Rods from God / "Project Thor"

Given the frequently quoted 6km/second, how many tungsten dart equivalents to a Tallboy could a Falcon Heavy or BFR put into a polar orbit? I seem to recall that there was a proposed conventional version of Pershing 2 that used an MRV consisting of a bundle of (depleted uranium?) darts to crater airfields. There seems to be little point in going for tactical nuke yields since tactical nukes 'splody' is incidental to their effectiveness, which comes from the radiation pulse. Also, as noted above and elswhere it might not be practical to use this against moving targets. However the equivalent of a really big conventional bomb dropped from orbit against a target that a bomber can't get to (like a factory, military base, shipyard or other critical infrastructure) seems like an interesting capability.
 
Brickmuppet said:
Given the frequently quoted 6km/second, how many tungsten dart equivalents to a Tallboy could a Falcon Heavy or BFR put into a polar orbit?
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Simple math. What is the mass of each "dart?" What is the payload capability of the launch system? Knock off some good percentage of the total payload to serve as the bus and de-orbit system, and there ya go.

There seems to be little point in going for tactical nuke yields
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Little possibility of it, either. Total "yield" of the kinetic weapons is substantially less than the total yield of the chemical propellants in the booster required to orbit them, and few boosters have enough propellant to be classed in the tactical yield capability, unless you're talking about pathetically small yield devices like Davy Crockett. Starship/Super Heavy has 3.4 kilotons of propellant in the first stage, 1.2 kilotons in the second, total of 4.6 kilotons. Some sizable fraction of that is simply tossed away due to gravity and aerodynamic losses. More lost due the mass of the buss and de-orbit systems. More due to drag losses to the weapons.

Starship is supposed to have a payload of 100 tons to LEO, at *about* 7.8 km/sec for a kinetic energy of the payload being ~3E12 Joules... or about 0.727 kilotons. That's for the *entire* payload. Cut the mass in half for bus/de-orbit, and you're down to 0.36 ktons. Split it, say, ten ways, and you're down to 0.036 ktons per weapon. Shave off some drag losses, and you're perhaps 0.02-0.03 ktons per. From 4.6 kilotons of explosive power on the pad, you're down to less than one percent of that per weapon for ten weapons.

You can do better by making the Starship stage fully expendable, but you're still tinkering with tiny percentages.
 
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Orionblamblam said:
Starship is supposed to have a payload of 100 tons to LEO, at *about* 7.8 km/sec for a kinetic energy of the payload being ~3E12 Joules... or about 0.727 kilotons. That's for the *entire* payload. Cut the mass in hald for bus/de-orbit, and you're down to 0.36 ktons. Split it, say, ten ways, and you're down to 0.036 ktons per weapon. Shave off some drag losses, and you're perhaps 0.02-0.03 ktons per. From 4.6 kilotons of explosive power on the pad, you're down to less than one percent of that per weapon for ten weapons.
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It's actually pretty efficient, if you need to hit some hardened targets without provoking nuclear escalation.
 
Orionblamblam said:
Brickmuppet said:
Given the frequently quoted 6km/second, how many tungsten dart equivalents to a Tallboy could a Falcon Heavy or BFR put into a polar orbit?
Click to expand...

Simple math. What is the mass of each "dart?" What is the payload capability of the launch system? Knock off some good percentage of the total payload to serve as the bus and de-orbit system, and there ya go.

There seems to be little point in going for tactical nuke yields
Click to expand...

Little possibility of it, either. Total "yield" of the kinetic weapons is substantially less than the total yield of the chemical propellants in the booster required to orbit them, and few boosters have enough propellant to be classed in the tactical yield capability, unless you're talking about pathetically small yield devices like Davy Crockett. Starship/Super Heavy has 3.4 kilotons of propellant in the first stage, 1.2 kilotons in the second, total of 4.6 kilotons. Some sizable fraction of that is simply tossed away due to gravity and aerodynamic losses. More lost due the mass of the buss and de-orbit systems. More due to drag losses to the weapons.

Starship is supposed to have a payload of 100 tons to LEO, at *about* 7.8 km/sec for a kinetic energy of the payload being ~3E12 Joules... or about 0.727 kilotons. That's for the *entire* payload. Cut the mass in half for bus/de-orbit, and you're down to 0.36 ktons. Split it, say, ten ways, and you're down to 0.036 ktons per weapon. Shave off some drag losses, and you're perhaps 0.02-0.03 ktons per. From 4.6 kilotons of explosive power on the pad, you're down to less than one percent of that per weapon for ten weapons.

You can do better by making the Starship stage fully expendable, but you're still tinkering with tiny percentages.
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Energy efficiency factors into a weapons usefulness, but it's a small consideration. The attractiveness of the tungsten dart concept (Rods from God) is its ability to deliver devastating force quickly, anywhere on the globe, for which there is no known effective defense (except burying the target deeper). Delivering the same force via a more efficient, slower, more vulnerable mechanism is an inferior solution if it doesn't get the job done, even if it is, according to an energy budget, more efficient.
If energy efficiency were a dominant consideration, energy weapons (lasers and such) would have no future, yet development continues.
If one were to do an energy budget for a bomb produced in (say) Des Moines, shipped to Charleston, thence to the UK, and flown to Stuttgart, how would it compare to the tungsten darts?
 
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Brickmuppet said:
Given the frequently quoted 6km/second, how many tungsten dart equivalents to a Tallboy could a Falcon Heavy or BFR put into a polar orbit?
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Depends how you construct the carrier satellite, you could build it up like a space station over time.
 
taildragger said:
Energy efficiency factors into a weapons usefulness, but it's a small consideration.
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Irrelevant to the point at hand, which was to debunk the oft-claimed power of Thor being equivalent to a "tactical nuke." A 5.56mm bullet is also nothing like a nuke, but pointing that out doesn't imply that the bullet isn't militarily useful.
 
Forest Green said:
Depends how you construct the carrier satellite, you could build it up like a space station over time.
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Or alternatively, you could construct a relatively lose satellite constellation with a command platform at its heart and some defensive ASAT/Anti-Missile weapons scattered around the outer edges.
 
Orionblamblam said:
taildragger said:
Energy efficiency factors into a weapons usefulness, but it's a small consideration.
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Irrelevant to the point at hand, which was to debunk the oft-claimed power of Thor being equivalent to a "tactical nuke." A 5.56mm bullet is also nothing like a nuke, but pointing that out doesn't imply that the bullet isn't militarily useful.
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Nobody cares about wasted energy, if they did nukes wouldn't exist. All that matters is how quickly, how many targets can be taken out and at what cost. There's also the chance of success.

Assuming that the CEP is only a couple of meters, depending on the size of the rod everything beneath it would be vaporized, including harden targets.
 
Grey Havoc said:
Or alternatively, you could construct a relatively lose satellite constellation with a command platform at its heart and some defensive ASAT/Anti-Missile weapons scattered around the outer edges.
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You mean like Brilliant Pebbles plus Brilliant Rods?
 
Talking about the maximum speed reached for a "rod of god", here some details:

For attacking hardened or deeply buried targets, the long rods would not outperform existing missiles equipped with conventional penetrating warheads. That's because the physics of high velocity impacts limits the penetration depth; basically, too much energy at impact causes the projectile to distribute its energy laterally rather than vertically. Tests done since the 1960s by Sandia National Laboratories, in Albuquerque, N.M., confirm that for even the hardest rod materials, maximum penetration is achieved at a velocity of about 1 to 1.5 km/s.
Above that speed, the rod tip liquefies, and penetration depth becomes essentially independent of impact speed. Therefore, for maximum penetration, the long rods would need to be slowed to about 1 km/s, thereby delivering only one-ninth the destructive energy per gram of a conventional explosive-or about 1.5 percent of the potential energy the rod had in LEO. The wasted energy would be immense, and the effort, cost, and complexity of such an orbital system would be entirely out of proportion to the results.

Source: Deblois, Garwin, Kemp, Marwell, Space Weapons, IEEE Spectrum, March 2005.
 
Temistocle said:
Talking about the maximum speed reached for a "rod of god", here some details:

For attacking hardened or deeply buried targets, the long rods would not outperform existing missiles equipped with conventional penetrating warheads. That's because the physics of high velocity impacts limits the penetration depth; basically, too much energy at impact causes the projectile to distribute its energy laterally rather than vertically. Tests done since the 1960s by Sandia National Laboratories, in Albuquerque, N.M., confirm that for even the hardest rod materials, maximum penetration is achieved at a velocity of about 1 to 1.5 km/s.
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Sounds out of date. Modern long-rod penetrators significantly exceed 1.5 km/sec.
 
Temistocle said:
Above that speed, the rod tip liquefies, and penetration depth becomes essentially independent of impact speed. Therefore, for maximum penetration, the long rods would need to be slowed to about 1 km/s, thereby delivering only one-ninth the destructive energy per gram of a conventional explosive-or about 1.5 percent of the potential energy the rod had in LEO. The wasted energy would be immense, and the effort, cost, and complexity of such an orbital system would be entirely out of proportion to the results.
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Er... the whole concept of kinetic strikes is not about penetration. It's about thermal explosion from compression heating, when rod hit the ground at supersonic velocities.
 
It's about the dissipation of a huge amount of KE very quickly into heat and sound/pressure. The rod was the wrong shape for penetration.
 
In the story "First Cup of Coffee War" (found in here: https://www.amazon.com/Future-Weapons-War-Baen-Book/dp/1416521127) the "Bad Guys" create rods made from scavenged DPU and a reentry sheathing. They use a commercial suborbital tourist booster to push an upper stage bus into a trajectory for a kinetic attack on the US targeting the Super Bowl which is to be attended by the VP among hundreds of other celebrities and thousands of fans.

Blast and penetration are not the main aim here but the extreme burst of x-rays generated as the DPU undergoes the impact event.

Randy
 
Dilandu said:
RanulfC said:
DPU
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What is DPU?
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Arjen said:
Depleted Uranium
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What he said :) It's suggested that it comes from scrap and expended rounds "littering" various sites from the Gulf War and Iraq/Afghanistan. I should also point out the bad guys are taken out by a kinetic drop from LEO by a US Stealthed* ("Space Debris" we swear :) ) tactical attack satellite which covers the landing/launch site, (payload for Israel) with a spread of de-orbited 'darts'. The US used a combination of ABM missiles, (got the bus but not before it launched and managed to knock one rod into a tumble which destroyed it) and laser armed LTA "BattleStat's" (Battle-Aerostat) which knocks down a second by damaging the TPS sheath and causing the last one to land a 'bit' (something like 20 miles) long. No real damage though an elderly couple where injured when their SUV was blown off the road by the impact shockwave.

* Part of the 'suspense' of the story is that by using the assets needed to confirm the attack and then deal with it by taking out the bad guys the main character has to make a decision to 'un-mask' the pretty extensive orbital asset (everything from recon to attack assets) system the US has set up which is going to be politically embarrassing to the US and raise significant questions on what ELSE the US might have in orbit.

Randy
 
They're reiterating that bullcrap claim again.

A Rod from low orbit is unlikely to hit at anything exceeding orbital speed, 7.8 km/s, unless it has been fired from a giant railgun. More probable speeds are 1-4 km/s.

An object at 3 km/s packs KE equivalent to its mass in TNT. An object at 7.8 km/s has KE around 6.8 times it mass.

If you want a kiloton impact, you need a 150-tonne Rod.
 
chimeric oncogene said:
They're reiterating that bullcrap claim again.

A Rod from low orbit is unlikely to hit at anything exceeding orbital speed, 7.8 km/s, unless it has been fired from a giant railgun. More probable speeds are 1-4 km/s.

An object at 3 km/s packs KE equivalent to its mass in TNT. An object at 7.8 km/s has KE around 6.8 times it mass.

If you want a kiloton impact, you need a 150-tonne Rod.
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Elon better get to work :)
 
bobbymike said:
chimeric oncogene said:
They're reiterating that bullcrap claim again.

A Rod from low orbit is unlikely to hit at anything exceeding orbital speed, 7.8 km/s, unless it has been fired from a giant railgun. More probable speeds are 1-4 km/s.

An object at 3 km/s packs KE equivalent to its mass in TNT. An object at 7.8 km/s has KE around 6.8 times it mass.

If you want a kiloton impact, you need a 150-tonne Rod.
Click to expand...
Elon better get to work :)
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Now he's promising a hour turn around;). Hard to invest in a subsonic stealth bomber a sortie rate of 1 every 2 days.
 
chimeric oncogene said:
They're reiterating that bullcrap claim again.
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Yeah, it's not clear how much we should read into this. A government official tweeting a link to something as stupid as this is a bit unsettling. It implies that this guy doesn't know diddly squat. In fact, the discussion about "prompt global strike" happened a decade ago, and it's about very different methods. So simply by tweeting that, this guy implies that he's clueless.
 
chimeric oncogene said:
They're reiterating that bullcrap claim again.

A Rod from low orbit is unlikely to hit at anything exceeding orbital speed, 7.8 km/s, unless it has been fired from a giant railgun. More probable speeds are 1-4 km/s.

An object at 3 km/s packs KE equivalent to its mass in TNT. An object at 7.8 km/s has KE around 6.8 times it mass.

If you want a kiloton impact, you need a 150-tonne Rod.
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What if it's been accelerated downwards by a rocket motor?
 
He was nominated to be Under Secretary of State for Arms Control and International Security Affairs but he was never confirmed, as far as I can tell. His background is in SOLIC and terrorism financing, so I doubt he has a really clear grip on this material. But it also doesn't much matter, because he's going to be in the job for about 3 more weeks.
 
blackstar said:
chimeric oncogene said:
They're reiterating that bullcrap claim again.
Click to expand...
Yeah, it's not clear how much we should read into this. A government official tweeting a link to something as stupid as this is a bit unsettling. It implies that this guy doesn't know diddly squat. In fact, the discussion about "prompt global strike" happened a decade ago, and it's about very different methods. So simply by tweeting that, this guy implies that he's clueless.
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I hope you're not just finding out politicians know diddly squat about most things. ;)
 
Forest Green said:
What if it's been accelerated downwards by a rocket motor?
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Possible, but the cost of launching the suitable rocket motor into orbit...

Orbital kinetic strikes are good weapon even without that; they are perfect choice against such targets, as, say, Chinese island fortresses.
 
Forest Green said:
chimeric oncogene said:
They're reiterating that bullcrap claim again.

A Rod from low orbit is unlikely to hit at anything exceeding orbital speed, 7.8 km/s, unless it has been fired from a giant railgun. More probable speeds are 1-4 km/s.

An object at 3 km/s packs KE equivalent to its mass in TNT. An object at 7.8 km/s has KE around 6.8 times it mass.

If you want a kiloton impact, you need a 150-tonne Rod.
Click to expand...
What if it's been accelerated downwards by a rocket motor?
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You have to get that motor (and its fuel) into orbit in the first place, with all the delta-v that implies. And then deorbit it again, which means even more delta-v.
 
Well, if we are talking about available kinetics, the full load of Falcon Heavy (in expendable version) could deliver about 60 tons of rods - i.e. (not counting the de-orbiting boosters) about ten 6-ton rods. The summary TNT equivalent on circa 7 km/s would be about 440 tons - 0,44 kt.

If we disperse the rods evenly, the 5 psi overpressure area would cover about 0,8 km2. Slightly more than a similar area for 1-kt nuclear bomb.

So in theory, we could deliver nuclear-scale destruction even with available measures.

The problem of orbiting rods concept is more the problem of reaction time; the rod must be in proper position to drop it. Unless we are willing to wait days till the rod orbit would intersect the target location, we need either A - the unreasonable large number of orbiting rods, or B - unreasonable big supply of delta-V for rods orbit inclination changes.
 
Dilandu said:
Forest Green said:
What if it's been accelerated downwards by a rocket motor?
Click to expand...

Possible, but the cost of launching the suitable rocket motor into orbit...

Orbital kinetic strikes are good weapon even without that; they are perfect choice against such targets, as, say, Chinese island fortresses.
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mmm, as with sand castles, you just need to let the tide come in. Some weapons could assist with that, probably without needing to go into space, and come back, first.
 
Fluff said:
mmm, as with sand castles, you just need to let the tide come in. Some weapons could assist with that, probably without needing to go into space, and come back, first.
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Actually there are more problematic that seems. To took out reinforced concrete island fortress you need either to go nuclear (which would be an escalation & allow Chinese to use nukes against your military objects), or use unreasonably large amount of conventional munitions. The same with submarine pens, hardened air bases, ect.

On the other hands, orbiting rods could smash island fortress/underground sub pen/underground air base without much problems.
 
Forest Green said:
What if it's been accelerated downwards by a rocket motor?
Click to expand...

Once more, with feeling: If you have a kinetic weapon, unless you play some terribly complex games with gravity by slinging it from planet to planet in a complex decade-long dance, you only get *out* of the weapon what you put *into* it.

Think of a bullet: how destructive is it? To first order, how much gunpowder was used tells you how destructive it is. Those fifty grains of gunpowder are the *maximum* total energy that can be packed into the bullet. So with a Rod From God, the total energy of the weapon will come from the rockets that boosted it. If you pile all the rockets used, from the multi-stage space launch system to the orbital maneuvering system to the de-orbit booster, do you have a nuclear weapons worth of energy? No, you don't, unless your weapon was hefted by a Sea Dragon.
 
I dont see this weapon as being used as a mass attack, mainly because of the scale of the earth v the costs, of launch mainly.

Rather see it as an ability to deliver a 'hellfire' anywhere, within minutes, in support of a SF team, or an agent in trouble. So a few hundred missiles should cover much of the occupied earth.
 
Orionblamblam said:
Forest Green said:
What if it's been accelerated downwards by a rocket motor?
Click to expand...

Once more, with feeling: If you have a kinetic weapon, unless you play some terribly complex games with gravity by slinging it from planet to planet in a complex decade-long dance, you only get *out* of the weapon what you put *into* it.

Think of a bullet: how destructive is it? To first order, how much gunpowder was used tells you how destructive it is. Those fifty grains of gunpowder are the *maximum* total energy that can be packed into the bullet. So with a Rod From God, the total energy of the weapon will come from the rockets that boosted it. If you pile all the rockets used, from the multi-stage space launch system to the orbital maneuvering system to the de-orbit booster, do you have a nuclear weapons worth of energy? No, you don't, unless your weapon was hefted by a Sea Dragon.
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There's no point to actually put it in orbit these days. Assuming you actually hit the target these days, which is completely possible given PGMs not as much energy is needed. I guess it's a matter of how many submunitions this concept can fit to make it worthwhile.

I assume Billingslea is bringing it up because of Russia's tactical nukes.
 
Fluff said:
I dont see this weapon as being used as a mass attack, mainly because of the scale of the earth v the costs, of launch mainly.

Rather see it as an ability to deliver a 'hellfire' anywhere, within minutes, in support of a SF team, or an agent in trouble. So a few hundred missiles should cover much of the occupied earth.
Click to expand...

Orbital mechanics don't help with this. It's going to take at least a few tens of minutes between starting a deorbit burn and actually hitting atmosphere And then there's a question of how long it takes to get an object to the right place in its orbit to begin that deorbit burn and actually hit the aimpoint you want. Without aerodynamic maneuvering (aka braking) you really don't get much cross-range adjustment here. So you need a lot of objects in a LOT of different orbits to have one available to deorbit onto a specific aimpoint on really short notice.
 
TomS said:
Fluff said:
I dont see this weapon as being used as a mass attack, mainly because of the scale of the earth v the costs, of launch mainly.

Rather see it as an ability to deliver a 'hellfire' anywhere, within minutes, in support of a SF team, or an agent in trouble. So a few hundred missiles should cover much of the occupied earth.
Click to expand...

Orbital mechanics don't help with this. It's going to take at least a few tens of minutes between starting a deorbit burn and actually hitting atmosphere And then there's a question of how long it takes to get an object to the right place in its orbit to begin that deorbit burn and actually hit the aimpoint you want. Without aerodynamic maneuvering (aka braking) you really don't get much cross-range adjustment here. So you need a lot of objects in a LOT of different orbits to have one available to deorbit onto a specific aimpoint on really short notice.
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That's probably why G2G with LEO maneuvering is better.
 

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