Hit a target from space, anywhere, in less than an hour.

[Battle Monkey of Zardoz]

Always was interested in Space. Space travel, planets etc.  So this article was interesting to me. The last part, pasted.  Makes me, well. A little worried.

With all the focus on the launch of the secret X-37B, another space launch by a Minotaur IV rocket from Vandenberg Air Force base in California received less attention, noted the Times Online. It was carrying the prototype of a new weapon that can hit any target around the world in less than an hour.

http://scitech.foxnews.mobi/quickPage.html?page=23952&content=37450536&pageNum=3#r_http%3A//scitech.foxnews.mobi/quickPage.html%3Fpage%3D23952%26content%3D37450536%26pageNum%3D-1

[Bogie]

IMHO, if they can do that, what we need is a buncha hundred pound tungsten rods, with a burn-off ceramic coating, and some stabilizing/rotation fins... Get it in the right spot, and chuck it toward the guys in the caves...
 

[MillCreek]

^^^ I remember reading about this from Larry Niven and Jerry Pournelle back in the '80's. "Rods from God" I think was the colloquial name.

[RevDisk]

Informally, it's called "dropping the bar".

You can use any heavy material that can withstand the heat, a tiny guidance package, and some control fins.  Accuracy would be about the same as any artillery round.  Say...   10-20m?  Maybe less if it rides a beam in.

Dirt cheap weapon system.  Most expensive part is getting it up the gravity well.  Per unit munition cost could be as low as $5k-$15k.  While it'd probably be a hair more expensive, I'd prefer tungsten to depleted uranium.  It'd be very expensive to put one or two in space, but it'd get very economical if you could put clusters of 40-80 at a go. 

BGM-109 is $569,000 per.  Plus costs of the launch vehicle (subs ain't cheap).

[S. Williamson]

So what sort of damage are we talking about here?

To (mis)quote Winston Churchill:

"Although personally I am quite content with existing weapons, I feel we must not stand in the path of improvement."

 

[Battle Monkey of Zardoz]

So what sort of damage are we talking about here?

If it hits your ass. DRT.  Close by, probably DRT. 

[dogmush]

I'm not a rocket scientist, but it depends on the size of the rod, right?

For a modest rod, say tac nuke size?  5-10 ktons is what I've been toldas a reasoanable target range. Less explosion, more penetration and kinetic damage, but big boom anyways. 

Does someone that's done the math more recently have a better idea?

[Phyphor]

Paging Physics...... 

[roo_ster]

I'm not a rocket scientist, but it depends on the size of the rod, right?

For a modest rod, say tac nuke size?  5-10 ktons is what I've been toldas a reasoanable target range. Less explosion, more penetration and kinetic damage, but big boom anyways. 

Does someone that's done the math more recently have a better idea?

Well, if I knew the mass of hte rod & the terminal velocity, I could do the calc right easy.

[Bogie]

Hmm... I wonder how big a moon rock one could move and launch...
 

[Battle Monkey of Zardoz]

Hmm... I wonder how big a moon rock one could move and launch...

Or just pluck an asteroid from the belt and hurl it down

[AJ Dual]

I've been a proponent of this type of KEW system forever.

In space ANY reaction drive that can push a mass somewhere with suitable accuracy has potential as a weapon. In vacuum, a pillow will do.

Although I wonder if a drop from LEO has much more energy than a sub-orbital ballistic path. I recall seeing impact footage of inert MIRV's at the Kwajalein atoll site. One of them impacted on the ground instead of the ocean just a few hundred yards from a camera.

I have no idea how fast it was going, but it was glowing, crossed/impacted in less than one frame of the video, and the explosion was not much more than you'd expect from a light aircraft or artillery shell. (The water plume from the one that hit a few hundred yards further out in the ocean WAS IMPRESSIVE though) Granted, the MIRV is a drag-stabilized cone, vs. an aerodynamically optimized dart, and orbit is more potential energy higher up the well than a sub-orbital trajectory.

http://www.youtube.com/watch?v=o8n59S8j2C0

However, if this is the closest real-world example I've ever seen to something even similar to God Rods/Thor in application, and if it's even within an order of magnitude. So it makes me wonder if there's a reason the DoD hasn't been all over orbital kinetics to date.

[MillCreek]

And in possibly related news, the X-37B launched from Florida today.  Speculations as to its purpose include fast launches of spy satellites, deployment of a spy satellite killer vehicle, or maybe Crowbars from Space.

[Gowen]

With all the focus on the launch of the secret X-37B

If it's a secret, hows come we knows about it?

[Bogie]

Ignore that big noisy thing rising out of the swamps, please...
 
You know, with all the hullabaloo over "smart bombs" and the like...
 
We know the area where most of the Taliban, etc., has sequestered themselves, right?
 
We have still have B-52s, right? Heck, I -know- we have C130s...
 
Let's load 'em up... Roofing nails, railroad spikes, whatever... Get to destination, open up, dump the load over the area of operations, and get out of the way for the next cargo. Repeat for a couple-three weeks. I figure after a little while, they'll -really- start to go cave-crazy...
 

[kgbsquirrel]

Well, if I knew the mass of the rod & the terminal velocity, I could do the calc right easy.

IIRC, if you were lofting a kinetic energy projectile instead of a warhead on a minuteman-III.... you're probably looking at a single projectile massing up to around 1100-1200kg (or three projectiles up to 350-400kg each) with an impact speed of around mach 18 sea level. MIRV's aren't designed to slow down on the way in. 

[MicroBalrog]

The beauty about this thing is not whatever payload it has.

It is that it can kill anywhere in the world, and there's nothing the bad guys can do about it. Any AA rockets they may have, any RADAR they may have, it's useless.

If you're Ahmadinejad, Nasrallah, Bin Ladin, whoever, now you know that whenever you leave your house, America can kill you.

Previously you could maintain the belief that they won't be able to deploy fast enough, or that your AA systems could shoot down their craft, or whatever. No longer.

Imagine the change of the world scene if all the terrorist leaders know that America can kill you at any moment, at will, and there's nothing you can do about it.

[roo_ster]

Hokay:

1m long and 10cm diam rod of tungsten massing  150Kg moving at mach 18 (6125m/s) will have the KE of .68Kilotons or 1.36 million lbs of TNT.

2m long and 10cm diam rod of tungsten massing  300Kg moving at mach 18 (6125m/s) will have the KE of 1.36Kilotons or 2.7 million lbs of TNT.

I suspect these estimates are conservative, since the projectiles would have a Cd closer to that of .04 (streamlined) than of .5 (cone)

For a single human, this is the very definition of overkill.


I did the calcs for a MBT gun KE penetrator first to get the method down.  You're talking 5900 lbs of TNT more or less.

There was a time I could have done hte calcs knowing the orbital vel, altitude, air density, horizontal displacement of the target, etc.  Been a while since I have done rocket science.

Code: [Select]

For KE Tank Round (wiki data)
Variable / Unit / Assumptions / Etc              Symbol            Value         Units         Notes
Velocity @ Impact                                   v                1740        m/s
radius                                              r               0.015        m
length or height                                    h                 0.6        m
volume                                             vol          0.0004239        m^3           h(pi*r^2)
densityU                                           dU                19.1        g/cm^3
densityU                                           dU               19100        Kg/m^3        1Kg/m^3 = 1000g/cm^3
densityW (tungsten)                                dW               19.25        g/cm^3
densityW (tungsten)                                dW               19250        Kg/m^3
Mass U Penetrator                                  Mu                8.10        Kg            dU*vol
Mass W Penetrator                                  Mw                8.16        Kg            dW*vol
Kinetic Energy @ Impact U                          KEu           1.23E+07        joules        .5*mv^2
Kinetic Energy @ Impact W                          KEw           1.24E+07        joules        .5*mv^2
Kiloton TNT                                       KtTNT          4.18E+09        joules
Kinetic Energy @ Impact U                          KEu           2.93E-03        KtTNT
Kinetic Energy @ Impact W                          KEw           2.95E-03        KtTNT
Kiloton                                            Kt             2000000        Lbs
Kinetic Energy @ Impact U                          KEu            5858.73        LbTNT         5858 lbs of TNT
Kinetic Energy @ Impact W                          KEw            5904.74        LbTNT         5904 lbs of TNT




For 1m Rod Dropped From LEO
Variable / Unit / Whatever                       Symbol            Value         Units         Notes
Start Orbit Height                                 Ho              150000        m             150Km
Start Velocity Minimum                             Vo                7814        m/s           Low Earth Orbit at 150Km
Rod Radius                                         Rr                0.05        m             10 cm diameter
Rod Length                                          h                   1        m             sad attempt to make calcs easier
Rod Frontal Area                                    A             0.00785        m^2
Rod Volume                                         vol            0.00785        m^3
Rod Mass                                          Mrod           151.1125        Kg/m^3        Tungsten, baby, cause its more dense
densityW (tungsten)                                dW               19250        Kg/m^3
Rod Coeff Drag                                     Cd                0.04        none          Streamlined body
Start KE in Orbit                                  KEo           4.61E+09        joules        Starting off 2 orders of magnitude greater than KE penetrator
Velocity at Impact                                 Vt                  18        mach          mach = 340.3 m/s @ 15degC
Velocity at Impact                                 Vt              6125.4        m/s           Very conservative, given a cones Cd = .5
Kinetic Energy @ Impact W                          KEw           2.83E+09        joules
Kiloton TNT                                       KtTNT          4.18E+09        joules
Kinetic Energy @ Impact W                          KEw               0.68        KtTNT
Kiloton                                            Kt             2000000        Lbs
Kinetic Energy @ Impact W                          KEw          1,355,120        LbTNT         1.36 million pounds of TNT




For 2m Rod Dropped From LEO
Variable / Unit / Whatever                       Symbol            Value         Units         Notes
Start Orbit Height                                 Ho              150000        m             150Km
Start Velocity Minimum                             Vo                7814        m/s           Low Earth Orbit at 150Km
Rod Radius                                         Rr                0.05        m             10 cm diameter
Rod Length                                          h                   2        m             Double length of rod
Rod Frontal Area                                    A             0.00785        m^2
Rod Volume                                         vol             0.0157        m^3
Rod Mass                                          Mrod            302.225        Kg/m^3        Tungsten, baby, cause its more dense
densityW (tungsten)                                dW               19250        Kg/m^3
Rod Coeff Drag                                     Cd                0.04        none          Streamlined body
Start KE in Orbit                                  KEo           9.23E+09        joules        Starting off 2 orders of magnitude greater than KE penetrator
Velocity at Impact                                 Vt                  18        mach          mach = 340.3 m/s @ 15degC
Velocity at Impact                                 Vt              6125.4        m/s           Very conservative, given a cones Cd = .5
Kinetic Energy @ Impact W                          KEw           5.67E+09        joules
Kiloton TNT                                       KtTNT          4.18E+09        joules
Kinetic Energy @ Impact W                          KEw               1.36        KtTNT
Kiloton                                            Kt             2000000        Lbs
Kinetic Energy @ Impact W                          KEw          2,710,239        LbTNT         1.36 million pounds of TNT


[Headless Thompson Gunner]

For a single human, this is the very definition of overkill.

I gather that the intended use is more tactical than anti-personnel.

And doesn't mach 18 seem kinda slow for a streamlined dart?  I haven't done any of the math, but intuitively it feels a little low.

[roo_ster]

For an area target, the idea of cluster sub-projectiles that make up 90% of the mass of hte munition dispersed over some optimal area would be, uh, awesome.  "DPICM from Heaven Hell."

I gather that the intended use is more tactical than anti-personnel.

And doesn't mach 18 seem kinda slow for a streamlined dart?  I haven't done any of the math, but intuitively it feels a little low.

Yes, I noted that mach 18 was conservative, given relative coefficients of drag (.5 for cones, .04 for streamlined bodies).

[kgbsquirrel]

I gather that the intended use is more tactical than anti-personnel.

And doesn't mach 18 seem kinda slow for a streamlined dart?  I haven't done any of the math, but intuitively it feels a little low.

Mach 18 is the open source re-entry speed for a cone shaped mirv. One of these to be precise...



I'm sure you could make a far more streamlined kinetic impactor using the combined mass of all three of those.

Thoughts for the orbital platform though... Hmmm. Perhaps a set of 6 satellites spaced out in an orbit of 0 inclination and a period of 2 hours? I'm guestimating (too lazy to look up the math right now) that an orbital period of that time would put it around 800-1200 miles up. The benefit to having 6 platforms with a 2 hour orbit? You'll always have a platform in place to drop one within 20 minutes or less.

@jfruser: So, assuming an intial speed of 20,000 MPH and an altitude of 1000 miles, if you kicked a penetrator of 1000kg out the door with just enough boost to allow it to fall in a trajectory to hit the target, what would the impact energy be?


ETA: This idea of a kinetic energy orbiting platform actually solves the ICBM lofted conventional weapon problem. With these you just invite all the nuclear powers over to inspect the penetrators being taken up to arm these satellites and verify that they aren't nukes. With the ICBM's the other powers would never be able to tell if they were nuke armed or not and that would likely invite some rather nasty responses.

Would you like to play Global Thermonuclear Warfare?  

Also, jfruser, do remember that there is an upper limit to how fast your impactor can travel, lest you incinerate it during atmospheric reentry. Perhaps a contour conforming ablative heat shield just thick enough to get it from orbital altitude to sea level?

[MicroBalrog]

For a single human, this is the very definition of overkill.

That depends grossly on who the human in question is. If it's OBL or someone like that, it could well be worth it.

[Marvin Dao]

However, if this is the closest real-world example I've ever seen to something even similar to God Rods/Thor in application, and if it's even within an order of magnitude. So it makes me wonder if there's a reason the DoD hasn't been all over orbital kinetics to date.

Because they make for spectacular silo busters and would destabilize the nuclear balance of power.

[Physics]

Weapons and math in the same thread?  I like it.  :)

[dogmush]

Jfruser, since you have the math done already.

At least one article talked about darts in the range of 6 meters long, 30 cm diameter, made of tungsten.  Big boom?

I'll see if I can dig that article up.

edit:
Found it, it was a popular science article.

Rods from God

I have no idea where their info came from or what the phrase "up to" means in this context, but it seems likely that given the choice of cheaper , but still effecive weapons, or really cool overkill America goes for the really cool every time.