Fortifying a planet

[cantab]

Planets (and other celestial bodies) are sitting ducks. Their courses are entirely predictable so an attacking force can shoot them with impunity from the other side of the solar system, or potentially beyond. While a planet does have the advantage of considerable size, mass, and physical resources which help it soak up the incoming firepower, the only really effective defense is to take the fight to the attackers, and that means having your own space vehicles that can close the distance. Missiles count for that. Ground-mounted weapons could certainly have a useful role but they're not going to be much good on their own.

Space stations I feel are even worse. They're also sitting ducks by definition (if they're capable of decent movement we call them spaceships instead) and they don't have any of the advantages planets do.

[Darnok]

Just spray liquid or "something like dust" cloud on low orbit, it should prevent enemy from seeing what is and where it is on planet.

[A35K]

Well, for the Galactic Empire, it is frequently mentioned they had the largest star fleet in history, so large that in fact it was never even close to being fully destroyed (its "remains" are still around/repurposed 30 years after the end of the Empire, in Ep VII, obviously used by the First Order). So if they wanted to make sure nobody entered a planet a huge orbital blockade of Star Destroyers would do the trick. Then fill the surface with AT-ATs, and, if they are truly dangerous enemies, send Darth Vader... 

[sevenperforce]

Related note...

Would it make sense to tow a bunch of smallish asteroids into really distant Earth orbits, to be pushed into the path of any oncoming planet-killers?

[K^2]

6 hours ago, Bill Phil said:

Well, I'll ask you this:

Are electric subs magic? Was the Moon Landing magic? Was the flip phone magic? Is nuclear power magic? What about flat screens? Video calls? All of these  things are from science fiction, in stories written and published decades before the real thing actually happened. 

First, let me point out that there is such a thing as hard sci-fi. There aren't many authors who try to stick to laws of physics and imagine how technology might actually work in the future, but there are some. These few examples aside, yes, all of these things were magic as written in the original setting.

I mean, I can use Skype on my phone to talk to someone in another country face-to-face. This was originally accomplished with magic mirrors in many folk tales. Are these no longer magic? Just because we've learned to replicate the effect with technology, doesn't make their original concept any less magic. How were the range and bandwidth issues resolved in the old sci-fi stories featuring wireless phones? I'll tell you how, they weren't. They magically went away. Same with power consumption issues. In real life, these didn't go away until we invented concept of cells and constructed immense infrastructure of cell towers. Sure, the result is the same, you have a device in your pocket that lets you talk to or even see someone on the other side of the world. But it works completely differently from magic point-to-point communication of every sci-fi story ever. The fact that they called their magic "radio" doesn't make it any less magical, because radio communication doesn't work like that.

[cantab]

58 minutes ago, Darnok said:

Just spray liquid or "something like dust" cloud on low orbit, it should prevent enemy from seeing what is and where it is on planet.

Any measure to obscure the planet likewise has its benefits, but it doesn't stop an attacker taking pot shots hoping to hit somewhere relevant, or just sending enough firepower at the planet to damage the entire surface.

29 minutes ago, K^2 said:

How were the range and bandwidth issues resolved in the old sci-fi stories featuring wireless phones? I'll tell you how, they weren't. They magically went away. Same with power consumption issues. In real life, these didn't go away until we invented concept of cells and constructed immense infrastructure of cell towers. Sure, the result is the same, you have a device in your pocket that lets you talk to or even see someone on the other side of the world. But it works completely differently from magic point-to-point communication of every sci-fi story ever. The fact that they called their magic "radio" doesn't make it any less magical, because radio communication doesn't work like that.

Five watts on the HF bands will get your signals to the other side of the world. Lack of total bandwidth prevents widespread adoption on the same scale as cellphones and antenna size is a real issue, but it's feasible in stories where not so many people will be using it. In space, if the other end of the connection has big infrastructure you can be received over solar system distance with low power.

 

[Hcube]

Best planet fortifications that come to my mind are the Ogame defenses ^^ classic shield domes, crappy missile launchers, heavy/light lasers, ion cannon, the great Gauss cannon and the almighty plasma turret !

Any Ogame fans/players in here ?  

Since it only has these small images it's all up to imagination, i used to imagine crazy space battles back when i played it

[fairytalefox]

@K^2 Magical thinking is the problem. People these days are used to use things they don't understand. You push buttons, you get the result. It's basically like magic (hello Mr. Clarke). Buttons as spells, electricity as mana, and we call our magic wands "remotes". When they think of something seemingly impossible, they don't believe it's actually impossible. They just say: "we need more wizards technicians".

Surely, science and technology can do much. But what some of us can't understand is that sometimes (read: quite often) the universe just doesn't work the way we want. It's not like lack of technicians, it's fundamental. Impossible things are impossible, no matter what. Like, when you're 8 years old, you can't subtract big numbers from small numbers because you don't know where it leads to. And you can't divide by zero because never ever. There are two different sorts of "can't". We should learn how to distinguish them.

Edited February 3, 2016 by fairytalefox

[Bill Phil]

2 hours ago, K^2 said:

First, let me point out that there is such a thing as hard sci-fi. There aren't many authors who try to stick to laws of physics and imagine how technology might actually work in the future, but there are some. These few examples aside, yes, all of these things were magic as written in the original setting.

I mean, I can use Skype on my phone to talk to someone in another country face-to-face. This was originally accomplished with magic mirrors in many folk tales. Are these no longer magic? Just because we've learned to replicate the effect with technology, doesn't make their original concept any less magic. How were the range and bandwidth issues resolved in the old sci-fi stories featuring wireless phones? I'll tell you how, they weren't. They magically went away. Same with power consumption issues. In real life, these didn't go away until we invented concept of cells and constructed immense infrastructure of cell towers. Sure, the result is the same, you have a device in your pocket that lets you talk to or even see someone on the other side of the world. But it works completely differently from magic point-to-point communication of every sci-fi story ever. The fact that they called their magic "radio" doesn't make it any less magical, because radio communication doesn't work like that.

I know about hard sci fi.

The electric sub wasn't magic, there was an entire chapter dedicated to explaining it. Granted, it may not have been accurate, but it was definitely scientific in the story.

In fact, most of the ones I mentioned were specifically technology, and some even had entire chapters dedicated to explaining it.

Also: space stations, GEO satellites, Blitzkrieg, tanks, credit and debit cards... The list is pretty big.

[K^2]

1 hour ago, cantab said:

Five watts on the HF bands will get your signals to the other side of the world.

Sure, and a single video conference takes up the entire bandwidth. Ok, maybe you can have ten with crummy quality and compression. This is not how communicators work in sci-fi.

@fairytalefox Absolutely. And it's kind of a shame, because we are nowhere near the point where technology is too complex for everyone to know at least the basic principles and limitations behind everyday things. You could fit pretty much everything electronic into a single university course and everything mechanical into another.

[Scotius]

Best defence is the good offence. Saturate the surrounding area with early warning probes until nothing can sneak by undetected. Park sufficiently powerful Task Group\Task Force to curbstomp any incursion short of all-out invasion. Have a fleet or two handy in striking distance from anything you want defended in case of an all-out invasion. Send rest of your forces hunting, steadily desintegrating all enemy bases, industrial centers, recruitment and staging areas you can find. And for the love of the Emperor - make sure all your officers read and understand Sun-Tzu's works. And Clausevitz too. And this one:

 

[K^2]

12 minutes ago, Scotius said:

And for the love of the Emperor - make sure all your officers read and understand Sun-Tzu's works. And Clausevitz too.

Don't let them read Machiavelli, though, or they'll realize what you're really up to.

[jrphilps]

1 minute ago, K^2 said:

Don't let them read Machiavelli, though, or they'll realize what you're really up to.

Hey, you're a math literate guy, I was wondering whether you could help me with a question. If we were to go with the star wars model and emplace gun batterys on the planets surface, how many would you need to completely cover the sky arc of an earth sized planet?

[Nothalogh]

Thunder well arrays on the planet surface, preloaded asteroids in orbit ready to be blown apart as debris fields, Orion powered asteroids as kinetic weapons.

Edited February 3, 2016 by Nothalogh

[Scotius]

43 minutes ago, jrphilps said:

Hey, you're a math literate guy, I was wondering whether you could help me with a question. If we were to go with the star wars model and emplace gun batterys on the planets surface, how many would you need to completely cover the sky arc of an earth sized planet?

It would be about 3600 emplacements, if they'd be built on a stiff grid. Hard to do on a planet - because of all those pesky oceans, swamps, valleys, mountains etc. that tend to mess things up for engineers and gunners.

[relin]

4 minutes ago, Scotius said:

It would be about 3600 emplacements, if they'd be built on a stiff grid. Hard to do on a planet - because of all those pesky oceans, swamps, valleys, mountains etc. that tend to mess things up for engineers and gunners.

Around the equator, right? That estimate seems low for just that latitude, much less all of them.

[jrphilps]

9 minutes ago, Scotius said:

It would be about 3600 emplacements, if they'd be built on a stiff grid. Hard to do on a planet - because of all those pesky oceans, swamps, valleys, mountains etc. that tend to mess things up for engineers and gunners.

Whoa, I didn't think it would be that many. That is quite a feat of engineering.

[Scotius]

Nope, equally across the planet's surface - don't forget about its curvature. Missiles can work around it - literally But beam weapons need line of sight to the target - or mirrors in right positions. Hence so many gun emplacements. It still might not be enough, A mountain range for example can obscure quite a lot of sky for some guns - forcing the defender to place some additional hardware to cover blind spots.

Edited February 4, 2016 by Scotius

[relin]

2 minutes ago, Scotius said:

Nope, equally across the planet's surface - don't forget about its curvature. Missiles can work around it - literally But beam weapons need line of sight to the target - or mirrors in right positions.

"Missiles" aren't exactly part of the "Star Wars" model @jrphilps was talking about, so I'm thinking turbolasers. And I'm not visualizing how one such turbolaser every ~6mi along the equator would be enough, much less one every ~55,000 mi². Could you explain where you got your answer?

[Scotius]

Because we are talking about space opera Works for me, anyway.

[cantab]

1 hour ago, jrphilps said:

Hey, you're a math literate guy, I was wondering whether you could help me with a question. If we were to go with the star wars model and emplace gun batterys on the planets surface, how many would you need to completely cover the sky arc of an earth sized planet?

The answer to this depends on how low you require the coverage to go. Unless you go to the extreme of giving the guns line-of-sight to each other (in which case the number needed depends on how tall the towers you put them on are), then there will be full coverage far out but blind spots close in.

[jrphilps]

34 minutes ago, cantab said:

The answer to this depends on how low you require the coverage to go. Unless you go to the extreme of giving the guns line-of-sight to each other (in which case the number needed depends on how tall the towers you put them on are), then there will be full coverage far out but blind spots close in.

I think I understand. Line of sight (LOS) is limited by the observers height, so a gun emplacement located high off the ground would have a longer LOS, and would hence be able to cover more ground. So I guess 3600 ion cannons is the minimum amount, unless you mount them on sky scrapers or something

[K^2]

1 hour ago, Scotius said:

It would be about 3600 emplacements, if they'd be built on a stiff grid. Hard to do on a planet - because of all those pesky oceans, swamps, valleys, mountains etc. that tend to mess things up for engineers and gunners.

What kind of a ceiling are you using for space? I am getting guaranteed full coverage of the sky above 60km with 332 stations. 12 on verts and 16 on each face of an icosahedron mapped to sphere.

1.1 * (4pi)/(pi arccos(R/(R+h))²)

This gives me the low end estimate based on solid angles. The factor of 1.1 accounts for the hex packing. This is about 250. Next possible packing is with 4 stations between any pair of the 12 verts. This puts total at 332.

 

Of course, the underlying assumption is that the surface is sufficiently smooth not to have any other kind of obstruction.

[fredinno]

7 hours ago, Darnok said:

Just spray liquid or "something like dust" cloud on low orbit, it should prevent enemy from seeing what is and where it is on planet.

You can still use Radar to puncture it to see what's going on, like we do on Venus. Of course, it makes it more difficult to invade, but this can also cause your own planet to cool and begin to freeze over.

6 hours ago, sevenperforce said:

Related note...

Would it make sense to tow a bunch of smallish asteroids into really distant Earth orbits, to be pushed into the path of any oncoming planet-killers?

I don;t think this would work.

[radonek]

20 hours ago, Darnok said:

Just spray liquid or "something like dust" cloud on low orbit, it should prevent enemy from seeing what is and where it is on planet.

Could work in kerbal space, but IRL orbiting objects are not on rails and can't pass through each other.