Thursday, September 23, 2010

Battletech Theory - Fusion Engine Discussion

Hey all, I just wanted to talk about a hotly contested and debated topic in Battletech....engines.  There are three main types of fusion engines used to power 'Mechs: standards, light and extralight (XL).  Most players have very strong preferences related to each type of engine.  I fall into the "I like them all" catagory, so I feel like I have somewhat of an impartial view.

Pre 3050, the engine debate is pretty unimportant.  Pretty much everything is standard fusion, with Star League relics might have an XL.  However, at 3050, with the Clan invasion, the TRO's went pretty crazy with XLs, especially after 3055.  It seems logical that the Inner Sphere, would want to put XLs on everything so they could pack more weapons, armor, and speed on these new 'Mechs.  However, fluff and mechanics diverge, like they always do and the debate rages on.

Mechanically, the main trade-off between the various types of engines is reduced weight, which free up more tonnage, and durability. Standard engines are heavy, but take up less crit spaces, meaning it makes the 'Mech more durable, since 3 engine crits cripples a 'Mech.  XL engines are light, but take up more crit spaces (6 more, 3 per side torso), making the 'Mech much more fragile to the 3 engine hit death.

Personally, the trade-offs and advantages and disadvantages of each type of engine is dependent on the role in which the 'Mech is designed to fulfill. 

Standard Fusions - This engine type is very vital in the modern battlefield.  By only taking up crit slots in the CT, it means that the 'Mech can survive side torso destruction.  'Mechs equipped with standard fusions are best served as soldier/brawler types.  Because they are typically slower and less heavily armed, they excel at making meat shields or "tanks".  You lure your opponent into attacking these 'Mechs by making sure they are easier to hit in comparison to other 'Mechs. 

XL Fusions - This engine frees up a lot tonnage.  This tonnage can be reinvested into a 'Mech in two main categories:  Weapons and Speed (bigger engine). There are two ways that XLs can be utilized.  The first, is to increase speed, significantly, in order to increase it's survivability.  Allowing the 'Mech to have a higher move mod, it increases the durability by damage mitigation (ie. missed shots).  The second, and more popular, is to pack more weaponry into a fire support platform.  Ideally, you don't want your fire support 'Mechs engaged in close combat, so the fragile nature of the XL engine is mitigated.

Where I think the XL gets a bad name is the liberal use by the canon 'Mech designers (freelancers) employed by the various entities that license the Battletech brand.  There are too many instances of XLs being dropped into slow and heavy brawler or light 'Mechs.  Either type die too quickly to side torso lose.  Only in certain circumstances, such as the Falconer, are great uses of XL to get speed and long ranged fire support, which keeps the 'Mech durable.  I'm not going to discuss specifics Mechs which illustrate bad ways to use XL engines, but I'm sure everyone knows a handful or two. 

The Light Fusion, is sadly a night widely used engine, mostly due to it's relative newest to the Battletech universe, I believe coming into the fold around 3062.  The lovely thing about this engine is that it has only 4 extra crits, not 6 like the XL.  Meaning, that side torso lose does not immediately cripple the 'Mech.  While this matters little for one-off battles, it is extremely important for campaign play, where a crippled 'Mech might have to left for dead, while one with a light fusion can still manage itself off the board.  The downside to the light fusion is that it's typically not enough saved weight to both increase speed and firepower like the XL.  You really have to pick one aspect to enhance.  It's easy to fall into the though process that you can improve both speed and firepower, but typically that's when light fusions end up looking bad. 

To summarize, all types of fusion engines are good, when used properly.  Fusions are great for enhanced durability.  XLs are great for 'Mechs reliant on speed (scouts and flankers) or are niched in the fire support role.  The light fusion is useful to add a little more zest to a 'Mech while still keeping it survivable.  That said, I'm interested to hear what everyone thinks about the various versions of the fusion engine.


  1. True.
    The use of a proper Engine is vital and will depend on either your preferred combo of speed/firepower/armour, the role of your 'Mechs...

  2. I think your comment on the nature of canon designs is very accurate - although it's not just canon mechs that suffer from easy XL death. I've seen plenty of homebrews that are the same.

    And whilst I like the Falconer, I still have a sneaking tendency to knock it down to 4/6 and a standard engine; the loss of the movement has almost always been less hassle than the increased durability! Unless it lets you get up to 7/11 (or better still 8/12) I find they're still too slow to avoid STD syndrome (Side Torso Death ;).

    I'm surprised you didn't look at the (even newer) Compact engines, as they seem to be having the same issues as XLs did - no one in canon seems to quite know what to with them... a case in point being the Wight. So much potential, so little gain!

  3. I didn't touch on the Compacts for precisely the reason you described...I don't know what to make of them. And, there's not really a good sample size of 'Mechs out there that use them to have any practical experience with them. Good points though, especially hitting the 7/11 speed mark as well.

  4. At a guess I'd say compacts don't get you much durability unless you use the saved torso space to cram your main weapons in the center torso so someone with a TC can't knock off the side torso with the big scary heavy PPC.

    For saving crits I would guess they're only ever useful on big quads.

    These are pretty much hunches though.

  5. As Klinktastic says, the sample size on designs with Compacts is pretty low. In the few customs I've used they work well - pack the CT with weaponry and you can just keep slugging along *effectively* even when crippled (when otherwise you'd just be an annoyance).

    It also helps eliminate the TAC issue - I find quad ER MLs to be handy as it gives reasonable range, no easy way to knock out one larger weapon and lots of padding for very little weight :)

    I haven't seen TRO: 3085 yet, but wouldn't be surprised to find there's more than a few new designs with them...

  6. I made this 'Mech which uses a compact engine -

    What I noticed is that for the cost (in C-Bills) and weight just doesn't validate the additional benefits of durability.

  7. That's going to be tough to kill but it's basically ignorable. If you dropped the HA, perhaps went for a HPPC or ER PPC + Heat Sinks or JJs, or really anything to give range+punch then it's going to be more effective.

    I've not been particularly happy with compacts (the increased cost in mass is considerable), but they have been effective, especially in Lance or above where you can hang them out as bait and let them keep on truckin' a bit longer than usual :)