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US Navy Railgun

05/13/2018 10:28 AM

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#1

Re: US Navy Railgun

05/13/2018 11:13 AM

Deer hunting will never be the same.

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#11
In reply to #1

Re: US Navy Railgun

05/14/2018 12:42 PM

A little late:

http://www.buckstix.com/howitzer.htm

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#2

Re: US Navy Railgun

05/13/2018 11:40 AM

I think this technology will suffer the consequences of unrealistic expectations. Accelerating any projectile that short of a distance to a velocity of Mach 7 will make it very unlikely for any intelligent controls to be placed in a projectile. Thus it will have tremendous range but little if any accuracy at that range.

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#3
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Re: US Navy Railgun

05/13/2018 12:09 PM

Estimating a constant acceleration for 5 meters and achieving a 2400 meters per second velocity (mach 7) requires an acceleration of 18,000 g.

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#12
In reply to #3

Re: US Navy Railgun

05/14/2018 9:17 PM

18,000 g does not make it highly unlikely that intellegent controls could be integrated into projectiles.

Shock hardened components and integrated devices are readily available and becoming moreso and cheaper, due in large part to cell phones and cell phone like personal electronics.

Cell phones can experience upward of 5000 g from a drop at chest height onto a hard ground surface....and regularly continue to function after many drops.

Projectiles that steer flight via onboard electronics have been developed for 50 bmg. If the muzzle velocity is anywhere near a typical 50 bmg round then acceleration already tollerated is well over 18000 g.

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#13
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Re: US Navy Railgun

05/14/2018 9:35 PM
Assume somewhere in the neighborhood of 1000 m/s muzzle velocity and a 1 meter barrel for a 50 bmg, if constant acceleration then 50bmg projectile accelerates from stop to muzzle in 0.002 seconds so 1000 m/s in 0.002 s is 500,000 m/s

2

1g is about 10 m/s2 so around 50,000 g acceleration, IF acceleration were constant down the barrel...which it isn't meaning real peak acceleration would be greater. So even if the self guiding projectiles are remakably slow compared to other 50 BMG projectiles, it is likely already comparable to the railgun projectile acceleration.

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#14
In reply to #13

Re: US Navy Railgun

05/15/2018 7:49 AM

I guess I should clarify my concerns. My high acceleration apprehension is not about the electronics and circuitry. Potting compounds can easily stabilize this concern. My apprehension is for the controls themselves. A sabot might be able to provide some mechanical support and isolation from the plasma ball during acceleration but getting anything to move precisely in order to change the aerodynamics of a mach 7 projectile seems like a tall order for me.

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#16
In reply to #14

Re: US Navy Railgun

05/15/2018 6:40 PM

I don't know much about hypersonic aerodynamics of control surfaces, but there are people who do and that understanding has been sufficient for production runs of equipment capable of maneuvering at speeds greater than mach 7 for decades.

Consider the Pershing II, which entered service in the 1980s. The the reentry vehicle guided itself to the target, steering at speeds exceeding mach 8 and performing a 20g nose up nose down to shed speed to get the correct final velocity.

The Pershing II is just one example of many. Consider the various MARV technologies and the x-15.

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#18
In reply to #16

Re: US Navy Railgun

05/16/2018 10:04 AM

And all of the examples you cite the mechanism to maneuver at mach 7 did not achieve mach 7 after an impulse of 10,000+ g acceleration. Also all of those examples were machines that at least started off much larger than a human being. The presented projectile is about the size of a person's arm. (Watch movement size mechanics are still sensitive to mechanical shocks. A 10,000 g impulse is one hell of a mechanical shock.) The X-15 did not achieve mach 7 let alone maneuver at sea level atmosphere at multiple mach velocities. Also no MARV maneuvers at mach 7 parallel to the earth's surface in one atmosphere of pressure.

Lastly, my apprehensions are certainly not an absolute impediment to any R&D project. Hopefully some of my apprehensions help to indicate some of the critical hurdles an R&D project is attempting to overcome.

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#20
In reply to #18

Re: US Navy Railgun

05/16/2018 3:58 PM

Fair enough.

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#5
In reply to #2

Re: US Navy Railgun

05/13/2018 1:22 PM

..."Current railgun technologies necessitate a long and heavy barrel, but a railgun's ballistics far outperform conventional cannons of equal barrel lengths. Railguns can also deliver area of effect damage by detonating a bursting charge in the projectile which unleashes a swarm of smaller projectiles over a large area.[38][39]

Assuming that the many technical challenges facing fieldable railguns are overcome, including issues like railgun projectile guidance, rail endurance, and combat survivability and reliability of the electrical power supply, the increased launch velocities of railguns may provide advantages over more conventional guns for a variety of offensive and defensive scenarios. Railguns have lmited potential to be used against both surface and airborne targets.

Although many arguments in favor of EM guns revolve around the assumption that greater muzzle velocity is always better, this is open to challenge.[40] Parametric relationships between range, payload weight, and launch velocity show that this is not a strong argument for many suggested EM gun applications.[41] For example, due to lower aerodynamic drag at launch, a slower but heavier projectile may actually fly farther than a lighter faster one, making the velocity limitations of chemical propulsion perfectly acceptable. In addition, explosive fragmentary warhead lethality is largely unaffected by velocity and does not require more demanding hit-to-kill guidance electronics that may not survive extremely high gun launch accelerations. Significantly, explosively formed penetrator and shaped charge warheads already drive what is technically a kinetic energy penetrator to velocities well in excess of EM gun launch capabilities, up to 8 km/s for a shaped charge, upon detonation with the target; and it has been demonstrated that with respect to armor penetration, increased impact velocity much above 2 km/s does not necessarily result in a deeper hole (although the crater may be wider as more energy is deposited with increased impact velocity).[42] "...

..."Railguns are being examined for use as anti-aircraft weapons to intercept air threats, particularly anti-ship cruise missiles, in addition to land bombardment. A supersonic sea-skimming anti-ship missile can appear over the horizon 20 miles from a warship, leaving a very short reaction time for a ship to intercept it. Even if conventional defense systems react fast enough, they are expensive and only a limited number of large interceptors can be carried. A railgun projectile can reach several times the speed of sound faster than a missile; because of this, it can hit a target, such as a cruise missile, much faster and farther away from the ship. Projectiles are also typically much cheaper and smaller, allowing for many more to be carried (they have no guidance systems, and rely on the railgun to supply their kinetic energy, rather than providing it themselves). The speed, cost, and numerical advantages of railgun systems may allow them to replace several different systems in the current layered defense approach.[46] A railgun projectile without the ability to change course can hit fast-moving missiles at a maximum range of 30 nmi (35 mi; 56 km).[47] As is the case with the Phalanx CIWS, unguided railgun rounds will require multiple/many shots to bring down maneuvering supersonic anti-ship missiles, with the odds of hitting the missile improving dramatically the closer it gets. The Navy plans for railguns to be able to intercept endoatmospheric ballistic missiles, stealthy air threats, supersonic missiles, and swarming surface threats; a prototype system for supporting interception tasks is to be ready by 2018, and operational by 2025. This time frame suggests the weapons are planned to be installed on the Navy's next-generation surface combatants, expected to start construction by 2028.[48] "...

..."In July, 2017, Defensetech reported that the Navy wants to push the Office of Naval Research's prototype railgun from a science experiment into useful weapon territory. The goal, according to Tom Beutner, head of Naval Air Warfare and Weapons for the ONR, is ten shots per minute at 32 megajoules. A 32 megajoule railgun shot is equivalent to about 23,600,000 foot-pounds, so a single 32 MJ shot has the same muzzle energy as about 200,000 .22 rounds being fired simultaneously.[84] The target firing rate, 10 shots per minutes, is then equivalent to firing 2 million .22 rimfire rounds per minute. In more conventional power units, a 32 MJ shot every 6 s is a net power of 5.3 MW (or 5300 kW). If the railgun is assumed to be 20% efficient at turning electrical energy into kinetic energy, the ship's electrical supplies will need to provide about 25 MW for 60s."...

..."

  1. Projectile guidance: A future capability critical to fielding a real railgun weapon is developing a robust guidance package that will allow the railgun to fire at distant targets or to hit incoming missiles. Developing such a package is a real challenge. The Navy's RFP Navy SBIR 2012.1 – Topic N121-102[90] for developing such a package gives a good overview of just how challenging railgun projectile guidance is:

The package must fit within the mass (< 2 kg), diameter (< 40 mm outer diameter), and volume (200 cm3) constraints of the projectile and do so without altering the center of gravity. It should also be able to survive accelerations of at least 20,000 g (threshold) / 40,000 g (objective) in all axes, high electromagnetic fields (E > 5,000 V/m, B > 2 T), and surface temperatures of > 800 deg C. The package should be able to operate in the presence of any plasma that may form in the bore or at the muzzle exit and must also be radiation hardened due to exo-atmospheric flight. Total power consumption must be less than 8 watts (threshold)/5 watts (objective) and the battery life must be at least 5 minutes (from initial launch) to enable operation during the entire engagement. In order to be affordable, the production cost per projectile must be as low as possible, with a goal of less than $1,000 per unit.


On June 22, 2015, General Atomics’ Electromagnetic Systems announced that projectiles with on-board electronics survived the whole railgun launch environment and performed their intended functions in four consecutive tests on June 9 and 10 June at the U.S. Army’s Dugway Proving Ground in Utah. The on-board electronics successfully measured in-bore accelerations and projectile dynamics, for several kilometers downrange, with the integral data link continuing to operate after the projectiles impacted the desert floor, which is essential for precision guidance.[91] "...

https://en.wikipedia.org/wiki/Railgun

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#6
In reply to #5

Re: US Navy Railgun

05/13/2018 4:45 PM

A power femand this high is usually met with Nuclear Power Generators on the ship.

However, I just wonder how useful this technology is. It involves transforming nuclear energy into mechanical energy, rather than blasting with the source energy from the beginning.

What I see here is a waste of resources. What is the point? Will making it cool help convincing people to pay for it?

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#7
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Re: US Navy Railgun

05/13/2018 6:33 PM

..." Zumwalt-class destroyers (DDG); they can generate 78 megawatts of power, more than is necessary to power a railgun. Engineers are working to derive technologies developed for the DDG-1000 series ships into a battery system so other warships can operate a railgun.[79] Most current destroyers can spare only nine megawatts of additional electricity, while it would require 25 megawatts to propel a projectile to the desired maximum range [80] (i.e., to launch 32MJ projectiles at a rate of 10 shots per minute). Even if current ships, such as the Arleigh Burke-class destroyer (DDG), can be upgraded with enough electrical power to operate a railgun, the space taken up on the ships by the integration of an additional weapon system may force the removal of existing weapon systems to make room available.[81] The first shipboard tests was to be from a railgun installed on an Spearhead-class expeditionary fast transport (EPF), but this was later changed to land based testing.[82] "...

https://en.wikipedia.org/wiki/Railgun#Naval_Surface_Warfare_Center_Dahlgren_Division

Zumwalt-class destroyer

https://en.wikipedia.org/wiki/Integrated_electric_propulsion

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#8
In reply to #5

Re: US Navy Railgun

05/13/2018 9:49 PM

I like the simplicity of the shotgun "bird-shot" solution to the accuracy problem.

I'm still apprehensive of any guidance technology surviving this acceleration. You should note that General Atomics' claimed that on-board electronics and not any mechanism to alter a trajectory survived the acceleration. Firing on a target 20 miles down range with a mach 7 projectile does allow for about 16 seconds of flight time in order to correct course. However, I suspect any steering/stability fins on the back of the projectile may have difficulty altering trajectory in the turbulent wake.

Regardless of how and if this technology develops, this will not be the the first time a promising military technology turns into a dead end nor the last time my apprehensions are solved by people with far more skills in the field than me. It will be interesting to see how this develops.

{I guess my barrel length of 5 meters was only a little generous.}

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#9
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Re: US Navy Railgun

05/13/2018 10:22 PM

I don't think they're trying to control the trajectory with the projectile itself, but rather to accurately track each shot making corrections with the aiming mechanism....

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#10
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Re: US Navy Railgun

05/14/2018 10:22 AM

The shirt and tie definitely add to the air of competence.

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#15
In reply to #10

Re: US Navy Railgun

05/15/2018 11:25 AM

The mushroom cloud and the flinch also add a lot to the performance.

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#17
In reply to #9

Re: US Navy Railgun

05/15/2018 9:20 PM

It's quite spectacular....

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#4

Re: US Navy Railgun

05/13/2018 1:09 PM
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#19

Re: US Navy Railgun

05/16/2018 11:12 AM

My main concern for this thing is that technically it is very complex and operationally the system is fragile in that any one failure takes down the entire system and that system ends up spread over a lot of territory with power supply, power transport, controls and turret. The standard naval gun is relatively simple by comparison. A short while ago some photos ran on the web that supposedly showed a Chinese rail gun on a ship. Behind the turret were some cargo container like structures that were believed to be power supply or control electronics. They appeared to be relatively soft targets and would make the rail gun itself useless if somehow the power supply or controls got perforated.

I'm not too concerned about aiming and accuracy and I'm also not too concerned about feasibility of intelligent controls or terminal guidance in the projectile. All of that has been handled at one time or another.

The rail gun in the turret can be reasonably hardened, but the power supply, control electronics and power transport end up needing to be packaged like a standard naval gun magazine and projectile and propellant handling system. I'd be curious to see what a hit on a capacitor bank would look like.

WW2 marked the end of the battleship and naval gun fire as a primary tool of naval combat, except as mobile battery for pre-assault bombardment in support of amphibious landings. The primary role was replaced by aircraft and later by missiles. Ships couldn't effectively get within gunfire range. I'm having trouble visualizing what a rail gun brings to the mix that makes a significant change. The turret explosion on the Iowa several years ago revealed that we no longer have the capability to make large caliber naval guns. The rail gun makes up for that to some degree in that the higher velocity gets you back to about the same energy delivery to target as the large caliber gun. The question in my mind is what you can use it for if you can't close the range to 100 miles and have significant problems avoiding fatal system damage.

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#21
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Re: US Navy Railgun

05/16/2018 6:46 PM

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#22
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Re: US Navy Railgun

05/16/2018 9:36 PM

Ah yes, the propaganda film for the USS Zumwalt. Did you wonder why this program was on the military chopping block after only one ship being built? Yes, by contract a total of three will ultimately be built. The USS Michael Monsoor recently set sail. The summary conclusion of the cited article:

"The Zumwalt is an unmitigated disaster. Clearly it is not a good fit as a frontline warship. With its guns neutered, its role as a primary anti-submarine-warfare asset in question, its anti-air-warfare capabilities inferior to those of our current workhorse, the Arleigh Burke–class destroyers, and its stealth not nearly as advantageous as advertised, the Zumwalt seems to be a ship without a mission."

Just like most radical changes in military technology, the fate and value of this class of ships is still in question. The size of the price tag is not in question.

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#23
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Re: US Navy Railgun

05/16/2018 9:53 PM

Might take on a different persona with a few railguns mounted...

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