In that book the projectiles were 100 metric ton cylinders of steel-encased rock and had an equivalent explosive yield of two kilotons. He didn’t give the dimensions of the “barge”, but 100 metric tons of lunar rock would form a sphere four meters in diameter.
To launch those from the moon required a gigantic linear accelerator. Two were mentioned in the book, one 100 km long, and the other 30 km long.
His math was correct: if you plug the numbers into this impact effects calculator it produces roughly 2 kilotons for 100 metric tons of rock (3000 kg/m^3) moving at typical reentry velocity of 11 km/sec: Impact Earth
The OP asked was it practically possible to build some weapon more powerful than nuclear weapons. Since nuclear weapons can be built to at least 50,000 megatons, it seems the answer is generally no. There is no practical way to accelerate sufficient mass from the lunar surface which produces more explosive yield than 50,000 megatons.
The only conceivable way to exceed this would be divert an entire asteroid of roughly 1 km in diameter or larger, but that would mass 3.45E12 kg, or 3,451 billion metric tons. Such a rock would exceed 50,000 megatons on impact.
However likely the only way to achieve that is using nuclear weapons in stand-off detonations to deflect it. No other method can produce sufficient deflection delta V on such a massive object. Even a 100 megaton warhead would only deflect it about 0.1 meter per sec. So even if that were possible, it would require use of many nuclear weapons, and the point is can it be achieved without nukes.
Attempting to deflect a 1km size asteroid without nuclear weapons produces vanishingly small delta-V. This calculator shows the largest current launch vehicle (Falcon Heavy) would only deflect a 1km asteroid by 0.05 millimeters per sec: Center for NEO Studies
Daniela Comelli1,*, Massimo D’orazio2, Luigi Folco2, Mahmud El-Halwagy3, Tommaso Frizzi4, Roberto Alberti4, Valentina Capogrosso1, Abdelrazek Elnaggar5, Hala Hassan3, Austin Nevin6, Franco Porcelli7, Mohamed G. Rashed3 andGianluca Valentini1
Version of Record online: 20 MAY 2016
See this thread from 2011 for discussion of the history of this; Posts #2 and #3 cite an earlier sighting (the first?) on this board; and Post #2, in particular, explains why it’s been so often seen here ever since. Upon a quick glance, some subsequent posts appear to give links to earlier sightings elsewhere in the Net universe.
For clarification, in this thread I am referring to kinetic or explosive power. Chem/bio agents or nano-bots, while lethal, are not about kinetic/explosive power.
There’s the anecdote that the original atomic bomb designers had some concerns that an atomic explosion might set off some sort of a chain reaction. Obviously this didn’t happen.
But is it theoretically possible to design a doomsday device to work that way? Can you initiate an atomic explosion that itself causes another atomic explosion which causes a third explosion and so on?
That’s how a fusion device works.
But, there’s no way that you can create a sustaining chain-reaction of either fission or fusion outside of a bomb. First of all, the elements in the environment are not easily split or combined, so they can’t be used as fuel. Even if we lived in a pure Deuterium atmosphere, the density is too low to permit fusion.
If we lived in pure Tritium, it might work…
No that is not possible. It is true early in the development of the atomic bomb there was speculation it might ignite a self-sustaining fusion reaction in the atmosphere. However calculations showed this could not happen:
Awwh, that’s a pity. What made me read this thread was precisely the expectation that someone would give a somewhat more realistic, less predictable answer. I was just about to give up until Commodore did it, right at the end of the page.
Jim Butcher has started a new series with The Aeronaut’s Windlass, which among other things features sentient cats with extended dewclaws that serve as a crude thumb.
The reason this method is attractive is that it multiplies the velocity of the impactor by nearly a factor of five, and the energy of impact is multiplied by a factor of more than twenty. So maybe Czarcasm was right; instead of a mass driver, we use an atomic-powered cannon to blast huge chunks of mountain at the Earth to take advantage of the gain in momentum.