How to kill blobs?

[Endie]

Wasn't Tera Joules the gap-toothed one with the dark hair in Gang Bang Auditions 14?

[WindupAtheist]

I saw this guy get kicked in the Tera Joules once.  It looks like it Mega Hertz.

[Murgos]

The only reason there is no fireball in space is because there is NO AIR.  The radiated energy from the nuke hasn't magically stopped propagating through space or disappeared.

You, know, like the mother fucking sun?

Anyway, math lols.

1 kiloton of TNT = 4.184 TJ (from physics factbook and also wikipedia)
1 megaton = 4.184 TJ * 1,000 = 4184 TJ or 4.184 x10^15 J

Surface of a sphere is calculated using 4*pi*r^2

If r = 10,000 m then the surface area that sphere is 1.25663706 × 10^9 m^2

4.184 * 10^15 J/ 1.26*10^9 m^2 ~= 3.3*10^6 J/m^2

OR for you idiots (Looking at you WUA) out there a 1 megaton explosion in outer space will have an energy density of 3.3 Mega Joules per square meter at 10 Kilometers.  Which in terms of force is 1 Mega Newton per meter square or about 250,000 lbs of force per meter square.

250,000 lbs of force PER SQUARE METER at 10 Kilometers.  They talk about the ships in Eve being a kilometer long.  Were talking about BILLIONS of pounds of force at 10 kilometers distance from a ONE megaton weapon being exerted on an object 1000 meters long x 50 meters high.

[Slayerik]

The only reason there is no fireball in space is because there is NO AIR.  The radiated energy from the nuke hasn't magically stopped propagating through space or disappeared.

You, know, like the mother fucking sun?

Anyway, math lols.

1 kiloton of TNT = 4.184 TJ (from physics factbook and also wikipedia)
1 megaton = 4.184 TJ * 1,000 = 4184 TJ or 4.184 x10^15 J

Surface of a sphere is calculated using 4*pi*r^2

If r = 10,000 m then the surface area that sphere is 1.25663706 × 10^9 m^2

4.184 * 10^15 J/ 1.26*10^9 m^2 ~= 3.3*10^6 J/m^2

OR for you idiots (Looking at you WUA) out there a 1 megaton explosion in outer space will have an energy density of 3.3 Mega Joules per square meter at 10 Kilometers.  Which in terms of force is 1 Mega Newton per meter square or about 250,000 lbs of force per meter square.

250,000 lbs of force PER SQUARE METER at 10 Kilometers.  They talk about the ships in Eve being a kilometer long.  Were talking about BILLIONS of pounds of force at 10 kilometers distance from a ONE megaton weapon being exerted on an object 1000 meters long x 50 meters high.

OH NOES, Murgos was playing possum and lands a devastating uppercut!!! Does WUA have the intestinal fortitude to get back up and keep throwing??!?!??1111?1!!!?!?

[Morat20]

The only reason there is no fireball in space is because there is NO AIR.  The radiated energy from the nuke hasn't magically stopped propagating through space or disappeared.

You, know, like the mother fucking sun?

Anyway, math lols.

1 kiloton of TNT = 4.184 TJ (from physics factbook and also wikipedia)
1 megaton = 4.184 TJ * 1,000 = 4184 TJ or 4.184 x10^15 J

Surface of a sphere is calculated using 4*pi*r^2

If r = 10,000 m then the surface area that sphere is 1.25663706 × 10^9 m^2

4.184 * 10^15 J/ 1.26*10^9 m^2 ~= 3.3*10^6 J/m^2

OR for you idiots (Looking at you WUA) out there a 1 megaton explosion in outer space will have an energy density of 3.3 Mega Joules per square meter at 10 Kilometers.  Which in terms of force is 1 Mega Newton per meter square or about 250,000 lbs of force per meter square.

250,000 lbs of force PER SQUARE METER at 10 Kilometers.  They talk about the ships in Eve being a kilometer long.  Were talking about BILLIONS of pounds of force at 10 kilometers distance from a ONE megaton weapon being exerted on an object 1000 meters long x 50 meters high.

There is no force. No blast. No thermal transmission at all. There'd be lots of radiation, however. If I'm reading that chart right, a 20kt blast will yield lethal radiation doses out to about 14 miles -- that's assuming the absence of any shielding. (I'm considering a 500 roet dose as 'lethal').

Actual blast and heat? Squat.

[Endie]

The only reason there is no fireball in space is because there is NO AIR.  The radiated energy from the nuke hasn't magically stopped propagating through space or disappeared.

You, know, like the mother fucking sun?

Anyway, math lols.

1 kiloton of TNT = 4.184 TJ (from physics factbook and also wikipedia)
1 megaton = 4.184 TJ * 1,000 = 4184 TJ or 4.184 x10^15 J

Surface of a sphere is calculated using 4*pi*r^2

If r = 10,000 m then the surface area that sphere is 1.25663706 × 10^9 m^2

4.184 * 10^15 J/ 1.26*10^9 m^2 ~= 3.3*10^6 J/m^2

OR for you idiots (Looking at you WUA) out there a 1 megaton explosion in outer space will have an energy density of 3.3 Mega Joules per square meter at 10 Kilometers.  Which in terms of force is 1 Mega Newton per meter square or about 250,000 lbs of force per meter square.

250,000 lbs of force PER SQUARE METER at 10 Kilometers.  They talk about the ships in Eve being a kilometer long.  Were talking about BILLIONS of pounds of force at 10 kilometers distance from a ONE megaton weapon being exerted on an object 1000 meters long x 50 meters high.

This makes no sense to me.  I mean, there are various correct pieces of arithmetic in there, but physics-wise the last bit is just plain weird.

Mind you, the mixing of imperial and metric disturbs me enough to begin with 

[WindupAtheist]

Jesus, Murgos, again you fucking fail.  Where the hell do I start?

Okay, first off, check your god damned numbers with a third party before you try this horseshit "Rawr math!" attack again.  Because both these guys and these guys say your 3.3 megajoules convert to 0.00078 tons of TNT, or 788 food calories.  Holy shit, the raw power of a couple of Big Macs.  Where the hell are you getting this quarter-million pounds of force shit?  There aren't blast waves in space any more than there are fireballs anyway.

Secondly, as Morat pointed out helpfully, it's the radiation we care about.  And while it may be lethal at extreme ranges against those who are unshielded, or walking around on the hull as I put it, let me throw a couple of gems from Wikipedia at you.

The character of the radiation received at a given location also varies with distance from the explosion. Near the point of the explosion, the neutron intensity is greater than the gamma intensity, but with increasing distance the neutron-gamma ratio decreases. Ultimately, the neutron component of initial radiation becomes negligible in comparison with the gamma component.

One standard design practice is to measure the halving thickness of a material, the thickness that reduces gamma or x-ray radiation by half. When multiple thicknesses are built, the shielding multiplies. For example, a practical shield in a fallout shelter is ten halving-thicknesses of packed dirt. This reduces gamma rays by a factor of 1/1,024, which is 1/2 multiplied by itself ten times. This multiplies out to 90 cm (3 ft) of dirt.

And lastly, you can try moving the goalposts with this "Energy doesn't disappear when there's no fire, stupid WUA!" crap all you want, but who the fuck do you think you're fooling?  What did you think was supposed to bother my hypothetical guys out on the hull in the first place?  Congratulations math master, you've again proven that you don't know what the fuck you're talking about.

You are down.  You are out cold.  Take what scraps of your dignity remain and get the fuck out of here.

[bhodi]

OK, I guess I have to get involved. You know I like superweapons, right? Yeah. OK let's begin.

In atmosphere, we are interested in the kinetic energy in a non-oscillating spherical wave, which is concentrated at the wave front -- your typical blast wave. We want a surface area figure, how much force, which happens to be inverse-cubed. We care about this in atmosphere, because once all that ionizong radiation gets absorbed by the atmosphere it ends up being ~90% of the energy released. Your end products after conversion are blast 40-60%, thermal radiation 30-50%, Ionizing radiation 5% and residual radiation 5-10% of total energy of the initial release (see below).

In space, we are interested in energy density only, which falls off as divided by radius-squared (equivalent to r=energy^1/2)

Now. 1 kiloton of TNT is not equivalent a 1 KT nuclear detonation. Your figures on this are just flat wrong, and I'm going to ignore the math here. You are trying to calculate a PSI spherical wave in space based on the released energy of TNT. I don't need to spell this out, since we are using neither TNT nor are we in atmosphere. Let's talk about what gets emitted when someone hits the big red button:

Ionizing radiation. Gamma rays and Neutrons. That's it. It does a whole bunch of funky stuff in atmosphere when it hits, converting it to thermal radiation (xrays, heat). Heating and vaporization of your immediate area creates expansion, which creates that pressure wave you keep trying to reference. We don't care about any of that. We aren't in atmosphere.

How do we stop Ionizing radiation? Dense material. It's measured in HVL or half value layer, the amount of material (in cm) that is required to reduce the radiation by half. The halving distance of lead is 1 cm, the halving distance of depleted uranium is 0.2 cm.

For all practical purposes, you could sit on top of a nuke with enough shielding. I guess I could work up the math on this, but it's pretty pointless -- you should be able to see that nukes in space don't do a whole lot unless, as was said, you were standing on the outside of the hull, assuming the hull is thick enough. You'd need no more than a few feet to stop anything but a direct hit.

[ajax34i]

Heh, I did the same math as Murgos the last time when he told me to stop and not derail, so I kept it to myself.  I also got the 3.3 Mil Joules / m2 at 10 km, but then I figured the radiation would be absorbed and converted to heat, rather than force.  So a ship would need how many centimeters of lead?  And it would need to be cooled; water-cooled I think there's like a 7 deg. C (12 deg. F) increase in the water temperature. 

[bhodi]

Fuck it, let's do some rough back-of-the-napkin math.

1 TeraJoule is equal to 10^12 Joules
1 kiloton of TNT = 4.184 TJ

Therefore, 1 KT of TNT = 4184000000000 Joules, or 4.184 × 10^12 J. Let's work up a few scenarios. 100 meters (direct hit), 1km (1000m), and 10km  (10,000m) away with a 1KT nuke yield.

Let's work backwards and see how much shielding we would need.

One rad is an absorbed dose of 0.01 joules of energy per kilogram of tissue, and a dose of 400-450 rads is lethal to your average human. gamma and xray RBE (biological effectiveness) is 1, so we can go straight math. Let's say we want no more than 100 rads (headache, decreased immune system and temporary sterility) and that your average crew member weighs 100kg.

1 rad for this guy is 1 joule absorbed, so he can eat 100 joules of energy in the form of gamma and xray EM radiation and all he gets is a bad headache and no babies for a while.

100m:
Inverse square law fun before it hits shielding: 4.184 * 10^12J * 1 / (100^2) = 4.184 * 10^12J * .0001 = 418,400,000J
22 halvings needed to bring shielding below our needs to 99.7

1000m:
Inverse square law fun before it hits shielding: 4.184 * 10^12J * 1 / (1000^2) = 4.184 * 10^12J * .000001 = 4,184,000J
16 halvings needed to bring shielding below our needs to 63.8

10000m:
Inverse square law fun before it hits shielding: 4.184 * 10^12J * 1 / (10000^2) = 4.184 * 10^12J * .00000001 = 41,840J
9 halvings needed to bring shielding below our needs to 81.7

Halving strengths:
9 cm (3.6 inches) of packed soil or
6 cm (2.4 inches) of concrete,
1 cm (0.4 inches) of lead,
0.2 cm (0.08 inches) of depleted uranium,
150 m (500 ft) of air.

So, only 22cm of lead or 4.4cm of depleted uranium is sufficient to stop a 1KT nuke from 100m away, a 'worse case' scenario.

Edit Disclaimer: This is gamma ray calculation only, I can't get reliable numbers on the gamma to neutron percentage or the neutron velocity, and neutron radiation goes right through this armor, but then is easier to block with a several-foot thick inner core of lighter weight material. Yes, the neutrons have mass, no it doesn't matter much. I'm too lazy to the heavy math required.

[Murgos]

One joule is the work done, or energy expended, by a force of one newton moving an object one metre along the direction of the force. This quantity is also denoted as a Newton-meter with the symbol N·m.

I fudged the vector (force has a direction, you know?) bit because I didn't want to do more math that would just be wasted on hamburger boy.  1 Newton is roughly .22 lbf.  I did screw up because the final number should have been closer to ~800,000 lbf, I forgot the 3.3.  I also fudged the numbers lower by a couple of orders of magnitude because the wave front of a nuclear explosion doesn't take 1 second to occur.  At a guess it's probably closer to 1 us.

The particles leaving a nuclear explosion do carry a force component, they are not all pure energy without mass, in fact, the alpha particle mass is 6.644656×10-27 kg and a beta particle is 9.109 × 10–31 kg.  I don't know how many particles are emitted in a nuclear explosion but it's not trivial and since they actually are travelling at relatavistic speeds in space, well it adds up.

Why someone would think there would be no pressure wave in the sudden acceleration of all the particles involved in the explosion is on beyond me.  Almost a hundred years ago someone correlated energy to mass.  I wonder who that was?

edit: I think most of you are missing the point that 10 km is such a small distance in stellar terms that you are confused about what's being discussed here.

[bhodi]

Oh, for fuck's sake. Stop splitting hairs. Yes, there is radiation pressure. It's such a small amount of the whole that it's insignificant, except that a VERY SMALL part of that 4.194 x 10^12 Joules contain a force component that is calculated with inverse cube law instead of inverse squared. The force is virtually nothing when compared with the whole and so I'm not bothering to calculate it with my back-of-the-napkin math. And we're ONLY talking about the neutron component, obviously, since the gamma ray component is essentially massless.

[Morat20]

Oh, for fuck's sake. Stop splitting hairs. Yes, there is radiation pressure. It's such a small amount of the whole that it's insignificant, except that a VERY SMALL part of that 4.194 x 10^12 Joules contain a force component that is calculated with inverse cube law instead of inverse squared. The force is virtually nothing when compared with the whole and so I'm not bothering to calculate it with my back-of-the-napkin math.

Imagine driving a Ford F150 down the road at 60 mph. Your car slams into a cloud of mosquitos. Despite the fact that you're taking two or three mosquitos per square inch at 60km, your truck is merely messy -- not destroyed.

Same for the particle mass emitted by a nuclear blast -- although at 10 km's you'd probably only catch a particle or two per square meter.

So, in effect -- and fuck, man, I linked to NASA already, a nuclear explosion in space releases no blast wave, no heat, and nothing to "impact" your ship. It does release a lot of radiation, but a 20kt blast drops below lethal at only 15km. There is no fucking "force" on the goddamn spaceship.

[Simond]

So, only 22cm of lead or 4.4cm of depleted uranium is sufficient to stop a 1KT nuke from 100m away, a 'worse case' scenario.

What about rolled tungsten, or nanofibres? 

[Fordel]

So in a nutshell, when John Sheridan setup the nuke minefield to destroy the BlackStar, it was in fact, totally bullshit?  :-D

[Murgos]

Yeah, right.  Nuclear explosions have no force when used in outer space.

What kind of crack are you smoking?

[bhodi]

Yeah, right.  Nuclear explosions have no force when used in outer space.

What kind of crack are you smoking?

Hey dumbass, they used fucking propulsion mass heated by the gamma rays:

At 1 microsecond after ignition, the gamma bomb plasma and neutrons would heat the channel filler, and be somewhat contained by the uranium shell. At 2-3 microseconds, the channel filler would transmit some of the energy to the propellant, which would vaporize. The flat plate of propellant would form a cigar-shaped explosion aimed at the pusher plate.

Let it go. You're grasping at straws and you don't know what you're talking about.

[Simond]

So in a nutshell, when John Sheridan setup the nuke minefield to destroy the BlackStar, it was in fact, totally bullshit?  :-D

You build x-ray laser or graser emitters around the warheads, transmuting the radiation into coherent beams of x-rays/gamma rays.

[bhodi]

Simond is correct :) Nuclear mines would actually be nuclear bomb-pumped laser/grasers with multiple spokes of death. Featured prominently in the honor harrington series.

[Morat20]

Simond is correct :) Nuclear mines would actually be nuclear bomb-pumped laser/grasers with multiple spokes of death. Featured prominently in the honor harrington series.

Goes back further -- Larry Niven used them in Footfall (Fuck you! It had a goddamn elephant with a ray-gun on the cover. Anyone would read that!) -- using nukes for propulsion and channeled some of it out via lasers and the like.

Hey, killing elephants is hard work.

[bhodi]

Hey, that one had one of my favorite weapons -- kinetic orbital bombardment, aka rods from god. AND it had the orion in it, too. I don't think it had relativistic kill vehicles in it, unfortunately.

[Morat20]

Hey, that one had one of my favorite weapons -- kinetic orbital bombardment, aka rods from god. AND it had the orion in it, too. I don't think it had relativistic kill vehicles in it, unfortunately.

No, but it did impress upon me the simple fact that "the high ground" means a huge amount when you're down at the bottom of a gravity well. You don't need explosives, lasers, beam-weapons, death-rays, nukes, or anything else.

Just rocks. And all you have to do is nudge them a bit, and they'll blast the shit out of whatever they hit.

[Murgos]

Yeah, right.  Nuclear explosions have no force when used in outer space.

What kind of crack are you smoking?

Hey dumbass, they used fucking propulsion mass heated by the gamma rays:

At 1 microsecond after ignition, the gamma bomb plasma and neutrons would heat the channel filler, and be somewhat contained by the uranium shell. At 2-3 microseconds, the channel filler would transmit some of the energy to the propellant, which would vaporize. The flat plate of propellant would form a cigar-shaped explosion aimed at the pusher plate.

Let it go. You're grasping at straws and you don't know what you're talking about.

I went and talked to one of the physicists here and came away with a few things.
1) I am wrong about blast effects.
2) You are wrong about radiative effects.  In space you can expect them to be maybe 20 times more effective than at sea level.
3) The energy released by a 1 megaton explosion at 10 Km would still be enough to cause severe damage due to the material attempting to dissipate that much energy into a vacuum, possibly even the vaporization of some portions of the craft and the destruction of the electronics.
4) Wrapping the nuke in a few tons of dense material would do a lot to cause highly damaging effects out to, in his terms, very large distances.

Hamburger boy still has no clue what he's talking about though.

[ajax34i]

4) Wrapping the nuke in a few tons of dense material would do a lot to cause highly damaging effects out to, in his terms, very large distances.

Actually, the material would have to be accellerated, so you have the nuke at the core, surrounded by something that can absorb radiation and change from solid to high pressure gas or plasma, then your shell of jagged metal bits, and the point would be to absorb all the energy of the nuke and convert it to kinetic on the metal bits (and thus the "few tons of dense material" effectively shield your target from radiation; you're now delivering kinetic, not radiation, with such a weapon).

I don't know if it's more effective to just have a huge-ass house-sized grenade with conventional explosives than this whole nuke business; the nuke sure packs a lot of energy into a small volume, but converting radiation -> kinetic isn't very effective.  It's probably a lot more effective to just shoot projectiles at the target, really.  Actually, kinetic missiles, best.

[Morat20]

I went and talked to one of the physicists here and came away with a few things.
1) I am wrong about blast effects.
2) You are wrong about radiative effects.  In space you can expect them to be maybe 20 times more effective than at sea level.

No, you're just not reading. It was in my link and several other people talked about how when there's no atmosphere to absorb radiation, it's considerably more lethal.

As I noted, a 20kt blast in vaccuum delivers a lethal dose out to at least 12 miles. That's to someone unshielded. Many people pointed out that shielding against that level of radiation is pretty trivial -- a few inches of metal, at most.

3) The energy released by a 1 megaton explosion at 10 Km would still be enough to cause severe damage due to the material attempting to dissipate that much energy into a vacuum, possibly even the vaporization of some portions of the craft and the destruction of the electronics.

Wrong, unless you're discussing an EMP effect. Once again, shielding handles that nicely -- and here's the cool thing about space. It's fucking cold. Since the nuke doesn't transmit heat, all that radiation your 3 inches of lead just absorbed radiates nicely into the gigantic heat sink you're floating in. Lead, DU, or plenty of carbon compounds can hold a great deal of heat -- and can even be tricked into venting it in one direction only. (It's done on the space shuttle all the time).

It's pretty easy to make sure heat flows out to space, even if the heat is generated by radiation absorption -- and the dose of radiation from a 20kt bomb in space isn't going to heat lead all that much.

4) Wrapping the nuke in a few tons of dense material would do a lot to cause highly damaging effects out to, in his terms, very large distances.

You mean "shrapnal"? I suggest to you that you consider the Air Force's general views on flack -- it's a big damn sky, and the odds of a piloted plane being in the same spot as undirected flack fire is minimal.

Space is even bigger, and you're going to smear it over a constantly expanding sphere -- at 10km, you'd need more than a few tons to have any hopes of reliably impacting vessels.

[Slayerik]

This thread delivers.....astrophysics.

[bhodi]

First, there isn't an EMP effect in space. That's created when it the gamma rays hit parts earth's atmosphere. I could whip out the details but they aren't interesting or pertinent.

For your #2, I've already said that space radiative effects are "about 20 times more effective" by explaining how it's primary emittance (gamma & neutron radiation) gets converted into thermal xrays and a blast wave. I'm not sure how that makes me wrong...

#3 is interesting, would depend heavily on the boiling point of the material plus how well it conforms to a 'perfect' black body radiator (a lot of the radiation gets reflected rather than absorbed, the question is how much). Fortunately, by eyeballing the amount of Joules that hit it at 100m indicates to me that it wouldn't even be close; you'd have to be inside that, possibly even score a direct hit.

#4 is pretty dumb if your physicist suggested it, as morat20 says, there's no such thing as effective 'flak' when we're talking about distances in km.

[Morat20]

#3 is interesting, would depend heavily on the boiling point of the material plus how well it conforms to a 'perfect' black body radiator (a lot of the radiation gets reflected rather than absorbed, the question is how much). Fortunately, by eyeballing the amount of Joules that hit it at 100m indicates to me that it wouldn't even be close; you'd have to be inside that, possibly even score a direct hit.

I think we're back at the "A nuke in space is only a problem if it goes off while in contact with your hull" zone.

You want to shoot space-ships, you either need directed energy weapons (those would be fun to target when your relative velocities started getting up about .5c) or, more likely, torpedos of some sort. Guided little mini-ships with shaped charges on the nose.

Mass drivers might work, assuming you were in really close or you had enough to blanket them no matter how they tried to manuever.

As someone else noticed, using a nuke to power an high-energy squirt would work better. Turn that energy into a lovely pumped laser that would bore a hole through an asteroid. You'd only have to worry about targetting (which, as noted, is difficult if your relative velocity is high enough).

[Endie]

I love bomb-pumped lasers.  Best sci-fi space opera weapon ever.

[JoeTF]

Those bomb laser thingy - I know you can theoretically make laser out of everything, but did anyone actually built it? Making mega-uber-pumped laser is cool, but how do you stop that mega uber pumping from vaporizing your uber roid driller?

The rods from god - won'tr they melt and most importantly - won't they just make a small hole that is really, really deep?

Lastly, doesn't most AA missiles use flaking efect? Noone stops you from putting an engine and proximity detonator on that nuke-grenade, you know and at least you won't have to go for direct hit. (plus, in an environment without atmosphere, evading incoming kinetic missiles doesn't seem like hard thing to do) 

[MahrinSkel]

Supposedly there were a couple of preliminary tests showing you could create a laser that way, but then we signed a treaty agreeing not to test nukes, even undergound.  So we know that it's possible to do it, but no actual system for creating them with a portable system or aiming them has been field-tested (or can be).  Which makes it the perfect defense contract.

--Dave

[Chenghiz]

Thanks for the space physics lessons, guys! :D

[Morat20]

Those bomb laser thingy - I know you can theoretically make laser out of everything, but did anyone actually built it? Making mega-uber-pumped laser is cool, but how do you stop that mega uber pumping from vaporizing your uber roid driller?

You explode the bomb in vacuum, and basically create "channels" of dense material which feeds the radiation up the tubes, IIRC. Space-opera wise, either they don't explain how they're doing it, or it's a nifty side-benefit of an Orion-style drive. (Nuke-pushed drive)

The rods from god - won'tr they melt and most importantly - won't they just make a small hole that is really, really deep?

First, coat them with ablative material (cheap stuff -- only has to work once). Secondly, no. When it hits, it releases a LOT of it's kinetic energy as heat. A small crowbar sized objetc would obliterate a battleship, assuming it was still crowbar-sized when it hit.

It's hull it. And melt lots of it. And superheat the water below it, which would leave you with a battleship with a huge hole in it, boiling water and superheated steam flying in every direction, and molten metal. It'd sink in seconds.

Lastly, doesn't most AA missiles use flaking efect? Noone stops you from putting an engine and proximity detonator on that nuke-grenade, you know and at least you won't have to go for direct hit. (plus, in an environment without atmosphere, evading incoming kinetic missiles doesn't seem like hard thing to do) 

Flak works if you can aim it, to an extent. You have a much better chance of hitting something that way. But just exploding flack in the sky, hoping to knock down a plane -- not so much,

[WindupAtheist]

God, this is great.  He just keeps coming back for more.  Posting the nuclear propulsion article without really reading it was priceless.

EDIT:  Also, Honor Harrington is indeed made of win.  I just started the series a little while ago, finished book three and need to get four.

[bhodi]

Supposedly there were a couple of preliminary tests showing you could create a laser that way, but then we signed a treaty agreeing not to test nukes, even undergound.  So we know that it's possible to do it, but no actual system for creating them with a portable system or aiming them has been field-tested (or can be).  Which makes it the perfect defense contract.

--Dave

Not *strictly* true. You can bomb pump with conventional explosives, too, depending on desired effect. For example, a non-nuclear EMP device. It's not really the same thing, I know.

You can learn everything you wanted to know about kenetic bombardment in this helpful wiki page. The only thing stopping us from deploying something like it right now is cost per kg to LEO.