Got a Real-World Weapon or Armor Question? Mk. VI

[Yora]

If railguns extend the range far beyond what conventional naval guns can achieve, into the hundreds of miles say, then I suspect there is a good offensive value for heavy armored warships; their survivability is already an asset IMO.

Supposed you could shot an iron bar over such distances. How would you handle shoting over the horizon? Supposed the gun is mounted 10m above the waterline and your target is as well, you would have a clear line of sight only for up to 30km (if I read this chart correctly). Conventional guns just shot in an arc and let gravity do the trick of bending the shells path. But at velocities to carry the projectile ten times and more that distance while still being effective, would gravity be enough to not shot over the target? If you shot it like a mortar, the impact would probably occur at merely terminal velocity and probably not very effective.

[Galloglaich]

Even if they could target and hit a railgun slug, I don't know that it would do any good. Laser ABM systems don't "burn" their targets, but rather the energy imparted by the high order lasing damages the target in a physical manner. For instance the ABL bursts the fuel tanks of a boost-phase liquid fueled rocket, or induces cracks in the propellant of a solid fueled one.

For a shell with a warhead, you might be able to cause it to detonate prematurely, but for a 100 kg slug, what can you damage?

agreed.


G.

[Galloglaich]

Supposed you could shot an iron bar over such distances. How would you handle shoting over the horizon? Supposed the gun is mounted 10m above the waterline and your target is as well, you would have a clear line of sight only for up to 30km (if I read this chart correctly). Conventional guns just shot in an arc and let gravity do the trick of bending the shells path. But at velocities to carry the projectile ten times and more that distance while still being effective, would gravity be enough to not shot over the target? If you shot it like a mortar, the impact would probably occur at merely terminal velocity and probably not very effective.

I think this is just ballistics, same as with other artillery or ballistic missiles, based on the mass and velocity you get a certain arc, I don't think the speed makes a huge effect on that though perhaps someone can correct me.

G.

[Autolykos]

But at velocities to carry the projectile ten times and more that distance while still being effective, would gravity be enough to not shot over the target?

Yep, until your projectile reaches orbital velocity at sea level, which is the case at slightly above 7900 m/s (v=sqrt(g*r)) - which still gives you more than enough kinetic energy to play with, even with relatively light projectiles.
EDIT: FTR, the kinetic energy is then 31MJ per kg of projectile weight.
(all of this disregards air friction, which is a rather big factor at these speeds...)

[hamishspence]

Given that a kg of TNT is equivalent to 4.1 MJ, the projectile's energy isn't all that impressive.

A 1 tonne projectile would be equivalent to about 7.6 tons of TNT.

For comparison, the Yamato class battleship's main guns fired projectiles weighing a bit more than a tonne.

[SlyGuyMcFly]

While it is strictly speaking an measurement of energy, TNT equivalents are generally used as a measurement of explosive force. You can't really compare the destructive potential of a kinetic projectile with a conventional explosive using TNT equivalents, due to rather different delivery mechanisms.

[hamishspence]

True.

I wonder if kinetic energy is more efficient, destruction-wise, than explosive energy?

Would, for example, a very large, very fast projectile with a K.E of 1 kiloton, do far more damage to a ship, than a 1 kiloton warhead would?

That said, they might work fairly similarly if fired at the ground- a 1 megaton kinetic projectile (such as an asteroid) might (on impact) produce a similar (but not identical) effect to a nuclear 1 megaton warhead exploded at ground level.

Only without the fallout.

[Spiryt]

Isn't "explosive" energy kinetic energy (of violently expanding air) too anyway?

With some heat, and more kinetic energy of stuff send flying by explosion?

I may be wrong or simplify it too much, of course...

[hamishspence]

My guess is that if the K.E. of the projectile, combined with the material the projectile is made of, will result in the projectile disintegrating, then the effect of the impacting projectile will be a bit like an explosive.

A bullet doesn't explode on impact- because the velocity is low and the material is tough.

But if the kinetic energy of the "bullet" is high enough- it would disintegrate spectacularly on impact. As would the outer surface of the object it's colliding with.

[HenryHankovitch]

Isn't "explosive" energy kinetic energy (of violently expanding air) too anyway?

With some heat, and more kinetic energy of stuff send flying by explosion?

I may be wrong or simplify it too much, of course...

Technically speaking, an "explosion" is any reaction, chemical or mechanical, which produces a sudden and significant burst of energy. This energy can be kinetic, thermal, or electromagnetic, and is usually a combination of all three.

What we normally think of as "explosives" are simply chemicals which, when a chemical reaction is initiated, release an extremely large amount of energy. The damage is caused by direct heat from the reaction, plus the sudden outward force caused by the massive increase in pressure at the center of the reaction, and subsequent expansion. Simply speaking, explosions push matter (including air) away from them at high velocity. In munitions, the real damage is usually done by the fragmenting metal case which is deliberately placed around the explosive, and which subsequently turns into tiny pieces of metal flung about at high velocity.

You don't need a chemical reaction to have an explosion, however. The initial Chernobyl accident resulted in a "steam explosion," as the overheating reactor caused the coolant water to suddenly flash-vaporize, producing an explosive burst of expanding steam.

The outward burst of energy released by a kinetic energy impact can definitely be referred to as an explosion. A kinetic-energy weapon hitting its target is going to convert a massive amount of its kinetic energy to heat and sound; this will cause an explosive effect, if the energy is high enough. A medium-to-large meteorite hitting the Earth can be calculated to have the explosive energy of a large nuclear weapon.

[imp_fireball]

Yep, until your projectile reaches orbital velocity at sea level, which is the case at slightly above 7900 m/s (v=sqrt(g*r)) - which still gives you more than enough kinetic energy to play with, even with relatively light projectiles.
EDIT: FTR, the kinetic energy is then 31MJ per kg of projectile weight.
(all of this disregards air friction, which is a rather big factor at these speeds...)

So even if the projectile doesn't burn up, how will it do damage to a ship? Won't it just make a very tiny hole?

Should it be made to flatten upon the hull? Should it expand due to air resistance (chemically treated round)? Should it just lower velocity once it reaches a certain density in a way that it will bounce around the ship at very high speeds and impose a hazard (without simply perforating the ship)?

[Autolykos]

Should it be made to flatten upon the hull? Should it expand due to air resistance (chemically treated round)? Should it just lower velocity once it reaches a certain density in a way that it will bounce around the ship at very high speeds and impose a hazard (without simply perforating the ship)?

Like you probably just noticed yourself (or are very close to), this problem is very similar to how a proper pistol or rifle bullet should be designed: It should be just soft enough that it gives of most (or ideally all) of its energy inside the target. Since parts of the projectile will probably start melting from air friction, I don't think softness is something one should give too much concern. Depending on how much of the projectile is molten, this will either just cause it to flatten a little on impact, enlarging the entry and exit holes, or it could "weld" itself through the hull like a HEAT projectile (without needing a shaped charge for this trick).
(That's not facts, just hard speculation...)
Besides, you can't really compare the energy given off by a HE shell with the kinetic energy of a solid projectile, since the parts of the HE shell retain their (relatively) low total momentum, causing a lot of the energy to dissipate harmlessly into the air, creating an impressive but totally useless fireball (unless you manage to detonate the HE inside the target, bunker-buster style). OTOH, the solid projectile gives off all its energy concentrated in one point and working in one direction - that's why APFSDS is a lot better at penetrating armor than HEAT.

[Subotei]

Even if they could target and hit a railgun slug, I don't know that it would do any good. Laser ABM systems don't "burn" their targets, but rather the energy imparted by the high order lasing damages the target in a physical manner. For instance the ABL bursts the fuel tanks of a boost-phase liquid fueled rocket, or induces cracks in the propellant of a solid fueled one.

For a shell with a warhead, you might be able to cause it to detonate prematurely, but for a 100 kg slug, what can you damage?

Its possible that to protect against the slug all you'd have to do is spoil its aerodynamic properties in some way - feasible with the right laser. Quite small amounts of damage could be enough to destroy its accuracy by causing it to wobble, tumble etc.

[fusilier]

Supposed you could shot an iron bar over such distances. How would you handle shoting over the horizon? Supposed the gun is mounted 10m above the waterline and your target is as well, you would have a clear line of sight only for up to 30km (if I read this chart correctly). Conventional guns just shot in an arc and let gravity do the trick of bending the shells path. But at velocities to carry the projectile ten times and more that distance while still being effective, would gravity be enough to not shot over the target? If you shot it like a mortar, the impact would probably occur at merely terminal velocity and probably not very effective.

I think that ballistically speaking shooting at great ranges isn't that difficult -- there's tons of practical problems, but in WW1 the Germans had several "Paris Guns" which shelled Paris from over 70 miles away.

Terminal velocity is tricky, but for dense objects with some aerodynamic qualities it can be pretty high, so I don't think there are many worries there. However, I do see what Yora is getting at: If the object is propelled to very high speeds to avoid detection, it still has to travel slow enough to arc over the horizon and hit its target. I'm not entirely sure how significant of an issue this might be. One other thing to consider, is that shooting to extreme altitudes the projectile will encounter less air resistance. This means it can build up more speed in the upper atmosphere, and while it will be bleeding it off as it falls into the lower atmosphere it may still be above terminal velocity when it hits.

However, this is related to something that I think is being overlooked. Battleships can move and change direction of travel! :-) Early on in WW2 there were attempts to bomb battleships with high-altitude bombers that were typically disappointing for this very reason (battleships had plenty of time to react to the incoming bombs).

Prior to WW2 those paying attention started opting for main guns that had good range, accuracy, and short shell flight times. This gave the opponent ship less time to change course. The original 16" American guns failed at this. While they were accurate, and delivered a big shell, they lacked range and took sometime longer to hit their targets. It was starting to be recognized that it was more important to simply hit the target more often, then deliver a really big shell. Obviously there are limits: you can't go too small and still expect to puncture an enemy's battleship's armor. The Italian 15" guns were highly praised in this regard (accurate with short flight times), and the British at one point considered fitting a larger number of 14" guns rather than 16" guns on some of their battleships for this very reason.

The Americans realized this and extended the length of their 16" guns to compensate, but this resulted in decreased accuracy (for a variety of reasons).

See this website:
http://www.avalanchepress.com/Overrated.php
The information is spread out over a couple of linked articles, and starts with specifics about their board game pieces.

Anyway, artillery firing long range at a moving target has to be pre-planned, because once the shot is in the air there's nothing that can be done to correct its path. Now a large object with a potentially lower terminal velocity, dropping from great range, might be detected early enough that a battleship can take evasive maneuvers. Speed, accuracy, and rapidity of fire are important. If you're shooting at a moving target, you want to get it "straddled" as quickly as possible, then lay on the rapid fire. Once the enemy knows he's taking incoming fire he will attempt evasive maneuvers.

Really big projectiles are one shot weapons, you have to hit the target the first time or its pretty much over. Long range ballistic projectiles have to be very accurate, and undetectable. Otherwise the enemy will start evading.

[Galloglaich]

Interesting post, I didn't know a lot of that stuff.

One thing I would add though, a huge difference between modern and early / mid 20th Century artillery is that today munitions are usually guided, either by laser, gps, radar or etc. (US warships in WW II used radar-guided aiming for their gunnery, which helped them close the wide gap with the Japanese who had been winning most of the surface engasgements in the first half of the war... but that radar was based on the ship. Today it could be in the munition itself, in a drone, a satelite, etc.)

So maybe your railgun needs some kind of 'smart' munition to be really viable. But I think that is well within the capability of todays technology.

G.

[Joran]

A semi related tangent to the Battleship disscussion. Why is the Navy bothering to to spend so much developing a Railgun platform when existing cruise missiles have comparable range and are already proven?

Well, the Railgun is supposedly going to be replacing the 5" guns; Vertical Launch Tubes will almost assuredly remain part of design of ships for a long time, so it's in addition to cruise missiles rather than replacing them.

In the new DDX/DDG-1000 series destroyers, the U.S. Navy is moving towards having an integrated power system, so everything runs off of electricity, including the main propulsion engines. This also increases the overall amount of electrical power on the ship. In addition to what everyone else said, cheaper ammo, longer theoretical range, inert ammo, the new Navy ships should have plenty enough electricity to run a rail gun.

[Spiryt]

Ok, so i didn't know where to put it, so why not here at least:

Something I've seen on MyArmoury :

Take a look

And...

Spoiler

Show

It's not so easy to spot itat first, but it's damn MODEL. In 1:6 scale... Can you imagine making mail, even butted representation in 1;6 scale?

Simply amazing, and

It also look quite accurate to me, and to many guys at MyArmoury... What do you think?

[Matthew]

Very cool looking; best Action Man I have ever seen.

Next the guy has to build a 1:6 scale crossbow and shoot him with it!

[Brainfart]

It's butted mail, it wouldn't give accurate results.

[Maclav]

I couldn't even imagine the work involved in riveting 1/6th scale maille. OMG.

It's butted mail, it wouldn't give accurate results.

[Galloglaich]

Ok I'm going to be a complete and total hyppocrite here and tell the world, I've been watching Deadliest Warriors again and really enjoying it. Yes it's still completely worthless as an historical or academic information source, but it's just cool watching them blow up, slice, stab and smash stuff. I really enjoyed the Rajput warrior episode, first time I'd seen someone use a chakrum against a real target and it looked pretty friggen deadly slicing through that column of meat. The khanda was cool too even though the guy using it looked kind of clumsy with it.

I also enjoyed the Somali pirate episode, their advocate was a really good shot with an Ak hit three manequins in a moving skiff (albiet only 50 and 100 meters away which is pretty close for an assault rifle, but it was still cool...) As was the point blank hit with the mini-uzi by the Columbian guys, 9 rounds right in the head pretty horrific, I always wondered how those machine pistols worked, they seem damn lethal at close range.

The melee combat with the grapnel was pretty absurd and par for the course for this show... but man I wish I had some of those pig carcasses and ballistic gel dummies with skeletons embedded, it's just pure little boy fun destroying those things would be great for a 'test-cutting' party. I hope they have a little BBQ with all that pork when they are done with it.

Anyway there I outed myself I'm a fan of that retarded show in spite of everything that drives me crazy about it. I'm probably contributing to the dumbing down of humanity by watching it but hey, I'm a sucker for simulated violence i guess.

G.

[Mike_G]

I do enjoy the test cutting, blowing *** up part of the show.

It's like watching The A Team. It's not something you brag about, but it's fun.

[Hawriel]

I do enjoy the test cutting, blowing *** up part of the show.

It's like watching The A Team. It's not something you brag about, but it's fun.

I brag about watching the A-Team.

[Autolykos]

I brag about watching the A-Team.

You mean, like you can actually take a FULL EPISODE?
SCNR

[Karoht]

I just saw the A-Team movie last night. Total cheese, but well written and very fun movie. Highly recommended.

[Joran]

For those snipers out there.

I've been watching Top Shot, a show where marksmen (and one woman) compete in a variety of shooting competitions.

In one episode, they had a long range shooting competition. The guy firing the rifle said he needed to compensate for the wind. He could estimate about how fast the wind was moving based on a flag placed at the target.

How do real-life snipers compensate for wind? Use the surroundings (brush, trees) as a pseudo-wind gauge? Have a spotter tell them how off they are? Actually plant a flag at the target?

[Norsesmithy]

By judging mirage, mostly.

Get the focus of your spotting scope (or rifle scope, but spotting scope is better) dialed in for the target, and then back it off a touch, so it's focused on the air between you and the target. Assuming the sun is out (and not directly in your face or at your back), you can see how the wind affects the convection currents in the air between you and the target, and this allows for rough wind estimation.

If you can't resolve the mirage, you can judge the wind based on other factors, but they are generally less accurate than mirage is.

[Johel]

Context :
For a simulation game, each player has to design a nation, taking into account all aspects (politics, security, economy, health, education, justice, transportation, demography, culture, diplomacy...).

I've covered most aspects and I'm down to the military part. Given the cost of acquiring and operating 4th and 5th generation aircrafts, I'm considering a air strike and air defense mainly based on small boats, trucks, infiltration teams and ballistic missiles.

Question :
With ground support for guidance and intelligence, can ballistic missiles currently replace fighter aircrafts (4th and 5th generations) ?
As an offensive weapon (ex : to support an invasion or do tactical strikes)
As a defensive weapon (ex : to provide anti-aircraft defense or to repel a ground invasion).
Please consider the following aspects :

• Capital Cost
• Maintenance Cost
• Manpower requirements
• Infrastructure requirements
• Flexibility
• Firepower (with conventional weapons)

Thank you

[Yora]

I'm not an expert on these, but I'm pretty sure ballistic missiles can not replace tactical bombers.
I think more often than not, you need a rather small missile or bomb and rarely have to get out the big ones. Smaller missiles just don't have the reach, so you need an aircraft to get them into firing range. A single aircraft can transport several missiles and can be reloaded with new missiles almost infinitely often. A ballistic missile is gone once it strikes. Maintaining a small fleet of tactical fighter-bombers would probably much cheaper.

And somehow you have to get the missile into the target. And I think in tactical situations, it's always much better to have a pilot do the targeting on site, than doing it remotely in a command center hundreds of milles away. If it is even possible at all to target a moving tank without having line of sight.

[Norsesmithy]

The other problem posed by using ballistic missiles in place of bombers is that an ally, enemy, or unaligned nation cannot tell whether a ballistic missile carries a conventional warhead or a nuclear warhead, until it hits.

And that makes people nervous and prone to aggressive action.