Thread: Artillery guns on satellites?

I'm a grade 11 student in high school, and just started my physics course.
Newton thought of a cannon on top of a mountain that, when fired with sufficient power, a cannon ball would achieve orbit.
The scary thing is... if there was artillery on a orbiting satellite, it could hit ANYWHERE on earth.
:S

A ballistic missile can do that. The payload of something launched from an orbiting satellite would be somewhat more limited, I would think.

An "artillery cannon" would knock the satellite out of its orbit. Newton, again, with that silly law of his.

For it to work, the "artillery" would have to be designed such that the release of the shell was with low energy. Perhaps a rocket assist on the shell itself. Then the artillery shell would need it's own guidance system since it's carrying its own propellant. At this point, it becomes a missile rather than an artillery shell.

This missile will now have to be shielded for re-entry and there would need to be a sufficient number of them in order to be effective. Eventually, the mass of the "artillery"-now-missile system becomes an economic issue, requiring some drastic re-thought. Wouldn't it simply be more effective and economic to launch a rocket that contains multiple warheads that split off from the original vehicle each with its own target after achieving orbit?

Heh, never thought about that stuff, shows what the heck I know :P Love this forum.
With such a weapon, I don't think it needs to be fired as much as dropped out of the satellite, with its own propulsion system. Ideally, it would be some form of explosive encased in a material that would allow it to survive re-entry, and just a small propulsion system to guide it towards the intended target.
Maybe you don't even need an explosive; just a very dense mass.
Was thinking instead of firing an explosive, just fire a mass. If this mass could survive re-entry of the atmosphere without burning up, and staying in tact (not sure what material could do that ) the amounts of acceleration from gravity would give it near unprecedented piercing capabilities. (hehe, using big words...)
The idea is to use gravity to give the mass its damage. So far in physics, we've learned the formula for velocity. For this, velocity 2 squared = velocity one squared + (2 x acceleration) (distance)
Saying you dropped the mass from a height of the atmosphere (I havn't been taught about air resistance yet, so this answer could be really off). Actually, I don't know how to calculate this XD cause I suppose gravity would be less the farther an object is from the center of the earth...
Anyways, I"m guessing, its a REALLY REALLY big number. It would pretty much be the force a asteroid hits the ground at, since the material doesn't burn up on re-entry.
?

Originally Posted by TPhaoimnaes

Maybe you don't even need an explosive; just a very dense mass.
Was thinking instead of firing an explosive, just fire a mass. If this mass could survive re-entry of the atmosphere without burning up, and staying in tact (not sure what material could do that ) the amounts of acceleration from gravity would give it near unprecedented piercing capabilities. (hehe, using big words...)
The idea is to use gravity to give the mass its damage. So far in physics, we've learned the formula for velocity. For this, velocity 2 squared = velocity one squared + (2 x acceleration) (distance)
Saying you dropped the mass from a height of the atmosphere (I havn't been taught about air resistance yet, so this answer could be really off). Actually, I don't know how to calculate this XD cause I suppose gravity would be less the farther an object is from the center of the earth...
Anyways, I"m guessing, its a REALLY REALLY big number. It would pretty much be the force a asteroid hits the ground at, since the material doesn't burn up on re-entry.
?

Yeah. If you drop a large enough mass out of orbit with sufficient heat shielding, it might even do damage comparable to a nuclear bomb (without all that nasty radiation. ) This is one reason I worry a bit about the prospect of a Moon colony.

Right now, getting a heavy mass into orbit is quite expensive. Enough so that I doubt anyone would seriously try and use that as an offensive strategy. However, if we had a city set up on the Moon, getting heavy objects from the surface of the Moon into Earth orbit would be much less difficult. If our Moon colony went to war with us, they could just throw rocks and wipe us out.

You are on the brink of reinventing the Rods from God.

Originally Posted by TPhaoimnaes

With such a weapon, I don't think it needs to be fired as much as dropped out of the satellite, with its own propulsion system.

If you just "drop" it, it continues in the same orbit. You have to decelerate it by burning fuel.

The idea is to use gravity to give the mass its damage. So far in physics, we've learned the formula for velocity. For this, velocity 2 squared = velocity one squared + (2 x acceleration) (distance)
Saying you dropped the mass from a height of the atmosphere (I havn't been taught about air resistance yet, so this answer could be really off). Actually, I don't know how to calculate this XD cause I suppose gravity would be less the farther an object is from the center of the earth...
Anyways, I"m guessing, its a REALLY REALLY big number. It would pretty much be the force a asteroid hits the ground at, since the material doesn't burn up on re-entry.
?

It would be no more energy than it took to put it into orbit in the first place. Actually quite a bit less because of inefficiencies. Does a ballistic missile cause much damage when it crashes into the earth?

The short answer here is that artillery on a satellite could hit anywhere on earth, given the proper orbital parameters.

Basically, an orbiting satellite has already performed the powered portion of a ballistic missile’s flight. An onboard “projectile” can receive a delta velocity imparted by the satellite to give it a trajectory causing it to land pretty much anywhere on earth. Of course, in order to survive, the projectile would need a protective coating as with current re-entry vehicles. An onboard guidance and propulsion system would improve its accuracy.

As to kinetic/penetration energy and damage capabilities, re-entry through the atmosphere tends to rob small re-entry vehicles (and meteoroids) of much of their kinetic energy and/or mass. I’d guess an impact kinetic energy approximately equal to or less than similar terrestrial cannon fire. It’s a matter of mass (ie, volume) versus drag (ie, cross-sectional area); that is, r³ versus r². For example, a 1×1×1 cube has one cube pushing through one square of air (mass/drag = 1/1 = 1); a 2×2×2 cube has eight cubes pushing through four squares of air (mass/drag = 8/4 = 2), and a 3×3×3 cube has 27 cubes pushing through nine squares of air (mass/drag = 27/9 = 3). So, more massive objects have a greater mass to resist the drag and more mass to survive the ablation of material, thus more mass and at a greater velocity at impact.

Awesome guys
Wish I could have these discussions in class, but nobody really likes science in my classes

Originally Posted by Harold14370

Originally Posted by TPhaoimnaes

With such a weapon, I don't think it needs to be fired as much as dropped out of the satellite, with its own propulsion system.

If you just "drop" it, it continues in the same orbit. You have to decelerate it by burning fuel.

You just have to plot a course that will land it inside the atmosphere, and then the atmosphere will handle the decelerating part.

The idea is to use gravity to give the mass its damage. So far in physics, we've learned the formula for velocity. For this, velocity 2 squared = velocity one squared + (2 x acceleration) (distance)
Saying you dropped the mass from a height of the atmosphere (I havn't been taught about air resistance yet, so this answer could be really off). Actually, I don't know how to calculate this XD cause I suppose gravity would be less the farther an object is from the center of the earth...
Anyways, I"m guessing, its a REALLY REALLY big number. It would pretty much be the force a asteroid hits the ground at, since the material doesn't burn up on re-entry.
?

It would be no more energy than it took to put it into orbit in the first place. Actually quite a bit less because of inefficiencies. Does a ballistic missile cause much damage when it crashes into the earth?

It's true that it's less energy total than what it took to get it up there, but you have to consider that all that energy is being delivered instantaneously at the moment of impact. Getting it up there would have involved a much slower acceleration than that.

As for ICBM's, I don't know what their impacts are like. I'm pretty sure only the tip that contains the warhead itself is left by that point in the trip.

This quote from wiki is interesting:

While the warheads of theater ballistic missiles are often conventional, ICBMs are nearly inseparable from their connection with nuclear warheads. 'Nuclear ICBM' is seen as a redundant term. Strategic planning avoids the concept of a conventionally tipped ICBM, mainly because any ICBM launch threatens many countries and they are expected to react under a worst-case assumption that it is a nuclear attack. This threat of ICBMs to deliver such a lethal blow so rapidly to targets across the globe has resulted in the interesting fact that there has never been any end-to-end test of a nuclear-armed ICBM.

http://en.wikipedia.org/wiki/ICBM

So, who knows what happens?

Now, if you launched it from the Moon, it would have a great deal more energy than if you launch it from low Earth orbit. That would be interesting.

Originally Posted by Leszek Luchowski

You are on the brink of reinventing the Rods from God.

That is a great article. Thanks for posting it.

I like the idea of a nuclear-level deterrent that isn't actually nuclear, so it doesn't leave radio-active waste all over the place. That makes it so, if someone ever did use a nuclear weapon, we could retaliate without destroying the environment. Of course millions would still die, but humanity itself might survive.

I hope nobody will ever do this, but I look at it the same way as a person driving in a car with their seat belt on. Naturally I hope not to crash my car, but if I do crash I like knowing we might not be wiped out.

It wouldn't be like a nuclear weapon in most respects; the kinetic energy just isn't there. It would be very good for penetrating the ground to destroy buried bunkers and whatnot, and would probably be very useful for destroying ships, aircraft carriers, etc. But you couldn't destroy a city with it like you could a nuclear weapon.

Originally Posted by kojax

You just have to plot a course that will land it inside the atmosphere, and then the atmosphere will handle the decelerating part.

I think it would be done by putting the weapon in a highly elliptical orbit, and then when you want to "fire" it you modify its orbit so that the ellipse now intersects the ground. So the projective isn't really slowing down much at all, it's just impacting the ground at near orbital velocity. You would want to design the projectile so that it slowed down as little as possible in the atmosphere, because it's basically diving directly at the target already and any loss of velocity will only make it do less damage. If the orbit was highly elliptical and had a very high apogee, it would take relatively little change in velocity to modify it so that the weapon's orbital path intersected the earth's surface. 500 kg of tungsten hitting an aircraft carrier at mach 20+ probably equals a dead carrier.

How about a satellite mounted railgun. Seven times the speed of sound has got a to make a pretty huge crater. Again though, the recoil would knock the staellite out of a stable orbit.

Because details of nuclear weaponry (and, thus, intercontinental ballistic flight) tend to be classified, let's look at meteroid data concerning re-entry through the Earth's atmosphere for some approximations for weaponry.

Consider the meteoroid impact information from the University of Tennessee (I have underlined for emphasis):

The average velocity of meteoroids entering our atmosphere is 10-70 km/second. The smaller ones that survive the trip to the Earth's surface are quickly slowed by atmospheric friction to speeds of a few hundred kilometers per hour, and so hit the Earth with no more speed than if they had been dropped from a tall building. For meteorites larger than a few hundred tons (which fortunately are quite rare), atmospheric friction has little effect on the velocity and they hit the Earth with the enormous speeds characteristic of their entry into our atmosphere. Thus, for example, it is estimated that the meteorite that produced the Barringer Crater was still travelling at 11 km/second when it struck what is now the Arizona desert 49,000 years ago. Such objects do enormous damage, because the kinetic energy carried by the meteorite is the product of the mass and the square of the velocity.

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Originally Posted by jrmonroe

Because details of nuclear weaponry (and, thus, intercontinental ballistic flight) tend to be classified, let's look at meteroid data concerning re-entry through the Earth's atmosphere for some approximations for weaponry.

Consider the meteoroid impact information from the University of Tennessee (I have underlined for emphasis):

The average velocity of meteoroids entering our atmosphere is 10-70 km/second. The smaller ones that survive the trip to the Earth's surface are quickly slowed by atmospheric friction to speeds of a few hundred kilometers per hour, and so hit the Earth with no more speed than if they had been dropped from a tall building. For meteorites larger than a few hundred tons (which fortunately are quite rare), atmospheric friction has little effect on the velocity and they hit the Earth with the enormous speeds characteristic of their entry into our atmosphere. Thus, for example, it is estimated that the meteorite that produced the Barringer Crater was still travelling at 11 km/second when it struck what is now the Arizona desert 49,000 years ago. Such objects do enormous damage, because the kinetic energy carried by the meteorite is the product of the mass and the square of the velocity.

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A roundish meteoroid will have very different aerodynamic properties than a pointy metal dart. ICBM warheads supposedly strike at up to 4 km/sec, and I don't think they're actually going at orbital velocities to begin with.

meteoroids entering our atmosphere is 10-70 km/second.

The result of the combined vector of Earth's orbit around the sun (~30km/s) and the orbit of the meteoroid (or it's source comet, asteroid etc) around the sun.

Why would you spend hundreds of millions of $$$ to put a pop gun in space?

satelite idea wouldn't be done because of how expensive it is to get everything up there, it's far more efficient to use a really big conventional bomb such as the delayed detonation MOAB.

however, if there is a moon colony it would be much more cost effective to mine and deploy the "rods from god"

the tactical benifit of the strategy is that it can penetrate deep into the earth and destroy tactical targets with little collateral damage.

The most ideal design of an dropped tungsten-kinetic "bomb" would be shaped as a water droplet. This is the most fortunate design in aerodynamics. (except from the dart,of course..)

Wouldnt it be more economically bearing to mount a hellishly powerful railgun on the moon or somewhere the gravity is in favor, and the recoil dosent do much?
Where its already ammo available..?

Originally Posted by hardraade

Wouldnt it be more economically bearing to mount a hellishly powerful railgun on the moon or somewhere the gravity is in favor, and the recoil dosent do much? Where its already ammo available..?

Building a huge rail gun on the moon would probably be very expensive, and require all sorts of new space ships, etc. On the other hand, we could send a cluster of tungsten darts into earth orbit and drop them drop them on people we didn't like with existing launch vehicles, for no more than the cost of the rocket+satellite.

Also, if the rail gun was on the moon it would take a long time for the projectiles to reach their targets on earth. The would probably be a problem for all sorts of reasons. Not the least of which being that your target might move before your shot reaches it, especially if you're shooting at something like an aircraft carrier.

A laser would be better, like on the new Crysis 2, its very possible and if we did need the use of a sort of ground assist type thing we could make one right now
Idk if it would be visible though... scary

Originally Posted by Scifor Refugee

Originally Posted by jrmonroe

Because details of nuclear weaponry (and, thus, intercontinental ballistic flight) tend to be classified, let's look at meteroid data concerning re-entry through the Earth's atmosphere for some approximations for weaponry.

Consider the meteoroid impact information from the University of Tennessee (I have underlined for emphasis):

The average velocity of meteoroids entering our atmosphere is 10-70 km/second. The smaller ones that survive the trip to the Earth's surface are quickly slowed by atmospheric friction to speeds of a few hundred kilometers per hour, and so hit the Earth with no more speed than if they had been dropped from a tall building. For meteorites larger than a few hundred tons (which fortunately are quite rare), atmospheric friction has little effect on the velocity and they hit the Earth with the enormous speeds characteristic of their entry into our atmosphere. Thus, for example, it is estimated that the meteorite that produced the Barringer Crater was still travelling at 11 km/second when it struck what is now the Arizona desert 49,000 years ago. Such objects do enormous damage, because the kinetic energy carried by the meteorite is the product of the mass and the square of the velocity.

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A roundish meteoroid will have very different aerodynamic properties than a pointy metal dart. ICBM warheads supposedly strike at up to 4 km/sec, and I don't think they're actually going at orbital velocities to begin with.

The only way to get a pointy metal dart to work is to make it spin at a gyroscopic speed. Otherwise it's apt to turn sideways in the air. And the easiest way to get it to spin at a gyroscopic speed would be to fire it initially out of a rifled cannon. But..... that would require us to put a cannon in space.


And, the problem with firing things from a cannon (especially one located on the Moon) is that then the enemy knows there are certain times of the day when you can't shoot them because the cannon in on the wrong side of the planet. Well....unless it's in geosynchronous orbit - which would be both awesome and a whole new world of expensiveness.

If you do the algebra you can work out the striking velocity of a mk84 bomb filled with cement that exceeds the energy release of a normal mk84 filled with tritonal impacting at an equal velocity. (Clue - cement is denser than the HE.) FWIF - my brother-in-law aided in the drop-testing of the T12 43000# conventional bomb. He told me it left a crater in the dry lake bed 125' wide by 90' deep despie having no HE aboard. (see Google for a T12 picture.)

The British TallBoy and Grand Slam bombs exceeded M1.0 in their fall. They both had canted tail fins for rotational stability.

any country with the ability to place any type of military ballistic system into orbit, already has a ballistic system capable of reaching out & touching someone anywhere on the globe. It would just be a waste of money

Originally Posted by WaltBJ

The British TallBoy and Grand Slam bombs exceeded M1.0 in their fall.

No they didn't.
Grand Slam would reach near-supersonic speed, approaching 1,049 ft/s (320 m/s), 715 mph (1150 km/h)

Supersonic terminal velocities may have been achieved IF the bombs were dropped from 40,000 feet.
The Lancaster could reach just over 20,000.

They both had canted tail fins for rotational stability.

Which was an accuracy issue, not a speed issue.

I think that launching a missile from a satellite would have the disadvantage that the missile would have a very poor terminal maneuvrability to hit the target from the desired angle.

Missiles launched from the ground or air often maneuver to hit.

However, a laser mounted on a low altitude satellite would perhaps be able to destroy or damage unarmored targets like aircraft on tarmacs.

There is talk that the F-35 may be upgraded with a 100kW laser some time in the future, although the range will probably be rather short, but that kind of laser technology may not be far.

Originally Posted by Nic321

However, a laser mounted on a low altitude satellite would perhaps be able to destroy or damage unarmored targets like aircraft on tarmacs.

The problem with a laser on a satellite (even one at low altitude) is that, currently, lasers lose about 1/3 of their power per mile of atmosphere traversed ¹.
Thus, the satellite will be firing into the worst possible case: the targets will always be line of sight but at the same time they're always a fixed distance away under an increasingly denser atmosphere the further away from the firing point you get.


1 I admit I haven't kept up (due to financial constraints) with the latest published figures ² so this may have changed, but that was the conclusion of joint US/ German tests of FELs (free electron lasers) some years ago.
2 Such figures are rarely published directly anyway: you have to read numerous reports and piece the information together.

Also, a laser will not have "pinpoint" accuracy after traversing through the atmosphere. No matter how tightly focused you make the beam, simple physics will tell you the light beam will become scattered as it passes through the medium.

I really cannot say how much scattering will occur without running the calculations (something I dont feel like bothering with right now) but I would assume somewhere between 10-50ft radius, possibly more.

Bombs dropped from aircraft are at aircraft velocity and they then gain more velocity during the fall. Falling at 1 G from 20000 (in a vacuum) yields 1131 fps. Add say 350 fps then subtract drag . . .


By the by shooting straight down with a laser the loss due to the atmosphere is almost exactly the same as shooting 7 miles horizontally at sea level. On top of Everest or in a jet aircraft at 35000 you are toast . . .
.

The F35's laser would be ideal for air combat - longer range than a gun and no lead required. Very simple sight, too. And all-aspect attacks. Buck Rogers lives!&

It's highly unlikely that the over-priced PoS F-35 will ever carry a laser as a weapon.
Given the size/ weight of current lasers (especially the generating gear) and the lack of internal volume in the F-35 (and all other fighters) any laser mounted on such aircraft will be of considerably less use in combat when compared to a gun or missile.
What counts at the target is delivered energy.
A laser won't cut it.

Originally Posted by Dywyddyr

It's highly unlikely that the over-priced PoS F-35 will ever carry a laser as a weapon.
Given the size/ weight of current lasers (especially the generating gear) and the lack of internal volume in the F-35 (and all other fighters) any laser mounted on such aircraft will be of considerably less use in combat when compared to a gun or missile.
What counts at the target is delivered energy.
A laser won't cut it.

I wonder how many times over the funds for this unnecessary craft could be used to pay off everyone's student loan debts in the states.

More of a waste when you consider that the equipment is expensive, extremely fragile, dangerous to be around, and a logistical nightmare. My 2 cents.

Originally Posted by Dywyddyr

A laser won't cut it.

I see what you did there, very bright of you

The laser proposed is a solid-state model and the weapon itself will be a cluster of the emitters. I read about the research contract about a dozen years ago in Av Leak and often wondered why no further news. It's out, now. At that the laser was to be powered by homopolar generator driven by the fan shaft (no 7fan in this model).