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Fuel-Air Explosives

Acknowledgements

Many thanks to Oerjan Ariander for giving me a tutorial on fuel-air explosives, for providing ideas and suggestions with regard to these rules, and for going over these rules to make sure they seemed reasonable.

Overview and Stargrunt II Background

Fuel-Air Explosives (FAEs) consist of a cloud of fuel, in the form of an aerosol, dispersed over an area and then exploded with a detonator. The main destructive force of an FAE is high overpressure, which is useful against soft targets such as minefields, armored vehicles, aircraft parked in the open, and bunkers. For more information, check out this page. These are also known as thermobaric weapons. Because of the vacuum they create after detonation, and the resulting rush of air back into the blast area, the Russian military calls them "vacuum bombs".

All human armies can use FAEs. Owing to their biotech abilities and their physiology, Phalons favour the use of fuel-air explosives (FAEs) as their high explosive weapon.

Note: many modern combat vehicles do not have the ability to form a complete seal against the outside elements. This is why contemporary thermobaric weapons are so dangerous against modern APCs. These rules assume that in the Stargrunt II universe armoured fighting vehicles are capable of being completely sealed. If adapting these weapons for use in a modern game, remember that it may be impossible to completely seal the vehicle against the effects of these weapons.

General Rules

FAEs come with the same sized blast radius as other artillery systems (see the Stargrunt II rulebook, page 46). An FAE's blast radius us double if it detonates inside a building or enclosed space (like a cave). This extended blast radius ends if it hits a blast wall (a wall designed to maintain internal integrity in case of an explosion, as decided by the scenario designer).

FAEs have an Impact of D10.

FAEs destroy minefields in the same way as regular Stargrunt II artillery.

Fuel-Air Explosives only work on planets with an atmosphere. The D10 Impact value assumes an atmosphere as dense as the Earth's atmosphere. Thinner atmospheres lower the FAE's impact. An atmosphere as thin as the Earth's on top of a mountain gives the FAE an impact of D8. Mars' atmosphere would give the FAE an impact of D6 or perhaps D4, as determined by the scenario's designer. A thicker atmosphere gives an FAE an impact as high as a D12. Any thicker than that, and troops — even Phalons — would need protective suits and specially sealed buildings anyway. Assume in those cases that the protective equipment and the thicker atmosphere mostly cancel each other out, and give the troops regular armour values and give the FAE a D10 or D12 impact.

FAEs Versus Infantry

Troops with hard, all-covering armour and included breathing apparatus — such as Power Armour and NSL panzergrenadier clamshell armour — use their regular armour values when defending against an FAE explosion. Phalons fall into this category, too, so Phalons caught in an FAE blast use their regular armour values.

Troops without all-covering rigid armour and breathing apparatus have an armour value of D4 versus FAEs regardless of the actual armour they are wearing.

FAEs ignore cover (except when used against troops in point targets; see the additional rules, below). There are no armour die shifts due to cover versus an FAE explosion.

FAEs and Point Targets

As per the Stargrunt II rulebook, a point target is a vehicle or a building. The effect on point targets and the troops within them differs greatly depending on whether the point target is "open" or "sealed". A point target is classed as "sealed" if it is airtight and all hatches, windows, doors, etc. are closed. A point target is classed as "open" if it is not airtight, or if it is airtight but a hatch, door, window, etc. is open.

The scenario designer has to indicate which buildings and vehicles are airtight and capable of being sealed before the game begins. Here are some general guidelines:

A building or vehicle that is not airtight offers no protection against FAEs. A point target that is airtight but is not sealed offers no protection against FAEs. This is important to remember. FAEs work due to air pressure, and even a small opening is enough to cause massive pressure within an otherwise closed building or vehicle.

Building Sealed Status

An airtight building is sealed if all the blast doors, windows, etc. are closed. A player declares whether or not a building is sealed when the game begins if he has troops within the building, or when troops first move into a building. A unit may not fire out of a sealed building unless it was specifically designed to allow this kind of fire. The scenario designer has to specify such buildings at the beginning of the game.

Once declared as sealed or open, it takes a Reorganise action or a Move action to change the building's status. These Move or Reorganise actions may also be used for other purposes, such as treating casualties (in the case of the Reorganise action) or moving into a building (in the case of the Move action).

Units may move in and out of a sealed building if it is empty, or it contains only friendly units. If a player wishes to enter or leave a sealed building and have the building retain its sealed status, it costs an additional 2" of movement over and above the regular movement cost for entering or leaving the building. This cost does not apply to open buildings. The player can ignore this cost if the unit enters or leaves a sealed building and declares that it is now open.

A unit may only enter a sealed building if it is occupied by friendly units, or it is empty. A unit can not enter a sealed building containing enemy units without first breaching a wall or door. Once breached the building is treated as open. (The scenario designer may choose to ignore this rule for some/all of the buildings in a scenario.)

Vehicle Sealed Status

Vehicles are handled differently from buildings. Whenever the vehicle's sealed status comes into question, roll the vehicle's Quality Die. If the result is greater than the vehicle's Leadership Value, the vehicle is sealed. Otherwise someone on the vehicle has left a hatch open or the crew is operating "unbuttoned", and the vehicle is not sealed. (See below for a more detailed and advanced way of handling sealed vehicles).

FAEs Versus Sealed Point Targets

This procedure is used for a sealed point target caught inside an FAE's blast radius:

  1. Roll the point target's armour die versus the FAE's D10 impact die. Use the point target's lowest armour rating for its armour die. For instance, a vehicle with 3/2 front/side armour would have an armour rating of 2 and would roll 2D12 for its armour roll.
  2. If the armour die is greater than or equal to the impact die, the target has suffered a non-penetrating hit. Roll for the non-penetrating hit as per the Stargrunt II rulebook, page 39, but treat a SUSPENSION hit as a SYSTEMS hit. Troops, civilians, and cargo inside the point target are immune to the effects of the FAE.
  3. If the armour die is less than the impact die, the point target has been disabled or destroyed as per the usual Stargrunt II rules. The point target has also been penetrated. Do not determine casualties using the regular vehicle and building rules. Instead, roll the FAE's D10 impact die versus the armour die of the troops inside the point target. Treat this as an FAE explosion (i.e. troops with rigid armour and breathing apparatus, and Phalons, use their regular armour die, while all others have a D4 armour die).

FAEs Versus Open Point Targets

This procedure is used for an open point target caught inside an FAE's blast radius, or for point targets that are not airtight:

  1. Roll the FAE's D10 impact die versus the armour die of the troops inside the point target. Treat this as an FAE explosion (i.e. troops with rigid armour and breathing apparatus, and Phalons, use their regular armour die, while all others have a D4 armour die).
  2. Roll the point target's armour die versus the FAE's D10 impact die, but reduce the target's armour class by 2. If a target had armour class 5 (and would therefore roll 5D12), reduce it to armour class 3 (3D12). The lowest any point target can drop to is armour class 0 (which is a D6, as per the Stargrunt II rulebook). Use a point target's lowest armour rating for its armour die. For instance, a vehicle with 3/2 front/side armour would have an armour rating of 2, reduced to 0, and would roll D6 for its armour roll.
  3. If the armour die is greater than or equal to the impact die, the target has suffered a non-penetrating hit. Roll for the non-penetrating hit as per the Stargrunt II rulebook, page 39, but treat a SUSPENSION hit as a SYSTEMS hit. If the armour die is less than the impact die, the point target has been disabled or destroyed as per the usual Stargrunt II rules.
Example: an NSL bunker (armour class 3) with Power Armour, Jagers and Panzergrenadiers are within the blast radius of a Phalon fuel-air explosive warhead. The bunker is open to the air, so the warhead has full effect on the inhabitants and the bunker's effective armour class is reduced to 1. The Power Armour roll D12 armour versus D10 impact. The Panzergrenadiers roll D8 armour versus D10 impact. The Jagers, however, roll D4 armour versus D10 impact. The bunker must now test to see if it survives the blast. A D12 is rolled for the bunker versus the D10 impact of the blast.

Advanced Rule: FAEs and Vehicles

The standard rule assumes that any time an FAE hits a vehicle it is sealed unless the vehicle fails a reaction test. Players would argue that when engaging the Phalons (or a human force with these weapons) that standard procedure would be for a vehicle crew to fight sealed until reasonably sure that the threat has subsided. These advanced rules are for players who don't mind keeping track of "sealed" and "open" vehicles. These rules apply to vehicles that can be sealed by way of hatches, etc. They do not apply to civilian vehicles, canvas covered trucks, etc.

In games where a defender is attacked by surprise in a situation where they think they are safe, assume the defender's vehicles are open. In games where an attacker is making an attack into an area he knows is hostile, the attacking player may assume that his vehicles are sealed or open at the player's discretion. In all other cases, make a Reaction Test the first time a vehicle is activated or the first time the vehicle is attacked. If the Reaction Test is failed, the vehicle is open.

It does not normally take an action to seal or open a vehicle (exception: see below). A vehicle is designated as sealed or open at the beginning of its activation. It remains in that state throughout its activation and until it is next activated. If desired, a unit may change their sealed/opened status during a Reorganise action.

Vehicles that transport infantry are a special case. The vehicle is declared open when the infantry load onto or unload from the vehicle. The vehicle stays in that state until the vehicle's next activation.

All communications with a sealed vehicle must be made with a communication roll, including Transfer Actions. This is regardless of whether or not the vehicle is within 6" of a command unit. If the command unit is inside the vehicle itsel a communication roll is not needed with the vehicle's crew (but a communication roll is needed to contact any unit outside the vehicle).

Snipers are allowed to target the crew or passengers of an open vehicle. Snipers cannot target the crew or passengers of a sealed vehicle.

Sealed units that have taken System hits cannot communicate with any other unit. They do not get to automatically change to open status when they are activated. They may, however, use a Reorganise action to open during their activation.