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GURPS rules for using contemporary explosives with the Demolitions skill. With some details about TL 7 explosives and the various more common trigger systems for explosives, plus some special trigger systems.
A demolition expert is needed to:
Example: Marc is a demolition expert (skill level 14) that wants to blow up an artillery piece. The GM rolls secretly against Marcs Demolition skill and rolls a 15. - Failure. The GM rolls again three times: 15, 16, 7. So the mistake occurred while setting the proper pattern. Part of the blast will go in the wrong direction, reducing effective damage to the target.Two or more demolition experts working together may check each others work and improve overall performance. Roll against the higher of both skill levels and add +1 for every level over 10 of the less skilled expert. Working together takes some more time (20 to 90 minutes to properly plant and fuse the charge).
Example: Marc (skill level 14) gets help by Sue (skill level 15). Use the higher skill of 15 and add +4 for an effective combined skill of 19. The GM rolls secretly and gets a 16. One of them noticed and corrected the wrong pattern. If it is important who made and who noticed the mistake, make a quick contest of skills.A demolition expert may double effectiveness of charges by proper tamping or using the shaped charge effect (Monroe effect).
For more information regarding demolitions see pp. HT23
in
GURPS
High-Tech or pp. CII64 in the GURPS
Compendium II. For a look at TL 5 explosives see the article about
Mercury
Fulminate, Acetylene and Blasting Gelatin. The article Throwing
Balls
of
Steel deals with Claymore-Style
Mines among other things.
The M112 block demolition charge consists of 1.25-pounds of Composition C4 packed in a Mylar-film container with a pressure-sensitive adhesive tape on one surface (adhesive tape will not adhere to wet, dirty, rusty, or frozen surfaces). The tape is protected by a peelable paper cover. In blocks of recent manufacture, Composition C4 is white and packed in an olive-drab, Mylar-film container. The M112 block demolition charge can be cut and molded to fit irregularly shaped targets while being easily attached to the target. The color of the wrapper aids in camouflage.PETN (Det Cord): Dmg 7d×2 per pound; 10y per pound; $100 per pound. Burns 4,000y per second, doing 1d concussion in each hex, plus flash and loud crack. Used to cut things, to blow holes and to prepare frame charges.
Dmg is 5d×4 per M112 block of 1.25 lbs. Cost is $100. REF 1.34.The M118 block demolition charge, or sheet explosive, is a block of four 0.5-pound sheets of flexible explosive packed in a plastic envelope. Each sheet of the explosive has a pressure-sensitive adhesive tape attached to one surface. The flexibility and adhesive backing of the sheets allow them to be applied to a large variety of targets. The 0.5-pound sheets can be cut to the desired dimensions and applied in layers to achieve the desired thickness. They are not affected by water and may be used in underwater demolitions. These sheets are to be cut with a sharp steel knife on a nonsparking surface. Do not use shears.
Dmg 7d x 4 per M118 block of 2 lbs. (7d per sheet of 0.5 lb.).Cost is $135. REF 1.14.
| US Army demolition charges (Name) | Composition | Unit Weight | Relative Effectiveness |
| Charge, Demolition: M112 Block | C-4 | 1.25 lb. | 1.34 |
| Charge, Demolition: M118 Block | C-4 | 4 x 0.5 lb. | 1.14 |
| Charge, Demolition: M186 Roll | PETN or RDX | 25.0 lb. | 1.14 |
Note: To work out the damage of individual charges use the 6d×2
per pound of TNT equivalent and multiply by the weight of the charge and
the relative effectiveness factor (e.g. the Charge, Demolition: M112 Block
weighs 1.25 lb. and has a REF of 1.34, so the GURPS damage is: (6d×2)
× 1.25 × 1.34 = 6d×3.35, or about 5d×4).
Fuel-Air-Explosives (FAE): Dmg 6d×10 per pound; $100 per pound. If good resources are available and something really big is to be blasted, consider FAEs for unmatched performance (see p. VE113, HT27). Relative Effectiveness (REF) is 5.0, FAE bombs are used since the late 1980s and the first FAE hand grenades are currently tested.
Thermobaric Weapons:
The OPFOR Worldwide Equipment Guide from the Threat Support Directorate
defines "thermobaric" as "HEI volumetric (blast
effect) explosive technology similar to fuel-air explosive and used in
shoulder-fired infantry weapons and ATGMs."
Burn temperature of the thermobaric mixture is 800+ °C,
but at any range the blast effects are much more serious than the thermal
effects. Thermobaric weapons have same REF as FAE munitions (REF 5) and,
in addition, they use the GURPS concussion rules for larger explosions
(see p. HT22), even if the amount of concussion damage is below 6dx200.
This doubles the increment at which damage is quartered. Damage is quartered
at 4 yards, 8 yards, 12 yards, and so on.
Example for a thermobaric weapon: The calculated damage of 6dx45 for the Russian RPO-A warhead (4.63 lbs.) results in a basic casualty radius of about 20 yards. That is far from the claimed 50 meters casualty radius in the open, but counting in A) the tendency for exaggerating their own achievements that is sometimes noticeable with Russians and B) the physical fact that a "slow" explosion with a prolonged pressure maximum would "fill" a building or street with overpressure rather than being immediately reflected like a fast explosion with a short pressure peak, one might speculate that the effect of a thermobaric warhead out in the open might be less effective (use the normal GURPS concussion rules) but the effect within the confines of built-up terrain, including more or less closed buildings is further enhanced, doubling damage and increasing effective range (see Explosion in Enclosed Spaces, p. UT23).
Combination Contact/Delay Trigger: See the respective entries under contact trigger and delay trigger. The combination trigger has four operation modes: "Contact", "Delay", "Or", and "And". "Contact" and "Delay" are just that. "Or" explodes either if a contact triggers it or - failing that - after a preset delay. "And" starts the delay countdown at contact (e.g. 20 seconds after a door is opened). The trigger is armed after setting one of the modes.
Command Trigger (Radio): The charge is detonated by remote control, using a specialized radio command unit (0.5 lbs.) or a coded sequence transmitted over any communicator .
Command Trigger (Wire): The charge is detonated by remote control, using a command wire and a command unit (0.5 lbs.).
Contact Trigger: The trigger is connected to a tripwire. This is not limited to use as a literal tripwire but may be connected to doors, vehicles, or items of potential interest for the target. Pulling or cutting the tripwire explodes the trigger. By rigging the tripwire to a target that can be moved by a hitting bullet a sniper can trigger the explosion. This leaves no command wires and creates no radio emissions, which may be detected and/or jammed by modern SIGINT equipment.
Delay Trigger: The trigger is set to explode after a certain delay. TL6 triggers may be set from 1 second to one week. TL7 triggers may be set from 1 second to 100 years.
Smart Trigger (Acoustic): Detects vibrations and can be set to explode if someone or something comes within 5 yards, or wait for contact. Smart triggers (acoustic) are programmed to differentiate between vibrations caused by different types of vehicles, enabling them to be set to only attack or ignore a particular motive systems (e.g. "tracked" versus "wheeled") or specific loaded weight ranges. The chance of them going of is the target's Size Modifier + 4, rolled on 3d. You may want to use the Passive Sonar Detection modifiers on p. VE172.
Smart Trigger (Infrared): Detects the heat signature of people
or vehicles and can be set to explode if someone or something comes within
5 yards, or wait for contact. Smart triggers (infrared) are programmed
to differentiate between heat signatures of people and animals and different
types of vehicles, enabling them to be set to only attack or ignore a particular
power system (e.g. "gasoline" versus "gas turbine") or specific power output
ranges. Infrared triggers are somewhat easier to detect than acoustic triggers,
because the trigger needs a line of sight. The chance of them going of
is the target's Size Modifier + 11, rolled on 3d. You may want to use the
Infrared and Thermograph Modifiers on p. VE170.
Electronics Trigger: Any electronic device can be modified to trigger an explosive by any function. This requires an additional Electronics Operation roll of the appropriate specialization (e.g. Electronics Operation [Communications] to rig a communicator to explode when receiving a certain coded signal; Electronics Operation [Computers] to rig a personal computer to explode when given the wrong bios password). Use the modifiers for work without plans or schematics (-2), without proper tools (-5), and when working outside your specialty (-4) if applicable.
Inertial Trigger: Detects his own motion. If this trigger is moved with any significant speed (more than 1cm in 10 seconds) or his spatial angles changed (more than 3 degrees in 1 second), if will trigger the explosive. At late TL7 inertial triggers are very small and quite cheap.
Sensor Trigger: Any kind of security sensor can be used to create
a sensor trigger. Common choices are beam sensors ("invisible laser tripwire"),
pressure sensors (sometimes triggered by lowering pressure), ultrasonic
sensors (triggered simply by motion), and electric circuit sensors (triggered
by breaking the circuit by moving or opening something, or by cutting the
wire). Uncommon types include barometric, temperature, photosensitive,
and hydrosensitive sensors.
