion: Population 3 or less, maybe you can personally fight their army without having a military unit to back you up.  Population 4 or more, probably not.