You are laying a large pneumatic gun onto a 50 metre target compound that can sit anywhere in the
360 degrees around you. There is no propellant charge and no fuse: everything the round does downrange is
decided by the pressure you spend, the mass you throw, the angle you set, and the bearing you lay on.
1. The gun, and why the numbers move
- 10 litre air receiver, 2 inch valve,
3 inch ID barrel 120 cm long, with a
tight pressure fit on the projectile so there is effectively no blow by.
- The launch is not treated as a simple energy sum. Each shot is integrated at two microsecond steps:
compressible flow through the valve as it opens over 3 ms, an energy balance on the gas behind the
projectile, static breakaway then running friction, atmospheric back pressure, and the weight component
along an inclined barrel.
ṁ = Cd·A_v·P_r·√(γ/RT_r)·(2/(γ+1))^((γ+1)/2(γ−1)) (choked)
d(m_b c_v T_b)/dt = ṁ c_p T_r − P_b A v m dv/dt = (P_b − P_atm)A − F_fric − mg sinθ
That is why the chamber never reaches the reservoir pressure, why the dwell time in the barrel changes
with mass, and why a heavier round takes more of the stored energy even though it leaves slower. Muzzle
velocity, muzzle energy, peak chamber pressure and dwell are all reported before you fire.
2. The atmosphere is not a constant
Every fire mission gets a real station: a site elevation, a barometric setting, a temperature and a
humidity. Density comes from the humid air relation and drops with altitude along the whole trajectory,
so the round thins out as it climbs.
ρ = (P − P_v)/(R_d T) + P_v/(R_v T) P(h) = QNH(1 − 0.0065h/T₀)^5.2559
The altimeter is live: set against the mission QNH it reads your site elevation on the ground, and the
needle follows the round up and back down through its arc. Watch the density altitude. A hot, high, low
pressure day will stretch the same firing solution by tens of metres.
3. Flight
Three dimensional, integrated at 240 Hz: gravity, quadratic drag against the moving air mass, and the
Coriolis acceleration for a gun at 32.8 degrees north. Wind is a real vector with a direction of its own,
so a crosswind pushes the round off the gun target line and you have to lay off for it. The drift is
reported live and the ground track is drawn on the plan view.
a = g + (½ρC_dA/m)|v − w|(w − v) − 2Ω × v
4. The warhead
Every round is incendiary and the filler scales with the projectile: a 375 g round lays a
4 metre pattern, the standard 500 g lays 5.3 metres, and a 1125 g round lays 12 metres.
The target compound is 50 metres on a side, so a direct hit is required. The fire that follows spreads
through whatever fuel it finds, driven downwind, and leaves the ground charred behind it. It can still
finish a compound on its own if you land upwind, but it is worth far less than putting the round on the
roof.
5. Scoring and controls
- Direct hit: 1000 points, minus 60 per extra round you needed (floor 250).
- Burned out by spreading fire: 300 points, minus 30 per extra round (floor 100).
- Space fire, ←/→ traverse,
↑/↓ elevation, [ / ] pressure,
Shift for fine steps. Click or drag the gun line to elevate,
the plan view to lay the gun.
- Traverse first, then solve the range. Both have to be right.