Space Battles, the physics thereof

[Heradel]

Gizmodo:

I had a discussion recently with friends about the various depictions of space combat in science fiction movies, TV shows, and books. We have the fighter-plane engagements of Star Wars, the subdued, two-dimensional naval combat in Star Trek, the Newtonian planes of Battlestar Galactica, the staggeringly furious energy exchanges of the combat wasps in Peter Hamilton's books, and the use of antimatter rocket engines themselves as weapons in other sci-fi. But suppose we get out there, go terraform Mars, and the Martian colonists actually revolt. Or suppose we encounter hostile aliens. How would space combat actually go?

First, let me point out something that Ender's Game got right and something it got wrong. What it got right is the essentially three-dimensional nature of space combat, and how that would be fundamentally different from land, sea, and air combat. In principle, yes, your enemy could come at you from any direction at all. In practice, though, the Buggers are going to do no such thing. At least, not until someone invents an FTL drive, and we can actually pop our battle fleets into existence anywhere near our enemies. The marauding space fleets are going to be governed by orbit dynamics – not just of their own ships in orbit around planets and suns, but those planets' orbits. For the same reason that we have Space Shuttle launch delays, we'll be able to tell exactly what trajectories our enemies could take between planets: the launch window. At any given point in time, there are only so many routes from here to Mars that will leave our imperialist forces enough fuel and energy to put down the colonists' revolt. So, it would actually make sense to build space defense platforms in certain orbits, to point high-power radar-reflection surveillance satellites at certain empty reaches of space, or even to mine parts of the void. It also means that strategy is not as hopeless when we finally get to the Bugger homeworld: the enemy ships will be concentrated into certain orbits, leaving some avenues of attack guarded and some open. (Of course, once our ships maneuver towards those unguarded orbits, they will be easily observed – and potentially countered.)
[...]

Whole thing's worth the read.

[Scattercat]

Metafilter's fun, innit?   

It was a pretty awesome article, though.

[Heradel]

Actually I got there from somewhere else, because I don't go to metafilter. That said, I don't remember where it was I did see it.

Also moved this topic to SF discussion, because I accidentally put it in About Escape Pod.

[Yargling]

Interesting observations - of course, even this is abit mute at this point - until we actually have some form of militarized space force, we can not accurately predict the exact restrictions such vassels would have in  practice. And further, experience is more likely to teach what tactics would truly be effective.

I do like the strategies and tactics described in the game Mass Effect's codex - it talks of hit and run tactics in deep space combat, as both sides have effectively ultimated mobility, with set piece battles occuring around strategically important stations and planets, where retreat is not an option. Further, in their world, the small ships have low velocity weapons, making extremely close range combat necessary for them, whilst the large ships have high kinetic energy weapons and dense kinetic barriers (all weapons in the game's universe are kinetic based; even small arms are based on the idea of hyper-accelerated slugs), and engage each other an extreme range.

Whilst they don't make mention of orbital physics, I found it interesting.

[Planish]

One of the commenters said:

This is like a 15 th century sailor predicting future sea battles rambling on about why you cant do such and such because sails can only do whatever. Much of the technology has yet to be invented or even thought of, so the best this guy can achieve is what will space battles be like "now".

I pretty much agree with them. Even if you could predict the technology of the future it doesn't mean you can predict the emergent gameplay applications. We all got lots of nukes, but they haven't actually been used since WWII other than as a threat.

Then there's that negotiation scene from The Lion In Winter

Henry II: The Vexin's mine.
Philip II: By what authority?
Henry II: It's got my troops all over it; that makes it mine.

There's really nothing to fight over in space, except for where it gives you the ability to control access (eg. jump nodes?) to resources you want. Everything is subordinate to that.
Right now, you can have all the air superority you can afford, but you need, say, tanks to hold the plot of land you've just taken. If land is what you are after. For the most part, it's some form of "winning the hearts and minds" of the populace to get what you want because the enemy is too diffuse, so you need to be able to put troops on the ground and keep them safe. What's the cool military gizmo they're working on these days? A pack-robot to carry sh*t.

David Weber did a pretty good job of it in the Honoverse. He got his people from system to system using a bunch of handwavium, applied phlebotinum, and a few wormholes, but once the fleets have jumped in at the edge of the system the rest of it is fairly conventional "ye canna' change the laws of" physics.

[Yargling]

One of the commenters said:

This is like a 15 th century sailor predicting future sea battles rambling on about why you cant do such and such because sails can only do whatever. Much of the technology has yet to be invented or even thought of, so the best this guy can achieve is what will space battles be like "now".

I pretty much agree with them. Even if you could predict the technology of the future it doesn't mean you can predict the emergent gameplay applications. We all got lots of nukes, but they haven't actually been used since WWII other than as a threat.

Then there's that negotiation scene from The Lion In Winter

Henry II: The Vexin's mine.
Philip II: By what authority?
Henry II: It's got my troops all over it; that makes it mine.

There's really nothing to fight over in space, except for where it gives you the ability to control access (eg. jump nodes?) to resources you want. Everything is subordinate to that.
Right now, you can have all the air superority you can afford, but you need, say, tanks to hold the plot of land you've just taken. If land is what you are after. For the most part, it's some form of "winning the hearts and minds" of the populace to get what you want because the enemy is too diffuse, so you need to be able to put troops on the ground and keep them safe. What's the cool military gizmo they're working on these days? A pack-robot to carry sh*t.

David Weber did a pretty good job of it in the Honoverse. He got his people from system to system using a bunch of handwavium, applied phlebotinum, and a few wormholes, but once the fleets have jumped in at the edge of the system the rest of it is fairly conventional "ye canna' change the laws of" physics.

Actually, Space Superiority is what space battles would be fought over, I reckon - be it over planets or asteriods. After all, the side with space superiority can provide planet wide fire support, mobile air bases that can't be reached by atmosphere only airplanes, and can potentially deploy ground troops/tanks/etc anywhere on the planet.

But of course, this is entirely theoritical, like you said; much like a medieval soldier trying to predict the future of warfare - I doubt he could have ever predicted the exponental growth in firearms and firepower, resulting in division of strength and concealment being key features of the modern battlefield.

[CryptoMe]

Fun read, but two points worth mentioning...

1) Small projectiles traveling at high speeds (roughly 10 km/s) can do a lot of damage due to the shock waves they set up in the target. One problem is that typical gun velocities are roughly 1 km/s, so we would need to seriously improve in that area.

2) An atmosphere is very good at breaking up and burning projectiles passing through it. Generally, anything less than a km in diameter doesn't make it to the surface, unless you are very precise about how you do it. So, I have some very serious doubts that the mentioned "spears" would be of any use in a space-to-surface battle.

[gelee]

Fun read, but two points worth mentioning...

1) Small projectiles traveling at high speeds (roughly 10 km/s) can do a lot of damage due to the shock waves they set up in the target. One problem is that typical gun velocities are roughly 1 km/s, so we would need to seriously improve in that area.

2) An atmosphere is very good at breaking up and burning projectiles passing through it. Generally, anything less than a km in diameter doesn't make it to the surface, unless you are very precise about how you do it. So, I have some very serious doubts that the mentioned "spears" would be of any use in a space-to-surface battle.

As you say, you must simply be precise, but it's really not that hard. We bring orbiters back in one piece all the time. Bring the object in at speed mkes things a bit trickier, but not prohibitively. The Moon Is A Harsh Mistress, I think, had a nice example of gravity well weaponry. Ditto Anathem by Stephens.

[CryptoMe]

Fun read, but two points worth mentioning...

1) Small projectiles traveling at high speeds (roughly 10 km/s) can do a lot of damage due to the shock waves they set up in the target. One problem is that typical gun velocities are roughly 1 km/s, so we would need to seriously improve in that area.

2) An atmosphere is very good at breaking up and burning projectiles passing through it. Generally, anything less than a km in diameter doesn't make it to the surface, unless you are very precise about how you do it. So, I have some very serious doubts that the mentioned "spears" would be of any use in a space-to-surface battle.

As you say, you must simply be precise, but it's really not that hard. We bring orbiters back in one piece all the time. Bring the object in at speed mkes things a bit trickier, but not prohibitively. The Moon Is A Harsh Mistress, I think, had a nice example of gravity well weaponry. Ditto Anathem by Stephens.

Just because we do it frequently, doesn't mean it isn't difficult (remember the Columbia disaster?). That's why they have so many ground people managing each re-entry. Can that scale of attention be paid to each weapon thrown down the gravity well? I think that once you increase the numbers to anything that is effective, managing each projectile becomes prohibitive.

If I remember correctly, in The Moon is a Harsh Mistress (sorry, never read Anathem), they threw their garbage down unmanaged, so they weren't making mid-course corrections. And, while they did use large chunks, not skinny little spears, I still don't think that would work.

Consider, to get the truly destructive forces of an impact event (like Barringer Meteor Crater in Arizona) you need some major speed (~10 km/s as I mentioned before). Most meteorites that make it to the surface of the Earth aren't traveling that fast because they started out small (<meter) and have been slowed down (and often broken up) by the atmosphere. As a result, they don't produce impact craters and they cause relatively little damage. To get the damage, you need the speed, and on a planet with an atmosphere that means you need SIZE. The impactor that created Barringer Crater is estimated to have been about 300,000 tons! And, this is considered to be the minimum size needed to reach the Earth's surface at required speeds. So, who has that kind of mass in orbit just waiting to be thrown down the gravity well?

[gelee]

Very good point about getting the mass up there in the first place.  As to Challenger and Columbia, I would think them quite a bit more fragile than, say, a rock.
In Anathem, Stephens makes reference to "rods" being used for orbital bombardment, but doesn't really describe them well.  In their effect, they were more like a bunker-buster than a MOAB.  Targeted, intense destruction, but not wide area of effect.

[Gamercow]

Hmm, why am I not seeing the words rail and gun put next to each other in that article?  Seems like the best possible solution to me.  Grab a piece of asteroid, cut it up into chunks, and then use rail guns to fire it out.  Lasers are good too, but depending on how much energy they take, might be prohibitive. 

The biggest thing I disagree with is the idea that orbital gravitation will create such an impact.  It will be a factor, yes, but I would think that if we were in contact with an alien race, we would have the ability to have ships that were nimble(as you can get) in space, and would be no more affected by gravitational dynamics than battleships are affected by ocean currents and tides.  Yes, there's an effect, but its much less than it was back in the day of sail.  We're in the day of sail right now.  Hell, we're in the day of rowboat right now. 

[CryptoMe]

Very good point about getting the mass up there in the first place.  As to Challenger and Columbia, I would think them quite a bit more fragile than, say, a rock.
In Anathem, Stephens makes reference to "rods" being used for orbital bombardment, but doesn't really describe them well.  In their effect, they were more like a bunker-buster than a MOAB.  Targeted, intense destruction, but not wide area of effect.

True, the space shuttle is more fragile than a rock, but scientific studies still show that you need 300,000 tons if you want to reach the Earth's surface at destructive speeds.

When you are talking about impacts on the Earth, "targeted, intense destruction" is inseparable from a "wide area of effect". Consider, if a meteor is less than 300,000 tons, it will break up in the atmosphere and fall to Earth at relatively slow speeds, causing very minimal damage. This is why you hear stories about how a meteorite hit a car and just left a dent. But, if the meteor is greater than 300,000 tons, it will not break up or slow down sufficiently. The resulting impact will be devastating and over a wide area; forming an impact crater at least 1 km (0.62 miles) in diameter and raining ejecta down over an additional 1-2 km. So, on the Earth, you can't get intense targeted destruction without wiping out a very large area. Unless you consider that a 2+km diameter area of destruction isn't a wide area of effect