4 ms·

Probably from dumping 32 megajoules of energy into the rails/barrel. I wouldn't be surprised if part of it is melting/igniting the actual hardware itself and pa

Probably from dumping 32 megajoules of energy into the rails/barrel. I wouldn't be surprised if part of it is melting/igniting the actual hardware itself and part of it is due to the friction of the projectile against the air. Remember that this is still a prototype and one of the big concerns since day one has been lifetime of the system. Essentially, it's probably still melting its own hardware (at least to some degree) every shot.

tjradcliffe 12y ago
32 MJ is actually not all that much... it's almost exactly the energy in a single litre of gasoline (44 MJ/kg, 32 MJ/l). The important thing about a railgun is not the total power put into it but that the power is dumped into the projectile continuously over the course of acceleration, which makes much more efficient use of energy than conventional weapons, which produce large initial accelerations followed by rapidly decreasing gains as the projectile moves along the barrel and the hot gases behind it expand (the limit of conventional technology is the so-called "light gas gun" that uses hydrogen as a propellant to maximize the speed of sound in the accelerating medium and produce a relatively flat pressure curve along the barrel.)
- metaphorm 12y ago
  well, that gives you an idea just how much chemical potential energy there is in gasoline. its pretty incredible stuff.
  - deeviant 12y ago
    It's a pretty incredible amount of energy. Just think if you put a gallon of gas in a car than hit the petal, then lets take away (or at least mostly minimize so that the car has same aerodynamics as a artillery shell) air resistance for fun. The car accelerates until it burns through a gallon of gas, so for maybe, what 10-30 minutes depending on the vertical it's constantly accelerating, I can even imagine what speed it could get up to if you discount mechanical limitations of the engine/tires/etc, but let's say at least 1000 mph, conservatively. Then car runs into a brick wall. That is the amount of energy in a gallon of gas.
    - metaphorm 12y ago
      its way more energy than that! car engines aren't even close to 100% efficient. all the heat that blows out your exhaust pipe is energy that the engine couldn't capture. ditto for heat of friction on the mechanical components, and heat that radiates into the air from the engine block.
    - stolio 12y ago
      For fun, KE = (1/2)mv^2 = 32 MJ -->[mathing intensifies]--> a 1,000 kilogram car moving at about 565 mph carries 32 MJ of energy, which is what 1 liter of gasoline carries. A gallon is about 4 liters, so at 100% efficiency it could get a 1,000kg car to ~1,130 mph or a 1,500kg car to ~925 mph. For reference, the same calculations tell us a quarter-pounder with cheese could get a 165 lbs (75kg) human up to 540 mph.
      - _lce0 12y ago
        now that's fast food!

tjradcliffe 12y ago

32 MJ is actually not all that much... it's almost exactly the energy in a single litre of gasoline (44 MJ/kg, 32 MJ/l). The important thing about a railgun is not the total power put into it but that the power is dumped into the projectile continuously over the course of acceleration, which makes much more efficient use of energy than conventional weapons, which produce large initial accelerations followed by rapidly decreasing gains as the projectile moves along the barrel and the hot gases behind it expand (the limit of conventional technology is the so-called "light gas gun" that uses hydrogen as a propellant to maximize the speed of sound in the accelerating medium and produce a relatively flat pressure curve along the barrel.)

metaphorm 12y ago
well, that gives you an idea just how much chemical potential energy there is in gasoline. its pretty incredible stuff.
- deeviant 12y ago
  It's a pretty incredible amount of energy. Just think if you put a gallon of gas in a car than hit the petal, then lets take away (or at least mostly minimize so that the car has same aerodynamics as a artillery shell) air resistance for fun. The car accelerates until it burns through a gallon of gas, so for maybe, what 10-30 minutes depending on the vertical it's constantly accelerating, I can even imagine what speed it could get up to if you discount mechanical limitations of the engine/tires/etc, but let's say at least 1000 mph, conservatively. Then car runs into a brick wall. That is the amount of energy in a gallon of gas.
  - metaphorm 12y ago
    its way more energy than that! car engines aren't even close to 100% efficient. all the heat that blows out your exhaust pipe is energy that the engine couldn't capture. ditto for heat of friction on the mechanical components, and heat that radiates into the air from the engine block.
  - stolio 12y ago
    For fun, KE = (1/2)mv^2 = 32 MJ -->[mathing intensifies]--> a 1,000 kilogram car moving at about 565 mph carries 32 MJ of energy, which is what 1 liter of gasoline carries. A gallon is about 4 liters, so at 100% efficiency it could get a 1,000kg car to ~1,130 mph or a 1,500kg car to ~925 mph. For reference, the same calculations tell us a quarter-pounder with cheese could get a 165 lbs (75kg) human up to 540 mph.
    - _lce0 12y ago
      now that's fast food!