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Rods from God / "Project Thor"

Brickmuppet

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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.
 

Orionblamblam

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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?
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
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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Dilandu

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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.
It's actually pretty efficient, if you need to hit some hardened targets without provoking nuclear escalation.
 

taildragger

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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?
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
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.
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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Forest Green

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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?
Depends how you construct the carrier satellite, you could build it up like a space station over time.
 

Orionblamblam

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Energy efficiency factors into a weapons usefulness, but it's a small consideration.
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.
 

Grey Havoc

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Depends how you construct the carrier satellite, you could build it up like a space station over time.
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.
 

trose213

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Energy efficiency factors into a weapons usefulness, but it's a small consideration.
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.
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.
 

Forest Green

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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.
You mean like Brilliant Pebbles plus Brilliant Rods?
 
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