Space Laser and warfare

[Sky Captain]

An armor with thermal superconductivity properties might be good against lasers because heat then would be instantly distributed over all hull and you would have to heat up the whole ship with laser fire to cause damage. Although I have no idea if thermal superconductivity is even possible.

 

[T.Neo]

The problem with a particle or gas shield is it tends to disperse with time, or laser fire. I'd imagine a shield of either would have to be quite thick to be "opaque". It would make a good defence against KKVs and nukes though.

Alternatively to the weapons-in-shield idea, remote drones carrying the necessary weapons/radiators could be linked to the main ship via cables, so they could fire far away from the ship without needing to lug around a fusion reactor.

Perhaps the best would be to have the ship as a long, spindly construction that is very narrow, and have the thick ice shield at the front where it needs to have a much smaller diameter than otherwise.

I think the drones are a brilliant idea- they could pop out behind the shield on cables and fire weapons at the enemy, and they could be relatively numerous and cheap, so if you lost one it wouldn't matter so much.

They'd probably have to reeled in during acceleration though, I don't think they'd be able to stay out on cables unless they have their own drive systems.

NSWR does have certain disadvantages relating to safety- if the pipes that contain the uranium tetrabromide fuel are damaged, then a nuclear reaction will start to occur. :suicide:

 

[Izack]

I'm not sure how they're a good defense against nukes. While nukes would probably be ineffective in space combat due to the sheer size of the playing field (you can only hit one ship with one shot, unless the enemy is incredibly stupid and groups them together), if you really want to take out a ship, a nuke's the way to go. No way any cloud of reflective particles, ablative armour and the best heat sinks money (in space dollars, of course ) can buy can disperse the thermal radiation from a nearby thermonuclear explosion.

Your argument against NSWRs seems valid. I'll have to rethink that... :blink:

 

[T.Neo]

Well, defence against a nuke depends a lot on how accurate it is. A direct hit is a kill, a a hundred meters away or so might cause some physical damage to the ship, and a nuke a few kilometers away might do negligible damage. A neutron bomb would allow you to capture an enemy ship more or less intact after killing the crew.

The thing about nukes though is that you can use your lasers or some form of point defence to take them out- a dust cloud could be an effective defence against a hypervelocity nuclear missle. Nukes don't really suffer sympathetic detonation. Though you would have to deal with the debris of the nuke still travelling towards you...

Perhaps the propulsion could be some sort of NTR- perhaps gas core (doesn't really have to enclose the fission products because this is occuring solely in space) using water as a propellant. Considering that there is now a very large block of ice on the front of the ship, this might be doable. with the lower efficiency.

But the ice shield must not be depleted, or else it won't be able to function as a very good shield.

Though a GCNR using water as propellant with a (thumbsuck) exhaust velocity of 17480 m/s and a Dv of 500 km/s gives me a mass ratio of 2.6 trillion. :uhh:

Perhaps it would be best to nail down what sort of Dv would be needed by an interplanetary military spacecraft of the sort...

 

[statickid]

The problem with a particle or gas shield is it tends to disperse with time, or laser fire. I'd imagine a shield of either would have to be quite thick to be "opaque". It would make a good defence against KKVs and nukes though.

<snip>

I would consider them (the particles) to be emergency counter measures, as in something that you eject because you need more time to do something else, like if a tank threw a smoke canister as a shroud, only the shroud would also have some protective qualities.

 

[T.Neo]

Illustrative concept;

Light blue- Ice shield/heatsink/propellant reserve.

Red- Propulsion and power.

Dark blue- Liquid water propellant.

Dark purple- Heat radiators.

Yellow and green- LH2/LOX auxilliary propellant.

Orange- Bays and rigging for tethered drones.

Light purple- Habitation section and auxilliary craft.

Grey- Main tensionary truss structure.

The radiators are supposed to remain behind the ice shield at all times- in this image, the engine exhaust will impinge on the radiators (wasn't paying full attention to what I was doing). The LH2/LOX is produced by splitting water, and is used for both any auxilliary craft, and for the attitude thrusters on the weapon drones.

The liquid water tanks are there so that water can be fed to the engines without needing to be continuously melted by the reactor.

 

[docabn]

In Jerry Pournelle's novels, lasers pretty much never miss once you are close enough. The warships are equipped with a handwavium spherical shield called a Langston Field which absorbs the laser energy and re-radiates it. The bigger the ship, the bigger the sphere, and the more surface there is to radiate, so when a fight starts it's all a mathematical game to see who wins.

In modern warfare the defense against the newest weapons follows this concept. Disperse the energy. I think that the simplest solution would be to somehow do the same.
The material should absorb energy and reflect it outward
The shape of the hull (possibly multiple tiny diamond cuts to give the laser greater surface area it needs to play across and so spread out the damage)

In the realm of energy beams unlike kinetic. The longer you can hold a sustained beam on a target the more damage you can do so....

You could also have an automated system of sensors that rolled the vessel so that a persistently focused energy beam is spread out over multiple parts of the hull and avoiding weaker areas.

In the future when learn to use unobtanium in order to survive striking interstellar matter a .99C any weapon we can imagine may not even be noticed by such hardy vessles.

 

[T.Neo]

In the future when learn to use unobtanium in order to survive striking interstellar matter a .99C any weapon we can imagine may not even be noticed by such hardy vessles.

Interstellar debris when travelling at relativistic speeds are indeed a big problem, but the Valkyrie concept may have a solution- using a droplet radiator as a continuously replenished shield, which is also used to cool the engines. The particles fall back to the ship as it accelerates and are recaptured, so the droplets won't fly through star systems and wreak havoc. The ship then uses thousands of thin whipple shields during deceleration, that hang in front of the rest of the ship on a cable.

Any unobtanium able to withhold it's integrity after being hit by particles at relativistic speeds would be a highly disruptive technology- it would allow for the construction of impossibly large megastructures, not to mention paper thin armor for tanks or ground troops...

As for Sandcasters:

And you can forget about laser defenses like Traveller style Sandcasters. There is no way that they can project a cloud dense enough to do any good.

Then he discusses holding particles in a shield using magnetic fields, but the general consensus is that it is more trouble than it is worth.

If you wanted to have the armor at a distance from the rest of the vessel, something like the shield idea proposed by Izack might be ideal.

 

[Izack]

Illustrative concept;

Light blue- Ice shield/heatsink/propellant reserve.

Red- Propulsion and power.

Dark blue- Liquid water propellant.

Dark purple- Heat radiators.

Yellow and green- LH2/LOX auxilliary propellant.

Orange- Bays and rigging for tethered drones.

Light purple- Habitation section and auxilliary craft.

Grey- Main tensionary truss structure.

The radiators are supposed to remain behind the ice shield at all times- in this image, the engine exhaust will impinge on the radiators (wasn't paying full attention to what I was doing). The LH2/LOX is produced by splitting water, and is used for both any auxilliary craft, and for the attitude thrusters on the weapon drones.

The liquid water tanks are there so that water can be fed to the engines without needing to be continuously melted by the reactor.

While it's not as visually appealing as the Soviet Orion battlecruiser concept, that's an interesting idea. When I imagined the concept the first time you mentioned it, I was thinking of Discover 1 from 2001 with a ball of ice instead of a ball of crew module. This image clarifies all that.
You're right, the engines here would tear up the radiators, but that could be easily fixed by either using 4 larger engines space apart from the radiators, or making the radiators shorter but longer by extending the vessel's total length.

 

[T.Neo]

I think the Orion battlecruiser was intended to do atmospheric takeoff and landing, hence the streamlined shape- I may be wrong. Either way it's just a rough representation.

The choice of a cylinder was mainly from a production complexity point of view- the cylinder is easier to construct, especially since it has several interior compartments. It could be even easier to construct a multisided prism for the ice shield, out of flat plates alone.

I'm not sure, but I think a cylinder is better in terms of area presented to the enemy. Not sure if angling the shell of the ice block would work very well.

Fewer, larger engines would both reduce the problem of heating on the radiators and simplify things quite a bit.

 

[ar81]

If you get to destroy an object in space it will create tons of debris that would mean an expensive cleaning orbit operation later.

Every piece that could hit another would create thousands of pieces that would create zillions of pieces, preventing orbits to be usable. Space garbage problem is quite serious.

Lasers would hardly be necessary, unless you want to vaporize small particles of space junk. But beyond that there is no reason to use a laser.

Now let us go to the background reasons for war.
There is no reason to make war in space.
It is just an empty orbit, and going to other planets is too darn expensive.
A war would blast in minutes some facilities that had a cost of billions and that took years or even decades to build.

For every kilogram of useful cargo you need 9 kilograms of fuel to deliver it to LEO. So it is very expensive to do anything in space.

The idea of a space mothership with fighters is an extrapolation of WWII to space, but certainly it would be more likely to ressemble sub war: Once you are visible, you are dead.

And the debris could harm lots of industries that would sue for billions of dollars. If you get to send debris into a commercial orbit, it could cost a government lots of money to cover lost revenue and also the orbit cleaning operation. So destroying a ship in space would be as charmy for business as causing an oil spill in the gulf and far more expensive.

Who may want to be the pilot who would shoot and ruin the economy of his country with a trigger happy attitude?

 

[Andy44]

Now let us go to the background reasons for war.
There is no reason to make war in space.

This is a technical discussion. Please stay on topic.

 

[Izack]

This is a technical discussion. Please stay on topic.

My sentiments exactly. I'm not a politician or a philosopher. I'm a creator of fiction.

 

[Ark]

Seems like the best defense against lasers would be redundant systems, partitioned fuel/02 tanks, and enough space suits for every crew member to suit up when at battle stations.

Lasers are really limited in the area they can damage, so you could keep fighting for a pretty long time if the crew is suited and your enemy can only hit a 1x1 foot area of the ship per shot. An enemy would have to completely destroy all two or three of your backup systems or blast open each and every section of propellant tank to finally take you out of the fight.

When you can't kill the crew outright by punching a hole in a hab module, it's actually pretty tough to fully destroy a spacecraft. High-speed kinetic weapons are useless because they'll just go in and out like buckshot through a paper bag.

 

[Izack]

High-speed kinetic weapons are useless because they'll just go in and out like buckshot through a paper bag.

This just suddenly occurred to me:
What about variable velocity projectiles? Say, you launch a large shell at a good velocity, but the shell explodes backwards wrt its velocity vector, sending out a spread out field of slower moving particles?

 

[T.Neo]

Objects tend to pack a big punch when they are travelling at hypervelocity. While they might be stopped by whipple shields, I'm sure a large enough object will overwhelm the shield (it will break up upon hitting the first shield but the debris will damage the second badly enough). A whipple shield also has limited effectiveness if it's shot full of holes (though how easy it would be to do that, if at all, is doubtful).

 

[ar81]

This is a technical discussion. Please stay on topic.

It is relevant and on topic because it makes the use of lasers practical or not, since this thread is about usage of lasers for war. If wars are not needed, then lasers will not be used for war. Lasers would be more practical for wiping out small debris mostly in an orbit cleaning operation.

 

[T.Neo]

If you have a laser able to "clean" LEO via partial ablation of debris, there is a high chance that it can be weaponised in some manner.

That's partially why it's never been implemented or tried. There was talk for using one to clear the ISS's orbit AFAIK, but it never came to fruition...

 

[Ghostrider]

Now let us go to the background reasons for war.
There is no reason to make war in space.
It is just an empty orbit

Two words: High Ground. Once you control the orbit, you deny the enemy reconnaissance and communication, and you can bomb him while he will have problems shooting you down.

A war would blast in minutes some facilities that had a cost of billions and that took years or even decades to build.

That happens in every war ever since industrialization showed up, and it hasn't been much of a deterrent.

For every kilogram of useful cargo you need 9 kilograms of fuel to deliver it to LEO. So it is very expensive to do anything in space.

We're talking Space Wars and you're using current figures to say it's not gonna happen? It's a purely speculative discussion for starters, and then again in the age before airships people would say there was no reason to fight in the air, it's just empty space. And they were right - it IS empty space and you cannot conquer clouds. But once you control the skies, you have one hell of a upper hand. Same with space, if you have assets in orbit you have an advantage over your opponents.

The idea of a space mothership with fighters is an extrapolation of WWII to space, but certainly it would be more likely to ressemble sub war: Once you are visible, you are dead.

This is the only part we agree on, but once you're visible you're still not dead. You are in Big Trouble but not necessarily dead. However your mission could be fraked big time.

And the debris could harm lots of industries that would sue for billions of dollars.

In wartime, sueing your government for damage to your commercial operations would get you ignored, jailed or executed depending on the mood of your leaders. Not an issue.

If wars are not needed

Then maybe the leopard will wipe away its spots and find a new job as a Kansas milk cow.

 

[T.Neo]

The idea of a space mothership with fighters is an extrapolation of WWII to space, but certainly it would be more likely to ressemble sub war: Once you are visible, you are dead.

The problem is, in space you are always visible... :shifty: