BattleTech has loads of equipment designed to improve the durability or survivability of a ‘Mech, but how good is any of it? How much protection does an AMS or ECM system provide? That’s a topic that always interested me, so now I’m making it your problem. To organize things, we’re going to discuss them in terms of the Defense Onion.

If you’ve never heard of the Defense Onion, I’ve included a handy graphic! The onion refers to each successive layer of protection you have against taking damage, and is used in plenty of other contexts beyond war gaming. Because of that, we are going to simplify each layer a bit or adapt its definition to our purposes.

The first two layers (Don’t Be There and Don’t Be Detected) are “strategic layers” because these are tied to decisions about who fights, where they fight, and what their objectives are. Successful use of either of these layers effectively prevents your ‘Mech from being attacked at all. Because of the all-or-nothing aspect of these layers, they will not receive the same level of analysis as the lower layers.

The first layer. Is your asset just really vulnerable to the expected opposing force or ill-suited to the mission objective? If so… don’t be there. This mostly applies to campaign play, and applies to equipment only rarely.

What equipment? Artillery, or extended range LRMs. If you’re on a different map sheet because you’re firing Arrow IVs as artillery, congratulations! You weren’t there.

The second layer. This is a somewhat weird one, because really it only applies to scenarios where you’re either playing Double-Blind Rules or where you’ve got the Hidden ‘Mechs rules in play. This comes into play with scenarios like Breakthrough, Hide-and-Seek, or Recon Raid. Rather than equipment, your biggest advantage here will be things like the Special Command Abilities found in Campaign Operations: Camouflage (p. 84) or Tactical Experts (Hidden Units) (p. 87). These SCAs grant you the use of the Hidden ‘Mechs rule, or expand it, where you get access to it.

While no equipment grants you the ability to be hidden, there are some that make it harder to detect you. Units with active probes can detect hidden ‘Mech at range, but several technologies can interfere with that. A Guardian ECM suite, Stealth Armor, Null-Signature, or Void-Signature System block the operations of most active probes, except Bloodhounds. Only an Angel ECM suite can block any probe (including Bloodhounds). However, the jamming provided by Guardian or Angel ECM is detectable.

The next three (Don’t Be Acquired, Hit, or Breached) are “tactical layers” because these are influenced by your turn-by-turn decisions and how you use the equipment you’ve brought. Any equipment here can be compared directly to an estimated equivalent in armor, although some of these bonuses are provided only under specific conditions. We’ll discuss each in terms of their equivalent weight in armor and the conditions under which they best function.

The third layer, and first tactical layer. Don’t be acquired is all about interfering with enemy targeting systems, which in BattleTech terms means Artemis IV or Streak systems. The only tech that interferes with those are Chaff Pods, Guardian ECM, Angel ECM, or ECM pods fired by iNarc launchers. Even though, technically, Anti-Missile Systems work toward the “Don’t Be Hit” layer because they intercept missiles that have already acquired their target, we’re going to class them here in Don’t Be Acquired because of how well they compare to ECM systems.

Guardian ECM creates a 6-hex bubble that counters Active Probes, C³ and C³i, Artemis IV and V FCS, and Narc Missile beacons. Guardian ECM weighs 1.5 tons and takes up 2 crit slots.

Angel ECM works exactly the same as Guardian, except it also counters Streak and forces Streak launchers to roll on the Cluster Table as if they were normal launchers. Angel ECM weighs 2 tons and takes up 2 crit slots.

For comparisons to armor, we’re going to focus on its capacity to block Artemis IV specifically since that is the most prevalent of the systems affected. If you’re mounting a Guardian ECM system on a ‘Mech, it had better prevent at least 24 points of damage to break even on what its tonnage would have given you in Standard Armor. If you check out last week’s article on Fire Control Systems, you’ll see that adding Artemis IV to an LRM 15 gives it on average an increase of 2 damage per attack. In fact, we can bring that table back with a new column!

So… this looks pretty bad for Guardian ECM at first. On a single ‘Mech, you would need to block Artemis IV from working on 13 successful attacks from an LRM 15 launcher before it’s better than the equivalent cost of armor on that same ‘Mech. But consider that the Archer ARC-5CS mounts four LRM 15s with Artemis IV. Against a ‘Mech like that, you’re potentially breaking even after 3-6 rounds of fire. But, more importantly, ECM is a 6-hex bubble that can benefit multiple ‘Mechs, not just the ‘Mech it’s mounted on! With that in mind, I think Guardian ECM is a pretty great investment for at least one ‘Mech in a lance.

Now, Angel ECM is up next. So we’re going to do the exact same thing, but looking at how much damage it can block on average from Streak SRM launchers. Because Angel ECM is a half ton heavier, our target is 32 instead of 24 but everything else stays the same.

To me, Angel ECM comes out even better than Guardian ECM in this contest because it allows you to throw your ECM carrier in people’s faces. Streak SRMs are, normally, a strong deterrent against getting up close. But here, it’s real clear how much damage your opponent is losing on those attacks. Being able to close on an opponent like that means you’ll be making sure their LRM boat is blocked by your ECM bubble, and that means reduced damage against the rest of the ‘Mechs in your lance since Angel ECM still blocks Artemis IV just like Guardian.

ECM pods let you tag an enemy ‘Mech with their own personal jamming field. Unfortunately, to do that you need to mount an iNarc launcher and carrier 1 ton of ECM pod ammo for it. That’s an investment of 6 tons and 4 crit slots to get 4 shots that might not hit. The benefit? You can run up and tag an LRM boat with an attack that instantly drops its average damage for every turn it’s attacking. First off, if this is your plan? Don’t. Bringing an iNarc launcher with only a single ton of ammo is a huge waste. So we’re going to assume that this ECM effect is only half of what the iNarc is being used for. So can 4 ECM pods block 3.5 tons of armor worth of damage?

That means we’d need to block 56 damage with an effect that doesn’t start until an attack has landed. If the enemy lance is 4x Archer ARC-5CS and we tag one per turn every turn starting on turn 3? Starting when an Archer is tagged, you’re negating maybe an average of 5 damage per turn (accounting for missed shots). If the game lasts 10 turns, you’re blocking (7×5)+(6×5)+(5×5)+(4×5) total damage, or 110 damage total. Even if your first two ECM pods miss, you’re blocking 55 damage on average.

My take is… I don’t necessarily like it. It weighs a lot for a bonus that’s very circumstantial and requires a lot of things to go right for it to work. But it can work.

While ECM systems effectively remove bonuses missile weapons would receive when rolling on the Cluster Table, AMS systems directly apply penalties to that cluster table. Unfortunately, unlike ECM suites, AMS does not apply to all missile attacks against an area of effect, or even all attacks against a single ‘Mech, but a single attack per turn. The good news is that makes them a lot easier to calculate.

The Inner Sphere AMS system weighs half a ton, takes up a single crit slot, and requires ammo. 1 ton of ammo takes up 1 crit slot and provides 12 shots. To me, that means 1 ton of AMS ammo can support two AMS launchers since I’d rather have 6 turns of double strength protection than 12 turns of a single AMS. So let’s look at this as a 2 ton, 3 slot system. When it’s used, it applies a -4 penalty to the Cluster Table result of normal launchers, or reduces Streak launchers to a result of 7 instead of 12. Same game as last time, how quickly do we get to 32 points of armor saved.

Using the numbers from the above table, we can calculate average damage for launchers impaired by an AMS system, then deduct that value from the average damage those weapons deal normally, and arrive at how much damage an AMS blocks on average. Remember, I’ve suggested we look at AMS as something to mount in pairs. So after 6 turns of fire, the AMS has run out. The table below shows only launchers whose total damage blocked exceeds 32 after 6 or fewer attacks.

If you think you’ll experience listed in the right column from the weapon listed in the left column, then your AMS system will (on average) save you more ammo than its tonnage cost you. If you couldn’t tell yet, I really love AMS systems. I think they’re a bargain.

But what about Laser AMS? They weigh 1.5 tons, take up 2 slots, and cost an extra 6 heat to operate instead of carrying ammo. They suck. Unless you’re already running a ‘Mech with lots of spare heat capacity, trading 1 ton of ammo for 3 tons of Double Heat Sink is a raw deal. Unless you’re planning to run some sort of guerrilla warfare where your lance never resupplies, you don’t need this. Even the Clan Laser AMs isn’t ideal. It saves a half-ton, a crit slot, and generates 5 heat instead of 7. Slap two Double Heat Sinks on that, and you’re doing for 3 tons about the same damage mitigation that Inner Sphere AMS achieves for 2 tons. The explosion risk is pretty minimal, especially if you run two AMS off one ton of ammo.

Chaff Pods are single use items that weigh 1 ton and take up 1 crit slot. When deployed, they have three effects: it creates a cloud of light smoke two elevations tall, creates a 1-hex ECM bubble, and acts as an AMS against all missile attacks (except or MRMs and Rocket Launchers). These effects last only during the Weapon and Physical attack phases of the turn they were deployed.

This triple effect is so potent that, more often than not, rather than reduce damage from an attack, or attacks, deploying a Chaff Pod may also deter an opponent from firing missiles at all on that turn and just wait to fire the next turn. Let me demonstrate with… yep, another table. First column is what type of ‘Mech is attacking, 2nd is the expected average of its missile weapons, 3rd is how much you would block on average, 4th is how much you would receive on average.

If you’re not following along with the Average Blocked column, I completely understand! First, I’m negating the Artemis IV. Second, I’m applying the -4 Cluster Table result. And 3rd? I’m multiplying by 0.71 to estimate the effect of the +1 to hit. Why 0.71? Because it’s easier than multiplying every damage value in the game by 0.5833 and working from there. For all these comparative statistics, I assume a attack is hitting on 7s (or 58.33% of the time). When an effect, like light smoke, grants a +1 to hit? Those attacks are now hitting on 8s (or 41.67% of the time). 41.67/58.33 = 0.7144, and I’m lazy so that ends up being 0.71 or 71% instead.

A single effective use of a Chaff Pod could block 28 damage from hitting, or, more likely, force your opponent to fire at some other target. That’s really powerful for something that only costs a single ton, and that doesn’t even account for any non-missile weapons that miss because of the to-hit penalty associated with light smoke.

This is the fattest layer of the onion and applies to everything that improves your TMM. That means stealth technologies (Chameleon Light Polarization Shield, Null-Signature System, Void-Signature System, Stealth Armor), larger engines, MASC, Supercharger, and Active Probes.

Engines, MASC, and Superchargers are a subject complex enough to merit an article of their own, so these will be held for a later article.

CLPS grants an additional +1 to-hit modifier against attacks made at medium range, or +2 against those made at long or extreme ranges. It costs no tonnage to install, but takes up 6 crit slots and costs 6 heat to operate. By every metric, this is one of the cheapest stealth technologies to employ. Even if equipped on a very slow ‘Mech, this is providing a huge boost to survivability.

Because CLPS costs heat and crit slots rather than tonnage, we’ll need to compare it a little differently. Let’s assume we’re mounting an extra two Double Heat Sinks and eating the left-over 2pts of heat generation. Now we’re using up 2 tons and between 6 and 12 crit slots. This makes it comparable to upgrading from Standard Armor to either Light-Ferro-Fibrous or Ferro-Fibrous.

In the absolute best-case scenario on a 100-ton ‘Mech, upgrading to Light Ferro-Fibrous and spending that Heat Sink tonnage on armor is gaining us 50 to 51pts of armor. But that +1 to-hit modifier is going to do more than that for sure. Mounting a Stealth system like this, you want to keep distance at 8-10 hexes away (for Inner Sphere opponents) and return fire with weapons using 5/10/15 ranges or longer. If, on average, 18 or more damage is aimed at your ‘Mech, then you’re making up that armor trade-off within 7 turns of gameplay.

Null-Sig works identically to CLPS except it costs 7 crit slots, 10 heat, and infantry ignore the effect. It’s also one of the only sources of stealth that can stack: Null-Signature and CLPS are allowed to stack with each other. So, being 10 heat, it’s all the same math as above but with two more Double Heat Sinks: 4 tons, 7 to 19 crit slots. So now, realistically, it’s got to save us 108 points of armor to make up its cost. Which is a lot harder.

Null-Signature Systems just aren’t as good as other options available, and stacking it with CLPS is really only worth it if you’re trying to build a Rifleman III style of sniper ‘Mech.

This is some Evil Word of Blake tech that grants you major TMM bonuses the less you move. At 0 hexes? +3 to-hit modifier. +2 at 1 or 2 hexes, +1 at 3 to 5, and no benefit for more than 6 hexes moved. You can get the same to-hit modifier from sitting still that you would otherwise get from moving 7 hexes, but it is at a cost: 1.5 tons, 7 crit slots, and 10 heat. Now, mount this on a sniper ‘Mech covered in Gauss Rifles, and you can ignore that heat problem. Which means this is a great way of getting to-hit modifiers on a stationary sniper, the sort of ‘Mech that would have struggled to move 7 hexes anyway.

On a well-built ‘Mech, the Void-Signature system is basically pure profit. You’re cutting your odds of getting shot by almost 30% (again, assuming an average to-hit number of 7) so you can stay still and not give yourself a +1 to-hit modifier for walking. If you’ve set yourself up in some woods or smoke? Even better. Void-Signature would need to save you 24 points of armor. Let’s imagine two scenarios: a sniper duel with an Awesome and a Striker that runs up to deal with the sniper problem.

Scenario 1, an Awesome AWS-8Q is firing at your sniper from 12 hexes away. This is a 4/5 pilot with no terrain in their way, not walking, and making shots at medium range. Your sniper is in light woods. That’s normally hitting on 7s. But now? That’s 10s. Instead of averaging 17.5 damage per turn, they’re now, on average, hitting with 1 PPC every other turn. That’s 28.6% less damage, taking less than 2 turns to recoup the tonnage spent.

Scenario 2, a Nightsky NGS-4S has run up to 4 hexes away. This is a 4/5 pilot with no terrain in their way, they’ve just run, and they’re making shots at medium range with 2x Medium Pulse Lasers and a Large Pulse Laser. Your sniper is in light woods. That’s normally hitting on 5s, now instead hitting on 8s. Instead of averaging 17.5 damage, (6+6+9)*0.8333, they’re averaging 8.75 damage per turn. At that rate, you’re getting your tonnage worth after just 3 turns.

I did say they’d be back! Active probes let you shoot through 1pt of light woods, or light smoke, like it’s not even there. Previously I talked about this as a pseudo to-hit bonus for SRMs. Today, let’s talk about it as a TMM source. If you can stand behind a light woods that you can shoot through unimpeded, but your opponent can’t? You’ve found a free TMM source.

This is comparable to the stealth technologies discussed above, but instead of a cost in heat it comes at a cost in positioning: you’ve got to actively seek out the situations where you get this benefit. As another cost, this is a short range tactic rather than a long range one. Because the Beagle Active Probe only has a range of 4 hexes, it’s not great for this role. Not at 1.5 tons, or the equivalent of 24 points of armor. But the Bloodhound? That’s got a range of 8 hexes for only an extra half-ton.

Let’s say you were using this to harass that Atlas from the previous example. You’re 8 hexes away and you’ve just run 6 hexes to take some shots at the Atlas, who has a 4/5 pilot. The Atlas has walked this round, so the total (not counting range modifiers) for that Atlas is 6 (3+1+2). Their 5x SRM 6s and 2x Medium Lasers at long range (10), and their AC/5 and LRM 10 are at medium range (8). You’re taking an average of 13 damage. Now, instead, you’re standing behind a light woods and their to-hit numbers have gone up to 11 and 9. Now, you’re receiving an average of about 7 damage instead. Where before you would have to choose between defending yourself and getting your best to-hit numbers, now you’re doing both at once and nearly halving the damage you might take.

Can you tell I really like the Bloodhound Active Probe?

The final tactical layer, this one almost exclusively tied to armor. I say almost exclusively because the single other tech that applies is the Blue Shield Particle Field Damper. Technically, Internal Structure types would apply under “Don’t Be Killed” because they’re defense that exists after your armor has been breached. But the real-world onion assumes that you can’t really survive internal strikes, and in BattleTech that’s not entirely true. Since Internal Structure compares so well to Armor, we will include it here under “Don’t Be Breached.”

Internal Structure has already been covered in a previous article, and armor involves more work than can fit here in the Defense Onion. Instead, we’ll cover a very minimal aspect: the number of armor points provided per ton of armor for several basic types.

This is a quirky one, since it only reduces damage from PPCs. That said, half damage on PPCs is a big reduction. The Blue Shield PFD costs 3 tons and takes up 7 crit slots, and somehow costs no heat to operate. This is a fantastically straight-forward one, since if it saves you between 51 and 68 armor points it’s breaking even. It does provide a biased benefit, in that it reduces more damage from Light or Heavy PPCs than it does from standard PPCs (since the halved damage is rounded down), but just looking at this from the point of view of normal PPCs it’s preventing 5 damage every time your ‘Mech gets shot with a PPC. That means getting hit with between 11 and 14 PPC blasts in a game to break even. That means you’d want to get shot at by 2-3 PPCs per round for a 10-round game without losing part of the Blue Shield PFD.

That is doable, and a side benefit of this tech is that Heavy PPCs are no longer a potential headshot kill weapon. If you plan on fighting a lot of Awesomes or hunting the Black Marauder, then Blue Shield PFD can work for you. But I’m skeptical of defense systems that are this specific.

Don’t Be Killed is a logistics layer because it’s not about your decisions before or during a battle, but determines what you can protect and what you can salvage from your own forces.

The final layer. Once you’ve hit this layer, you’ve already lost something. This isn’t about preventing that loss, but limiting how many more losses are suffered. Any equipment that makes sure the ‘Mech is salvageable or that the pilot doesn’t die, falls under this layer. Technologies that apply to this layer include CASE, CASE II, full-head ejection, and MechWarrior Aquatic Survival System.

None of these techs are things I can easily put an armor equivalency to, except maybe CASE II. But I don’t have a strong incentive to do those numbers, least of all considering that we may see some new rules for CASE and CASE II in the near future. So I think I’m happy leaving off with these here.

This was a terrible idea. Do you see how many sections this came out at? This is like a double feature article, since my target is usually around 2k words. No wonder this came out late this week, but I hope it’s a good read!