Author Topic: The physics of starting fires  (Read 664 times)

Iceweb

  • Warrant Officer
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  • Posts: 769
  • Lyran Engineer
The physics of starting fires
« on: 25 May 2018, 17:42:34 »
For some reason I got interested in what are the physics behind how you would start fires in the BTU. 
I get how flinging lasers and explosives around a flammable area could start a major fire by pure chance and bad luck, but I am having trouble seeing how you would intentionally start a fire with weapons designed to pierce BattleTech's magic armor. 

I know that lasers can be dialed down (even if it is an optional rule). 
Can the nuerohelmet detect that you want to start a fire and communicate that to the computer and it would adjust your warload to increase the odds of getting an ignition without blowing the hell out of the flammable materials? 
It seems like lasers could be programmed with an ignition pattern to heat wood with maximum dispersal patterns. 
I'm just not sure if there would be a better way. 

Missiles or autocannon rounds are going to explode and could start a fire, but I am not sure how you know where to shoot to get a working blaze going. 
Would the combat computer be set with fire starting options? 

Does using alternate ammo effect the chance of starting a fire in the boardgame at all? 
I would imagine AP ammo or acid SRMs would be much less effective in setting a blaze than standard ammo, but I don't think the rules say their target numbers are altered at all. 

I would love to hear from our military members on the board about how real world military equipment would be effective if you were trying to start a fire but not destroy the target. 
Maybe that would help me to wrap my mind around how it would work in the BTU.

Nicoli

  • Master Sergeant
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  • Posts: 313
Re: The physics of starting fires
« Reply #1 on: 25 May 2018, 17:53:05 »
Most rounds types are usually going to have some sort of tracer burning on the back of it to help adjust aim if need be. These are pretty notorious for starting fires at military ranges. Most smoke munitions would start fires fairly easily as burning something is still the best way we have found to produce smoke, white-phosphorus is still pretty common. Lasers as we really don't have a lot of experience yet with the high-power lasers like Battletech no clue.

Fire mechanics in Battletech though are frankly insane. Nothing outside of dedicated incendiary rounds or flamers would have a chance to start a hex wide fire during a game. Even the fires on ranges usually take 20-30 minutes to get going any serious size.

Nightlord01

  • Lieutenant
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  • Posts: 1559
Re: The physics of starting fires
« Reply #2 on: 26 May 2018, 07:34:31 »
For some reason I got interested in what are the physics behind how you would start fires in the BTU. 
I get how flinging lasers and explosives around a flammable area could start a major fire by pure chance and bad luck, but I am having trouble seeing how you would intentionally start a fire with weapons designed to pierce BattleTech's magic armor. 

I know that lasers can be dialed down (even if it is an optional rule). 
Can the nuerohelmet detect that you want to start a fire and communicate that to the computer and it would adjust your warload to increase the odds of getting an ignition without blowing the hell out of the flammable materials? 
It seems like lasers could be programmed with an ignition pattern to heat wood with maximum dispersal patterns. 
I'm just not sure if there would be a better way. 

Missiles or autocannon rounds are going to explode and could start a fire, but I am not sure how you know where to shoot to get a working blaze going. 
Would the combat computer be set with fire starting options? 

Does using alternate ammo effect the chance of starting a fire in the boardgame at all? 
I would imagine AP ammo or acid SRMs would be much less effective in setting a blaze than standard ammo, but I don't think the rules say their target numbers are altered at all. 

I would love to hear from our military members on the board about how real world military equipment would be effective if you were trying to start a fire but not destroy the target. 
Maybe that would help me to wrap my mind around how it would work in the BTU.

As someone who's both set and extinguished more fires than I care to count by naval gun fire, I can tell you one thing: Forget what you know about starting fires! Don't worry about phosphorous, while it burns hot, it is generally only in tiny amounts and will only start a smoldering burn leading to eventual blaze, and stays on the round. Fire Point Detonating (PD) instead! The explosions will fling trace amounts of explosive and residual propellant not already burnt onto nearby foliage, the intense blast squeezes all the moisture out of the air and causes localized heating conducive to combustion. It doesn't take many heavy rounds to start a range fire, which is why we now use Training/Practice (TP) rounds only on the NG ranges. That and one of our DDGs used the wrong cheat sheet and put some rounds into the street of a local town (thankfully TP and an empty street)! But we don't like to talk about that incident (hint, as an FFG sailor, I most certainly DO like to talk about that incident, a lot)  >:D

Putting these fires out is quite annoying, as they tend to rapidly grow into an established fire which is why we had a 4x4 firetruck and massive water tank we took with us. It's hard, thankless work, and when I was on a ship the range monkeys used to routinely complain to us that we'd started a fire. Our Gunnery Officer once jumped on headset with a particularly irate Chief, and asked him what he wanted us to do, pull in and lend a hand? We then took off speed fast for our next serial.

In summary, it's very easy to start a bush fire using explosive ordnance, I imagine lasers would be similar, if they can put out enough energy to melt armour, it's highly likely they have enough energy to cause combustion in just about any combustible material, no matter how wet. The physics of a laser will work nicely in its favour, as it delivers intense heat alongside a shock, perfect for dispersing water vapour and rapidly heating the material past flash point into the combustion zone.

 

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