Realistic Space War

[tater]

There is no "blockade." The asteroid belt is not much of a thing, and if Earth actually needed any, they'd simply get some, or are you somehow assuming a colony can become not only self-sufficient, but make claim on some vast, empty area of the solar system with any sort of plausible force behind that claim? It's just not a thing.

[Bill Phil]

1 hour ago, radonek said:

Pretty silly. Sorry. Distance in space combat is mostly function of light lag. If you can use active stuff like LIDAR, you are at point blank range already. Jumping to visual vicinity gives about as much sense as  two naval carriers trying to hook and board each other.

Because its way easier problem to solve then "how to get stuff from bottom of deep gravity well without incredibly expensive rocket boosters". 
 

But you're doing that anyways. The Sun's gravity well, and Jupiter's. 

If the gravity is too low there's really no point in massively settling there. Heck, planets and moons kind of suck anyways. They have gravity wells which increase energy required to transport things, and thus cost. Not only that, but any settlement will have to have centrifuges if they don't want to have health problems. The best place to have a colony is a major L point or freespace. 

3 minutes ago, tater said:

There is no "blockade." The asteroid belt is not much of a thing, and if Earth actually needed any, they'd simply get some, or are you somehow assuming a colony can become not only self-sufficient, but make claim on some vast, empty area of the solar system with any sort of plausible force behind that claim? It's just not a thing.

You could take control of material processing centers, effectively limiting usable resources. That's not easy, though.

[tater]

24 minutes ago, Bill Phil said:

You could take control of material processing centers, effectively limiting usable resources. That's not easy, though.

Move asteroid to Earth.

[magnemoe]

56 minutes ago, tater said:

There is no "blockade." The asteroid belt is not much of a thing, and if Earth actually needed any, they'd simply get some, or are you somehow assuming a colony can become not only self-sufficient, but make claim on some vast, empty area of the solar system with any sort of plausible force behind that claim? It's just not a thing.

My scenario require borders to be drawn like borders on an map even at sea, this is taken seriously up towards war. it also requires that the useful near earth asteroids are used up as they fall naturally into earth's zone, and yes the border was drawn 150 years earlier in an attempt to increase industrialization of space. 

Politicians in the US who hate gambling obviously regret the decision to grant Indian territories state rights. Yes it was long overdone, the effect was also pretty predictable. Tiny countries between larger ones tend to be tax or moral havens. 
Portugal to Finland and back only tanking in Andorra is common for EU trucks.

[Bill Phil]

5 minutes ago, magnemoe said:

My scenario require borders to be drawn like borders on an map even at sea, this is taken seriously up towards war. it also requires that the useful near earth asteroids are used up as they fall naturally into earth's zone, and yes the border was drawn 150 years earlier in an attempt to increase industrialization of space. 

Politicians in the US who hate gambling obviously regret the decision to grant Indian territories state rights. Yes it was long overdone, the effect was also pretty predictable. Tiny countries between larger ones tend to be tax or moral havens. 
Portugal to Finland and back only tanking in Andorra is common for EU trucks.

Except that continents tend to not move any decent length in a human lifetime. Planets, asteroids, moons and the like aren't like that. You can't really draw "borders" in space. 

Also, 2D sea is not 3D space.

51 minutes ago, tater said:

Move asteroid to Earth.

Unless they drop the asteroid onto Earth, then it's possible to gain control of the asteroid.

[magnemoe]

Just now, Bill Phil said:

Except that continents tend to not move any decent length in a human lifetime. Planets, asteroids, moons and the like aren't like that. You can't really draw "borders" in space. 

Also, 2D sea is not 3D space.

True, however politicians don't agree and they make the rules  
It would also be no problem to draw an line as in anything with PE inside Earth and Ap inside Mars orbit  belong to Earth, anything with Pe more than 4/5 of average Jupiter to Mars distance is outer space and not belt territorium. 

Yes this is random rules, be free to put up an structure like an old jack up oil platform on any underwater coral reef and raise any random flag
Note you might get away with it for years if you only do stuff like serving fishing boats. 

[Bill Phil]

1 hour ago, magnemoe said:

True, however politicians don't agree and they make the rules  
It would also be no problem to draw an line as in anything with PE inside Earth and Ap inside Mars orbit  belong to Earth, anything with Pe more than 4/5 of average Jupiter to Mars distance is outer space and not belt territorium. 

Yes this is random rules, be free to put up an structure like an old jack up oil platform on any underwater coral reef and raise any random flag
Note you might get away with it for years if you only do stuff like serving fishing boats. 

But then you would have asteroids crossing through different territories. Who would own them?

[jwenting]

A space war would have one side sit in the asteroid belt and lob big chunks of rock at the other until they surrender or more likely die.

[p1t1o]

5 hours ago, jwenting said:

A space war would have one side sit in the asteroid belt and lob big chunks of rock at the other until they surrender or more likely die.

Is there much fissile material in the belt? Just a thought.

[jwenting]

10 minutes ago, p1t1o said:

Is there much fissile material in the belt? Just a thought.

no need for nukes when you can throw a 10 megaton rock on a city...

[p1t1o]

Just now, jwenting said:

no need for nukes when you can throw a 10 megaton rock on a city...

Throw it with what? You gonna haul thousands of tons of propellant with you or can you mine something out there, and if so, how fast?

I was thinking more of swarms of tiny, barrel-sized megaton warheads heading towards the belt. A lot harder to see coming or to intercept than a giant asteroid. Although only one asteroid would have to get through...

[radonek]

1 hour ago, p1t1o said:

Is there much fissile material in the belt? Just a thought.

Our very own  dirtball was  made from same material as asteroids. During planet formation heavy elements tend to fall down to the core, so if anything asteroids will have more fissile material then what we can lay our hands on earth. Also more gold, platinum, iridium and other shinies.

[wumpus]

12 hours ago, jwenting said:

A space war would have one side sit in the asteroid belt and lob big chunks of rock at the other until they surrender or more likely die.

If you are really feeling nasty (and have the time or are building a MAD-based insurance policy) you can have your "Navy" out in the Oort cloud.  Killer asteroids are something you can detect (assuming all the asteroid detectors in Venus orbit or so haven't been blown up yet) and play tug-of-war with.  Killer comets come in with only one orbit and are much harder to deflect (and break up easily if you hit them hard enough to divert).

Space war: The only winning move is not to play, since 1957.  Seriously, since it appears possible to build "terminator"-type probes that will eliminate any detectable life, it seems unlikely that any single species can survive a space war (it can be assumed that a second species can be sufficiently advanced to trivially wipe out the first as part of terraforming process).  Anybody who remembers life before 1989 understands that people *will* build systems where the "only winning move is not to play", and that they [both the weapons and the people] still exist on Earth.

[Elukka]

I have doubts about the practicality of asteroids as weapons. Even small asteroids suitable to destroy a city take a lot of energy to move and everyone can see you doing it. They'll have months to prepare and take any action against you they might like. The Chelyabinsk meteor was estimated at around 13 000 tonnes and had kinetic energy equivalent to a nice strategic nuke. With a steep entry angle, it could have done a lot of damage, but you're still talking pushing 13 000 tonnes of rock for the effect of a single nuke.

Asteroids that threaten the entire planet, dino-killer scale, are in a whole different ballpark. Obviously they'd do a lot of damage, but we just couldn't move them in the foreseeable future. Taking a roughly middle estimate for the Chicxulub impactor's mass you've got ten trillion tonnes of rock to push. I don't quite know how much delta-v you'd need to impart on it to make it to cross paths with Earth... Maybe 5 km/s would be a reasonable assumption? It's gonna be the same order of magnitude at least. Chemical rockets would need absurd amounts of fuel to do this, so let's go with something a bit beefier. Let's do Orion.

If you figure an isp of, say, 4000 seconds... To apply 5 km/s to the dino-killer, the rocket equation says you'll need 1.36*10^12 tonnes of propellant. It's a low mass ratio, only 10% of your total mass will be propellant, but since the dry mass is so ginormous that still means you need a trillion tonnes of pulse units to move this thing. There's probably more expedient ways to wage war if you have a trillion tonnes worth of nukes. Or the industrial capability to mine ten trillion tonnes of rocket fuel.

Edited April 19, 2016 by Elukka

[sojourner]

"Rods from god" - google it.  You don't need huge asteroids to do damage, just give something enough d/v  and it will kill.

[kerbiloid]

Earth vs Mars.

Earth continuously and unsuccessfully tries to convince Mars to build greenhouses for food and declare its independency.
Mars grins and declines that again and again.
Earth keeps sending supports to Mars - as has no choice.
 

11 hours ago, Elukka said:

If you figure an isp of, say, 4000 seconds... To apply 5 km/s to the dino-killer, the rocket equation says you'll need 1.36*10^12 tonnes of propellant.

If calculate with ISP= lightspeed (i.e. with antimatter propellant), millions tonnes of antimatter looks even more ridiculous.

Edited April 20, 2016 by kerbiloid

[Atlas2342]

2 hours ago, sojourner said:

"Rods from god" - google it.  You don't need huge asteroids to do damage, just give something enough d/v  and it will kill.

Now, imagine that with a small amount of antimatter inside. That's real damage...

[p1t1o]

1 hour ago, Atlas2342 said:

Now, imagine that with a small amount of antimatter inside. That's real damage...

At a certain point, a projectile's kinetic energy exceeds its mass-energy. After this point, adding antimatter gives more energy from its physical mass than it can from annihilation. You'd be better off using the antimatter as propellant to increase velocity, this increases the impact energy *more* than adding an AM warhead.

You have to already be going quite fast for this to be the case however, as in already relativistic.

 

Beneath that point, adding AM to anything, even say, a traffic light, will turn it into a city-killer, so being a kinetic kill weapon would be kinda moot in that case

 

**edit**

Coupla back-of-the-napkin calculations later and it appears the turning point is around 85%c, where (relativistic) KE exceeds mass-energy.

It should be possible to calculate the speed at which adding other warheads becomes pointless due to the same effect.

Eg: For thermonuclear warheads (or anything that isn't AM...) the turning point will be significantly lower.

**edit#2**

Another few calcs and it looks like for a thermo-nuclear warhead of maximum theoretical efficiency (6kilotons per kilogram), the turning point (assuming you can convert its energy to thrust at 100% efficiency) is at around 2.5%c.

For a TNT warhead (@1MJ/Kg) the turning point is at around 1500m/s. A projectile travelling faster than this has more KE than the explosive energy contained in an equal weight of TNT.

This is a direct explanation for why tanks have moved towards KE penetrators rather than explosive warheads - and also explains why longer-range weapons still use shaped charges.

SCIENCE!

Edited April 20, 2016 by p1t1o

[Cifu]

2 hours ago, p1t1o said:

NT warhead (@1MJ/Kg) the turning point is at around 1500m/s. A projectile travelling faster than this has more KE than the explosive energy contained in an equal weight of TNT.

This is a direct explanation for why tanks have moved towards KE penetrators rather than explosive warheads - and also explains why longer-range weapons still use shaped charges.

SCIENCE!

 

Well, not so perfectly.

First: In the AFV's, the KE (kinetic energy) vs. CE (chemical energy, ie.: HEAT) are a difficult question, and there is a reason why the KE rounds have around 1600-1800m/s speed at the impact:

 

 

The answer is superplasticity. There is a "sweet point" about the impact speed and the penetration of the APFSDS round.

[p1t1o]

4 minutes ago, Cifu said:

Well, not so perfectly.

Of course, that was super-simplified, like many things there are a great many factors. But it can already be shown that a ~20kg APDSFS projectile @ 2km/s has ~40MJ of KE, whereas 20kg of TNT has ~20MJ of explosive energy.

But of course KE (or CE) are not the only factors that decide penetration, but its an illustrative situation

[Cifu]

13 minutes ago, p1t1o said:

Of course, that was super-simplified, like many things there are a great many factors. But it can already be shown that a ~20kg APDSFS projectile @ 2km/s has ~40MJ of KE, whereas 20kg of TNT has ~20MJ of explosive energy.

But of course KE (or CE) are not the only factors that decide penetration, but its an illustrative situation

Well, this again a thing, that need to be consider - in space (sorry, IN SPACE!!!!).

KE energy is very straightfoward in theory, the projectile hit the target, target face X amount of energy. The CE energy is the same, explosion occur, target have to endure X amount of energy from the blast.

But if the projectile are hard and the target is soft, then the projectile fly through the target and not deliver it's energy. Yepp, the target have least two holes, but still, the Kinetic Energy not realized fully on the target.

The same occur in the case if we have CE warhead, and our ship have certain blast-proof outer shell (like whipple-shield, aka spaced armor).

So actually there soooo many factor we need to consider in a hipotetical space war and we cannot say the KE is much better than CE in this field of battle...

[kerbiloid]

2 minutes ago, Cifu said:

But if the projectile are hard and the target is soft, then the projectile fly through the target and not deliver it's energy. Yepp, the target have least two holes, but still, the Kinetic Energy not realized fully on the target.

In "Expanse" this happened when they were captured by a Mars battleship.

[Darnok]

On 16.04.2016 at 0:48 PM, todofwar said:

If a new colony, like Mars, was trying to gain independence I wonder if their best move would be to trigger Kessler syndrome and lock up the earth for a while 

Haha sure... tell me which country, here on Earth, is fully self sufficient and independent?

They would shot laser into Earth to burn power grids, destroy satellites and starting rockets. And if that would be not enough they could use asteroids and bombard Earth, I would target Yellowestone

[p1t1o]

Well an Earth-Mars conflict could resemble NATO vs. ISIS if Mars has only been colonised for a relatively short time, or it could be closer to an Earth vs. Earth scenario if we are talking some far-future timescale.

The two scenarios are so far apart in terms of what the conflict would look like that it is probably important to specify.

For example:

Earth vs primitive Mars. Mars has the advantage that their entire ecosystem won't be crashed by any asteroid hitting the planet. On the other hand, a small targetteds strike could potentially wipe them out wholesale.

Earth vs. Earth-like Mars. Both sides have similar advantages and disadvantages, it either stalls into a "Cold War" kind of stalemate, probably involving biosphere-MAD, or it flares up into an internecine spasm which does tremendous damage to both parties.

Right or wrong, those are two very different pictures.

[radonek]

14 hours ago, p1t1o said:

Well an Earth-Mars conflict could resemble NATO vs. ISIS if Mars has only been colonised for a relatively short time, or it could be closer to an Earth vs. Earth scenario if we are talking some far-future timescale.

You forgot to factor in two significant facts. First, Earth's mighty industry have to spend significant energy to get their stuff out of the well. Second, Mars is "up" in Suns gravity well, which pretty much gives Martians kinetic weapon for free.

So, one quite reasonable Martian War scenario is that martians quickly deploy few small guided Rods, use them to destroy Earthlings precious spaceports and arrive to dictate their terms.

For exactly this reasons any such war would more likely be waged between Moon loyalists and Belters. Like I said, planets are overrated.