BattleMechs (BM), IndustrialMechs (IM)
Interstellar Operations (p. 90)
Tight-stream electromagnetic pulse weapons (TSEMPs for short) were derived from abandoned Word of Blake research based on the original Star League’s Centurion Weapon System project. First introduced by the Republic of the Sphere as a single-shot version, a newer repeating-fire version eventually followed. As the name implies, TSEMPs are basically targeted-EMP weapons, intended to disrupt or even shut down opposing machinery—including BattleMechs—without relying on the harpoon line/fusion surge of Jihad-era tasers. Although their use also tends to interfere with the firing unit’s other advanced electronics, stealth equipment, and targeting systems, the TSEMPs’ effectiveness and reusability eventually rendered taser weapons obsolete.
TSEMP weapons are only effective against targets weighing no more than 200 tons and only deliver effects against conventional infantry if they are cybernetically augmented (in which case, a successful TSEMP attack is resolved as a standard machine gun, delivering 2D6 burst damage to the unit).
Both the TSEMP Cannon and the one-shot TSEMP (TSEMP OS) deliver attacks in the same manner as standard direct-fire energy weapons, but ignore any effects from specialty defenses (such as heat-resistant and laser-reflective armors or the Blue Shield PDS).
Except as noted above when attacking cybernetically-augmented infantry, TSEMPs inflict no physical damage to a target unit. Instead, upon any successful hit, the attacker makes a second 2D6 roll to determine the effects, applying a –2 to the result if the unit is powered by steam engines, or –1 if the unit is powered by internal combustion engines. An additional –2 modifier is added if the target weighs 100 tons or more. Any modified result of less than 2 is treated as a 2.
The TSEMP Effects Table shows the range of results the roll result required to cause any effects by target unit type. A result of that falls under the “No Effect” range for a unit indicates that the target suffers no significant effect from the attack. A result that falls under “Interference” indicates that the target’s sensors and electronics experience a surge that will apply a +2 to-hit modifier for all weapon attacks and sensor operation checks, while also treating the target unit as though it is operating within a hostile ECM field. A result that falls under the “Shutdown” column indicates that the unit experiences a shutdown effect.
Any effects from a successful TSEMP attack will last until the End Phase of the turn after the target unit was hit, after which the target will resume operating normally. An effect of “NA” means the specified target cannot be affected by a TSEMP attack.
In addition to affecting its target, the unit firing a TSEMP will automatically suffer the effects of a TSEMP-delivered Interference effect on itself (as described above). Furthermore, because the TSEMP Cannon requires time to recharge, the weapon cannot be fired in consecutive turns.
Multiple TSEMP weapon attacks against the same target in the same turn add a +1 modifier to the Effects roll against that target (to a maximum stacking modifier of +4). Each Effects roll resolves separately, so the first TSEMP hit resolves with no stacking modifier, while the second receives a +1 stacking modifier, the third receives a +2, and so forth. This stacking effect only applies to the Effects roll, however; multiple Interference effect results will not stack.
May be mounted on any available unit type with adherence to the following construction rules:
Not allowed if Fuel Cell, Internal Combustion, Primitive Fuel Cell, or Primitive Internal Combustion is selected for the unit’s Engine Type