Re: what is the difference b/t an atomic bomb and a neutron bomb?

The good old fashioned atomic bomb uses a relatively thick blanket of uranium-235 or plutonium-239 with some type of fissile trigger to split (fission) as many of the atoms of U or Pu as possible in the shortest period of time. This of course generates a great deal of heat, some of which is used to fuse some heavy hydrogen (deuterium and tritium) at the core of the bomb. This has the effect of enhancing the yield rather a great deal but the excessive heat from the fission results in the formation of a large "mushroom cloud" and generally a great deal of collateral damage results from the fire storm and the vacuum created at ground zero. From a revenge standpoint that's a great way to make the enemy not attack you first. From a strategic standpoint, it's not a great idea. Keep in mind that the bombs detonated in the development of nuclear weapons and the two dropped on Japan are a far cry from the type of destruction you would get from a modern fission/fusion nuclear warhead. People can live in Hiroshima and Nagasaki today. A modern weapon would have a much greater yield and render the landscape radioactive for quite some time.

Hence the idea for the "enhanced radiation nuclear weapon" or colloquially: the neutron bomb. The concept here is to have as small of a fission blanket as possible, or preferably none at all, and generate all of the energy from fusion of duterium and tritium. The weapon detonation would probably yield only as much as a kiloton or so (this is speculation due to the obviously classified nature of the topic) but would result in many many times more radiation than in a "conventional" nuclear weapon.

So, what happens? In fusing deuterium and tritium, you get an abundance of high energy neutrons along with all the other radiation you would normally get. These neutrons have two additional major effects. First, anything directly exposed will not have to worry about being alive for very long. Secondly, the neutrons will interact with materials that they hit and generate among other things, high energy gamma rays. Gamma rays are much more penetrating and you get the added "benefit" of getting more than one gamma per neutron so even well shielded things and people will be vulnerable to neutron bombs. Hence, the strategic use of this device would run along the lines you mentioned in that very little property damage would result from a "modest" explosion, the radiation levels would decrease very rapidly and this would leave the infrastructure intact to be used by the attacking force. (Of course no one mentions the need to deal with all the bodies lying about, but that would be the case never the less.)

As for delivery, a neutron bomb should theoretically be very small. Small enough to be delivered by a 220mm long range artillery shell, a small cruise missile, an aircraft, or even by a person cleverly placing it on top of the tallest object near the target, say a building top. As for drawbacks, I suppose that's a matter of selective ethics. Strategically, they are much more expedient for taking territory quickly. In a rules of war argument, some may argue that this is particularly mean or cruel even though the alternative is roasting in a nuclear fireball. You are welcome to decide for your self on that issue.

I hope this adequately answers your questions.

Scott Kniffin
Senior Engineer
Orbital Sciences Corp.
NASA Goddard Space Flight Center