How much velocity or kinetic energy do we need to give a cannon ball in space, to hit the earth with as much energy as an atomic bomb? Let's assume that this cannon ball is made of titanium, so that it doesn't disintegrate across the atmosphere upon entry. Thread started at Forum 4 Politics on 05-04-2012 03:49 PM
Asteroids with diameters of 5 to 10 m (16 to 33 ft) enter the Earth's atmosphere approximately once per year, with as much energy as the atomic bomb dropped on Hiroshima (about the equivalent of 15,000 tonnes of TNT). These ordinarily break up in the upper atmosphere, and most of the solids are vaporized before they hit the earth. It is not currently within human capability to accelerate any significant quantity of mass to speeds that would make it anywhere near as powerful as a nuclear weapon. However, one interesting fact is that a space station in orbit around earth is moving at such a high velocity that it actually has more energy than chemical explosives. An object in "low earth orbit" moves at 27,400 kilometers per hour, and has an energy density of 33MJ/kg, while the powerful explosive HMX has an energy density of 5.7MJ/kg. This means that 2 grams of mass in low earth orbit has about 62 times as much kinetic energy as a bullet from a rifle, which also weighs about 2 grams.
It is not beyond comprehension that, in the future, we could be capable of re-directing a large asteroid so as to not hit the Earth....OR.....Maybe re-directing a smaller asteroid to hit a selected area of the Earth? One wonders.
Another little interesting fact: If humans ever managed to make an anti-matter bomb, only 60 percent of the bomb's potential energy would be converted to a useful explosion. The annhilation of protons with anti-protons releases 40 percent of its energy in the form of neutrinos, which mostly just pass through ordinary matter without affecting it.
A hydrogen bomb can be build big enough that the limit to destruction is the horizon. A hydrogen bomb would be much larger than an anti-matter bomb (depending on the size of containment), 60% of way too much is still way too much. We will be able to steer asteroids long before we can manufacture enough anti-matter to use as weapons.
A neutron bomb is basically just a thermonuclear (hydeogen) weapon, with as little uranium (or other fissionable material) as possible. Fusion still gives off radiation, but without the long-lived radioactive isotopes of fission.
Good! So this is more of an engineering challenge than science now. Maybe that with the US or Chinese military budgets, this very sophisticated and clean weapon can finally be manufactured and marketed.
