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Navy Tests Mach 8 Electromagnetic Railgun

Posted by timothy on from the do-not-look-at-with-remaining-eye dept.

hargrand writes "Wired magazine has a story and publicly released video of the Navy test firing of a 32 megajoule electromagnetic railgun: 'Reporters were invited to watch the test at the Dalghren Naval Surface Warfare Center. A tangle of two-inch thick coaxial cables hooked up to stacks of refrigerator-sized capacitors took five minutes to power juice into a gun the size of a schoolbus built in a warehouse. With a 1.5-million-ampere spark of light and a boom audible in a room 50 feet away, the bullet left the gun at a speed of Mach 8.'"

11 of 440 comments (clear)

  1. I've heard that before by marcovanb · · Score: 4, Informative

    I've heard that before "Rule Britannia, Brittania rules the waves...".

    1. Re:I've heard that before by KonoWatakushi · · Score: 5, Informative

      While the defense budget is no doubt way out of control, this is not at all the sort of thing that worries me. It has no practical military value in the near term, and at least produced interesting results.

      I'm more concerned about other high-tech anti-personel weapons or robots, that will inevitably be pointed at people, possible even at our own citizens before long.

      Speaking of waste, and far more disturbing at that, take a look at what the anti-terrorism efforts have spawned. I really had no idea of the scale of it. Having this turned against our own citizens as the fascism ramps up is truly frightening.

    2. Re:I've heard that before by Jenming · · Score: 5, Informative

      The energy is not the same, however, it might not be less.
      When you launch with a rocket, the rocket accelerates throughout the journey, making the maximum in atmosphere speed lower.
      If you launch with a railgun, it starts _really_ fast and then slows down until it hits orbit. The fastest part of this trip is done at the highest air pressure. Which is really bad due to the exponential increase in drag as you increase speed. You would also need to take into account the added weight of heat shielding.

      The comparable amount of energy would be launching a rocket with one large explosion on the ground. I would imagine that many of the same problems would exist whether this was done with a railgun or a bomb. I would not assume that the energy used was less.

      Now if you launched from the moon (or anywhere else without an atm) then the railgun would have energy advantages.

      --
      Morpheus, God of Dreams.
    3. Re:I've heard that before by Alef · · Score: 3, Informative

      Which is really bad due to the exponential increase in drag as you increase speed.

      Drag increases quadratically with regard to speed, not exponentially. People really ought to stop using the term "exponentially" to mean "more than linearly".

  2. Re:Mach 8 to Orbit? by Rakshasa+Taisab · · Score: 5, Informative

    Mach 8 = 2 722.32 m/s.

    Escape velocity being 11.2 km/s, so the answer is no.

    --
    - These characters were randomly selected.
  3. Re:Mach 8 to Orbit? by Interoperable · · Score: 4, Informative

    Escape velocity is the velocity required to leave orbit, not to maintain a stable orbit. Of course, low Earth orbit is about 8 km/s, so still no.

    --
    So if this is the future...where's my jet pack?
  4. Re:Mach 8 to Orbit? by sulimma · · Score: 5, Informative

    If something is thrown or shot, the orbit will go through the point the shot was fired. You have a problem if that is on earth surface. Even if you are fast enough for a stable orbit you need a rocket to shift that orbit away from your starting point.

  5. Re:Mach 8 to Orbit? by Rockoon · · Score: 3, Informative

    At a deceleration of a constant 10m/s^2, it would still take 270 seconds to stop going up (the deceleration would actually decrease the higher it goes, but I'm not accounting for drag.. so its a tradeoff) it will have an average speed of 1.35km/s.

    Thats 270s * 1.35km/s = a height of 364.5km, so it could conceivably enter into the region we call 'low earth orbit' which is between 160km to 2000km.

    I dont know where to begin to calculate the drag as it rises, so I wont bother to calculate the decreasing deceleration either.

    Might be able to shoot down satellites .. or throw some stuff up for the International Space Station to catch (347km altitude at perigee)

    --
    "His name was James Damore."
  6. Re:Yay! by bcmm · · Score: 4, Informative

    Submarines don't surface to launch ballistic missiles. They come near to the surface, communicate using an antenna on a small buoy, then launch from just below the surface. See this this pic from Wikipedia.

    --
    # cat /dev/mem | strings | grep -i llama
    Damn, my RAM is full of llamas.
  7. Re:Yay! by gtall · · Score: 4, Informative

    Well, the U.S. economy has a GDP of a little north of $14 trillion. The current defense bill is about $720 billion. And somehow this $720 is supporting a GDP of $14 trillion?

    Incidentally, the U.S. deficit is about $1.4 trillion for FY2010 which ended Sept. 30. The total debt is about $14 trillion (no relation to the GDP number, the latter is per year, the former spans decades of financial mismanagement).

    The rich, say the top 1% of the pop. pay approx 37 % of all the income tax in the country. The top 20% pay about 85% of the income taxes. The bottom 50% of the pop. pay no income tax.

    It is important to have a sense of proportion, it can keep you from making unwarranted assumptions.

  8. Re:The video is cool, but... by Ksevio · · Score: 3, Informative
    Well according to the Washington Post article on it:

    It streaked down range, generating a small sonic boom, and traveled about 5,500 feet before tumbling to the ground harmlessly.

    So not all that interesting.