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Bit of a weird question, but lemme explain. I want to make shields that block lasers but don't block projectiles, As lasers in my world are very powerful.

I heard that military grade lasers can be dissipated by rain, so my first idea was a water vapor cloud, but I don't know how one would hold that in place. My second idea was making some kind of magnetic fluid that still dispersed lasers, and was held in place using magnets.

I want to know if this is feasible for space combat. I'm open to alternate methods, all it needs to do is block lasers in a vacuum.

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  • $\begingroup$ (a) I assume you mean believable when you say feasible as no technology exists to do what you're asking. (b) Lasers do what they do via light and heat. No matter what material you suspend as a shield, it must either reflect or ablate. If reflection is imperfect, something must ablate or some portion of the laser will penetrate the shield. See ablative armor. The idea of a laser simply stopping is nonsensical (read: infeasible) because the energy (read: heat) must go somewhere. Now, if we could deflect without reflection… Ah, gravity. $\endgroup$
    – JBH
    Commented Mar 18, 2023 at 19:54
  • $\begingroup$ 'fluid' and 'pressureless vacuum of space' are terms that scientifically usually never go together in the same sentence. Fluids usually do not have bonds between the atoms or molecules, That is why they 'seek their own level' on Earth. In a pressureless vacuum environment, there is, of course, no pressure to bind the 'fluid' into a sphere, nothing to create 'surface tension. Fluids 'boil' in a pressureless (vacuum) environment. You would not be 'constraining' a fluid, you would be constraining a 'gas'. $\endgroup$ Commented Mar 18, 2023 at 21:56

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Regarding your idea of a water vapor cloud, it is correct that lasers can be dissipated by rain or other forms of moisture in the air. However, creating a stable water vapor cloud in a vacuum environment like space would be challenging, as there is no atmospheric pressure to contain the cloud. Moreover, the water vapor cloud may also interfere with other spacecraft systems and sensors.

Your second idea of using a magnetic fluid to disperse lasers is also interesting. Magnetic fluids, also known as ferrofluids, are liquids that contain magnetic particles that can be controlled by a magnetic field. By applying a magnetic field, the magnetic particles can be aligned in a way that creates a barrier against laser beams. However, the effectiveness of this approach would depend on the strength of the magnetic field and the properties of the laser being used.

A plasma bubble could potentially work as a shield against lasers. Plasma is a highly ionized gas that can absorb and dissipate electromagnetic radiation, including laser energy. By creating a bubble of plasma around the spacecraft, the laser beams would be absorbed and dispersed by the plasma, potentially providing protection.

To create a stable plasma bubble, a magnetic field could be used to contain the plasma. The magnetic field would have to be strong enough to keep the plasma contained and prevent it from expanding and dissipating. The plasma could be generated by ionizing a gas or by using a plasma generator.

However, it's worth noting that creating a plasma shield would require a lot of energy and resources, and the effectiveness of the shield would depend on the strength and properties of the laser being used. Additionally, plasma shields could also interfere with other spacecraft systems and sensors, so careful design and testing would be necessary.

Another option to consider is using a material that absorbs or reflects laser energy. For example, certain materials like graphene or carbon nanotubes can absorb laser energy and dissipate it as heat. Similarly, a reflective material like a mirror could reflect laser beams away from the spacecraft. However, these materials may not provide complete protection against high-powered lasers.

In conclusion, while it may not be possible to create a perfect shield that blocks all forms of laser attacks but not physical projectiles, there are some possible solutions that can offer some level of protection against laser attacks. It's worth noting that in a hypothetical space combat scenario, a combination of different defense mechanisms, including traditional armor, electronic countermeasures, and defensive maneuvers, would likely be necessary to survive and prevail.

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  • $\begingroup$ "...and dissipate it as heat." There is no such thing as 'heat'. We left that train station way back almost two centuries ago. Weird how we still hang on to the concept long after we dispelled the idea that 'fire' was an 'element'. 'Heat' is a term loosely attributed to the vibration of molecules, In our contemporary earthly world, we 'dissipate heat' through conduction - we transfer the molecular vibrations to some other substance in contact with it., There is no conduction in space. $\endgroup$ Commented Mar 18, 2023 at 21:47
  • $\begingroup$ There is no conduction in space? I don't think you mean that. The "dissipate it as heat" comment refers to a highly effective conductor that would rapidly transfer the energy from a small area to the larger area not being attacked. From there it might conduct further into the ship or radiate out. $\endgroup$
    – Hukk2010
    Commented Mar 19, 2023 at 22:37
  • $\begingroup$ For conduction to occur, the two substances have to be physically connected. Conduction on Earth is done through the atmosphere - direct transfer air molecule to air molecule. If there is a 'large area' of some solid, then there is no need for the 'ferro fluid cloud'. 'Heat' is NOT a 'thing', it is a state of matter. The degree to which the molecules vibrate. If the cloud is dense enough to conduct heat, it is dense enough to stop missiles. $\endgroup$ Commented Mar 20, 2023 at 3:18
  • $\begingroup$ I agree with the principle that conduction requires contact, however, the quote you gave was in reference to a coating on the surface of the ship and so the 'in contact' requirement is fulfilled. I never suggested that the cloud or plasma would use conduction as a way to disperse energy, radiation would be its principle method. Heat is a useful concept as there is a common (mis)understanding of the term that can be used to communicate ideas. This question is not tagged as hard science so I am using appropriate terms. I don't think this is the forum for this argument though! $\endgroup$
    – Hukk2010
    Commented Mar 21, 2023 at 7:55
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Plasma, being a cloud of free electrons and positively charged atomic atoms, can block a laser without appreciable effects on projectiles.

A magnetic field alone would do nothing to a laser, and anything solid or liquid, while affecting the laser, would also dissipate part or all of the energy of a projectile moving through it.

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Is your laser defence more efficient than a coat of aluminium foil?

No moving parts. Light is easily reflected. However at high intensities, the mirror will be damaged and the metal becomes a plasma. This absorbs light and re-emits it in random directions, destroying the coherence of the beam.

You could have multiple layers of foil. Or foil backed with water bubbles. This feels a bit like armour of very high velocity impactors: an outermost layer breaks up the coherence of the attack, and spreads it over a large area that the lower layers might resist.

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