The U.S. Navy Rides the Rail

American Thinker ^ | April 6, 2013 | Brendon S. Peck

[Kozak]

You sound just like the Admirals who “knew” airplanes would never sink Battleships.

[null and void]

Pearl Harbor is too shallow for air dropped torpedoes...

[Chainmail]

OK, swell: we have a gun system that can throw a 40 pound projectile 100 miles, more or less, with a time of flight of 6 minutes.

Here are the questions that necessarily follow:

1. Have they overcome the issue of rail erosion? Early rail guns ate the rails into uselessness after 2-4 shots.

2. Have they resolved issue of payload? The accleration forces encountered and the ferocious electromagentic energies and induced heat pretty well eliminated any kind of conventional explosives, fuzes, detonation trains. And please don't give me the "kinetic energies of the superfast projectiles will devastate whole grid squares" horsepucky - all projectiles decelerate to their aerodynamic terminal velocities when they get into the decending branch of their trajectories. What do we get for our 6 minute wait - a 40 pound hunk of iron?

3. Given the problems of 2. above, what kind of terminal guidance is available? A 100 mile shot is a long ways for a nonrotating projectile to fly and still expect it to be anywhere near a point of aim. The Paris Gun shot 93 miles but it had a range probable error the size of Paris itself. Not particularily effective. In the world of artillery, noise is useless, hitting is everything.

4. Let's get back to the 6 minute time of flight. Unless you are shooting at a large stationary target - like a building - 6 minutes is an eternity, particularly if the target is coming towards you. 6 minutes is almost completely useless in most combat scenarios, since most worthwhile targets move.

Lastly, to answer the whiz kids out there with the correspondence school degree in physics, yes there is huge recoil: Newton's Third Law is still in effect. The hand-wavy stuff I have read so far about "magic magnetic fields" is sadly wrong. Add that to the large RF pulse at launch which will give the firing platform's position away to the entire world when it fires, there are lots of issues yet to overcome before the rail gun is more than a cash cow for major defense contractors.

[Paleo Conservative]

The Navy’s railguns are expected to have ranges equal to or gretaer than 220 nautical miles, which is Beyond Visual Range (BVR) for the 5 inch projectile.

Imagine one scaled up to shoot 16 inch projectiles. The Navy already has electromagnetic rail systems designed to catapult aircraft from carrier decks. A 16 inch projectile is much lighter than a fighter/bomber.

[wxgesr]

How to the engineers design the offices nearby so the computers don’t become victim to the magnetic field?

[ClearCase_guy]

I am open to Defense cuts. Lord knows DoD does not spend its money wisely. But the ability to instantly strike targets at greater than 200-mile ranges, using inert materials as ammunition is a quantum leap forward in war-making. Since 1941, the very essence of Power Projection has been the aircraft carrier. What you're looking at here is the next step -- it's the successor to a weapon platform that was dominant for 70 years.

If we don't build it, and China does ... then we will find ourselves being so weak we have to apologize and backdown from looming conflicts in backwater places like North Korea.

[justlurking]

Recoil will be no more massive than that from a conventional chemical propellent gun.

You can't compare them directly: it's like apples and oranges.

If a chemical propellent launches an explosive warhead, the explosive delivers most of the destructive energy to the target. The speed of the projectile is less critical: it's the amount of explosive and the shape of the charge.

All of the destructive energy delivered to the target by a railgun is kinetic energy. Therefore, it must be generated by the launcher. And there must be enough speed to counteract the drag through the atmosphere between the launcher and the target.

The question is in the balance: how does a 40-lb projectile at hypersonic speeds compare to a larger/heavier explosive projectile at supersonic speeds? Only after equalizing those can you compare the recoil.

[null and void]

The question is in the balance: how does a 40-lb projectile at hypersonic speeds compare to a larger/heavier explosive projectile at supersonic speeds? Only after equalizing those can you compare the recoil.

And when you do that they end up being roughly equivalent.

Roughly.

It's not orders of magnitude higher. It's not flip-the-ship-over or drive it bodily under water.

[justlurking]

OK, swell: we have a gun system that can throw a 40 pound projectile 100 miles, more or less, with a time of flight of 6 minutes.

How did they derive that? At 5,600 mph, the flight time would be 64 seconds (100/5600 * 3600).

I see it in the article, but I'm a bit skeptical -- unless they are considering a ballistic trajectory that has a high apogee.

[ClearCase_guy]

Yup. The weight of the broadside for an Iowa-class battleship is greater than 24,000 lbs. That's 600 times the weight of the 40-lb projectile under discussion. Sure, speed has greatly increased, but by a factor of 600? I don't think so.

The great thing about a ship, is that you can rock it back with tremendous force, and it (generally) just bobs back as if nothing happened. That's why a Destroyer makes a good platform for this weapon system.

[justlurking]

And when you do that they end up being roughly equivalent.

I'm skeptical. Show me the math.

In one case, you are launching a projectile that initiates a chemical reaction at the target to inflict the damage. It doesn't have to be fast, it just has to be fast enough to reach the target without additional propulsion.

In the other case, you are launching the projectile with sufficient energy to inflict the damage, plus enough additional energy to compensate for the parasitic drag (which is not linear to speed) before it reaches the target.

I'm not claiming it is insurmountable. I just don't believe it is "roughly equivalent", unless your definition of "roughly equivalent" means "same order of magnitude". If that's the case, I don't agree.

[justlurking]

3. Given the problems of 2. above, what kind of terminal guidance is available? A 100 mile shot is a long ways for a nonrotating projectile to fly and still expect it to be anywhere near a point of aim. The Paris Gun shot 93 miles but it had a range probable error the size of Paris itself. Not particularily effective. In the world of artillery, noise is useless, hitting is everything.

The article suggest GPS guidance, but I'm curious about that. I'm sure a receiver could be ruggedized to withstand the forces of launch, but I don't know if it's possible to build a receiver that could provide guidance at that speed.

And that's separate from the problem of the ionized plasma that is created by hypersonic flight through the atmosphere. I don't know the speed at which it first occurs, but it does only occur at the leading edges. The shuttle was able to maintain communication by transmitting "out the top" to TDRS relays.

[Bender2]

Re: Recoil will be no more massive than that from a conventional chemical propellent gun.

From http://en.wikipedia.org/wiki/Railgun

Considerations

The power supply must be able to deliver large currents, sustained and controlled over a useful amount of time. The most important gauge of power supply effectiveness is the energy it can deliver. As of December 2010, the greatest known energy used to propel a projectile from a railgun was 33 megajoules. The most common forms of power supplies used in railguns are capacitors and compulsators which are slowly charged from other continuous energy sources.

The rails need to withstand enormous repulsive forces during shooting, and these forces will tend to push them apart and away from the projectile. As rail/projectile clearances increase, arcing develops, which causes rapid vaporization and extensive damage to the rail surfaces and the insulator surfaces. This limited some early research railguns to one shot per service interval.

The inductance and resistance of the rails and power supply limit the efficiency of a railgun design. Currently different rail shapes and railgun configurations are being tested, most notably by the United States Navy, the Institute for Advanced Technology, and BAE Systems.
Materials used

The rails and projectiles must be built from strong conductive materials; the rails need to survive the violence of an accelerating projectile, and heating due to the large currents and friction involved. Some erroneous work has suggested that the recoil force in railguns can be redirected or eliminated; careful theoretical and experimental analysis reveals that the recoil force acts on the breach closure just as in a chemical firearm. The rails also repel themselves via a sideways force caused by the rails being pushed by the magnetic field, just as the projectile is. The rails need to survive this without bending and must be very securely mounted.
Heat dissipation

Massive amounts of heat are created by the electricity flowing through the rails, as well as by the friction of the projectile leaving the device. The heat created by this friction itself can cause thermal expansion of the rails and projectile, further increasing the frictional heat. This causes three main problems: melting of equipment, decreased safety of personnel, and detection by enemy forces. As briefly discussed above, the stresses involved in firing this sort of device require an extremely heat-resistant material. Otherwise the rails, barrel, and all equipment attached would melt or be irreparably damaged.

In practice the rails are, with most designs of railgun, subject to erosion due to each launch; and projectiles can be subject to some degree of ablation also, and this can limit railgun life, in some cases severely.

That said, it will take tougher sailors as some areas need to be economized... to pay for the research--

Now, who says there are no True Patriots... anymore!

[ClearCase_guy]

Math is not really my strong suit. But here are the figures needed for the calculation:

Iowa-class guns (16 inch): They fired projectiles weighing from 1,900 to 2,700 pounds (850 to 1,200 kg) at a maximum speed of 2,690 feet per second (820 m/s) with a range of up to 24 miles (39 km).

The ships had 9 of these, and they could all fire in unison. That's 24,000 lbs of ordinance traveling 2,690 feet per second.
We're talking about the recoil of a 40-lb shell traveling mach 6 or 7.

Equivalent? I don't know. But I don't think the boat will sink.

[volunbeer]

You sound just like the Admirals who “knew” airplanes would never sink Battleships.

---

Well played! Mankind has difficulty anticipating the changes in technology and our instinct is to dismiss anything beyond our realm of understanding. Technology is expanding so quickly that it is difficult to comprehend the technology and how the technology will change the status quo. I applaud the Navy for understanding this and overcoming those that dismiss a changing world.

Weapons are going to change in ways we cannot begin to imagine and our military should stay ahead of the curve. Too many folks are emotionally (and financially) invested in the idea of the gigantic aircraft carrier projecting force just as most were emotionally invested in the supremacy of the battleship prior to WWII.

We should not put all of our eggs in the basket of aircraft carriers because there are some incredibly lethal (and relatively inexpensive) weapons out there that could destroy them. I love carriers and aircraft as much as the next cold war kid, but weapons like this (and drones) could render them obsolete.

[justlurking]

Equivalent? I don't know. But I don't think the boat will sink.

You've provided a lot of information about chemically-propelled artillery on the USS Iowa. However, can you directly compare 9 of these fired at one time, to one 40-lb shell fired at hypersonic speeds?

I'm not referring to just the launch: what's going to happen at the target? 24,000 lbs of high explosive vs. 40 lbs at Mach 7 (presuming it maintains that velocity)? It doesn't seem like much of a contest, but I'm willing to listen to a convincing argument.

Show me that math. That's not a direct challenge to you -- I'm just trying to show that it's not a simple comparison.

[neverdem]

Why 2012 Postmortems Overstate Republican Woes

The End of an Illusion (The science for man made global warming, climate change, etc. isn't there.)

Democrats have doubts about Obamacare too

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Some noteworthy articles about politics, foreign or military affairs, IMHO, FReepmail me if you want on or off my list.

[null and void]

Per wiki as cited by Bender2 at post #33:

As of December 2010, the greatest known energy used to propel a projectile from a railgun was 33 megajoules.

How does that compare to a 16" gun on a battleship?

Funny you would ask...

E=1/2MV²

A 16" projectile weighs about 1000 kg (AP=1 225 kg, HC and Nuke=862 kg)

Muzzle velocity for a 50 calibers barrel is about 800m/s (AP=762 m/s, HC and Nuke=820 m/s)

1/2*1000*800*800=32 megajoules.

I submit that is roughly the same as 33 megajoules.

[ClearCase_guy]

I guess I was confused about the initial question.

I thought the discussion was about recoil -- given the force (x) at launch, will a railgun sink the ship that fires it? The figures I provided were geared toward the observation that battleships dealt with enormous recoil, and did OK. I think the recoil from a railgun will be quite manageable.

If that is the topic, then explosive warheads and damage done at the target don't come into the discussion at all.

But, if we want to explore the topic of dealing damage, I offer this:

The Mk. 8 APC (Armor-Piercing, Capped) shell weighed 2,700 lb (1225 kg) and was designed to penetrate the hardened steel armor carried by foreign battleships. At 20,000 yards (18 km) the Mk. 8 could penetrate 20 inches (500 mm) of steel armor plate. At the same range, the Mk. 8 could penetrate 21 feet (6.4 m) of reinforced concrete.

Penetration by a 40-lb slug of metal traveling at mach 7? I do not know. But the kinetic energy would be significant. And in terms of ammunition storage, you could send over about 70 rail gun shells for every 2,700 lb explosive shell. Again, I cannot do the math, but at 10 times the range, the kinetic power delivered by the rail gun would seem to be nice to have.

[null and void]

I guess I was confused about the initial question.

I thought the discussion was about recoil -- given the force (x) at launch, will a railgun sink the ship that fires it?

It was.

When we proved the concept couldn't be poo-pooed based on recoil, the subject was abruptly changed.