Tactics for ground combat in vacuum

[Trailblazer]

So you want to fight a battle on an airless moon or planet?  This is a deadly environment: each time a 'Mech or vehicle takes a hit, there is a chance of devastating decompression in the location hit.  Infantry take extra casualties.  This means you really want to get as many hits against the enemy as you can, and keep the hits against your own forces to a minimum.

How to do this?

-Use indirect fire.

The ideal way to fight in a vacuum is to get in some hits without being hit at all.  The only reliable way to do this in BattleTech is to use indirect fire.  So if the terrain is at all favorable to such a strategy, you want to position your LRMs and artillery outside the enemy's line of sight, with spotters placed where they are hard or impossible to hit (ideally at very long range from enemy forces).  Get in as many salvoes of indirect fire as you can before the enemy manages to get in LOS.

-Fight defensively if possible.

The above procedure is much easier to use when you're defending instead of attacking.  So the defender has huge advantages on a map with some sight-blocking elevation.  The ideal position is LRMs behind a hill or in craters, with spotting units positioned on an even higher hill behind the LRMs.  Don't be afraid to lie down with your 'Mechs behind level 1 hills and fire LRMs from prone position if that keeps you out of the enemy's sight.

Gun emplacements are also extremely strong in vacuum.  Buildings don't get breached.  Again, strong advantages to the defender if the map is right.

-Move fast if you do attack.

You want to minimize hits against your own units when you take the offensive as well.  This means charging at maximum speed to get the best defensive modifiers.

-Attack with cluster weapons.

LB-Xs and SRMs are ideal; the more hits, the more chances for decompression.

-Bring standard engines.

Any side torso breach is a mission kill on all Inner Sphere XL 'Mechs, and very serious trouble on Clan XL and IS LFE designs.  The best defense in vacuum isn't armor (although armor helps), it's a standard engine.

-Bring numbers.

An assault 'Mech isn't that much harder to bring down in vacuum than a light.  But two 'Mechs are twice as hard to bring down as one 'Mech.  Vacuum is the only setting where I'd feel safer fielding two light 'Mechs than one assault.

[AlphaMirage]

Good work Trailblazer, its too bad there is no MASS equivalent for vacuum. Additionally if Hargel pods are available putting one of those in the CT is another level of protection

[Weirdo]

Bring Infantry.

These troops work better on the defense due to the rarity of space-rated transports(unless you're willing to use Small Craft), but if you can sucker a mech into range of a well-armed platoon, your can reasonably expect to disable a location every salvo or two.

Only deploy them in fortified or rough hexes as they'll get cut apart in the open, and it's reasonable to assume there won't be any woods hexes available.

[Trailblazer]

Bring Infantry.

These troops work better on the defense due to the rarity of space-rated transports(unless you're willing to use Small Craft), but if you can sucker a mech into range of a well-armed platoon, your can reasonably expect to disable a location every salvo or two.

Only deploy them in fortified or rough hexes as they'll get cut apart in the open, and it's reasonable to assume there won't be any woods hexes available.

Good call, I haven't used infantry in vacuum but this has a strong ring of truth to it.  Isn't there a canon xenoplanetary infantry unit with range-15 support lasers?  That would be brutal on a lot of maps.

Seems like BA would be pretty good too.

[Trailblazer]

I should add as well, if you have a map where indirect fire is impracticable, the LB 2-X becomes the ideal weapon.  Fast omnis loaded with LB 2-Xs might be the best possible offensive force in such an environment.

[Weirdo]

This might actually explain some of the otherwise-mocked configs of the 3050 Omnis where you got a fast mech with a very light cannon as the primary armament.

[Trailblazer]

This might actually explain some of the otherwise-mocked configs of the 3050 Omnis where you got a fast mech with a very light cannon as the primary armament.

Yeah, given that heavy use of indirect fire is considered dezgra, an Ice Ferret A would be pretty optimal for Clan-on-Clan vacuum combat.

[Weirdo]

Same goes for that one Koshi with the Ultra-2, I forget exactly which one it is.

[Daryk]

Don't forget AOE weapons.  Thermobarics are out for obvious reasons, but regular old AOE weapons work just fine.

[Weirdo]

Oh good lord, mortars.

IDF, AE, good range, and a cluster rating that can best be described as 'numerous and belligerent'. >:D

[Daryk]

Exactly!  >:D

[DevianID]

I never liked that vacuum disabled the mech location on a breach.  Water, ok, flooding an LRM20 would make you not want/able to fire it.

I do like the Vacuum rules in that they detail just how many holes a mech is getting as it gets shot up.  It kinda shows that the armor isnt as magic as we think--seals are popping and stuffs coming lose with every hit, even if no critical component can be damaged like with structure damage.  I just cant visualize why breached stuff is breaking in a vacuum, but not also on a planet.

Edit: As for weapons/tactics, hidden units and range are bigger deals.  You really want to shoot in such a way that you cant be shot back.  Either with an ambush where shooting is in the movement phase, or with a gun that outranges your opponent.  The idea that the ultra and lbx2 mechs were the 'vacuum' trial mechs really makes a ton of sense to me--I'm stealing that for my clan campaign.

[Trailblazer]

Oh good lord, mortars.

IDF, AE, good range, and a cluster rating that can best be described as 'numerous and belligerent'. >:D

Whoa, yup.  I usually play with level 2 stuff but yeah, mortars would be devastating.

I never liked that vacuum disabled the mech location on a breach.  Water, ok, flooding an LRM20 would make you not want/able to fire it.

I do like the Vacuum rules in that they detail just how many holes a mech is getting as it gets shot up.  It kinda shows that the armor isnt as magic as we think--seals are popping and stuffs coming lose with every hit, even if no critical component can be damaged like with structure damage.  I just cant visualize why breached stuff is breaking in a vacuum, but not also on a planet.

Yeah it makes close to zero sense for the weapons, you can kind of imagine it with gyros and engines, like maybe those have components that can't be made very pressure-resistant for some reason.

[Iceweb]

On paper the clan RAC2 should be obscenely deadly in a vacuum environment.  Insane range and a large amount of tiny holes.  Sure the weight is an issue, but compared to the LBX2 I think it is a worthwhile upgrade.  On the other hand you are starting to compete against HAGs and Gauss with the tech level.   
I mention the Gauss because sure you only get one hole check but if you take all the armor off it is an auto breach of course. 

For IS tech if you are getting in knife fighting range I would recommend some tandem charge missiles.  SRMs are great for the lots of holes and the extra of a tandem punching through gives that extra, though no special effect for vacuum (I just really like tandem SRMs)  For best use of course use a MML so you can poke with LRMs at range and indirect, and when you get the knife fighting range your SRMs are ready to go.   

For sheer amount MRM can toss a lot of missiles even if they are 5 point clusters.  Due to the range you either need knife fighting again, or a C3 network that isn't disrupted.  All fun choices.  And makes me wonder why no one ever made a MRT for underwater work.     

[MarauderD]

Agreed on the LBX and RAC qualities--many small holes in vacuum equals certain death. 

[Colt Ward]

I should add as well, if you have a map where indirect fire is impracticable, the LB 2-X becomes the ideal weapon.  Fast omnis loaded with LB 2-Xs might be the best possible offensive force in such an environment.

Lol, thought of that halfway through reading the topic, though I was going to say LB-5X, just to increase the hits.

But IMO it would also make armor like the Zoyra with it's LB-5X, ECM, and decent armor for a light tank pretty good- and can function as AA tanks for a position too.

[Weirdo]

You'd have to seal them against vacuum first, but yes. :)

[Colt Ward]

You'd have to seal them against vacuum first, but yes. :)

Some . . . or you can just put them in hostile enviro suits like the GDL did in 3SW.

[Weirdo]

Not everything that happens in a book can be done in the game. That's one that cannot.

[Colt Ward]

Sure it can, a quick playing with MML . . . give it a FCE as the book said and even penalized with the weight of full environmental sealing vs the limited they actually performed and you still have 5 spare tons.

We just do not have a sheet for it yet, and since the only time I can really see that being done is in a campaign it would just take a GM handwave.  Just like the average sized Kai can wear Elemental armor, a Vedette could be tricked up like in the story.

[Weirdo]

...how is what your just described NOT

seal them against vacuum first

?

[Colt Ward]

Because it was a half-way sealing, which is why the crews wore environmental suits in the book.  The Vedettes still took exposure damage and IIRC was going to lead to maintenance problems in that environment.

[Weirdo]

So I'm trying to understand your prior post, because I might have misread it.

You *didn't* use a fuel cell and seal the tank?

[Colt Ward]

In the fiction they did not do a full seal IIRC- which is why they wore enviro suits.

[pokefan548]

In a campaign setting, I see no reason why combat vehicle crews couldn't be outfitted with spacesuits or environment suits at the discretion of the GM. We have rules for determining the number of crewmen in a vehicle, which handles the cost and stocking of the suits. However, in a BV-matched game, we unfortunately cannot account for the crew's BV cost which means that any armor providing encumbrance or a damage divisor can't be accounted for. Ultimately, I think it comes down to player adjudication.

[Weirdo]

There is no adjudication. The rules are 100% clear. A vehicle crew in space is either inside a fully sealed vehicle, or they are fully dead.

Again, there are many things that happen in fiction that flat-out do not work on tabletop. "Just stick'em in suits" is one of those things.

[Fortyone]

There is no adjudication. The rules are 100% clear. A vehicle crew in space is either inside a fully sealed vehicle, or they are fully dead.

Again, there are many things that happen in fiction that flat-out do not work on tabletop. "Just stick'em in suits" is one of those things.

I agree with you that that is how the rules are written, but I'm gonna have to invoke p. 9 of TacOps and "make up the rules that work for you," on this one.

The vacuum rules are bad. You'd have to be desperate AND suicidal to fight in those conditions. You're telling me that a battlemech, the premier engine of war and death for the last 500+ years, has a 1 in 6 chance of being destroyed from any CT damage whatsoever??? And internal components can't function without some kind of atmospheric pressure??? And nobody in half a millennium has thought that, just maybe, there's a design flaw that should be corrected in every mech going forward??

Because that's what the rules mean to the lore.

[Trailblazer]

The rules that are *really* bad and unplayable are the low-G rules.  No, the lunar rover didn't move 6x faster than regular Earth cars, lololol

[pokefan548]

A lot of the planetary condition rules have lots of weird oversights and spots, though a lot of that can be chalked up to not wanting to make each entry three pages long. In particular, a lot of rules that should have a very severe impact on aerospace do... absolutely nothing, or nearly nothing. So you're telling me that the only effect that atmospheric pressure (barring a total lack thereof) has on aerodynes is how far they have to travel to lift off?

So yeah. Unfortunately for the time being, those rules will kind of inherently require some degree of player adjudication for them to make an ounce of sense, especially for non-'Mech units.

[Weirdo]

The rules that are *really* bad and unplayable are the low-G rules.  No, the lunar rover didn't move 6x faster than regular Earth cars, lololol

"Unplayable" and "You don't like them" are two very different things. Please be accurate.