yeah, I guess that is the fallacy with SF. The author can pretty much do anything they want with it.

As several people have posted on another forum in another time, "science fiction is just fantasy with lasers".

This is mostly because in many SF/SciFi stories (there is technically a difference, in that SF is more written and more scientifically accurate than the "whoosh!! ZAP ZAP ZAP!!!" Hollywood-style SciFi genre) use many handwavium (I wave my hands and say "I have inertial compensators for multi-million-G accelerations!! WHEEEE!!!!") items, and explain them with technobabble (think Star Trek explanations of their gear. I would say that the unintelligebility factor cubes with the squaring of the technobabble factor, but don't quote me ).

More "scientifically plausible" items are 'unobtainium'. Note that handwavium/technobabble usually tells you what you can do, unobtainium usually tells you what you can't.

My personal perspective is that- in a hard SF scenario, most industry would still be located on a planet's surface, as 1) that's where most of the people are, 2) it's probably where most of the materials are, and 3) people don't really tend to want to go to a very potentially deadly place to work.

Hence, most of the defenses will be planet based. However, 1) a planet will also likely have its own (probably small) cadre of spacecraft for defense; 2) a planet will likely also have large, very difficult to destroy "battlestations" that would be somewhat analagous to SoaSE:Entrenchment starbases.

Because I would also postulate that highly inhabitable (terran, jungle, ocean, ice, desert) planets are at a premium (or somewhat scarce), just dropping nuclear weapons (or similar, as antimatter just can't be good for a planet's biosphere) or maybe giant planet-killer rocks just isn't a good idea. Mostly because devastating a planet would be bad for everyone. All around.

In contrast, a super-high-intensity conventional warfare would likely also not be the way to go. This is because, as has become apparant, modern, conventional warfare can probably take as many or even more lives than thermonuclear war. As a result (and also because I think this is cooler), I postulate the use of "cap troopers", that is, orbitally-deployed infantry that are "dropped" onto a planet's surface (more like into the lower atmosphere) with "capsules" (hence, "cap"-trooper; also note that I drew this from Heinlein's book Starship Troopers, and not that abomination (in comparison to the book) of the movie.). Such troopers would also be backed by dropship-deployed artillery and armored battlegroups, but the infantry (which are equipped with power-armor, and said infantry also carry "peewee" nukes, capable of destroying local targets, such as: water plants, power plants, distribution centers, manufacturing centers, &c) are the main fighting force.

As a result of the above, it would also happen that for raiding ops, said troops would deploy without armorial (tanks, arty systems) support. This would also make the raids much less costly than a conventional-style attack.

Anyways, that's my take. What do you think Koiju? And, what might you take be?

Well, for one thing, I think you are assuming a lot about the potential enemy. You said that it would be bad for everyone to use a nuke, but that's assuming they aren't an alien life form from a radioactive planet. Any life form that evolved on a more radioactive planet is likely to preffer a more radioactive atmosphere, and thus it would actually be in it's interest to specifically drop nuclear bombs on other peoples planets.

Now, as for if it's even possible for such a life form to exist? I don't know, but since I don't know, I'm not going to assume they don't, on the off chance that they do.

To be honest, my take on it is, that if we have the technology to build giant space stations that can support massive populations, as well as colonise alien worlds, I'm pretty sure our terrerforming technology can easily cope with nuclear fallout or other scars left behind from planet bombing, and it therefore wouldn't surprise me in the least if we used powerfull bombs on planets.

I would assume that each race, or even factions within races, would use different tactics, in the same way different countries on modern day earth use different tactics when going to war. Some might use more precision weapons, while others would just blow stuff up and deal with the consiquences later.

So I'd say that some would do what you propose, but others would just bomb the crap out of the planet. Thus if I were to be in charge of defense, I'd want to cover every angle. I'd have anti-air guns on the planets surface designed to 'shoot down' any incomming 'cap troopers' or other invading military hardware (note: these wouldn't be designed to shoot in to space itself, only in to the atmosphere to destroy any incomming exlosive ordenance or drop pods). I'd then have un-manned space bound platforms in orbit (probably missile launching, so there's no heat sink or momentum issues), these would be harder to destect due to having no habitation modules (though I know it's still not impossible, just harder, especially with your planets own warmth as background thermal 'noise'). These would be to assist the other orbital defenses and ships in orbit to help prevent anything reaching the planet in the first place.

I'd probably also have space bound sensors of various kinds to detect any in-comming potential threats.

So in a nutshell, I'd cover my bases by using a mix of different things, though most of my planetary based defenses would be specifically designed to 'shoot down' entities trying to enter the lower atmosphere, rather than actually firing in to space itself. This is because it's much easier to design a weapon that only fires into your own atmosphere (as opposed to all teh way out into space) and really, that's the primary purpose of planetary weapons, to stop your enemy from landing on the surface (or to shoot explosive ordenance out of the sky, obviously giant rocks are going to be a different problem).

To combat space to planet energy weapons, I'd probably employ shields at a much lower level in the atmosphere, designed to dissipate the energy of the weapon.

(that turned in to less of a nutshell, oh well!)

[EDIT]: Oh, and on the front of how I'd stage an invasion: I'm not a very aggressive person, so I'm less likely to invade anyway, but if I did, I'd be more likely to attempt the Advent way of convincing the population that we're better (and this is one of the reasons why I play Advent, and why I'm looking forward to Diplomacy )

hmm, well, very interesting. I think quite a bit does have merit.  I do suppose I am assuming a lot about the enemy, but I also assume a lot about the "environment", in that planets similar to Earth (or really just Terran/Jungle/Woodland/Ocean/Desert/Ice planets in general) are rather rare, while atmosphereless rocks are more normal.

Space bound sensors are really the only way to go, as through atmosphere they have a LOT to sift through. I like the idea of putting missile buses into (likely LEO) orbit, and the background heat of a planet will likely make it VERY difficult to find them with IR sensors. Active sensors, which tend to be a "I'M RIGHT HERE!! LOOK AT ME!!! SHOOT ME SHOOT ME!!" device when, well, active, would likely be best.

As for the AAA (Anti-Aircraft Artillery; this is actually the technically term for anti-aircraft weaponry, even if it is a big gatling-type weapon) weapons against the cap troopers, there are some issues-

1. You're looking for a pod no more than 5 meters long. That means your radar should be very sensitive to the very (ideally anyway) uniformly shaped pods. That is to say, the pods are uniform in exterior shape, so that they are essentially perfect cylinders with 2 perfect hemispheres, 1 at each end.

2. The pods in Heinlein's book actually popped apart at an altitude (either preset or trooper-decided); they used a disposable skin that sloughed off (this allows them to withstand the heat of entry better; plus it makes a lot of "chaff" to distract radar), and the pod itself, once it pops apart, becomes a bunch of metal that is supposed to "look" like my troopers.

Just to help you understand the above statements a bit better (if necessary), this is a typical drop procedure:

Spaceship enters orbit; it can be high-earth, geostationary, or LEO. The ship then deploys as many pods as necesary to fully deploy its trooper complement. The ship then can offer fire support, or leave orbit and hide up "above" the gravity well. The pods enter atmosphere, and at a certain altitude, pop apart (after they have already sloughed off the first 2-3 skins for entry).

The sky is "filled" with a bunch of "troopers". For a typically raid, a single company of troopers is landed at a critical point (I will arbitrarily say that an operation of more than 5 companies (100 men/company) is a small-scale operation; if it involves 1000+ men, it is a full-scale invasion, especially if armored artillery is included). The troops themselves are supposed to free-fall for a particular amount of time, then trigger some chutes (said chutes are also used for the initial in-atmosphere decent phase, after entry; these slow it down so you don't die on impact).

The main advantage of this is that it is very complementary of a "strike hard, strike fast" combat doctrine. The main problem (as I see it) is the disposable nature of the pods- this makes them better for making a bunch of "decoys" upon the drop, but completely useless if you need to do more than one drop, and you only have enough pods for one drop.

On the flip side, the pods are light enough and cheap enough (in theory) that carrying a quantity of 400-500 is perfectly feasible for a warship that carries 100 troopers (300-500 would be more the norm). This is also assuming I have the space inside the warship.

True, they would be hard to hit directly, but as I understand it, most AAA is designed to be AoE, in order to give them a decent chance of causing some damage. Even a small amount of shrapnel will spell doom for a parachute, or your heat resistant plating.

I doubt a full scale invasion would go unnoticed, even when the pods are quite small, one would only need to blast away at the obvious cloud of invading drop pods (and their ejected shells) and your bound to score a decent number of hits. Any way of thinning out the numbers while they can't defend themselves is going to make it a whole lot easier for your own ground defense forces. Your ground defense forces probably already outnumber their invasion force, unless they have brought in a massive armada of troop carriers, which wouldn't stand as much of a chance getting through your wall of LEO missile batterys, and if they did have enough supporting warships, we're talking such a massive invasion force that I'm not so sure your gonna stand much of a chance no matter what you do (unless you can match their force with an armada of your own in orbit defending the planet).

Haha, THis just turned into a Whiskey vs koiju thread.

In response to criticizing my "big rock make planet dead" arguement and being called a "moron"

Any energy weapon will ionize and irradiate, any physical will damage mantle and create shockwaves, or earthquakes and volconic activity. Assaulting a planet by entering its atmosphere and either taking out targets close up, or landing troops is the only way to take a plaent without massive ecological damage.

Therefore if you are killing a planet, and that is the point, dop a rock on it. You dont want those people around anyways.

not necessarily 52500.

I didn't actually call YOU a moron. I meant that you (not actual you BTW) would have to be rather unintelligent to drop a giant rock onto a planet that is far to valuable a resource to destroy.

To Koiju- the power armor used by cap troopers is designed to take direct 57mm hits. I think shrapnel isn't going to be too much of a problem (except for the chutes, but the trick is so that they slow down enough so they don't die on impact. And the suits have "jump-jets", so that will also help).

You missunderstand the perpose of the AAA, it is not to directly kill any troops, but instead to disable whatever mechanism they are using to give them a safe landing (parachute, heat resistant plating, whatever) and then just let gravity do the work for you. Even minor damage to heat resistant plating will cause it to utterly fail and the thing it's protecting will burn up on entry. Heat resistant plating isn't very good at resisting physical damage, as a rule.

Also, in the far flung future, where the enemy has power armoured troops, I'd expect our AAA to be firing something significantly more leathal than 57mm bullets/shells (such as rail guns, lasers, plasma, photon torpedos or [insert futuristic weapon of choice here])

if were going to talk realistically then you have to be realistic about the type of people incharge of the military. some will forsee those planets being useful and for the space rock...........well, some will decide if they cant have it, no one will.

Like a miltary planet, or an extra bothersome race (humans).

not to  allegiance:

Seriously though, on earth when it comes to fighting, we take care not to kill civillians (most of the time) and we have limited space, so occupation is viable. In space, due to distances and realistic birthrates for mankind at least, it isnt a realistic solution to occupy an enemy planet. Much more to kill everything, find something that will support life and go from there. Unless you have a few hundred million people to hang out, or are advanced enough to subjugate with smaller numbers.

THough if you are fighting an interstellar war, you can assume you aren't THAT much more advanced.

Edit: @ Whiskey, I appreciate the distinction. As I go through yesterday's posts It seems I got angrier and angrier through the day.

52500- thanks. It is probably my fault though, as I did say "moron" without the distinction at first.

Koiju- As for 57mm hits, what I really mean is 57mm hit equivalents.

For a Railgun, you need a lot of power (as railguns can never be 100% efficient), for lasers, it gets iffy in an atmosphere, as you have to deal with a lot more variables than space.

As for a plasma weapon, well, plasma weapons are more or less going to be about as effective as a gun that shoots steam (see Atomic Rockets site, reachable through projectrho.com), and what do you mean by "photon torpedoes"?

I ask because: a "photon" weapon can refer to a laser of some sort, as lasers simply shoot beams of photons (which are "light" particles, and also have no rest mass, so they can travel at c). If you mean "Photon Torpedoes" a la Trek, then sorry to dissapoint, but those, well, aren't going to work the way you'd think.

The maximum energy possible IS correct, as 1.5 kg matter+1.5 kg antimatter=64.3 megatons TNT equivalent, but the problem is 1) if in atmosphere, getting the AM to hit the target without reacting with the atmosphere itself; 2) getting the AM to actually react with the target; and 3) AM would be of greater use as a bombardment weapon TBH.

I also must note that a ship CAN launch empty pods with the loaded ones, or simply drop pod-shaped decoys. This will complicate the firing solution of the weapons, as the question of "which are the troopers, and which are decoys" becomes apparent.

Lol, when I said all those different weapons I wasn;t 'serious' in that way.

I just named random 'futuristic' style weapons without thinking about just how realistic they are (I could disscuss the reasons why plasma is actually very unlikely to ever happen, but that's a different disscussion).

My point was simply that in the future, I'd expect something more effective than what we have today

That sounds like an awesome idea!

It would be great being able to build great big cannons into the side of dead asteroids, would be quite intimidating to incoming fleets aswell.

Here is the FaultyLogic Guide to planetary attacks:

If you care about the civilians-

    1.take out orbital defenses, use precision firing on ground instalations, land troopers, blah blah blah...

If you Don't Care-

     1. Enter gravity well

     2. Bomb/nuke/raze surface until all enemies & defenses are dead

     3. Terraform surface to satisfaction

This guide has been approved by the Interstellar Committee on Planetary Destruction 

"If you can't win them over, nuke the @!$@#^$% out of 'em!"