Impact Physics

[jseah]

Deal serious damage on the ground?

I'll be satisfied with this.  Nuke-like effects without radiation fallout and logistical simplicity. 

[bean (OP)]

As a more serious question, what would a "Planetkiller" weapon try to achieve?
Deal serious damage on the ground?
Kill the Atmosphere?
Kill all inhabitants?
Or actually damaging the planet?

All of these are possible to some extent.  The current RKV-light under discussion would be a super-nuke, with a damage radius on the order of hundreds of kilometers.  Bigger objects would likely kill the planet, but the problem is getting them there.  Unless, of course, Steve allows us to shove them out of transports.

[jseah]

Don't think you want to kill planets anyway.  Just remove the... inconvenient biologicals.  =)
EDIT: late game, when it is possible, perhaps you might want to frag some moon somewhere to make a point, but even then I doubt that sort of thing will be used even as a last resort. 

The idea is to develop a different way to nuke planets besides slow and easier to intercept (relatively) nuke missiles.  Cost effectiveness wise, I think the nukes and kinetics are in the same ballpark but I believe kinetic missiles will win out once past the early tech levels. 

We shall just have to see when we get to play. 

[ollobrains]

Ok how about smaller nuclear warheads or fusion warheads based on smaller impact and explosion but able to travel faster, perhaps if they get so far into the planet they might render some environmental damage or even a mini terraformer warhead full of gas canisters that might change an atmospheres composiition

[bean (OP)]

Don't think you want to kill planets anyway.  Just remove the... inconvenient biologicals.  =)

That leaves two reason to kill a planet, then.
1. It's the easiest way to remove said biologicals.
2. It makes mining way, way, easier.
No, three reasons:
3. Fun

EDIT: late game, when it is possible, perhaps you might want to frag some moon somewhere to make a point, but even then I doubt that sort of thing will be used even as a last resort. 

The idea is to develop a different way to nuke planets besides slow and easier to intercept (relatively) nuke missiles.  Cost effectiveness wise, I think the nukes and kinetics are in the same ballpark but I believe kinetic missiles will win out once past the early tech levels. 

We shall just have to see when we get to play. 

Kinetics are excellent when you wish to destroy a couple hundred kilometers radius.  Not so good if you just want to kill a city.

Ok how about smaller nuclear warheads or fusion warheads based on smaller impact and explosion but able to travel faster, perhaps if they get so far into the planet they might render some environmental damage or even a mini terraformer warhead full of gas canisters that might change an atmospheres composiition

Inside the planet itself?  That would take an incredibly big warhead.  And a kinetic is going to do all the environmental damage you'd ever want.  That big of a heat pulse will not be a good thing, nor will any aftereffects from the shockwave.

[Panopticon]

I don't know that it would be easier to extract minerals from a planet you have killed. If you have wiped out the population then you can't use them as slave labor, also you have likely destroyed any of the facilities you could have re purposed. If by kill you mean break up the planet, I don't think it would be particularly easy to sort through a densely packed debris field that a broken planet would leave behind.

[ollobrains]

In that case a new asteroid field might form after a planet explosion ie planet killer

[Arwyn]

If your looking to actually crack the planet, kinetic is probably the way to go, but it would have to be big and fast.

If your just looking at icing a city, or disposing of obnoxious biologicals, then nukes/radiological weapons are the way to go. Its faster, cheaper, and from a strategic perspective a much easier weapon that say a tailor made biological weapon. They also don't tend to mutate like a biological might.

Cobalt bombs for example, are intensely radioactive, but the half like only around 5 years. If you don't like waiting that long, there are other types of radiological/nuclear fallout weapons that have even shorter durations.

Sodium-24: 15 hours
Gold-198: 3 days
Tantalum-182: 115 days
Zinc-65, 245 days

Of course those half lives are only for the isotopic materials, and are generated by a regular nuke, which is going to leave a LOT of regular radioactive contamination around. In theory, these isotopic nukes were small yield but intensely radioactive for short durations. Kill the bad guys and then roll into town a week later, is more less what they were designed for. Nobody has actually BUILT one, but the theory is there.

From a game perspective though, it might be a bit too much like GFFP. Also, some aren't exactly practical. Sodium has unpleasant reactive qualities that make it challenging to handle, and gold is a bit too pricey to be lobbing it around in mass produced nuclear weapons.

The other problem is that while the intense gamma ray emitters die off fairly quickly, the remaining isotopes from the blast are still present and due to the decreased yield and blast radius, could be possibly more concentrated in a smaller area.

You COULD use the current genetics research tree do do a biological warhead, and the idea has gotten used in a couple of games (thinking Sword of the Stars in particular) but the RESEARCH costs and time to do a tailor made bio-weapon for an alien race you dont have much info on is going to be huge.

Once again, you start getting into GFFP, which Steve hasnt been really thrilled about in the past, and the other problem, is that if the NPR's get to use them like players, they WILL use them. Unless of course Steve feels inclined to do a lot of AI coding to factor in racial militancy or xenophobia before the NPR gets weapons release for the bad stuff....
Either way,

[ollobrains]

And then u would need some form of GFFP counter as well i get the general idea.  Well lets see what our MIA programmer has to say when he wakes up

[jseah]

1. It's the easiest way to remove said biologicals.

Expensive though.  Planet-cracking costs way too much energy, like building a dreadnought sized missile.  2.7 fuel-mass ratio on a 10kton engine will be 27ktons of fuel... which is 27 million litres.  Very expensive even by TN aurora standards.  Easier to use a boat load of kinetic missiles to scour the surface.  Or just plain old-fashioned nukes and dirty bombs. 

A 10kton impact at 100kkm/s relative though (5E22 J).  =D  Everything on the planet is dead.  Probably lose a good chunk of the crust and atmosphere. 
Practical, no.  Makes a point, that it does.  (we can do this and we are not afraid to use it.  Don't piss us off)

For least property damage, I think the cobalt bombs mentioned will beat anything else.  Kinetic missiles are just not good at precision work.  Neither are nukes, I might like to mention. 

[Mel Vixen]

Well if you get enough particles into the air you could force a "nuclear" winter or you could destroy the ozon-layer with something more vicious then CFCs but both arent neither fast nor economical convenient. Rocks are cheap if we still could use massdrivers. Goldbombs would work althought you would need a few hundret to level a planet which makes me wonder what damage it would do to the ecosphere.
I would try to target food-sources thus the plantlife of a planet to kill its inhabitants if i have Bioweapons at hand. If i would have to kill Earth i would target Bees and other polinating insects. On the other Hand/paw/pod/claw/tentacle (or whatever your species has) you could add your own invasive lifeforms for example simple algae or grasses to a planets ecosphere. This can have interresting effects, take the first mosses on earth, they caused a Iceage on theyr first appearence.
 
Man i hate to plan Planetwide genocides, on those scale everything behaves like freaking coackroaches.

[bean (OP)]

My knowledge of cobalt bombs (or any other types of salted nuclear weapons) suggests that they aren't terribly effective.  For one thing, they definitely don't leave all property undamaged.  For another, the half-life is long enough that you probably won't get much out of it either.  The half-life is 5 years, so if it is intense enough to kill everybody, I'm not going in for a couple decades.
If you wish to kill off a planet, kinetics are the best option.  For scenarios when you only want a small area, slow kinetics or nukes work well.  Visible lasers do, too.  Maybe Steve could add those.  It would make specialized bombardment craft useful.

Expensive though.  Planet-cracking costs way too much energy, like building a dreadnought sized missile.  2.7 fuel-mass ratio on a 10kton engine will be 27ktons of fuel... which is 27 million litres.  Very expensive even by TN aurora standards.  Easier to use a boat load of kinetic missiles to scour the surface.  Or just plain old-fashioned nukes and dirty bombs.

I was thinking about unlikely scenarios, such as strong enough defenses that only your dreadnought-sized missile can get through.  In that case, cracking the planet is a side-effect of destroying your enemies.  Not likely, but possible.
And that list was mostly in jest, anyway.  Not something that's going to happen very often, certainly not often enough to bother coding in.

[liq3]

hxxp: what-if. xkcd. com/20/

tl;dr.  A 100-foot diameter diamond hitting earth at . 99c would punch it's way to the mantle and probably end all life (at the very least cause mass extinction). 

[swarm_sadist]

I don't think you seem to understand, liq3.

Check the density of diamond, then check how much mass a 100m diameter ball has. Next, determine how much energy it would take to reach anything remotely close to .99c, then determine what sort of energy it would take in game. Try to design a ship that can do this with end game tech, 'try' being the key word.

While everyone just cranks up the numbers to justify kinetic weapons, at those energy levels I could just build a giant laser than could vaporize the crust. That way I would not have to wait for my space rock of solid diamond to accelerate at the target, wouldn't need to aim the weapon from far away, and would not have to worry about any mass in the way to alter it's course or slow it down.

[liq3]

You don't need to get to . 99c though.  That'd be a planet killer.  0. 01c would be enough to do massive localized damage. 

Also it's 100foot, not m.