6 ms·

Gasoline has 10x the energy (MJ/Kg) than TNT, but it's not a "bomb". Being a "bomb" is about energy release rate. A battery is still controlled by its chemistry

by thechao 2mo ago

Gasoline has 10x the energy (MJ/Kg) than TNT, but it's not a "bomb". Being a "bomb" is about energy release rate. A battery is still controlled by its chemistry.

emptyfile 2mo ago
[dead]
trollbridge 2mo ago
One of the problems with gasoline is its explosive nature, which the fuel storage and delivery system of a car attempts to mitigate. It has a better profile for burning off than a battery though since it will spill out and burn away from the vehicle.
- not_the_fda 2mo ago
  Gasoline isn't that explosive. You can shoot up a gas tank and it will just burn. What you see on TV is movie magic. Gasoline vapor can explode, but you need the right air to fuel ratio and a spark.
  - SV_BubbleTime 2mo ago
    Uh… gasoline has a super high vapor pressure. If you start out at the wrong ratio, it does what it can to make that ratio right. I’ve seen a few gasoline fires that start by burning, and then much more rapidly expressing potential.
    - capitainenemo 2mo ago
      Requires a good mix though. The parent is still correct. Mythbusters spent a long time trying to get cars to blow up in a dramatic hollywood fashion in various episodes and determined that under most conditions it wouldn't happen. They did get it to happen, they just had to try really hard. In most accidents the gas tank will not blow up.
      - vablings 2mo ago
        High velocity accidents where the gas is quickly dispersed into the air is pretty much the only way that happens.
        jojobas 2mo ago
        Even then it's just a slow-burning fireball, not detonation, no shockwave.
        vablings 2mo ago
        Still more than enough to burn your windpipe, skin to 2/3rd degree and permanently disfigure you
        jjk166 2mo ago
        All of which are symptoms of burning, not explosion.
        capitainenemo 1mo ago
        And was still not really possible without some really unlikely conditions. Not that car fires aren't dangerous, regardless of whether the vehicle is ICE or otherwise, but the fireball thing doesn't really happen.
- leonidasrup 2mo ago
  "Fast X: why cars don’t really explode when they crash" "Petrol and diesel can only explode when under pressure and mixed with air and in the case of petrol, have a small amount of energy added in the form of a spark or a flame. Engines pressurise the fuel/air mixture in the cylinder and so produce small, confined explosions which turn a crankshaft and drive the wheels." "When cars are involved in collisions, fuel lines are often torn and petrol leaks out onto a hot engine. Liquid petrol can catch fire in the presence of air. But it can’t explode because it’s not under pressure and is in the liquid phase rather than a vapour." https://theconversation.com/fast-x-why-cars-dont-really-explode-when-they-crash-205068 https://theconversation.com/fast-x-why-cars-dont-really-expl...
vikramkr 2mo ago
Liquid gasoline does not have anywhere near the energy of TNT, or even a battery for that matter. It contains basically zero releasable energy. It needs oxygen or another oxidizer to react with to actually release any energy. TNT and batteries' energy density calculations include the oxidizer and the oxidizer is in close proximity to the fuel (molecularly so in the case of TNT). If you 10x the "energy content" of gasoline it's still rate limited by access to oxygen. If you 10x the energy density of a battery (the type with the oxidizer contained within the battery, not a fuel cell or metal air battery) you've got 10x the energy ready to be released quickly if oxidizer and fuel mix in unfortunate ways
- lightedman 2mo ago
  "Liquid gasoline does not have anywhere near the energy of TNT," Energy density of gasoline is approximately 44 to 45 megajoules per kilogram. Energy density of TNT is approximately 4.184 megajoules per kilogram.
  - deleted 2mo ago
    [deleted]
  - vitally3643 2mo ago
    [flagged]
    - lightedman 2mo ago
      I read it all and even what is stated is mostly wrong UNTIL THE EXACT UNIT IS SPECIFIED. And I'd know because I have to work with this IN ORBIT. I've had this conversation a dozen times in meetings with military and government.
  - K0balt 2mo ago
    A snickers bar has nearly 5× TNT’s energy per kilogram—TNT merely has the habit of being extremely impatient about releasing it.
    - 2mo ago
duped 2mo ago
Poorly stored gasoline can spontaneously combust, though. So more like a firebomb.
- not_the_fda 2mo ago
  No it can't. To combust it needs ~ 500F. If you left it out uncovered in the open and allowed the it to vaporize with a spark nearby, it might explode, but thats not spontaneous combustion. Gasoline sitting in a sealed container wont spontaneously combust.
  - swiftcoder 2mo ago
    Didn't everyone have one of those old mechanic friends who liked to put the cigarette out in the can of gas to scare the tourists?
    - SV_BubbleTime 2mo ago
      That is definitely one of those “it worked the first 50 times no problem” tricks.
    - PunchyHamster 2mo ago
      ...it was probably diesel not gasoline
      - swiftcoder 2mo ago
        Oh, it was most definitely gasoline. As long as there is no vapour hanging above the container, it works just fine... as the neighbour post says, the first 50 times. Then one day the old timer blows up himself and the shop
- ridgeguy 2mo ago
  Gasoline doesn't do that. Perhaps you're thinking of the following? What it does do is slowly polymerize, becoming useless as an ICE fuel in time, typically in a year or two. This is why backup generators should run on propane, which has no degradation mechanism.
jimt1234 2mo ago
> Gasoline ... it's not a "bomb" My teen years would beg to differ, when some neighborhood friends and I decided to experiment with gas and bleach. The neighborhood residents, fire department and local police also had an opinion, too. (We all got into BIG trouble. Definitely one of the dumber things I did as a teen.)
- CamperBob2 2mo ago
  Bleach? What does that do? My high-school crowd stopped just short of building a multistage FAE device. I left early for college and everybody else was short of cash, and that was the end of our neighborhood R&D program. All pre-9/11, needless to say. It's a lot less fun when the possible punishment goes from detention at lunch to waterboarding in Gitmo.
  - jimt1234 2mo ago
    We used to take a half-full can of gas, then get a ping pong ball, drill a hole in it, fill it with bleach, then put tape over the hole. Drop the ping pong ball in the gas can, screw the lid on really tight, then wait. It used to take about 10 minutes for the gas to eat its way into the ping pong ball, but when it did, and the bleach mixed with the gas... boom! The scary part is only worked, maybe, half the time. So there would be cans of gas/bleach just sitting in a field, waiting to explode or release really harmful chems into the air. We were kids, young and stupid.
    - CamperBob2 2mo ago
      WTF. Seriously? Just plain old Clorox? Which is ~95% water? BRB, stopping by the laundry room on my way to the garage...

by thechao 2mo ago

Gasoline has 10x the energy (MJ/Kg) than TNT, but it's not a "bomb". Being a "bomb" is about energy release rate. A battery is still controlled by its chemistry.

emptyfile 2mo ago

[dead]

trollbridge 2mo ago

One of the problems with gasoline is its explosive nature, which the fuel storage and delivery system of a car attempts to mitigate. It has a better profile for burning off than a battery though since it will spill out and burn away from the vehicle.

not_the_fda 2mo ago
Gasoline isn't that explosive. You can shoot up a gas tank and it will just burn. What you see on TV is movie magic. Gasoline vapor can explode, but you need the right air to fuel ratio and a spark.
- SV_BubbleTime 2mo ago
  Uh… gasoline has a super high vapor pressure. If you start out at the wrong ratio, it does what it can to make that ratio right. I’ve seen a few gasoline fires that start by burning, and then much more rapidly expressing potential.
  - capitainenemo 2mo ago
    Requires a good mix though. The parent is still correct. Mythbusters spent a long time trying to get cars to blow up in a dramatic hollywood fashion in various episodes and determined that under most conditions it wouldn't happen. They did get it to happen, they just had to try really hard. In most accidents the gas tank will not blow up.
    - vablings 2mo ago
      High velocity accidents where the gas is quickly dispersed into the air is pretty much the only way that happens.
      - jojobas 2mo ago
        Even then it's just a slow-burning fireball, not detonation, no shockwave.
        vablings 2mo ago
        Still more than enough to burn your windpipe, skin to 2/3rd degree and permanently disfigure you
        jjk166 2mo ago
        All of which are symptoms of burning, not explosion.
        capitainenemo 1mo ago
        And was still not really possible without some really unlikely conditions. Not that car fires aren't dangerous, regardless of whether the vehicle is ICE or otherwise, but the fireball thing doesn't really happen.
leonidasrup 2mo ago
"Fast X: why cars don’t really explode when they crash" "Petrol and diesel can only explode when under pressure and mixed with air and in the case of petrol, have a small amount of energy added in the form of a spark or a flame. Engines pressurise the fuel/air mixture in the cylinder and so produce small, confined explosions which turn a crankshaft and drive the wheels." "When cars are involved in collisions, fuel lines are often torn and petrol leaks out onto a hot engine. Liquid petrol can catch fire in the presence of air. But it can’t explode because it’s not under pressure and is in the liquid phase rather than a vapour." https://theconversation.com/fast-x-why-cars-dont-really-explode-when-they-crash-205068 https://theconversation.com/fast-x-why-cars-dont-really-expl...

vikramkr 2mo ago

Liquid gasoline does not have anywhere near the energy of TNT, or even a battery for that matter. It contains basically zero releasable energy. It needs oxygen or another oxidizer to react with to actually release any energy. TNT and batteries' energy density calculations include the oxidizer and the oxidizer is in close proximity to the fuel (molecularly so in the case of TNT). If you 10x the "energy content" of gasoline it's still rate limited by access to oxygen. If you 10x the energy density of a battery (the type with the oxidizer contained within the battery, not a fuel cell or metal air battery) you've got 10x the energy ready to be released quickly if oxidizer and fuel mix in unfortunate ways

lightedman 2mo ago
"Liquid gasoline does not have anywhere near the energy of TNT," Energy density of gasoline is approximately 44 to 45 megajoules per kilogram. Energy density of TNT is approximately 4.184 megajoules per kilogram.
- deleted 2mo ago
  [deleted]
- vitally3643 2mo ago
  [flagged]
  - lightedman 2mo ago
    I read it all and even what is stated is mostly wrong UNTIL THE EXACT UNIT IS SPECIFIED. And I'd know because I have to work with this IN ORBIT. I've had this conversation a dozen times in meetings with military and government.
- K0balt 2mo ago
  A snickers bar has nearly 5× TNT’s energy per kilogram—TNT merely has the habit of being extremely impatient about releasing it.
  - 2mo ago

duped 2mo ago

Poorly stored gasoline can spontaneously combust, though. So more like a firebomb.

not_the_fda 2mo ago
No it can't. To combust it needs ~ 500F. If you left it out uncovered in the open and allowed the it to vaporize with a spark nearby, it might explode, but thats not spontaneous combustion. Gasoline sitting in a sealed container wont spontaneously combust.
- swiftcoder 2mo ago
  Didn't everyone have one of those old mechanic friends who liked to put the cigarette out in the can of gas to scare the tourists?
  - SV_BubbleTime 2mo ago
    That is definitely one of those “it worked the first 50 times no problem” tricks.
  - PunchyHamster 2mo ago
    ...it was probably diesel not gasoline
    - swiftcoder 2mo ago
      Oh, it was most definitely gasoline. As long as there is no vapour hanging above the container, it works just fine... as the neighbour post says, the first 50 times. Then one day the old timer blows up himself and the shop
ridgeguy 2mo ago
Gasoline doesn't do that. Perhaps you're thinking of the following? What it does do is slowly polymerize, becoming useless as an ICE fuel in time, typically in a year or two. This is why backup generators should run on propane, which has no degradation mechanism.

jimt1234 2mo ago

> Gasoline ... it's not a "bomb" My teen years would beg to differ, when some neighborhood friends and I decided to experiment with gas and bleach. The neighborhood residents, fire department and local police also had an opinion, too. (We all got into BIG trouble. Definitely one of the dumber things I did as a teen.)

CamperBob2 2mo ago
Bleach? What does that do? My high-school crowd stopped just short of building a multistage FAE device. I left early for college and everybody else was short of cash, and that was the end of our neighborhood R&D program. All pre-9/11, needless to say. It's a lot less fun when the possible punishment goes from detention at lunch to waterboarding in Gitmo.
- jimt1234 2mo ago
  We used to take a half-full can of gas, then get a ping pong ball, drill a hole in it, fill it with bleach, then put tape over the hole. Drop the ping pong ball in the gas can, screw the lid on really tight, then wait. It used to take about 10 minutes for the gas to eat its way into the ping pong ball, but when it did, and the bleach mixed with the gas... boom! The scary part is only worked, maybe, half the time. So there would be cans of gas/bleach just sitting in a field, waiting to explode or release really harmful chems into the air. We were kids, young and stupid.
  - CamperBob2 2mo ago
    WTF. Seriously? Just plain old Clorox? Which is ~95% water? BRB, stopping by the laundry room on my way to the garage...