Μilitary Questions & Answers

That is the basis of an ion engine, where material is ionised (ie strip off electrons to give the material a magnetic charge and then accelerate them in a magnetic field in a loop to very very high speed and then direct it out the rear of the engine to produce thrust.

Mostly useful in space as the amount of material going through the engine is tiny but its enormous velocity can still provide effective thrust.

Compared with a chemical rocket it produces a tiny amount of force, but its advantage is that it could be run for months rather than minutes or seconds for a chemical rocket.

Also because the exhaust velocity is enormous the potential top speed is vastly higher... but takes weeks to achieve...

No good for aircraft, but fantastic for space craft in orbit or long range missions.

The main problems heating material to the temperature of a plasma is that it will melt most materials engines are made of. Of course using ceramic materials that can sustain high temperatures and still retain strength is one solution but also using magnetic fields to keep the plasma from touching the lining or components of the engine would be another idea.

Of course the whole purpose of high temperature is high speed and volume of air flow through the engine. A scramjet allows supersonic flow through the engine and has no theoretical upper speed limit in the air... so it could operate as a jet engine on the runway and then use bypass air as a scramjet from about mach 2 up to orbital speed. It would use air from the atmosphere while flying inside the atmosphere so it would need to just carry fuel for operating inside the atmosphere, but if you went into space then a supply of oxygen to burn with the fuel could mean use of the engines from stationary on the runway, to scramjet in the air and fuel and o2 in space...

EM technology will likely advance and allow better control of exhaust and also allow different materials to be used.

Of course an anti grav system would be the best... a huge ship that has no weight (weight is mass times gravity...) if you can counter gravity then you can accelerate your craft easily to any speed you want... You can also counter the effects of acceleration like the do in spaceships depicted in hollywood movies and TV shows.

Accelerating from zero to light speed like they do in Star Trek would crush the crew and the contents of the ship to a pulp.

We really don't know how gravity actually works right now... is it a beam or is it a field...

Information I know about black holes suggests it is a field emitted by particles with mass but that obey the laws of this universe... ie cannot exceed the speed of light.

Just a brief summary... a black hole is actually a point of infinite gravity where normal matter is crushed out of existence.

That means for any given time the actual matter mass of a black hole is close to zero, but because the mass "field" created by matter cannot exceed the speed of light once matter crosses the event horizon the field assumes the matter is still there and so continues to effect other matter as if the matter is still there.

In actual fact the actual matter moves past the event horizon and eventually meets the point of infinite mass... the singularity where it is totally destroyed... crushed out of this universe.

As matter passes the event horizon the "mass field" of the black hole gets bigger but the actual mass eventually returns to zero when the matter is destroyed.

The fact that the gravity continues as if all the mass that entered the black hole is still there suggests that gravity is a field but a field that cannot exceed the speed of light.

Yes... I know it is weird...

If you could generate a gravity field or even reverse it then propulsion could simply by gravity field... counter the gravity of the earth and the gravity of the moon and the Sun will help you take off... not just counter the gravity of the earth but repel it and you can take off with only air resistance to worry about.

There are very few places in this universe with no gravitational fields as the gravitational field of all matter extends infinitely... though it is dramatically effected by distances so the gravity of the earth that is closest to you effects you rather more than the gravity of the dirt on the other side of the earth.

If you compress the earth to the size of a small coin all of that mass acting together would create a small black hole. By spreading the mass of the earth to the size of the earth it is much less powerful... but fortunately powerful enough to hold a breathable atmosphere...

That is just creating artificial gravity through inertia.

Gravity is simply acceleration of matter towards mass... it can be simulated in a large ring by spinning that ring at a rate where the physical vector change feels like gravity... think of a rock being swung around your head on a string... if the string breaks the stone will travel in a straight line but while the string remains holding the stone the stone continues to orbit around you being constantly pulled off a straight course into an orbital course by the string... replace the string with a ring and spin the ring... once you get up to a certain speed things on the inside of the ring will remain against the inside the ring...

OK... lets take this step by step...

The old IR guided missiles used to be tail chase weapons... basically the IR sensor in the nose detected heat sources and looked forward... you had a big circle in your HUD and you turned your aircraft so that the enemy aircraft was within that fixed circle which represented the field of view of your missile on your wing...

Once the target was inside the circle you got a hum to tell you how strong the lock was... once it was strong enough you fired the missile and then were free to manouver.

A strong lock meant the seeker could see a hot part of the target... once fired the missile turned and flew directly at the target... it didn't need to know where the target was going or how far away it was... they had short range sensors so if it got a lock it was probably in range.

Of course the missile flying directly at the target means that when the missile got there the target will have moved... as the target moved the missile would tail chase and its superior speed above the speed of the target means it will catch up and hit the target... but if fired from behind the hottest thing it could see was the engine so most of the time it tail chased in went up the tail pipe.

Improved missiles used a superior seeker design... instead of putting the target in the centre of the view and flying directly at it... it would fly straight with the seeker following the target... that generates changes in the angle of the target seeking camera... from this information the missile can turn in the direction the target is moving to lead the target so that the missile is flying where the target is going to be.

Very simply if you look at a target and you adapt the movement of the vehicle you are in so that you don't need to move the camera to follow the target.... it remains in one place in your field of view... not moving up or down or left or right, but your vehicle is getting closer and close to the target then eventually you will either hit the target or you will run out of fuel.

By flying on an angle to stop the target moving in your field of view rather than just flying directly at it you are matching courses but you are getting closer and closer... so you will hit the body of the target and not tail chase.

You just work on information about the angle of the target to the missile... it does not even need a moving IR camera... the position of the target in the field of view is enough to intercept without knowing the speed or direction of the target.

It does mean it is down to the pilot to ensure you don't fire at too great a range... an SR-71 flying at mach 3 you could hit head on, but if you are behind it there are not many IR missiles that will be able to chase it down before it gets out of range for instance.

Obviously the same method applies to a manouvering target it is just harder with more course changes... the process is still very simple.

Thanks, Garry. I suspected it would be something to do with the seeker angle relative to the missile, or the target angle relative to the seeker. Either/Or.
Though, for future reference, don't feel the need to define something from the ground-up; not with me at least, unless I mention otherwise. Might save you some time, and me some reading. For instance, paragraphs 6-9 are all I was after. The rest I either already knew, or could have reasoned out.

I don't think you are an idiot but it makes no sense explaining some bits and not others when I really didn't know what you knew and what you didn't.

I didn't just explain it for you either... I am sure there are plenty of people who didn't really think about and work out how they worked or perhaps made some false assumptions...

We've established how an IR missile is able to fly a pseudo-predictive route, and we know the same for a Radar guided missile (both SARH and ARH), but how do the two compare?

Well first of all there are old IR seeking missiles... newer ones.... and brand new state of the art ones.

For the very old missiles they just saw hot points and generally guided on the hottest thing they could see. Flares or the sun became decoys so the guidance logic often improved the design and logic of the seeker to go for the not so hot targets... which led to flares of different intensities released in groups.

UV filters were also used to tell the difference between the sun and flares which give off UV rays and aircraft surfaces which don't.

Finally new state of the art IR sensors use imaging seekers like thermal cameras that can actually see images and they pretty much become all weather day night TV guided missiles where you can select a part of the target to aim for...

The middle missiles were getting more sophisticated and after working out the direction of travel aimed slightly ahead of the hot point... meaning they hit the body of the aircraft instead of its tail pipe... making the warhead much more effective in destroying the aircraft.

Radar guided missiles generally have a larger warhead and a proximity fuse but generally go for the radar centre of the target... which is pretty much the best place to hit it, so aiming off is not really useful for them.

They use different inputs to determine their flight path, yet I wonder if one is more efficient than the other. The obvious go-to would be the radar guided, due to the information their guidance is based on.

Actually a disagree... radar is active and warns the enemy it is under attack... it also generates a signal that can be jammed or targeted itself.

It is perfectly possible to have rather small missiles... perhaps MANPADS size with a passive radar homing head... an ARM or anti radiation missile... that could be launched at the last second to shoot down in incoming AAM like Meteor or AMRAAM or R-77.

The new short range IIR guided missiles the Russians are supposed to be working on also have an anti missile function... as an AAM for fighters and bombers... as a short range defence missile for the Army and a CIWS missile for the navy... using datalinks to attack targets in a lock on after launch mode all completely passively.

Yet, the professional consensus over the last half century has been that radar missile seekers are appallingly reliable, while IR seekers are perceived as somewhat more consistent. One could assume, however, that this was directly related to the fact that one is an active seeker and the other passive; and so in one case, the would-be target has the option to manoeuvre, and in the other, they would not(most of the time).

This opinion is dirtied by the fact that IR guided weapons are generally short ranged and the most effective ones are generally fired from fairly close range from behind the target, while radar guided missiles are generally fired from greater ranges and their guidance alerts the target it is under attack.

Missiles move very quickly but have very small control surfaces so their ability to manouver is not that good... older missiles don't have good fields of view so once it blows past a target it wont swing around and reacquire them like in bad american movies.

It is the old story... you will most likely be killed in war by the bullet you never see coming...

Long story short:
Of Radar and IR seeking missiles, which would respond better to a manoeuvring target such as a jet? Would it be range specific? Would it be a negligible difference?

With modern IIR guidance you could use datalinks and lock on after launch for both missile types... the IIR missile would be passive but both would have an IR signature that would alert the target to the threat... except against third world countries.

Nothing is guaranteed a kill.

A mix of as many types would offer a pilot the best range of options for a kill.

For this it would be interesting to dig up info on missile statistics and whatever public domain info there is floating about.

The problem is that there is next to no information on the performance of Soviet and Russian T model missiles in real combat.

Export model Soviet fighters that had IR guided missiles were exported with Sidewinder based missiles... ie the MiG-23s had R-3S rather than R-23R and R-23T missiles let alone R-24R and R-24T.

The MiG-31 continues to use R-40TD missiles and for targets like the SR-71 in a head on interception they should be ideal... fast missile... big warhead... easy straight flying target...

The general consensus AFAIK is that the R-60MK is a good missile but not as good as late model Sidewinders... more a self defence missile.

The R-73 is better than late model Sidewinders in terms of range and manouver performance and seeker sensitivity.

Only the very late model AIM-9X with its IIR array seeker has a better sensor, but it really needs a helmet mounted site to make use of it high offboresight capabilities... something left off the F-22s to save money.

The R-73... even the first models had better flight performance.

This has been discussed before...

There are some rounds designed to defeat armour using HE force... the British in particular love the HESH or high explosive squash head rounds... the kill mechanism is basically consider the round to be a big blob of HE with a tail mounted fuse.

You fire at the target... muzzle velocity is not important in this case.

The round impacts the armour plate and flattens out creating as big a surface area as possible and then the tail fuse detonates the HE causing shock waves to move through the armour. The kill mechanism is for the shock waves to make small metal flakes on the inside face of the armour to detach and be thrown around inside the turret... these flakes are better known as spall.

If an armour piercing round comes to within 10-20% of penetrating armour it can often generate spall too which is lethal to crew even though the armour is not actually penetrated.

Anti spall linings reduce or eliminate the effectiveness... which can be as simple as a few layers of Kevlar cloth inside the armour to catch the spall and stop it killing or injuring the crew.

What really killed the ammo in anti armour use is that most modern armours have layers and often include a spaced armour with pockets of empty space where shockwaves don't pass very efficiently.

I remember during desert storm the UK media was over the moon when one of their warrior IFVs survived a hit by a main tank gun round... wow... super IFV armour. Except it turned out that it was a HESH round that hit externally mounted add on armour, so of course it would not be effective.

The ammo is still useful against soft targets or buildings or bunkers... but time delayed HE rounds would be more effective exploding inside the target rather than on the outer surface.

For blowing down a wall to make an entrance way it is good if a bit excessive. (note when assaulting a fortified town don't use existing doors or windows because they are likely already booby trapped... make your own doorway...)

Anyway... standard modern artillery shells don't deform and flatten and then explode like HESH so they would not be very effective in that role, and of course with modern armours such attempts to kill the crew are not so effective anyway due to spaced armour, ERA and other add on armour types that create a space between the outer armour and main armour, and anti spall liners.

Of course if HE didn't kill tanks then how could aircraft kill tanks?

Most rockets were inaccurate and most cannon not powerful enough during WWII to be super effective in the anti armour role.

The 152mm guns used by the Soviet Union in the anti armour role were described as not powerful enough to penetrate but could knock the turret off smaller tanks and damage heavier ones to remove them from combat.

Abrams tanks have been knocked out with IEDs as small as 50kgs and a 155mm HE shell is in the 40-50kg payload range.

Most modern tanks would be safe from near impacts, but a direct hit would smash optics and shred tracks and might destroy critical components like engine or crew.

It is hard to say... I would think that a guided 152mm HE shell landing on a NATO tank would kill it, or render it useless.

I would have to say a 203mm or 240mm HE shell (110kg or 130kg) should do the job with a direct hit too.

The problem is that direct hits only happen with guided rounds.

Back in the 1990s there was a lot of talk about very high velocity anti tank missiles... related to the SA-19 two stage missile, where the main rocket motor accelerated the missile to about 1.2km/s... and presumably the missile itself would be another rocket motor that accelerated the missile to much higher speeds for the terminal effect required.

It didn't really amount to much, but solid rocket fuel has limitations, whereas scramjet motors can be made rather small and would be rather interesting.

Certainly if you can get the velocity up high enough you can actually save money by using cheaper materials for the penetrator which would make them rather more viable weapons too.

Of course there is the self forging fragments, which are low velocity weapons that detonate a HE charge about 50m from the target, where the explosion is focused and is designed to reform a flat disc of material into a penetrator moving at 3km/s or so. It is not super effective because the shape created is not usually pointed and looks more like a shuttle cock used in badminton... if it had a sharp point it would penetrate much better... but is still pretty useful... mainly for top attack use against the thin top armour of vehicles.

Also don't rule out APFSDS rounds... even in the 1960s there were designs of APFSDS rounds that had ramjets fitted to them to retain speed on the way to the target... having a scramjet would vastly improve performance and make it much more practical...

My understanding is that 3km/s is the balance point... if you chart penetration being the result of velocity and mass of the penetrator, you generally get the best improvements in penetration when increasing velocity. Once you get above 3km/s however the benefits of increasing velocity don't increase very much but the energy required to get higher speed increases. This suggests that rather than putting more energy into the projectile to get even higher speeds it is much more efficient to make the projectile heavier... which normally means longer as wider increases drag and increases speed loss per second.

Against armour the concentration of energy is critical, but of course a 15kgs of most materials you could accelerate to 3km/s would be devastating... even a 4kg tungsten shell with 11kgs of chocolate blamanche inside would be devastating at 3km/s... at such speeds and energies even solids act like fluids anyway... lead is a very soft metal but it is used inside harder metal jackets to allow the bullets to have high densities and therefore higher momentum to move through the air more efficiently and to have more effect on target.

Very high velocity very light bullets are effective on light targets.... the light targets almost explode... but against heavier animals they tend to break up and often lack penetration.

At point blank range a subsonic .22lr lead projectile is comparable to 50 cal Browning ammo when fired into water... in fact the .22 ammo might be more lethal as the enormous energy of the 50 cal round will probably shatter the projectile on impact with the water, while the .22 round might actually injure you over a distance of a few metres.


New EM gun technology will likely lead to smaller calibres and much higher velocities too.