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by Antti Lahtinen
Last weekend I was toying around with a FF&S1 weapon design spreadsheet, and I wrote a design sequence for direct energy input versions of plasma and fusion weapons. I used the design rules from FF&S1 and "Striker II", and combined them with the DEI rules form FF&S2. Instead of using EPG plasma cartridges, the design DEI rules state the amount of energy and hydrogen used for each shot.
When I examined the resulting weapons I was surprised to see the excessive recoil values. To see if the recoil value was reasonable, I checked the recoil impulse, recoil velocity and recoil energy with the following assumptions:
1) The weapon is considered as kinetic energy weapon, so that all energy and mass is used to cause kinetic damage. (Plasma might have thermal effects, but assuming that the effect is purely kinetic will result to higher recoil.)
2) All the hydrogen fuel used in one shot is fired at target as a kinetic projectile. (Some of the fuel might be used as coolant, but assuming that all is used as projectile will result to higher recoil.)
I made a few sample weapon designs and checked the resulting recoil values against several existing weapons.
The RFP-10 is a compact rapid-pulse fusion pistol, capable of firing two shots in a second. The weapon uses single-chamber plasma focus device to launch a high-velocity plasma sheath towards target. The firing unit is only 1.5 cm long, and the launched plasma sheath begins to spread so rapidly that the weapon is ineffective against bodyarmor beyond 30 m range. The visual effect of firing the gun resembles a directed explosion.
According to FF&S1 this fusion pistol has recoil value "14". One real-life weapon which has the same recoil values is the M2HB machine gun (12.7 mm BMG). The M2HB has recoil 14 when the weapon is fired at full-auto from hand rest (without tripod).
The calculated recoil values for the fusion pistol (with above assumptions) are: Recoil impulse: 2.2 Ns Recoil velocity: 2.1 m/s Recoil energy: 2.3 J
For comparision, the same values for a few sample pistols are:
|.22||0.7 Ns||3.2 m/s,||1.1 J|
|.25||0.8 Ns||3.6 m/s,||1.5 J|
|.32||1.5 Ns||2.1 m/s,||1.5 J|
|.380||2.0 Ns||3.0 m/s,||3.0 J|
|9 mm||3.1 Ns||3.4 m/s,||5.4 J|
|.45||4.1 Ns||3.8 m/s,||7.9 J|
|.357||5.1 Ns||5.3 m/s,||13.7 J|
|.44||7.4 Ns||5.4 m/s,||20.0 J|
According to this, the fusion pistol should have roughly as much recoil as a .380 ACP pistol. In FF&S1 terms this should be about recoil "2". The final values for the fusion pistol are:
|RFP-10||3||(1-2-0)||S:2,B,2||15 m||0||14||1 kg||0.05 kg||2||12||189 Cr|