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    Usefulness of rail guns

    kvs
    kvs

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    Post  kvs Wed Oct 21, 2020 5:05 pm

    There appears to be a lot of unreasonable value ascribed to rail guns. Here are some of the main points that were raised in several
    posts under different threads:

    1) Atmospheric friction at low altitudes is a problem. Even if ceramics and ablative coatings can deal with the heat, they may not deal
    with the shock acceleration.

    2) Rail guns are just ballistic guns and not scifi wunderwaffen. So attacks on cruise missiles and similar is not any sort of
    superiority aspect of these weapons. Small missile interceptors are more effective since they are not limited by any line
    of sight.

    3) They consume vast amounts of energy. Even though the US routinely propagandizes their development and planned
    deployment on ships, this remains always in the future after years of hype. And installing them on ships is actually
    practical with the right sort of power plant. Using rail guns to take out cruise missiles in the mountains on some truck
    is dreaming in technicolor.

    It appears that rail guns are more useful in orbit outside the atmosphere, but there you have the problem of power supply.
    So they are a scifi spaceship weapon with limited utility in any real world situation for the foreseeable future.


    LMFS
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    Post  LMFS Wed Oct 21, 2020 5:39 pm

    Agree, to reach very long distances a softer propulsion working over long periods of time works much better than a very strong one concentrated in a very short period of time, since extremely high initial speeds generate also extremely high drag (drag raises with speed squared) that drain more kinetic energy from the projectile the faster it flies, this can be seen in any missile range simulation. So the rail gun is a fancy concept but its principle of operation has not so much potential as some appear to think.
    GarryB
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    Post  GarryB Thu Oct 22, 2020 4:56 am

    An EM gun is interesting, but with dumb kinetic projectiles it would be rather limited...

    Modify the projectile to be essentially a flying engine... a scramjet... with some capacity to manouver, and you could be looking at the ability to shoot down hypersonic manouvering threats just from rate of fire... a 152mm gun with manouvering projectiles of 30-40kgs including engine and fuel with beam riding guidance perhaps... an incoming threat will be flying very high so the round could initially be lofted up high and then directed towards the incoming threat... launch 10 of them in rapid succession with a HE frag warhead to spread say 10kgs of fragments into the path of the incoming threat.

    Use an AESA for guidance and tracking of target and projectile.

    Obviously the initial velocity needs to be fairly high... say 3km/s and the scramjet maintains that speed as it climbs to altitude and then the projectile can roll over and accelerate horizontally... the incoming target will detect it is being tracked and will likely determine how far the radar is from the target... a good missile should be able to determine if the radar is near the target so whether the radar can be flown around or if evasive manouvers need to start...

    The idea for the EM gun on the US ships was stupid... they need to take an existing gun type like a 152mm gun or 203mm gun and modify it into a hybrid to improve performance of currently used guns so whatever you end up making is widely deployed and used in numbers and has affordable ammo.

    A joint venture with the Army to spread costs and increase production numbers is critical too to making it cost effective and useful... and indeed if the weapon is actually useful... a 152mm gun with a range of 180km for instance would be valuable for both Army and Navy... a 203mm gun with a range of 300km would be interesting too...
    LMFS
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    Post  LMFS Thu Oct 22, 2020 9:29 am

    If the projectile itself has integrated propulsion, what you want is to shoot almost vertically to cross the dense layers of atmosphere as fast as possible and then have the ramjet or scramjet working at their operational altitude. So the rail gun would itself have rather direct little use in terms of range but just to bring to projectile to speed. Without forgetting that a normal gun can already bring a projectile close to or beyond 5 M for ramjet or scramjet propulsion to work.

    So EM propulsion is very good for catapults on carriers for instance, but I remain sceptic regarding rail guns.
    kvs
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    Post  kvs Thu Oct 22, 2020 6:49 pm

    Step function-like acceleration is bad, period.   It really is like taking your computer and hitting it with a sledge hammer.  
    The miracle of EM is supposed to be the super-fast projectile speed.   But that is only worthwhile in scifi space battles
    where there is no atmosphere to ablate and slow down your hunk of metal projectile.   In the real world, in the lower
    atmosphere a huge amount of that energy is lost to atmospheric friction.  

    The concept is really a waste of time.   Just the power supply problem is absurd.  We have hypersonic rockets that
    can accelerate real warheads to relevant speeds.   They are self contained with their own power source in the form
    of rocket fuel.    Even if they are "heavy" they are still much lighter and smaller than the combined rail gun and
    power supply.  

    Rail guns are a "solution" looking for a problem.

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    GarryB
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    Post  GarryB Fri Oct 23, 2020 3:20 am

    The technology and materials develop that need to be developed to make it work will have enormous value across the range of technology of vehicles... from electric drive tanks and armour to cars and bikes and trucks and buses and ships and planes and helicopters and UAVs.

    Electric drive systems, super magnets, plasma handling... hydraulics (heavy dangerous dirty) could be replaced, the applications of this sort of technology can be very broad... it doesn't need to be ultra focused single use stuff... an EM cat can launch an aircraft through to a smaller much lighter projectile moving at enormous speeds but also all sorts of things in between and the electrics to drive it.

    History is filled with technology breakthroughs from making weapons... the biggest drive for miniaturised computer technology was a lack of rocket motor thrust.
    Imagine the progress and breakthroughs when the money is actually spent on making vehicles independent of fossil fuels... imagine solar power developing as far and as fast as computing power... well that is asking a bit much.
    kvs
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    Post  kvs Mon Oct 26, 2020 6:38 am

    GarryB wrote:The technology and materials develop that need to be developed to make it work will have enormous value across the range of technology of vehicles... from electric drive tanks and armour to cars and bikes and trucks and buses and ships and planes and helicopters and UAVs.

    Electric drive systems, super magnets, plasma handling... hydraulics (heavy dangerous dirty) could be replaced, the applications of this sort of technology can be very broad... it doesn't need to be ultra focused single use stuff... an EM cat can launch an aircraft through to a smaller much lighter projectile moving at enormous speeds but also all sorts of things in between and the electrics to drive it.

    History is filled with technology breakthroughs from making weapons... the biggest drive for miniaturised computer technology was a lack of rocket motor thrust.
    Imagine the progress and breakthroughs when the money is actually spent on making vehicles independent of fossil fuels... imagine solar power developing as far and as fast as computing power... well that is asking a bit much.

    This sort of development is happening in many other areas already. One such example is the Avangard hypersonic glider.

    The H. G. Wells mega gun launch to orbit makes vastly more sense since the acceleration shock is relatively smaller. Small-ish
    rail guns that would be mounted on ships will not be able to use guided or even explosive-loaded projectiles.

    And Russian/Soviet scientists have been working on rail guns for decades. So fundamental research is being done regardless of
    any practical utility for the sci-fi variants of these devices. But there is no way to circumvent physics. Rail guns are power
    hogs and that is what limits their application for small, mobile purposes. If this was not an issue then tanks would have been
    using rail guns for a long time.

    GarryB
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    Post  GarryB Mon Oct 26, 2020 8:39 am

    And before lasers the idea of death beams was stupid because any ray powerful enough to kill someone at a distance would surely kill the user first... but with research and money and time they have developed lasers and other directed energy weapons that would be suitable for what might have been considered impossible in the past.

    The point is that right now they are likely delaying the production of their big ships... destroyers and cruisers... because they have introduced a lot of new technology on the Kuznetsov... something like a catapult but clearly not an EMALS yet, with talk from the company that developed it suggesting new electrical systems being fitted... hint hint... vague suggestion vague suggestion...

    A new ship with vastly smaller and more compact power systems and managed electrical power systems should lead to quite a few improvements in performance and offer to provide power for all sorts of things... if not an EM gun then like some form of laser or maser... the first ones don't have to be perfect... they will be a generation ahead of the competition anyway.

    There was talk of the Coalition 152mm gun using EM boosting and plasma propulsion to extend the range from 70km to 180km without reducing the shells size to unusable sizes...

    AFAIK they already microwave the propellent to improve performance too.

    Tanks got guns well after ships and have never carried anything anywhere close to some of the guns fitted to ships... the smallest they got for big guns was train mounted and they were ridiculous...
    thegopnik
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    Post  thegopnik Sun Mar 14, 2021 12:41 am

    Russia did use catapults to launch ramjet drones. Unlike the U.S. strategic launch long range canon, i think it would be a great idea to use a canon where a missile just has a scramjet engine.

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