There was a comment in this post about TMIAHM, and Heinlein's idea about waging a war on earth from the moon by tossing rocks at it with a catapult. For those interested, a query to Henry Spencer resulted in a couple old sci.space.* threads debunking the notion, here and here.

Having read parts of the sci.space thread, I gotta say I agree with the criticism that Heinlein very greatly over-estimates the explosive power of a few rocks. That said, a politically independent Luna could be in a position to drop rocks on sensitive targets (such as Diego Garcia? Pearl Harbor? White House? Kremlin? Saudi oil terminals? China's Three Gorges Dam?)

Also, the ability to send clouds of pebbles into critical Earth orbits (suddenly annihiliate Earth's geo-syncs with lunar pebbles?) is far more feasible.

I stand by my geo-political (cis-lunar political?) assertion -- in the long term, a Luna that is politically independent from Earth will be a source of instability. And that will cause Terrans to have continuing interest in what happens on eth Moon, so the "escape the government" folks will need to go further out to successfully "escape the government"

I also seem to recall that Taylor Dinerman wrote an essay (Space Review?) that Luna may well serve as the 22nd century's version of what Gibraltar was for the British in the Age of Sail. Such key strategic points are a bad place to people to settle down at if their objective is to just be left alone.

I skimmed the threads; they don't seem to debunk the idea of throwing rocks so much as pointing out problems with the launch system, power source problems and interception and damage that 'a rock' could do.

In defense of RAH

* his characters knew about the first problem. They built a second catapult and there was some wordage tossed around that to this day it's location is the Lunar Republic's best kept secret'.

* I am pretty sure sure that the 'rocks' were put into the same canisters they used to ship rice; whatever shape they took they were used to get stuff to earth - in the case of weaponized rice carriers they simply didn't slow down.

Or something like that - it's been years and years since I read the novel.

I agree with you Brian.

Exactly HOW the Luna-tics would leverage that gravity well into a strategic advantage may not be clear but there are a great many possibilies and with better and better computer chips (no huge sentient machine necessary) lobbing 2000 kilograms of PGM bearing ore onto a pin-point target will only get easier and easier and 2000 kg of rock will bust open nuclear power reactor containment vessels or a handful of "splash" shots a half kilometer off Chicago's lake-front would cause more than enough damage.

2000 kg of gravel spread in a circle having a 1/4 kilometer radius would do nasty things to a major airport. Not thermo-nuclear capability but plenty of capability nonetheless.

= = = =

One advantage of using space elevators is that incoming bulk payloads can be restricted to equatorial orbits.

If NORAD detects an incoming lunar parcel NOT on a trajectory to attain a very low inclincation orbit maybe they can react sooner rather than later. Long term, using equatorial orbits for entering and leaving LEO would

(a) reduce the threat to northern hemisphere cities; and

(b) make space debris more manageable by keeping most of it within better defined corridors.

I just saw a Science Fiction book at Borders called Caris or Garis, with the premise that a bunch of rich people moved off planet and set up their own government and of course chaos thus ensued.

I did not buy it but I should have. It is the first to take the space tourist metaphor to a certain conclusion.

OTOH, I don't really see anything disputing the effectiveness of a lunar catapult. You apparently just need 5-10% (according to Henry Spencer) of the final impact energy (assuming the payload is deadweight with no maneuvering capability).

If one wanted to generate a 25 kiloton impact (which is roughly 10 trillion joules of energy) every hour or a 600 kiloton impact every day, that would be mean at most 300 MW of generation capacity. The material used would be more relevant since low density materials would lose most of their energy in the atmosphere. That's a lot of heat to hide in the Heinlein scenario, but it's not infeasible (eg, you should be able to dump a lot into the ground or transport it far away before you radiate it out to space. And if you target major infrastructure like cities, bridges, oil refineries, nuclear plants, etc, then you can generate a lot of damage.

Sure it's been overestimated, but the idea still seems viable to me.