Whatever happened to Rods from God?

How many of youse remember 'Rods from God'?
a non-warhead space-based weapon. the destructive power would come from the mass of the metal and the kinetic force from dropping from space (or near-space altitude). I never got details; apparently they had some kind of guidance setup.
there were rumors that some of the classified shuttle missions involved these. I guess they would launch and deploy a satellite with them.

in WWI aviators dropped big darts over the trenches. The soldiers apparently told horror stories about those things piercing right through their helmets. early version of the same concept.

does anyone know if they ever deployed these? are they flying over us now? or was the whole thing dropped due to cost and/or feasability?

a reply to: Coelacanth55

Tungsten-tipped poles about the size of a telegraph pole dropped from low Earth orbit.

We are not allowed weapons in space and i think the cost of getting them up there was somewhat cost-prohibitive.

a reply to: andy06shake

We aren't allowed WMDs in orbit. We're allowed weapons in orbit. But Rods From God was never going to be a thing. They're not accurate, and they're about the equivalent of a 2000 lb bunker buster at impact. Their only advantage is reaction time. Getting them to orbit requires a heavy lift rocket, or something like the shuttle, and loading them would require an extremely risky space walk once they were fired, if they could get them up there to begin with.

a reply to: Zaphod58

We aren't allowed WMDs in orbit. We're allowed weapons in orbit.

Even some speculation the Russians fired a gun from one of their first space stations if memory serves might have been Soyuz 1.

Tungsten telegragh pole sized rods accelerated to relativistic speeds by some sort of rail gun?

According to Peter F Hamilton's books, I believe?

a reply to: Oldcarpy2

Aye, i think that rings a bell.

These rods though i seem to recall would be accelerated by Earth's gravity to typically several kilometers per second, depending on the altitude from which they are dropped.

originally posted by: Zaphod58
a reply to: andy06shake

We aren't allowed WMDs in orbit. We're allowed weapons in orbit. But Rods From God was never going to be a thing. They're not accurate, and they're about the equivalent of a 2000 lb bunker buster at impact. Their only advantage is reaction time. Getting them to orbit requires a heavy lift rocket, or something like the shuttle, and loading them would require an extremely risky space walk once they were fired, if they could get them up there to begin with.

I'm going to quibble here. It is true that they first have to get to orbit and that is traditionally too expensive. However, if Elon gets his Starship working (and I'm betting he will) the cost to deliver mass to low earth orbit is going to go down by one or two orders of magnitude, and that changes the cost-effectiveness calculation of a lot of these schemes.

Also, the original rods from God plan from Lowell Wood and his band of merry pranksters did not require spacewalks or human spaceflight in the loop at all.

In addition to reaction time, the other advantage is that you don't have to fly an expensive aircraft with a crew in it over hostile territory to deliver them.

On the other hand, rods from God would work well on stationary targets (like missile silos) but probably can't compete with conventional weapons for mobile targets.

I've been thinking recently that there could be special use cases where rods from God could be the solution. North Korea, for example.

a reply to: andy06shake

They need to reach near relativistic speeds to do the damage, dropping them relying on gravity alone wouldn't do it.

Might ruin your day, though?

a reply to: Oldcarpy2

Depends on what you mean by damage.

The composition and mass of the rods combined with the velocity they strike the target would seem to dictate how much destructive force they could potentially unleash.

But we certainly would have problems shielding targets against them or detecting and shooting them down.

Again through getting them up there is simply cost-prohibitive, never mind illegal, and like Zaphod58 points out there are issues with accuracy.

Same thing can be achieved with conventional bunker busters hence not much need given the problems associated with them.

Its science fiction thus far, let's hope it stays that way.

a reply to: andy06shake

For some reason I am reminded of this sort of ancient kinetic weaponry.

"Fetchez la vache":



MAN: Fetchez la vache!
CUT BACK TO battlements. A cow is led out of a stall
CUT BACK TO ARTHUR
ARTHUR: Now that is my final offer. If you are not prepared to agree to my demands I shall be forced to take ... Oh Christ!
A cow comes flying over the battlements, lowing aggressively. The cow lands on GALAHAD'S PAGE, squashing him completely
Cow Over The Battlements
| ROBIN: What a cruel thing to do
| BEDEVERE (Choking back tears): It hadn't even been milked
ARTHUR: Right! Knights! Forward!
ARTHUR leads a charge toward the castle. Various shots of them battling on, despite being hit by a variety of farm animals
ARTHUR (as the MAN next to him is squashed by a sheep): Knights! Run away!

One problem I see is one rod will be mostly useless. You will have to put up hundreds in a pattern like starlink to be effective. One will only be able to target a spot on the ground once or twice a week at most.

And what fuel are they going to use? You can't just let them go. They will just float there in orbit . You will have to do a deorbit burn and with all the mass of the tungsten rod, that will take a lot of fuel and a large engine.

Where would anyone mine that much tungsten just to build the rods? A 1/4 inch rod and inch long is over $5 use so a single telephone pole will be extremely expensive. Nukes would be cheaper.

Now if we get to asteroid mining, just throwing rocks on your enemie would be both easy and cost effective.

originally posted by: Oldcarpy2
a reply to: andy06shake

They need to reach near relativistic speeds to do the damage, dropping them relying on gravity alone wouldn't do it.

Might ruin your day, though?

No they don't.

Here's how Lowell Wood--the original advocate for rods from God--used to think about it.

1 kilogram of TNT has 4.184 MegaJoules of energy release when it explodes. How fast would a 1 kilogram kinetic energy impactor have to be traveling when it hit the earth to have the same energy release? You set the kinetic energy of the impactor ( 1/2 m V^2) equal to 4.184 MegaJoules and solve for V, the velocity. It turns out that the speed for which a one kilogram kinetic impactor has the same energy as one kilogram of TNT is about 2.9 kilometers per second. (That's about Mach 8.4 at sea level). Any speed above that and the kinetic energy impactor wins out. Since an impactor in orbit would start with about 7.8 kilometers per second of velocity, it only has to retain about 40% or so of that velocity to be more effective than a conventional bomb of the same weight.

ICBM warheads typically are going about 3 km/s when they hit the ground, and they start from an entry velocity that's only about 80% of orbital velocity. A rod from God would have a lower drag coefficient than an ICBM warhead, so it would be relatively easy to maintain terminal velocity well above the 3 km/s level.

a reply to: Boomer1947

A recent Chinese (yes I know) study shows that they aren't nearly as effective as claimed in sci-fi. They hit hard, but even against concrete, they don't penetrate well. There's very little difference between a medium and high speed impact too. At 1.2 km/s the maximum penetration depth is 80x the diameter of the rod. So a 1 foot diameter rod would penetrate roughly 80 feet of material. Increasing that speed to hypersonic levels doesn't increase the penetration significantly. A USAF study showed that terminal velocity of the rod would be somewhere around Mach 10, and that a conventional bomb of similar weight provides similar destructive power.

a reply to: Zaphod58

I think I saw that. too much of the energy would be used up on impact.

wouldn't mind testing some on that mountain in Iran where they're hiding their nuclear program...

originally posted by: Zaphod58
a reply to: Boomer1947

A recent Chinese (yes I know) study shows that they aren't nearly as effective as claimed in sci-fi. They hit hard, but even against concrete, they don't penetrate well. There's very little difference between a medium and high speed impact too. At 1.2 km/s the maximum penetration depth is 80x the diameter of the rod. So a 1 foot diameter rod would penetrate roughly 80 feet of material. Increasing that speed to hypersonic levels doesn't increase the penetration significantly. A USAF study showed that terminal velocity of the rod would be somewhere around Mach 10, and that a conventional bomb of similar weight provides similar destructive power.

I would be interested in seeing that study. The terminal velocity depends on the ballistic coefficient of the rod. The higher the ballistic coefficient, the higher the terminal velocity. All the studies I'm familiar with from when I worked on hypersonic penetrators assume very long, skinny cones that have ballistic coefficients much higher than that of an ICBM warhead, for instance. So I would think the terminal velocity could be as high as Mach 12. That would give about 40% more explosive energy than a conventional bomb of the same weight.

Also, I would note that 1.2 km/s is far too low a speed to actually vaporize the penetrator material, which is part of the effect. At 1.2 km/s, the penetrator body would remain largely intact, assuming it was constructed of high strength alloy steel (which is a common assumption for penetrators dropped by supersonic aircraft). By contrast, the rods from God are usually assumed to be constructed of Tungsten or depleted Uranium. At 10 or 12 km/s the Tungsten or Uranim would vaporize and form a high speed jet of molten metal--basically creating a self forging round or shaped charge effect.

Also, I think that the penetration depth depends more on the length than the diameter. A rule of thumb is that a penetrator will displace a mass of soil or rock equal to its own mass. Since Tungsten is almost 10 times more dense than soil or concrete, it should penetrate about 10 times its length. For a 20 ft long rod, that would be about 200 ft.

a reply to: Boomer1947

The study found that it did create a jet of plasma, but the rod was vaporized as it impacted so there was no extra metal to penetrate deeper. The penetration depth was based on the diameter of the rod, not the length.

Both the USAF and Chinese found that the drawbacks to them far outweighed the benefits of them. The USAF over twenty years ago, and the Chinese more recently. It’s a great sci fi weapon, but not so great in reality.

a reply to: Boomer1947

As I read the WWII British TALLBOY 12000 lb bomb would accelerate to super sonic velocity when dropped from a Lancaster
bomber at altitude

Would penetrate dozens of feet into the ground before exploding

In one case were used to destroy an important viaduct by exploding under ground to destroy it by shock wave

Anyone remember those very large "domes of light" Russia was deploying in the 80's?

They probably weren't intended to blind early warning sats and - unless Russia has leapfrogged its science to Star Trek levels- they certainly weren't meant to defend against physical projectiles such as missiles or RFTG's.

A half decent theory seems to be that they were in fact "force fields" (as per Sarfattis white hole conjecture) - and if correct - would provide a good start point in identifying what type of systems they were anticipating defending against.