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The Military

Navy Uses Railgun To Launch Fighter Jet 314

Posted by samzenpus
from the quick-launch dept.
Phoghat writes "In 2015 the aircraft carrier USS Gerald R. Ford will take to the seas and the plan is to use a railgun to launch planes, instead of steam powered catapults. From the article: 'The Navy developed its Electromagnetic Aircraft Launch System as a replacement for the steam catapults currently used on aircraft carriers. The EMALS is a linear induction motor that's capable of accelerating a 100,000 pound aircraft to 240 miles per hour in the space of 300 feet. Compared to a steam catapult, the railgun catapult is much smaller, more efficient, simpler to maintain, gentler on airframes, and can deliver up to 30% more power. It's also capable of being cranked down a whole bunch, meaning that it can also launch smaller (and more fragile) unmanned drones.'"

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Navy Uses Railgun To Launch Fighter Jet

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  • by John Hasler (414242) on Wednesday December 22, 2010 @10:08PM (#34648846) Homepage

    n/t

    • Re: (Score:3, Interesting)

      by icebike (68054)

      Same accelerator concept though. Maybe what they have built is flexible enough to handle both roles.

      Linear induction motor that's capable of accelerating a 100,000 pound aircraft to 240 miles per hour in the space of 300 feet.

      One wonders how is that any easier on the airframe?

      Anyone know how you calculate G-forces in this kind of acceleration?

      • by blackraven14250 (902843) on Wednesday December 22, 2010 @10:16PM (#34648890)
        I would guess it's easier on the airframe because it can have a different acceleration curve. I imagine a steam driven catapult as having high power at the onset, but lower power at the end, while an electronic method like this can have a more gradual push.
        • by Pharmboy (216950) on Wednesday December 22, 2010 @10:21PM (#34648928) Journal

          I also wonder if it is simply a smoother curve, with less bumps and jarring. This would seem to be much better for a controlled acceleration, not just at G force or final speed, but for the entire range in between. With steam, it would seem they just pushing it at full throttle for the whole distance.

        • by Brett Buck (811747) on Wednesday December 22, 2010 @11:12PM (#34649222)

          Perhaps. But depending on the capacity of the steam reservoir - which is presumably huge on a nuclear aircraft carrier - the pressure drop is almost certainly negligible. What the motor permits (just looking at the performance aspects) is the acceleration curve to be tailored to the airplane.

          • by kindbud (90044) on Wednesday December 22, 2010 @11:46PM (#34649336) Homepage

            Perhaps. But depending on the capacity of the steam reservoir - which is presumably huge on a nuclear aircraft carrier - the pressure drop is almost certainly negligible.

            It's not. I've manned the steam generator control station on an aircraft carrier, and the drop in water level and steam pressure is dramatic and it takes several minutes to recover. Of course, we had 16 steam generators on the USS Enterprise in the 80's. Perhaps the newer carriers with just 4 steam generators (2 per reactor) are more efficient. But I do recall flight ops were a very very busy time for the MMs in the hole.

            This looks like a big improvement. Electricity generation is a much closer to a steady-state kind of operation for a naval nuclear power plant.

            • by Anonymous Coward on Thursday December 23, 2010 @08:56AM (#34651138)

              Perhaps. But depending on the capacity of the steam reservoir - which is presumably huge on a nuclear aircraft carrier - the pressure drop is almost certainly negligible.

              It's not. I've manned the steam generator control station on an aircraft carrier, and the drop in water level and steam pressure is dramatic and it takes several minutes to recover. Of course, we had 16 steam generators on the USS Enterprise in the 80's.

              32. Eight reactors, 4 steam generators per reactor.

              Perhaps the newer carriers with just 4 steam generators (2 per reactor) are more efficient. But I do recall flight ops were a very very busy time for the MMs in the hole.

              ...

              Nope. Somebody was lying to you. We just needed to watch our water levels in the secondary. Which on the EnterPig you had to be on top of anyway - and that was 20+ years ago. I can't imagine how bad that ship is now.

              Of course, some could fuck up even the watching of water levels. One PPWO "lost" 7,000 gallons of water - and it wasn't even during flight ops. Since the 4 steam plants on the Enterprise could be interconnected in some ways, he was calling around to the other EOS's trying to find his lost water. The joke in the wardroom later was, "How the hell can you lose 7,000 gallons of water? And not be able to find it? 7,000 gallons of water will find YOU!" Prior to this incident, this one officer's nickname was "Rock" - as in "dumb as a". After someone remarked "He's not a rock, he's a fucking boulder" because of the "lost" water, he was known as "Boulder".

              The full nickname has been redacted to protect the not-so-innocent.

        • by arivanov (12034) on Thursday December 23, 2010 @02:54AM (#34649936) Homepage

          Not necessarily. Multiple injection steam pusher is a concept old as the world. Most submarine launchers are like that - as the missile goes up more nozzles come into play on the sides giving it a good enough kick to clear the submarine and the water above it without breaking it in the process.

          The article misses the biggest advantage of electric vs steam. Electric has a much lower chance of failures in sub-zero temperatures. Steam is a nasty business at -5 or less. It condenses and freezes at all the inevitable leaks along the catapult pusher path. A couple of launches and the pusher is bound to get stuck damaging the aircraft in the process.

          IMHO, A ship with an electric catapult (or a ramp) has "Arctic/Antarctic war" stickered all over it. On the positive side this means that we are done with the Gulf and its surroundings. On the negative side this is one place which has seen very little war (except the North Atlantic portion of the Arctic in 1941-44).

          • by sean.peters (568334) on Thursday December 23, 2010 @09:31AM (#34651350) Homepage

            Steam systems are a nightmare to maintain in any weather conditions - switching from steam to electricity has been an ongoing process in the Navy for decades. The old Charles Adams class DDGs had all-steam propulsion plants - meaning that every oil pump, fuel pump, and every other system ran on some kind of steam. Those guys spent their lives maintaining steam turbines. As time has gone by, the Navy has gotten away from steam in a big way for exactly that reason - all that steam technology required a lot of sailors to keep running, and sailors are expensive. For what it's worth, I'm qualified as a Navy Engineering Officer of the Watch (EOOW) in 1200 lb steam, so I have some considerable personal experience with this.

            I also think that you're likely to get performance improvements from EMALS. So I really doubt that this move has much to do with an anticipated Arctic war - there are big advantages to moving away from steam in any weather conditions.

      • Jerk [wikipedia.org] is probably what you should look at, not acceleration.

        • by rrohbeck (944847)

          Agree. It looked like the acceleration could be smoother at the beginning, in the first 10th of a second. There was a big jerk at first.

      • by krygny (473134)

        ... Anyone know how you calculate G-forces in this kind of acceleration?

        No details provided but I'd assume you can vary the current with a high degree of [computer] control. Increasing the inertia gradually, rather than an instantaneous kinetic release of steam.

      • Re: (Score:3, Informative)

        by GloomE (695185)

        v = 400km/h = 111m/s
        s = 100m

        v^2 = 2as

        a = v^2/2s

        a = 12321/200

        a = 61m/s^2

        g = 9.8m/s^2

        a = 6.3g

        • by jklovanc (1603149)

          This calculates the average acceleration over the distance. What if the acceleration is not constant. As has been stated by another poster, steam catapults accelerate better at the start than at the end. What if the initial acceleration was 8.3g at the start and linearly declined to 4.3G at the end. The final velocity would be the same and the average acceleration would be the same but the stress on the aircraft and pilot would be higher.

          Another poster touched on a valid point about jerk. Nothing instantane

      • by Anonymous Coward on Wednesday December 22, 2010 @10:39PM (#34649042)

        Same accelerator concept though.

        No, it is not. It is far more similar in concept to a mass driver.

        A railgun consists of two parallel, electrically conductive rails, each connected to one terminal of a charge storage device (usually a capacitor, but if you've got something better, go with it). The charge storage device is charged to full power, and then a conductive projectile is placed across the rails, completing a circuit.

        The completed circuit resembles a large inductor, in that it is a large conductive loop with current flowing through it, whose inductance is proportional to the area enclosed by the loop. The magnetic field generates a force upon all the components of the railgun, but since the projectile is the only part not rigidly fixed, it is moved by the force. The force acts to increase the size of the inductive loop, driving the projectile away.

        The key component to note here is that the projectile needs to be conductive, not ferromagnetic, and the rails must be exposed in order to pass current. This limits military applications because the presence of dirt in the rails could break the circuit, causing an electric arc flash, causing the system to act more like an arc welder. Also, the rails wear out due to the heating caused by the lack of superconductivity.

        Read the Wikipedia articles for Railgun and Mass Driver more details.

        • [continuing] A linear induction motor on the other hand is build of a fixed long rail of coils, individually controlled. The moving part is a magnet (or another coil, but that's more difficult albeit more powerful). By enabling the different coils in the right sequence the magnet moves.
          A mag-lev train works in the same way, but of course these use the magnetic fields for friction-free bearings as well.
      • by LetterRip (30937)

        One wonders how is that any easier on the airframe?

        Anyone know how you calculate G-forces in this kind of acceleration?

        It isn't the total acceleration, it is the change in acceleration (jerk) that stresses the airframe. The steam catapult has a lot of jerk, the induction system can minimal jerk.

      • by MattskEE (925706)

        Same accelerator concept though. Maybe what they have built is flexible enough to handle both roles.

        No, they're not the same concept, and the electromagnetic plane launcher that they are building here cannot readily be re-purposed as a railgun.

        The EMALS [navy.mil] (electromagnetic air launch system) is a Linear Induction Motor which works just like a standard AC motor except it has been laid out flat instead of in a circle. The launch carriage has a set of alternating magnetic poles (the stator) and it is driven by a

        • The EMALS [navy.mil] (electromagnetic air launch system) is a Linear Induction Motor...

          Actually, it's a linear synchronous motor.

          • by MattskEE (925706)

            >The EMALS [navy.mil] (electromagnetic air launch system) is a Linear Induction Motor...

            Actually, it's a linear synchronous motor.

            Right you are, thanks for the correction. A linear induction motor would actually be closer to a railgun, although still not quite there.

          • by MorePower (581188)
            Cooool! How do you put field current into the, um, rotor? (carriage, I guess)? I guess metal wheels would work.
        • by nospam007 (722110) *

          "I could see a role for LIM directly as a weapon only..."

          It fires armed airborne bomb/missile launchers, sounds like a weapon to me.

          • by fluffy99 (870997)

            "I could see a role for LIM directly as a weapon only..."

            It fires armed airborne bomb/missile launchers, sounds like a weapon to me.

            Actually they are developing railguns for launching projectiles and weapons. If the weapon doesn't need to have a chemical propellant it makes it much smaller and you can carry a lot more. All electric propulsion is being worked on as well. This is all part of the larger Navy initiative towards all-electric ships. Electricity is cheap and plentiful when you have up to 8 reactors onboard.

            As a side note, the Navy did a study for converting smaller ships to nuclear instead of oil. The cross-over point for

        • by afidel (530433)
          I could see a role for LIM directly as a weapon only if there were some application where you need to launch a relatively very heavy projectile at relatively small exit velocity.

          I wonder if you could get a LIM up to enough velocity to launch shore bombardment shells? Then again I'm not sure enough electro-chemical storage for such a system would be any less dangerous than a powder magazine if it should be hit =)
      • With all this talk of railguns, vectors and accelerators, I am dissapointed that no one has posted Mikoto Misaka.

        http://www.youtube.com/watch?v=Iv2v6WpuUG0 [youtube.com]

        Is no one here a Raildex fan?

  • by O('_')O_Bush (1162487) on Wednesday December 22, 2010 @10:08PM (#34648848)
    Now they only need a more efficient way of catching the planes when they land.
    • by radish (98371)

      I'm imagining a giant electro magnet.... :)

    • by nanospook (521118)
      Jello..
    • Re:Very cool (Score:5, Interesting)

      by reaper (10065) on Wednesday December 22, 2010 @10:45PM (#34649098) Homepage Journal

      When I was working on the arrestor portion in 2001, we had a system controlling two linear induction motors attached to the arrestor cable. Turns out that yes, you can use this type of system to stop planes, it is effective in many situations where planes come in at odd angles (the system pulls the plane towards the center of the deck), and you can recover power from it.

      However, if you wire the position encoders backwards, the motor cores eject quite violently as soon as the control system is turned on. Thankfully, interns are surprisingly good at dodging.

      • So what you need then are arrestor cables for the induction motors.

        Yo dawg! I heard you like stopping dawg! So I put an arrestor on your arrestor so you can stop while you stop.

  • by RyuuzakiTetsuya (195424) <taiki AT cox DOT net> on Wednesday December 22, 2010 @10:20PM (#34648916)

    "Dear Gaddafi, I sent you some EMAILS. I hope you get them."

    -- President Sarah Palin.

  • by Usagi_yo (648836) on Wednesday December 22, 2010 @10:20PM (#34648920)
    USS Gerald R. Ford? You have to be kidding me. What's next. USS Chevy Chase?
    • USS Gerald R. Ford? You have to be kidding me. What's next. USS Chevy Chase?

      Trust me, many Navy vets (including this one, who served on a carrier) are tired of the Navy naming our biggest capital ships after politicians. Layups like George Washington or Thomas Jefferson, no problem. But Gerald Ford? Really? There's a feeling in the Navy that we should stick to traditional names.... the Essex, the Hornet, the Lexington, etc, for our most prominent ships. But don't look for this practice to end, because appealing to political egos helps grease the Congressional appropriation machine.

    • Re: (Score:3, Interesting)

      by Wyatt Earp (1029)

      You know that Gerald Ford had a naval career right? He lead a fire control team that saved the escort carrier USS Monterey.

      Ford, Carter and George H.W. Bush all had naval careers, both Ford and Bush were on carriers and have carriers named for them, Carter was in the submarine service and has a submarine named for him.

    • The aircraft carrier Gerald Ford was sunk today, and eaten by a pack of senseless sea-wolves. It was delicious.
  • What I'm curious about is why they're using catapults at all - the Russians [wikimedia.org] and the Brits [wikimedia.org], for example, use a "ski jump" instead. And I read somewhere (unfortunately, I can't remember where - damn you, source blindness!) that that approach is actually better, in terms of aircraft launch rate, as you don't have a complex catapult system that has to be reset for every plane.

    So... why are US carriers using catapults, when they seem to me to be just another point of failure? Can someone enlighten me?

    • because US Navy needs to launch large aircraft with significant payload (unlike the brits or russians)
    • by icegreentea (974342) on Wednesday December 22, 2010 @10:53PM (#34649150)
      The maximun launch weight on pure ski-jump systems are much much lower than catapult launches. The old British carriers for example were stuck launching Sea Harriers which had a max take off weight of 12000kg. The F-18 (the original one... they've all been replaced by heavier planes) had an EMPTY weight just 1000kg less than that. It's max take off weight from a US Carrier was almost over twice that of the Sea Harrier.

      The new British carriers (suppose to launch Eurofighter variant) will also have a catapult.

      The catapult is another point of failure. That's one reason there's 4 on a ship. And that's reason why US had an advantage. They had an unbroken string of experience designing, building, and maintaining catapult systems since the end of WW2.
    • by LWATCDR (28044) on Wednesday December 22, 2010 @10:56PM (#34649162) Homepage Journal

      Yes because cats are a better solution.
      You can launch heavier aircraft with a cat than with a ski jump. The Russians and UK can not operate aircraft like the E-2. Also the UK is going to put cats on their latest carrier because the F-35b may fail.
      Also a Ski jump can not launch while the carrier as at a stop which can be useful.

      So yes the sky jump has one benefit but a lot of drawbacks. The Russians used them because it was a low risk for their first real carrier. The brits used them because they only had the Harrier. It did work very well for the Harrier but the Harrier was not as good of a fighter as the F-14 or F-18. It also was not as good of an attack aircraft as the F-18, A-6, or A-7. But it was better than nothing.

      • by jklovanc (1603149) on Wednesday December 22, 2010 @11:43PM (#34649322)

        Where fighter and bombers get all the glory there are a few equally important heavy aircraft that need catapults to launch:

        AEW:
        Aircraft such as the the E-2 Hawkeye http://en.wikipedia.org/wiki/Northrop_Grumman_E-2_Hawkeye [wikipedia.org] are critical to hiding the location of the fleet. If the enemy sees a ship based radar they know where the ship and usually the fleet is. If they see an airborne radar the fleet could be very far away. Also airborne radar can see further.

        COD;
        Carier Onboad Delivery, Need those critical parts or personel delivered outside of helicopter range? Need to evacuate critically injured personnel? You need a long range aircraft to do it.

        Tankers;
        Need to extend range to a target? Need to loiter for long periods on CAP. Need a sip of fuel to get back to the carrier because you used to much afterburners in the fight? Tankers are your friend. This role is currently done in the US Navy by the F/A-18E/F http://en.wikipedia.org/wiki/F/A-18E/F_Super_Hornet#Tanker_role [wikipedia.org]

        Without catapults none of these aircraft would get off the deck.

      • by afidel (530433)
        The Brits converted their F-35B order to F-35C's in October.
  • I am immensely tickled to hear that steam power is still being used in some modern context, even if I only learn of it as it is being phased out. I had never realized that this was how aircraft carrier slingshots worked. Are there any other interesting uses of steam power these days, outside of electricity production?
    • Its the bread and butter of hospital sterilization, but i dont know how interesting that is.
    • Steam turbines are basically the way to turn an external heat source into mechanical energy. Typically this is just used to generate electricity since it's so much more convenient to work with, but for a few applications the turbine will be attached directly to something other than a generator (say, a propeller on a big boat). Steam can also be used even more directly; as a heat source / heat transfer mechanism (say, for heating groups buildings particularly in colder climates), for cleaning carpets, for st
  • The amusement park in Ohio? They've got a roller coaster [wikipedia.org] that uses the same technology to launch, and it's pretty incredable. There are also a few [wikipedia.org] rides [wikipedia.org] in other parks that use liner induction motros to basically fling you straight up...I havent had a chance to ride those, but I imagine that's about as close most of us will get to a carrier fighter launch. Riding Maverick is what made me realize that being a figher pilot must be kind of like trying to use a computer while riding a roller coaster.
    • by NekSnappa (803141)
      Actually it's more like taking a physics exam, programming you GPS, and talking on the phone. All while driving a Formula 1 car.
      And since we're talking about carrier based planes here. Imagine that you stop the car by catching the axels on a cable while going full speed.
  • Fighters of the future...
    We use railguns to shoot them up.
    We use railguns to shoot them down.
  • Drones are more fragile? I thought they should be more robust as there are no humans in them.

    But, of course, if they are built essentially as a glider with a mini engine it may well be the case.

  • I used to work with an old guy whose job was to run the catapult on a carrier during the Korean War. He had some good stories about stuff they launched off the deck to "test" the catapult. The best one was an aircraft tractor that had been wrecked during a drag race below decks. Boredom and sailors don't mix.

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