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Planetary bombardment as a terror weapon

B

batmagoo

SOC-9
Please pick this apart!

I'm working on a scenario for my players where they discover several collapsable 'mattress springs' floating near the jump point at 100 diameters. Each one has a small guideance computer, and several attidude jets. They are not moving.
One of the arrays has a 'cannister' 1m in diameter, about 2m long, filled with 12 two meter lawn darts, made of solid hull quality steel.
The cannister is eqipped with a small boost motor to launch it, and an ARM style seeker. The lawn darts themselves are unguided, and seperate from the cannister in the upper atmosphere during reentry.

Any guesses as to how much energy they would produce on impact?

Chuck
 
For a size 7 planet (using earth based approximations) a 100D free fall ignoring atmosphere will give the falling object a velocity of between 5 and 10 km/second.

A thicker atmosphere will dampen this to some extent, a thinner one will help. In a thicker atmosphere more energy is lost on the way down slowing the descent. The energy is the same, just one is more sudden.

At 10km/s this should release Mass(in Kg)/2 * 10^8 Joules.

Assuming a 200 kg dart this would be approx 10^10 joules (10,000,000,000 joules)

To put this in perspective a Ton of TNT releases 4,184,000 joules.

So about 2.4 kiloTon, give or take. On some planets as low as the 0.1 kiloTon range, on others up to 10 kiloTon or so.

Not a terrifying weapon. Moderately scary though. Equivalent to small nukes.
 
What you're describing sounds a lot like the Project Thor idea fom the 1960's.
It was proposed by Jerry Pournelle (during his day job) as a way to combat massed Soviet armour formations.
There seems to be very little information on the net. A lot of folks have heard of it but no hard data. From what I remember, packets of titanium rods would be placed in orbit and released on a ballistic course towards the target. Apparently titanium could survive the re-entry heating.
I think that Thor penetrators were smaller; maybe 20kg? You could try running these numbers through veltyens equation.
There's a link here
to calculate velocity through Earth atmosphere.

For a quick and dirty answer, be careful where you point those things. ;)
 
Originally by Sigg Oddra:
Wouldn't they all just burn up on entry to the atmosphere at that speed
Click to expand...
Hence the wanting a thinner atmosphere. In a thicker atmosphere there is more energy lost to resistance, if the object cannot accept this energy then it will burn and break up.

There is the same amount of energy involved regardless of the atmosphere. Going with a dart has the problem that it will act quite nicely as an earth penetrator, this is somewhat of a problem in that the energy will be released over time, rather then near instantaneously. Less shockwave, less objective damage, much the same as a thicker atmosphere.

Despite all this small nukes are still nukes. There is a lot of energy being sprayed around by the impact.

Edit: When I say not scary, it isn't a donut maker like a 5000 ton steel ball impacting at 3000km/s (0.01C) (~ 5 teraton equivalent)
 
Uh, I get 4,184 MJ per ton of TNT
http://www.convert-me.com/en/convert/energy
So a 200 Kg "lawn dart" at 11 Kps is not quite 3 tons of TNT. At that speed it will vaporize on contact with anything solid (especially since it will be white-hot from the passage through the atmosphere, so you get an explosion of vaporized missile and target. Not much penetration though (same principle as a meteor bumper, AKA a Whipple shield).

I preferred to use a pattern of forty, 50 Kg projectiles, which should give a blast pattern something like a Vietnam squadron of B-52s on an "Arclight" mission.
 
This is the same as dropping a small asteroid from orbit, no? Why make them dart shaped? Make 'em the shape of a d20 - bigger impact footprint. Not a lot of accuracy without guidance. Neat idea, tho. I'm not sure why you would think it would vaporize - meteorites don't. Unless you include the Tunguska theory - and that was an explosion before inpact.

Dameon
 
Originally posted by Piper:
What you're describing sounds a lot like the Project Thor idea fom the 1960's.
It was proposed by Jerry Pournelle (during his day job) as a way to combat massed Soviet armour formations.
There seems to be very little information on the net. A lot of folks have heard of it but no hard data. From what I remember, packets of titanium rods would be placed in orbit and released on a ballistic course towards the target. Apparently titanium could survive the re-entry heating.
I think that Thor penetrators were smaller; maybe 20kg? You could try running these numbers through veltyens equation.
There's a link here
to calculate velocity through Earth atmosphere.

For a quick and dirty answer, be careful where you point those things. ;)
Click to expand...
Jerry Pournelle has mention of this idea somewhere on his sprawling website (jerrypournelle.com) -- which is a great bloglike thing, by the way.

His later suggestions involved tungsten rods the size of telephone poles. Guaranteed to take out a city, I think. Early after 9/11 he suggested dropping such things on Iraq as an -- ahem -- behavior modification tool. And yes, tungsten can take a lot of heat, which I think is why we use them in lightbulbs?
 
I seem to remember it being called "Skyhook" in an Analog I have somewhere. I don't remember offhand who wrote the story, or which issue (all the Analogs went to pre-move storage a couple of weeks ago), but I think it credited Project Thor for the idea. Somebody calculated terminal velocity for the things in Earth's atmosphere when I brought it up before, and it didn't seem such a great idea after that. (Of course, they might have been wrong.)
 
That NASA site for terminal velocity ain't much good. You need coeficient of drag, Reynolds number for various velocities and air densities at alttude.
http://www.grc.nasa.gov/WWW/K-12/airplane/dragco.html

And then you get to integrate the reults over a 100 km colmn of air of gradualy increasing density. Not today, thank you.

Meteors do (mostly) vaporize with violence. That is were you get craters. Nearly all meteors have lousy aerodynamcs so they burn off a lot of mass and energy in the atmosphere. Only the biggest make it to the ground. Or Tunguska, probably a comet relic that was so light that it blew up on contact wih the atmosphere.

Tungsten telephone pole from orbit... 10 m long, 0.3 m diameter, 11 g/cm3, say about 5 tons. 7 km/sec. 122,500 MJ, almost 30 tons of TNT. Impressive, but nt a city killer.

At a conservative 5 km/sec thats 15 toms of TNT. At the lower velocitt the tungsten doen't explode and it should penetrate well enough to reach Sadam's command bunkers.
 
Sorry for the bum link. It looked okay to me but I don't have the math to really assess that sort of thing. My bad.
10 metres seems larger than I remember of Thor. Were they really going to be that big or was this a Sadam-specific idea?
 
Dropping a crowbar from orbit is a wonderful way to store destructive energy, but the big broblem is the energy release. Bombs of all types are destructive because the energy release takes place within an extremely short time span generating a sharp pressure wave. If your crowbar stikes an armored surface like a battleship deck or a tank, it will release that energy very quickly, generating a pressure wave. If on the other hand, your crowbar stikes water or sand, the bar will slow down very quickly, but will not generate nearly such a deadly pressure wave. If you want something more than a hole the size of your crowbar, you must ensure it will vaporize on impact, not just dig in.
 
I assumed 10m x 30cm from the description "telephone pole"


You want vaporization? Just make sure you hit at 11+ kps
 
Vegascat said: If on the other hand, your crowbar stikes water or sand, the bar will slow down very quickly, but will not generate nearly such a deadly pressure wave. If you want something more than a hole the size of your crowbar, you must ensure it will vaporize on impact, not just dig in.

Thats the reasoning for the ARM style seeker. So it will point at the biggest radiation source, ie. city, starport, military installation etc, before it deploys.
I figured 20-50% of the darts would actually hit and destroy something of value, while the rest would just poke 8" holes in the ground, and the odd building.
file_23.gif


chuck
 
GChuck,
I would think (unless on a rural world) that you would tend to hit a lot of hard objects that would cause holes larger than 8". There is plenty of mass under (and in) city streets/downport ramps/buildings to provide for mass-energy-conversion explosions.
 
Originally posted by GChuck:
Please pick this apart!

I'm working on a scenario for my players where they discover several collapsable 'mattress springs' floating near the jump point at 100 diameters. Each one has a small guideance computer, and several attidude jets. They are not moving.
One of the arrays has a 'cannister' 1m in diameter, about 2m long, filled with 12 two meter lawn darts, made of solid hull quality steel.
The cannister is eqipped with a small boost motor to launch it, and an ARM style seeker. The lawn darts themselves are unguided, and seperate from the cannister in the upper atmosphere during reentry.

[SNIP}
Chuck
Click to expand...
From the military viewpoint:

A. Someone can't afford an orbital bombardment cruiser, but can afford this.

B. I leave the math to the experts on the previous pages. A Terror weapon? Possibility. A 'Poor man's automated interdiction system'? Another possibility. Depends on what the planet has to offer or attack/ interdict/ strike at.

C. Possible loophole in the SPA or equivaent's orbital coverage [Any system with D-class port or less vulnerable to this type of insertion weapon unless they have a Scout base present that updates the systems navigation beacon satellites].

D. Possible weapon of choice for a corporate war--limited damage and ammunition, not necessarily a nuke but does give WMD damage on impact so Imperial War scruitiny can be narrowly avoided [and I mean NARROWLY IMTU].

E. Data on targetting computer a High priority recovery for tracing culprits.


F. depending on campaign, Players might either destroy or recover said weapon systems. Certainly 'jacking' them and using them for their own purpose should have its FULL penalty[ies]--see D.

G. The folks who had them put there won't be happy with Players at all once they scrag or knock them out. If your [players are smart they'll find out who put them there, and let the Imperial Authorities know about it. Won't stop a corporate vendetta, but they'll at least have one planet VERY grateful to them.

Nice to meet ya--I'm that evil Traveller GM back from Iraq they warned you about. Welcome to CoTI btw.


Slainte!
 
There is plenty of mass under (and in) city streets/downport ramps/buildings to provide for mass-energy-conversion explosions.
Click to expand...
'Less you're using a fissionable, there won't be any mass/energy conversion going on. Conversion of kinetic energy to heat, yes, but no loss of mass.
 
womble,
You're right. I didn't say that well at all. The mass (plasticrete, pipes, subway trains, etc.) would help to convert the kinetic energy to heat quickly, rather than slowly.
 
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