Saturday, October 15, 2016

Shield: Reactionary Armor

In my last post I showed you guys how to stat up HEAT rounds, which is great if you're up against heavy armor.... but what if you're the one in the heavy armor?

Well in that case, it's time for your armor to get a little reactionary!

Notice! Massive Update!
Hey guess, I found that the numbers I used in my original write up were off so I have re figured a lot of the stats.

If you remember from my last post I mentioned  that a major weakness in how HEAT weapons work is in the fact that it needs to go off at a very specific stand off range to work effectively. If something disrupts that, its penetrating drops drastically.

This is the key to how Reactive Armor works. At its core Reactive armor is two metal plates that has a layer of explosives sandwiched between them. When a HEAT round hits and detonates, the shock causes explosive layer to go off which bows out the upper metal plate. This does three things.

  • 1) Bring the metal plate into contact before the HEAT rounds jet has time to fully stabilize.
  • 2) Generates a counter force that slams into the jet, helping to break it up.
  • 3) Increases the effective distance the jet needs to cover before it can reach its intended target and hopefully forcing it to go past its effective stand off range. 

As stated above the primary way this effect is achieved is through using high explosives. While effective, it's explosive nature possess a danger to near by troops who can  injured by the blast and spalling from the Reactive Armors plate. This fact has lead to the development of different means to get the metal plates to "react" without needing explosives. This had lead to the development of Non-Explosive Reactive Armor which uses an inert material that bows outward when hit with a sudden shock. This has the advantage of not only not producing a dangerous blast but is able to survive multiple hits but offers less protection. Unlike normal Explosive Reactive Armor it can also be stacked for a layered defense. A hybrid option called Self-Limiting Explosive Reactive Armor has also been developed which uses a combination of an inert layer and a small explosive charge. It has the same effectiveness as normal Explosive Reactive Armor but is more complex and expensive and does not have a multi-hit survivable capability. It also has an explosive danger but a much lower one then full Explosive Reactive Armor.

The latest development in Reactive Armor has been Electric Reactive Armor which uses a high voltage current to disrupt the HEAT jet but this is a topic for another post.

Below is a breakdown of the rules you need to create your own Reactive Armor. These rules cover normal Explosive Reactive Armor, Non-Explosive Reactive Armor and Self-Limiting Reactive Armor. Note that using Reactive armor does require a little extra paper work.

Reactive Armor has a split DR. The higher value protects against shaped charge and piercing attacks and is counted as having one level of Harden (see Basic Set pg. 47 for more) against shaped charges. The lower value protects against all other damage. This higher DR value is 5× higher then lower DR value for Explosive and Self-Limiting Explosive Reactive Armor and 2.5× higher for Non-Explosive Reactive Armor.

When an area covered by Explosive or Self-Limiting Explosive Reactive Armor is hit roll 1d. Add the Coverage Modifier and a modifier of -1 per previous hit on that location. If the total modifiers here are 0 then don't bother rolling, the area if totally covered. If -1 or lower roll. If the total is 1 or higher then the Reactive Armor is hit and defends as normal. If the total is 0 or lower then an uncovered area is hit and the Reactive Armor has no effect.

Every time every time an area with Reactive Armor is hit keep track of it, once the total modifier is -6 or lower all the reactive plates in the area have been depleted and the Reactive Armor no longer protects it. 

Example: An area that is covered in Reactive Armor that has 2/3rds coverage is hit by a shaped charge attack that has been hit twice before! The player rolls 1d and subtracts 1 for having 2/3rds coverage and another 2 for its two previous hits for a total of -3. The roll a 4 for a total of 1, the shot just barely lands on a protected area! The player notes that they now have 3 previous hits, next time they'll roll at -4.

If  Explosive or Self-Limiting Explosive Reactive Armor is hit with an attack that does less half its lower  Base DR value the Reactive Armor is NOT set off and does not count as a previous hit. 

Example: A set of Reactive Armor that has DR 500/100 is hit for 49 points of damage. Since this is less then 50 the plate is not set off and this does not count as a previous hit.

Non-Explosive Reactive Armor works differently. Only roll to see if a location is hit if it has less then full coverage and this chance does not go down if it is hit. Instead treat the area as Semi-Ablative  (see Basic Set pg. 47 for more) but since the area has a split DR a slight rule adjustment is needed. When enough damage is done to an area to ablate it, subtract the DR from the lower Base DR and recalculate its higher DR value vs. shaped charges and piercing attacks from that.

Example:  A set of Non-Explosive Reactive Armor that has DR 375/150 and is hit with an attack strong enough to ablate 3 points of DR, drop it's lower Base DR value to 147 and then re-figure it's new higher DR value as 147×2.5 or 367.5 which we round up to 368. It's new DR value is 368/147.

Part I: Assumptions

Think Up a Concept
Think about what you are going to protect with Reactive Armor, how much of it are you going to cover, the entire thing or just the more vulnerable parts? What kind of HEAT rounds are likely to be used against it? How advanced and how powerful are they? Is what you're covering something worth the enemy  hitting with biggest HEAT round they have? Once you got an idea of the kind of threats you are going to face you can start stating up the protection you need.  

Example: Even with their Electromagnetic Armor, Heavy Battlesuits are vulnerable HEAT weapons. Since they're fairly high profile targets, the enemy is going to use whatever anti-armor weapon they have on hand against it even if it would be overkill. Sounds like we better make some advanced sets of reactive armor tiles to defend them. 

Pick the Reactive Armors Tech Level
You all know the drill by now. Pick the TL you want your Reactive Armor to be. This will effect how much it weighs for given level of protection and therefor how much it costs.

Example: Since both  advancements at TL10 make HEAT rounds far more prolific as well as the fact that the Heavy Battlesuit is TL10 as well, TL10 seems like a good TL to start at. 

Choose the Reactive Armor Type
Explosive and Self-Limiting Explosive Reactive Armor generates an explosive, though Self-Limiting Armor has a smaller blast effect but costs more.

Non-Explosive Reactive Armor gives lower all around protection but is non-explosive and can survive multiple hits and is treated as semi-ablative. It can also be layered for more protection.

Example: Since we want this Reactive Armor to be fitted to Heavy Battlesuits which in turn operate near normal ground troops. Non-Explosive Reactive Armor seems like a good idea but its reduced protection could be a liability so we opt for Self-Limiting Explosive Armor as a middle ground. 

Choose the Reactive Armors Quality
Higher quality Reactive Armor gives more protection for a given weight but costs much more while cheaper quality armors save you money but are heavier for the protection they give.

The Quality options are:
  • Standard: The base line for a given TL.
  • Cheap: A lower quality set of Reactive Armor. They cost half as much but give 2/3rds as much protection. Effectively a set of Reactive Armor one TL lower then standard.
  • Advanced: Next generation Reactive Armor. Gives 1/3rd more protection but costs five times as much. It is effectively one TL higher then standard.
Example: Since battlesuits have lower surface area then most vehicles and tend to be seen as high value targets most governments are going to spend a little extra to protect them .

Choose how much DR the Reactive Armor Gives
Choose how much basic DR the Reactive Armor will provide. This will determine its base weight. Explosive and Self-Limiting Reactive Armor gives 5× this Base DR against piercing attacks and shaped charges and also has one level of Harden  against shaped charges (this effectively doubles its DR against shaped charges) while Non-Explosive Reactive Armor gives only 2.5× the Base DR against piercing and shaped charge attacks but also counts as Harden.

Example: At TL10 a man-portable 110mm HEAT round that does 6d×11(10)  is a disturbingly easy thing to make. This can penetrate DR 2,310 on average and even with Electromagnetic Armor a TL10 Heavy Battlesuit can only offer up DR 300 against a HEAT round on it's most protected area! Pop goes the battlesuit! So to figure out Base DR our Reactive Armor will have first we take the average penetration of 2,310 and since Reactive Armor has a level of Harden against HEAT this halves it down to 1,155. Since the Heavy Battlesuit can contribute DR 300 to this the Reactive Armor only needs to add DR 855 to stop the HEAT round. Now that we have have how much DR we need to be proof against this threat, we can take 855 and divide it by 5 to get a base DR of  171.
Now that we have the base assumptions, lets move on stating up the Reactive Armor.

Step II: Base Stats

Base Reactive Armor Weight
This will give you how much the Reactive Armor will weigh per square foot of coverage.

Base Weight =  (DR×Qu)/TL

DR is how much Base Damage Resistance the Reactive Armor will Provide.
Qu is 0.83 if Cheap, 0.55 if Standard and 0.37 if Advanced.
TL is 1 at TL9, 1.5 at TL10, 2 at TL11 and 3 at TL12.

Example: Our Reactive Armor is TL10, Advanced and has a Base DR of 171 so it weighs  (171×0.37)/1.5 or 42.2lbs per square foot.

Base Reactive Armor Cost
This will give you the Reactive Armors Base Cost per square foot of coverage.

Cost= Wt×Qu×T×$3

Wt is the Base Weight of the Reactive Armor.
Qu is 0.5 if Cheap, 1 is Standard and 5 if Advanced.
T is 1 if Explosive or Non-Explosive Reactive Armor, 2 if Self-Limiting Explosive Reactive Armor. 

Example: Being Advanced Self-Limiting Explosive Reactive Armor and having a Base Weight of 42.8 lbs, a square foot of it costs 42.8×5×2×$3 or $1,284 which we round up to $1,300. Pricey but worth it if it brings our battlesuit troopers back home in one piece. 

Explosive Hazard
If the Reactive Armor is Explosive Reactive Armor or Self-Limiting Explosive Reactive Armor, it will set off an explosive blast if hit. The damage is crushing with the explosive modifier, this damage effects what the armor is attached to as well as anything else with in its explosive radius. It also causes Incidental Fragments, treat as lose scrap (see Basic Set pg. 415). If the Reactive Armor is Non-Explosive then is just does crushing damage to the armor it is bolted too.

Dice of Damage = Rt×square root of (Reactive Armors Base Weight)

Rt is 0.24 for Explosive Reactive Armor, 0.17 is Self-Limiting Explosive or Non-Explosive Reactive Armor.

Ideally the armor the Reactive Armor is attached too should have DR equal to at lest 6×dice of damage with an absolute minimum DR of 3.5× dice of damage.

Example: Weighing 42.8lbs the Self-Limiting Reactive Armor does 0.16×square root of(42.8) or 1.04 dice of damage when it goes of which becomes 1d cr ex. Since even DR 5 would completely protect against this, our Heavy Battlesuit is fine.

Legal Class
LC is 2 for Explosive and Self-Limiting Explosive Reactive Armor and 3 for Non-Explosive Reactive Armor. 

Example: Since this set of Reactive Armor is Self-Limiting Explosive Reactive Armor it is LC 2.

Stating it Up
Now that we got all that, let's condense all this information into an easy to read stat box.

The write up should contain 2 notes:
  • [1] Use the higher DR value against shaped charge and piercing attacks and the lower value against all other types of damage.
  • [2] If an Explosive or Self-Limiting Explosive Reactive Armor note how much crushing explosive damage it does, the minimum damage needed to set off the Reactive Armor (equal to half the armors Base Lower DR) and that it causes incidental fragments, treat as lose scrap. If Non-Explosive Reactive Armor list how much crushing damage it does to the armor its attached to and note that it's Semi-Ablative.
TL Armor                                         DR           Wt/Area   Cost/Area    LC    Notes
10 Heavy Battlesuit Reactive Armor  885/171    42.8        $1,300             2         [1, 2]

[1] Use the higher DR value against shaped charge and piercing attacks and the lower value against all damage.
[2] Explodes for 1d cr ex damage when hit by an attack that does at lest 86 points of damage. Causes incidental fragments, treat as lose scrap.

Step III: Application
Now that we know what your Reactive Armors base stats look like, use these following rules for how to apply the Reactive Armor to objects and vehicles.

First figure out the total surface area the section you are going to set up for Reactive Armor has in square feet. This is going to be hard to figure out for most vehicles but even rough approximations can work. A typical car is going to have about 200-300ft22 and a Tank will have over 1,000ft2
Once you've figured out the total area that you want coverage, think about  if you want the whole area covered. While it's normally a good idea to cover as much area as possible, it's not always possible do to cost or weight limits.

Take a look at the coverage options below and choose an option. The one you do will effect how much it weighs and cost to cover the needed area, but how hard or easy it is for an attack miss an uncovered area.

Coverage       Coverage Modifier
Full:                    -0
2/3rd:                 -1
1/2:                    -2
1/3rd:                 -3
1/4th:                 -4
Less then 1/4:    -5

Example: As a rough estimate, the Heavy Battlesuit has about 21% more surface area then the average person but we're not going to want to cover the entire battlesuit with Reactive Armor. Instead we focus on protecting the front torso of the armor. The frontal surface area of the average person is about 3.5ft2 which would be scaled up to ~4.2ft2. To save a little weight and money, we are going to go for 2/3rds coverage. In a first hit situation it would roll 1d-1 to see if a covered area was hit. 

Actual Weight and Cost
Once we know the total surface area the Reactive Armor is going to be attached to and how much of that is going to have coverage we can figure out the total weight of Reactive Armor needed to provide that level of coverage and ow much it will cost.

Actual Weight  = (Bw×A)/Cv

Bw is the Reactive Armors Base Weight.
A is the total surface area the area has in square feet.
Cv is 1 if Full Coverage, 1.5 if 2/3rd Coverage, 2 if 1/2 Coverage, 3 if 1/3rd Coverage, 4 if 1/4th Coverage and 8 if Less then 1/4th Coverage. 

Example: Our Reactive Armor has a Base Weight of 42.8lbs and is going to cover 2/3rds of a 4.2ft2 area giving it a final weight of 118lbs. 

Actual Cost: = (Bc×A)/Cv

Bc is the Reactive Armors Base Cost.
A is the total surface area the area has in square feet.
Cv is 1 if Full Coverage, 1.5 if 2/3rd Coverage, 2 if 1/2 Coverage, 3 if 1/3rd Coverage, 4 if 1/4th Coverage and 8 if Less then 1/4th Coverage.

Example: With a Base Cost of $1,300 and a coverage of 2/3rds of 4.2ft2 it has a final cost of ( $1,300×4.2)/1.5 or $3,640 which we round off to $3,600. 

Also keep in mind that Non-Explosive Armor can be stacked, If you do so multiply the Reactive Armors weight, cost and DR by how many layers you add. 

Example: Let's say we were stating Non-Explosive Reactive Armor instead for the same area and coverage giving us the same weight and cost of 118 lbs and $3,600 but DR 428/171 instead. Now let's say we want to double the layer, it would now weigh 236 lbs, cost $72,000 and have DR 855/342.


  1. Good one! I have needed to reference ERA for something I've done in the past ( ) which I'm 95% sure you've read already. I eyeballed it as just being worth some Ablative DR (though in retrospect I don't believe I conveyed it as well as I had intended - it's not Ablative so much as it is used-and-gone). It's actually kinda weird that HT doesn't have anything on ERA, rules-wise.

    I have more vehicles to be coming in the future - eventually - if it is something I can't find hard-and-fast statistics on the ERA (or if it is completely fictional to begin with) then I will see about referencing this article to resolve it.


    1. Yeah, I'm going to dig into spaced armor in the future as well.

      ERA is still relatively new and in the experimental phase so there's not too much that's easy to find on it but from what I've seen the fact it doubles an armors defectiveness vs. HEAT is something I remember reading from press junkets I've stumbled across.

      I'm still working on ERA, I'm not sure if I should keep it in line with RAW in that it simply doubles normal armors DR vs HEAT (triples if the armor is laminate) or do something a bit more detailed.


      Wait... writing that made something click in my head... I think I got a way to do both!