Timeline for How to protect your ship against TW-range lasers?
Current License: CC BY-SA 4.0
22 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Dec 29, 2020 at 12:21 | comment | added | Darth Biomech | "why?" Because if the laser is in terawatt range, and your mirror reflects 99.999999% of the light frequency of the laser, the remaining tiny percentage is still powerful enough to erode the mirror, which will cause it to reflect less light, which will accelerate the erosion, until it's rapidly not a mirror anymore. | |
| Jun 20, 2018 at 15:34 | comment | added | user71659 | @MSalters For example, consider ZBLAN glass. At its minimum ZBLAN has a loss of 0.01 dB per km. You can make a thick all-dielectric reflecting structure with very low loss. | |
| Jun 20, 2018 at 15:29 | comment | added | user71659 | @MSalters There is no "surface current". A surface current is a result of charges being moved in a conductor due to the E field. A wave in a dielectric, like a Bragg mirror or a dielectric resonator has no surface current because the charges are bound in the atoms, there is no conduction. There is a displacement current due to polarization. These are two different phenomena, Ohmic loss in the first case, dielectric loss in the second. Therefore, Bragg mirrors or other dielectric, plasmonic structures, can have much higher power handling than metallic mirrors. | |
| Jun 20, 2018 at 7:43 | comment | added | MSalters | @user71659: Those have currents in each thin layer. Same problem, just multiplied. And of course, angle-dependent which is a bit of a problem for a shield. | |
| Jun 20, 2018 at 0:43 | comment | added | user71659 | @MSalters "you need a surface current". Not true. Just make a thick all-dielectric Bragg mirror. | |
| Jun 19, 2018 at 20:03 | comment | added | JBH | For the same reason that it's difficult to distinguish where the sky ends and the ocean begins on days when the ocean is highly reflective. In space, the background of the viewer is fundamentally identical to the background of the mirror. Even if a planet is your background, that reflection occurs along the curvature of your ship, making it (like the sky) more difficult to see against the planet. If you had to use mirrors against visible light lasers, you'd want all the reflection you can get to help with camoflauge. | |
| Jun 19, 2018 at 19:04 | comment | added | L.Dutch♦ | @JBH, why? your background is not highly reflective, so you would stand out anyway | |
| Jun 19, 2018 at 18:49 | comment | added | JBH | The benefit of a highly mirrored surface is that it would make you nearly invisible. | |
| Jun 18, 2018 at 20:08 | comment | added | joojaa | Your mirror does not have to be your hull it can be several mirrors deep. Or you can throw some mirrors at the enemy. | |
| Jun 18, 2018 at 15:27 | comment | added | Gryphon | @Demigan these people obviously have some pretty fantastic heat sinks/transfer mechanisms, so I could see a protracted, minutes-long "duel" of sorts between two ships to see who burns out first. | |
| Jun 18, 2018 at 15:23 | comment | added | Demigan | @Gryphon yes, Unfortunately from what I know you wouldn't be saying "90% and holding" but "90..." and then your shield would already have reached 0% and terawatts of energy would have cooked everyone inside the ship. But considering the ability to fire a TW laser without cooking the ship using it he could have mirrored surfaces that burn away much slower in his story. | |
| Jun 18, 2018 at 14:20 | comment | added | thepizzaelemental | Keep in mind, if you have a solution that involves turning a part of your ship reflective, firing a laser at your sensor cluster will likely leave your crew temporarily blind enough for an old-fashioned kinetic projectile to land. | |
| Jun 18, 2018 at 13:53 | comment | added | Gryphon | @Demigan Interestingly, this actually gives a valid reason for saying "shields at 90% and holding". | |
| Jun 18, 2018 at 11:32 | comment | added | MSalters | The non-linear bits are which turns the mirror into plasma. But even if we ignore that, photonic crystals still have to work by the same mechanism. Reflection is not magic; you need a surface current both to suppress the further travel of the incoming laser beam as well as generating the outgoing beam. | |
| Jun 18, 2018 at 11:19 | comment | added | L.Dutch♦ | @MSalters, who said metal mirrors? metal mirrors don't go past 90% reflectivity, photonic crystals can reach 99% and above. With interesting non linear effects, too... | |
| Jun 18, 2018 at 11:16 | comment | added | MSalters | Sorry, won't work. "Reflectivity of 99.99%" assumes you're in the linear domain, but that's not the case with TW beams. Reflection of electro-magnetic radiation works because the incoming EM radiation creates a surface electric current. This current then causes an outgoing EM field. Obviously this works as long as the current is below the maximum possible current in materials. (It also explains why good conductive materials like metals reflect so well). Cooling is no solution - the TW laser flash-evaporates the surface. It then turns the resulting vapor into a plasma cutting lance. Oops. | |
| Jun 18, 2018 at 11:13 | comment | added | L.Dutch♦ | @Ckankonmange, those mirrors are not designed for handling TW... | |
| Jun 18, 2018 at 10:25 | comment | added | Demigan | @L.Dutch considering they are able to fire a terawatt laser for minutes and dealing with the waste energy, a few MW energy in the armor doesnt seem a problem. I would be more concerned with how a burned mirror immediately loses its reflectiveness meaning that less than a second after the beam hits you are taking the full terawatts of energy. | |
| Jun 18, 2018 at 10:09 | comment | added | Ckankonmange | Look at Lunar Laser Ranging experiment for mirrors that always reflect to the sender. | |
| Jun 18, 2018 at 10:06 | comment | added | L.Dutch♦ | @Alexcommil, managing MW of excess heat in space is not easy... attempt to overload by continuous firing could be a possibility | |
| Jun 18, 2018 at 9:23 | comment | added | Alexcommil | Tiled orientable water cooled mirrors are a possibility then. But then we try to destroy the cooling/orientation part with conventional projectiles and then fire lasers again. damn you, counter measure to counter measure! | |
| Jun 18, 2018 at 9:15 | history | answered | L.Dutch♦ | CC BY-SA 4.0 |