Vehicle Engines question

[evilauthor]

Okay, so I was going over the construction rules in TechManual when I noticed something... odd. Combat Vehicles can't use Fuel Cell or Fission Engines, but Industrial Mechs can. Is there any in-universe reason for this? I mean we're experimenting with fuel cell powered vehicles NOW. Why wouldn't the Inner Sphere use fuel cell engines as a lighter alternative to ICEs?

[rlbell]

I think vehicle fuel cell and fission engines were added in TacOps.

[evilauthor]

I think vehicle fuel cell and fission engines were added in TacOps.

OKay, but why can't combat vees use them?

[A. Lurker]

If you look further, you'll find that support vehicles can use fuel cell engines just fine straight out of the TechManual. It's just one of those historical oddities of the canon BT universe that they never really caught on for combat vehicle use -- though to be fair, every unit type that can use them seems to assign them the exact same Tech Rating as a full-featured fusion engine, and if I had the choice between a lighter and somewhat cheaper engine on the one hand and one that allows me to more easily mount energy weapons and basically waves good-bye to refueling worries and explosive tanks on the other, I could definitely kind of see the advantages of the latter.

[evilauthor]

If you look further, you'll find that support vehicles can use fuel cell engines just fine straight out of the TechManual. It's just one of those historical oddities of the canon BT universe that they never really caught on for combat vehicle use -- though to be fair, every unit type that can use them seems to assign them the exact same Tech Rating as a full-featured fusion engine, and if I had the choice between a lighter and somewhat cheaper engine on the one hand and one that allows me to more easily mount energy weapons and basically waves good-bye to refueling worries and explosive tanks on the other, I could definitely kind of see the advantages of the latter.

Ah, I found the reference.

Interesting note: Fuel Cells don't require additional shielding. Fusion engines DO. According to the tech manual, a Fuel Cell system weighs 1.2 times that of a standard fusion engine. But on a vehicle, fusion engines spend half again their weight on extra shielding, so on any vehicle that doesn't use energy weapons, a fuel cell system effectively weighs LESS than a fusion engine (1.2 vs 1.5).

[cray]

OKay, but why can't combat vees use them?

Combat vehicles can use fuel cell and fission engines under Tactical Operations rules.

[A. Lurker]

Yes, fuel cell engines don't require additional shielding and so can easily be lighter than fusion ones. But that and the single free heat sink they get are already the only two advantages they enjoy over internal combustion engines...otherwise they work just the same, and for that you had to get to a tech level/rating that also allows you access to fusion power already.

So while a fuel cell-equipped combat vehicle as allowed by TacOps can potentially carry more armor and weapons than a fusion-powered one, at least as it doesn't try to mount much in the way of energy weapons...the fusion-powered one will present much less of a logistics headache due to needing much less fuel (for game purposes pretty much none at all) and being safer to operate, thus helping preserve trained crews (fuel tank crits may take out the engine, but won't blow up the whole thing -- add CASE to guard against ammo explosions and you're about as safe from crew death via inopportune crits as the rules allow). Given the apparent size of the armies of the Star League, which shaped many of the military traditions of the BT universe, I think I can see why fusion won out.