"Realistic" Space Combat/Travel Discussion Thread

[ODST]

If you want to obliterate your planet-based target, simply wheel out the kinetic strike satellites with giant tungsten slugs to drop on the target. If you want the target intact, you're gonna have to establish aerospace superiority, disable planetary defense weapons, and safely ferry troops to the surface. Fighters and Assault Dropships much?

[Sponge]

I'm interested in space-to-ground tactics. Assuming we establish a base on say, Mars or the Moon, what tactics could be employed to assault it if necessary?

Orbital bombardment? Fire from the skies? If bunkers are built deep into Martian or lunar soil [in lack or a better word], they could survive quite a beating, and serve purposes outside of sheer military protection (e.g. radiation shielding).

Or what if you needed the habitat intact, or at least mostly intact, and you needed to send in a strike team. How exactly is that carried out?

If you wanted it in tact, orbital bombardment would be pretty much out of the question. If you just wanted it gone, high yield nukes (probably much higher yield than those used in ship to ship combat), should do the trick, I suspect. Specialized rails, as ODST alluded to, could also work. They would have to be able to survive entry into an atmosphere (not nearly as hard to do if we're talking about the moon, being that it has virtually no atmosphere), and would have to be carrying a considerable amount of kinetic energy upon arrival. On earth, you'd gain velocity during reentry. You wouldn't get nearly as much if you were bombarding the moon.

As far as ground assaults are concerned, space ships such as the ones on which this discussion primarily focuses do not land. They're simply too massive to get back up again. I'm also not convinced that the thrusters used to move fighters and such in space would be able to provide the necessary lift to keep something flying in atmospheric conditions (again, not much of a problem for moons and other small masses). I'm just about positive that ion engines are all but worthless in an atmosphere. I could be way off on this, so feel free to correct me if anyone knows more about the subject. Assuming I'm correct, specialized landing craft would have to be employed. They'd likely be bigger than fighters, but still relatively small. Maybe a capacity of around 10 troops plus equipment? They'd have thrusters to maneuver in space, as well as turbines or futuristic equivalent to provide the necessary lift once they got to the surface. As far as what kind of equipment the strike force would be using, I haven't the slightest idea. Something would have to be used to either blow down or cut through reinforced doors. Since your personnel would be limited by the number of space to planet transports you had in your hangar bay, technological superiority, good planning, and stealth would be paramount.

[natan_j]

Thing is, where you're attacking a planet, you have a couple to many ships, while the enemy has a couple yottagrams of rock to hide in. It's quite easy for them to plant hundreds of single-shot missile launchers all over the surface, along with a couple skyward-facing sensors, while they live quite safely miles underground. Said missile launchers and sensors would be near impossible to distinguish from the surrounding surface, while your ships are quite visible 300 degrees Kelvin or higher dots against the 3 degrees Kelvin backdrop of space.
Also, since what you're attacking is probably a self-sufficient colony, and you likely have only limited supplies, it becomes an reverse of the classic siege; kill your entrenched, highly supplied enemies before you run out of ships or food.
Landing troops after clearing out any defending ships would be a high-cost tactic, as you have more mouths to feed, and it'll take a lot more fuel to bring along the heavily equipped soldiers you would be landing. And if they fail, you can either request reinforcements for a second try, or head home defeated.
Orbital bombardment sounds like it would be the best tactic, since you can throw a couple asteroids from the local belt at the enemy's population centers. If you needed to capture the cities intact, you'd probably have to try to force them to surrender. And if they have reinforcements coming, it's unlikely that they'll give up that easily.

[Thunderbird Anthares]

on the topic of G/S defences,any active scanners would have high enough EM emmission to be easily targeted and taken out,passive scanners would not be as useful as you could only use them to fire cannons and such (gravity hurts cannons)

if you would fire autolock missiles using passive sensors,those would move with initially slow velocity when overcomming planetary gravity,thus easier for point defence to lock on and fire

considering target aquisition,same rules as with spy sats apply
we already have powerful enough optics to recognize a keyring lying on a ground,given enough time a ship with such probes or satelites could identify all targets before the defenders would know there is a enemy fleet in nearby

my 2 cents anyhow

and when playing Mass Effect,the ingame encyclopedia pointed a couple of things i then started to think about
to stealth a ship in space you basically just need to radiate heat in direction behind your ship,and the "stealth heat shield" in front would have to absorb radar waves - imho doable

[Verminator]

If you want to wreck the surface of a planet, simply dropping natural satellites and large asteroids from orbit is a surefire way to completely trash the place. Think about it - drop a penny from the top of the Empire State and you can crack the pavement below, or kill someone if you hit them. Drop a bunch of big rocks from orbit, and the carnage you cause would be incredible. If they try to intercept them, they either spread the destruction wider or cloud up their atmosphere and trigger the equivalent of a nuclear winter, and even so, if you've executed the attack right, there's no way they'd be able to hit them all. If you want complete planetary death, an extreme solution would be to attach some powerful thrusters to one of the planet's moons, if it has them, and drive it like a molten missile into the planet's crust. There's almost no way that the attack can be stopped once underway, and you will almost certainly make the planet completely incapable of supporting any kind of life. If you've already got spaceships, creating the technology to trash a planet wouldn't be hard. In fact, if you've got ships capable of interstellar flight, then you've likely got incredibly powerful and radioactive nuclear reactors that you can adjust to detonate in the planet's atmosphere, and bring on some kind of mega-Chernobyl. It's taking the planet whole that would be the problem. You'd have to invade cities using more conventional forces and seize centres of power if they don't surrender. You could blackmail them with the threat of bombardment though, and perhaps destroy cities one by one until they give in. I suppose it depends how unscrupulous you'd be prepared to be, and if you're invading planets it's likely you're not prepared to screw around anyway.

[Anna]

Think about it - drop a penny from the top of the Empire State and you can crack the pavement below, or kill someone if you hit them.

Nitpick: No you can't. A penny doesn't have enough mass to do any significant amount of damage, even if dropped from such a height. At terminal velocity, it can't even break human skin, although it will leave a nasty welt.

[Draco18s]

Think about it - drop a penny from the top of the Empire State and you can crack the pavement below, or kill someone if you hit them.

Nitpick: No you can't. A penny doesn't have enough mass to do any significant amount of damage, even if dropped from such a height. At terminal velocity, it can't even break human skin, although it will leave a nasty welt.

Yay mythbusters!

[Sponge]

on the topic of G/S defences,any active scanners would have high enough EM emmission to be easily targeted and taken out,passive scanners would not be as useful as you could only use them to fire cannons and such (gravity hurts cannons)

Passive scanners (sensors) are still quite effective. It's harder to find something, but once you find it, you're not going to loose it. The fact that a ship's drives will be pumping out coolant several hundred K above background temp makes things much easier to fire.

if you would fire autolock missiles using passive sensors,those would move with initially slow velocity when overcomming planetary gravity,thus easier for point defence to lock on and fire

I don't know where all this overcoming gravity stuff is coming from. I also envision missiles being more advanced than anything we have today. They'd have to be able to resist PD somehow, likely with plates of light armor. They'd have large stores of fuel so that they could get up to incredibly high speeds, they'd have sophisticated on-board computers to compensate for enemy movement and make on-the-fly decisions. They'd also have their own sensor suite, so that they could track their target independently of the ship that launched them. Drop them and forget about it.

and when playing Mass Effect,the ingame encyclopedia pointed a couple of things i then started to think about
to stealth a ship in space you basically just need to radiate heat in direction behind your ship,and the "stealth heat shield" in front would have to absorb radar waves - imho doable

I love Mass Effect. Still, their stealth ship is not plausible. You could technically radiate the majority of your heat through a single location, but you'd be spitting out the same amount of infrared, if not more. Anyone behind you would know you're there. Even the temperature of the ships innards is likely to be around room temp (~300K), which is many times hotter than the 3K temperature of space. Absorbing energy in front of the ship is also futile. That energy has to go somewhere. You can't just absorb it and say it's gone.

simply dropping natural satellites and large asteroids from orbit is a surefire way to completely trash the place.

HOW? Remember, this is "realistic near future" This would require unrealistic amounts of energy. Natural satellites are WAY out of the question. The only feasible method would be to go to the nearest asteroid belt, attach massive thrusters and their requisite fuel, and wait a decade or so for them to get to the planet. Better method? Nukes. Really, really, really big nukes. Several hundred megatons, or even in the gigaton range, are not out of the question.

[ArcaneDude]

I love Mass Effect. Still, their stealth ship is not plausible. You could technically radiate the majority of your heat through a single location, but you'd be spitting out the same amount of infrared, if not more. Anyone behind you would know you're there. Even the temperature of the ships innards is likely to be around room temp (~300K), which is many times hotter than the 3K temperature of space. Absorbing energy in front of the ship is also futile. That energy has to go somewhere. You can't just absorb it and say it's gone.

The Encyclopedia also sais (I think) that they dump the heat in some kind of tank (with liquid nitrogen or the like probably). But that's only temporarily, hence why they can't stay stealthed for long. They have to release the heat eventually. And I do believe a ship's hull can be insulated sufficiently to avoid heat leaks from simple room temperature.

On the topic of intercepting railgun shots; Point defense lasers are pretty plausible in the near future, and certainly in space. They already exist, but they're big-ass turrets used to fry a missile's electronics. In the future, they may be able to vaporize things, though.
On the other hand, they'd need a lot of energy.

On the topic of missiles; in theory, they wouldn't need that much fuel. Once they reach their proper velocity, all they'd need is maneuvering thrusters to track and maybe some auxiliary fuel in case they have to cross a dust or debriscloud or something. Inertia'll keep them flying in a vacuum anyways. I say in theory, I'm no expert.

On the topic of dropping troops, you'd need a loooong campaign. Space superiority, then bombarding planetary AA defenses, then establishing air superiority, and then a ground operation. Sea campaigns would be fairly useless, as most boats can be shot down from space or from the air. Unless the enemy base you want to capture is at sea, of course.

[Sponge]

At long ranges, the goal would be to get your missiles there as fast as possible. This accomplishes two things:
1. you kill your target before they kill you
2. your missiles become harder to intercept

There's also the concept of using the missile itself as a rail, designed to penetrate the hull by hitting it with tons of kinetic energy. Once it's inside, it can detonate, likely destroying the ship in one fell swoop. The missile's computer would have to determine on the fly whether it had enough energy to penetrate the hull.

[ArcaneDude]

That's true. On the other hand, putting huge fueltanks on your missile will make it accelerate slower.

Possible solution; a missile pre-accelerated by a railgun.

[Sponge]

Yes, it will accelerate slower with lots of fuel. As it burns fuel, its rate of acceleration will increase. I'm sure there's some balance between your final velocity and how much fuel you're carrying, but providing the fuel is light weight, I'm thinking the more the merrier. Launching them from a sort of railgun is a pretty good idea, but being that they'd be much more massive than your typical rail, the velocity they had at launch would represent only a tiny fraction of their final velocity. Still, every little bit helps. You just have to weigh the importance of that little bit against the extra mass the extra rail cannons would cost you in relation to just dropping the missiles and pressing "go."

I'd like to do some numbers on this. Unfortunately, finding the acceleration of an object that is constantly decreasing in mass (until the fuel burns off) is fairly tricky. Furthermore, I have absolutely no idea the rate at which a futuristic rocket would burn its futuristic fuel.

[Himura.Kenshin]

Yes, it will accelerate slower with lots of fuel. As it burns fuel, its rate of acceleration will increase. I'm sure there's some balance between your final velocity and how much fuel you're carrying, but providing the fuel is light weight, I'm thinking the more the merrier. Launching them from a sort of railgun is a pretty good idea, but being that they'd be much more massive than your typical rail, the velocity they had at launch would represent only a tiny fraction of their final velocity. Still, every little bit helps. You just have to weigh the importance of that little bit against the extra mass the extra rail cannons would cost you in relation to just dropping the missiles and pressing "go."

I'd like to do some numbers on this. Unfortunately, finding the acceleration of an object that is constantly decreasing in mass (until the fuel burns off) is fairly tricky. Furthermore, I have absolutely no idea the rate at which a futuristic rocket would burn its futuristic fuel.

Or how fast the futuristic rocket burning its futuristic fuel would go, compared to how much faster it would go being fired out of a futuristic rail cannon.

[Skull13]

Me and my buddies in EVE discussed dogfights in space, deeming them the equivalent of steering a dead turtle in an ice rink (AKA: Not feasible.) Fuel burn would be tremendous, and keeping someone in view would be nigh impossible, let alone getting behind them. We then discussed weaponry. Barring distances of more than, say... ten light seconds (or 2,997,924.58 kilometers in free space), we concluded that lasers would be practically unstoppable, armor can't really get any better than today's can (save for self-repairing nanorobotic armor, but that doesn't exist yet.) and that the only way explosives could work well is to shoot large swarms, hoping lasers don't blow them all to bits. We did discuss the possibility of chaff to disperse laser fire, but that was met with mixed results.
Now, I don't think missiles would work at distances of 3 million km, personally, but if it can be proven otherwise, I'll listen.

[DeathsHands]

Minor wall of text ahead!

Skull's right. Dogfighting would be pretty much impossible. The smallest things I'd see 'dogfighting' are frigate class vessels (size depends on you). And landing them, that would be pretty damn hard.

I don't think fuel would be as big as a problem as it sounds. You could use ion rockets; all you'd need is sunlight, or a battery/generator. You would accelerate slower, but it's more efficient (besides, you probably weren'accelerating that fast in the first place).

On the subject of space-to-surface engagements, the space-borne participant is at a large disadvantage. Assuming the the defender has had time to prepare (which he most likely did), then the defender would probably have tons of surface-to-space Missile launchers/cannons, that fleet is pretty much done for, unless troops managed to land and locate the surface-to-space defenses (which is very unlikely).

On the subject of an actual planetary landing, I see a two possiblities: A ship that is dropped high into the atmosphere by a troopship that flys down to a certain level of the atmosphere and deploys troops (via parachute, pod whatever; somewhat likely), or a single-burn-no-return dropship that's dropped into the atmosphere by a troopship that can somehow manage to land safely without being shot down (very unlikely). The resulting conflict to take over the whole planet could range from months to years, unless the defender surrendered by threat of bombardement (assuming their surface-to-space defences were destroyed). Reconstructing/repopulating a conquered planet would take decades, probably. Taking over a moon or an asteroid would probably be alot simpler and shorter (and likely could be done in a manner of hours). Maybe there would be some kind of interstellar Geneva Convention that would set about some rules regarding planetary assualt/occupation.