Space Combat Techniques Discussion

[eyu100]

how are you gona hold it in place?

You could use a shell, or just hold it by adhesion.

 

[T.Neo]

Again: any sort of aerosol or whatnot to diffuse the beam or reflect it or whatever would have to be far too dense than is actually possible.

Same with ablative armour. It's best to put a whole lot of mass between you and the laser, not specifically design it so that it ablates. You want something that is hardest for the laser to cut through, like carbon (low albedo, but that can be solved perhaps by the inclusion of titanium dioxide particles).

You could use a shell, or just hold it by adhesion.

It would be an utter nightmare. Imagine what would happen to it during acceleration...

And even a liquid is not perfectly reflecting, AFAIK. It'll still get blasted away by the laser, or at least turned non-reflective.

Do we get UCGO combat vehicles?

We will be modelling ground combat, but not with UCGO. UCGO does not support weapons.

 

[docabn]

What about a large liquid mirror?

Heck with a liquid mirror. Make the entire exterior out of liquid encased in glass with a energy scattering bacground made of a material similar to the tiles on the shuttle. The fluid is kept constantly circulating and run the fluid through trubines that take advantage of the heated fluid converting it into energy. (Heating from the sun would also contribute to this.). But by heating the circulating fluid the enemy is simply adding power to your own laser system.

 

[T.Neo]

Heck with a liquid mirror. Make the entire exterior out of liquid encased in glass with a energy scattering bacground made of a material similar to the tiles on the shuttle. The fluid is kept constantly circulating and run the fluid through trubines that take advantage of the heated fluid converting it into energy. (Heating from the sun would also contribute to this.). But by heating the circulating fluid the enemy is simply adding power to your own laser system.

It won't work. Glass for example, isn't perfectly transparent, so the energy it absorbs will cause it to vaporise.

I think we're going to try to implement lasers... they're kinda hard to do though. You could fire an invisible vessel travelling at the speed of light, but then vessels that intersect the "beam" won't take damage. We're thinking though

Considering that it would take a photon a 300th of a second to travel 1000 kilometers, any other vessels intersecting the beam shouldn't be a problem.

 

[docabn]

It won't work. Glass for example, isn't perfectly transparent, so the energy it absorbs will cause it to vaporise.

This is how I envisioned this working:
Imagine an empty but sealed coke can floating in a 2L Coke Bottle but filled with water of course. put it into space and let it freeze, most of the way. Use a pluming system to constantly move the water inward toward the center of the bottle near the can, keeping the ice on the outside.
Begin rotating the massive ship, so that the sun has time to warm the Ice on one side while the water on the other side begins to freeze again. The freezing and thawing process could be harnessed to produce energy as well as offer the craft significant protection against solar radiation and small bits of matter that might intercept the craft and produce damage.
This would also protect the craft against most any weapon I can think of.
The weak points being the plumming system, and wherever you put the dock.
However it would mean that the craft was extreamly massive and would require a significant amount of propellant to move. So perhaps this makes more sense for a orbiting station or platform.


The original material holding the ice in is still important but once the ice is largely frozen, shooting holes in the outer encaasement is not a horrible problem. And one that is much easier to repair than the main functional portion of the craft.

 

[Izack]

Considering that it would take a photon a 300th of a second to travel 1000 kilometers, any other vessels intersecting the beam shouldn't be a problem.

I agree, somewhat. There isn't much of a chance of an object coming between the source and the target for the duration of a high-energy stream a few seconds long.

But what about a lower-energy, long-duration shot, that would track the target for several minutes?

Also, instead of modeling it as an uber-fast vessel, why not make it instantaneous over short ranges? As you said, a photon travels 1000km in 1/300 s, and from Earth to Luna in 2 and a half seconds, so any combat taking place in LEO is going to have a negligible lightspeed delay.

 

[T.Neo]

Your idea makes more sense as armor than a power collection platform (photovoltaics or even solar thermal would probably be more efficient, and if it's any sort of warship you'll hopefully be carrying a nuclear reactor as well).

I proposed a concept for an interplanetary combat spacecraft using an ice shield in this post. The trick is to use the ice as fuel as well as armour, thus eliminating the need to carry exorbitant amounts of fuel to lug around all the armor.

But what about a lower-energy, long-duration shot, that would track the target for several minutes?

I have a feeling that a ship being subjected to such an attack would detect it pretty early on and jink the beam with it's thrusters, making it ineffective.

 

[Ghostrider]

Well, the best defence against a relatively short-range weapon such as a laser should be "blast the weapon's platform into red-hot fragments because it can come near enough to use it"...

 

[Usquanigo]

Well, the best defence against a relatively short-range weapon such as a laser should be "blast the weapon's platform into red-hot fragments because it can come near enough to use it"...

True 'nuff. But why would a laser be in any way a "short range weapon"? Given the speed and fact that it can't be detected until it hits, the only range would be objects getting in the way. In LEO, that might be a problem, but GEO and interplanetary space it wouldn't be such a problem.

Using things like missiles might actually be more difficult since you would have to be so well positioned to fire, the enemy would see it coming and work to avoid being in position to be hit.

 

[docabn]

shoot first, shoot fast, shoot often...:yes:
yeah fire superior fire power is always the best option
but good standoff, thick armor, and a small target profile help too.:hmm:

 

[Urwumpe]

True 'nuff. But why would a laser be in any way a "short range weapon"? Given the speed and fact that it can't be detected until it hits, the only range would be objects getting in the way. In LEO, that might be a problem, but GEO and interplanetary space it wouldn't be such a problem.

Don't forget the detection and travel time delay problems. Also a laser still looses power by the beam widening over distance (compared to normal light, it only has the advantage that it does not widen by refraction), since you have no infinitely large aperture.

 

[Kevon Daye]

Don't forget the detection and travel time delay problems. Also a laser still looses power by the beam widening over distance (compared to normal light, it only has the advantage that it does not widen by refraction), since you have no infinitely large aperture.

This is a process known as [ame="http://en.wikipedia.org/wiki/Diffraction"]Diffraction - Wikipedia, the free encyclopedia[/ame]

"Propagation of a laser beam:
The way in which the profile of a laser beam changes as it propagates is determined by diffraction. The output mirror of the laser is an aperture, and the subsequent beam shape is determined by that aperture. Hence, the smaller the output beam, the quicker it diverges. Diode lasers have much greater divergence than He–Ne lasers for this reason.
Paradoxically, it is possible to reduce the divergence of a laser beam by first expanding it with one convex lens, and then collimating it with a second convex lens whose focal point is coincident with that of the first lens. The resulting beam has a larger aperture, and hence a lower divergence."

Also, while it may be very difficult to spoof the laser itself in combat, even at ranges as close as 15 to 20 km, visual acquisition of a target can be difficult,requiring the use of a targeting computer, and as evryone knows a computer is anything but infallible. See where I'm going with this?.

 

[Urwumpe]

Thank you, I didn't remember the correct term and was too busy searching it.

 

[Izack]

I don't see how visual acquisition of targets is a problem. The main thing about laser aiming would be to keep the beam on the target, eh? That would require careful observation and predictions at a high frequency, though, so a targeting computer is still essential.

 

[Urwumpe]

I don't see how visual acquisition of targets is a problem. The main thing about laser aiming would be to keep the beam on the target, eh? That would require careful observation and predictions at a high frequency, though, so a targeting computer is still essential.

And anticipate the motion of the target correctly, even at short astronautical distances, you can already make even perfect sensors and laser guidance miss you, even with modest accelerations. All because of the round-trip time (Target->Sensors->Guidance->Control->Target)

With realistic sensors and laser guidance systems, you have even at much shorter distances a good chance to make it miss you, an existing anti-ship missile like the Klub could already be able to "dodge" a laser.

 

[Usquanigo]

I don't see how visual acquisition of targets is a problem. The main thing about laser aiming would be to keep the beam on the target, eh? That would require careful observation and predictions at a high frequency, though, so a targeting computer is still essential.

With enough power, you don't need a long time on target for damage. Most of the most destructive lasers in labs today are all capacitor based and when demonstrated it's a very short pulse with a loud bang and impressive damage done.

Even then, I would imagine that might be better than a long time fixed on target because it would be easier to build up a much larger charge. Even if you have a fusion engine on board (as opposed to maintaining that level of power draw).

And... if you're firing at a cap ship, it's not going to move very far very fast (not to mention will be presenting a big target area to begin with), and if it's a smaller ship, then it won't have much armor and fuel is a big issue, so it can only maneuver just so much.

Plus, in orbit, you're only going so far anyway. I'd bet most beam weapons could be articulated enough to be able to follow almost any move any target could manage. Especially if targeting is linked not only to the weapons gimbals, but also the ships own RCS system.

---------- Post added at 05:50 PM ---------- Previous post was at 05:48 PM ----------

And anticipate the motion of the target correctly, even at short astronautical distances, you can already make even perfect sensors and laser guidance miss you, even with modest accelerations. All because of the round-trip time (Target->Sensors->Guidance->Control->Target)

With realistic sensors and laser guidance systems, you have even at much shorter distances a good chance to make it miss you, an existing anti-ship missile like the Klub could already be able to "dodge" a laser.

True... but like I said above, you're only going to move so far, so fast, for so long. Reaction mass/fuel for RCS, ship mass, and orbit all limit things quite a bit.

 

[Urwumpe]

True... but like I said above, you're only going to move so far, so fast, for so long. Reaction mass/fuel for RCS, ship mass, and orbit all limit things quite a bit.

Yes. Just like a 50 GW laser doesn't power itself by the power of Grayskull. You only need to dodge long enough to either leave the range of the laser or have the firing ship power the laser down for cooling or power constraints.

 

[Usquanigo]

Yes. Just like a 50 GW laser doesn't power itself by the power of Grayskull. You only need to dodge long enough to either leave the range of the laser or have the firing ship power the laser down for cooling or power constraints.

Or, the attacking ship targets a large capital ship, gets a fix and tracks it for a bit, then fires. The target doesn't know when to jink or where.

The attacker could even fire several simultaneous pulses which would cover predicted location, as well as all possible locations (if they zigged when you thought they would zag) - they're only going so far.

That also assumes a pretty big distance too (between combatants).

 

[Urwumpe]

There is no stealth in space though. You can't fire a laser without already mooning the solar system with your radiators before you fire. And if you try to point your radiators away from the target, you show it the rest of the universe.

You would need even active cooling of the frontal side of your spacecraft for preventing it getting heated by radiation and produce a strong streak on any passive IR sensor (incoming radiation = outgoing radiation + conduction to coolant). If you try that, you need a huge radiator surface = you will become a bigger radar target...

Its not easy to surprise a target in space.

 

[Usquanigo]

Perhaps.... IF you need to open all that stuff in advance.

But, lets play that game, let's assume the distances are that great, and you do need to open all that up (like the Minbari thing of opening gun ports, or the Argo (Yamato) swiveling it's deck guns at something) - ....when do you fire?

That's what I was saying. You're tracking, and you may be showing hostile intent. But when, as the target, do you jink, and where? Again, you're only going so far, and you don't know when they are going to pull the trigger, or if in fact they actually will (though you'll assume it). But in all probability, due to factors of your own size, direction, orbit, etc, the predictive targeting computer on the attacking ship will likely blast you no matter what you do - and if that same ship decides to hit all the potential places you could go with multiple pulses, then you're really hosed.