Deflector shields and visible light

[Borgholio]

So on the drive to work this morning I found myself wondering about a potentially lethal weakness in deflector shields. In most versions of sci-fi, shields are permeable to visible light. Light from a spotlight or the sun will pass through the shield, reflect off the hull of the ship, and back out again. Projectiles, particle beam weapons, and other physical objects are usually stopped.

So with that said, is it a function of the amount of energy? Sunlight typically being low-amounts of energy are allowed to pass through while an energy beam is blocked? Or is the visible light wavelength of the spectrum allowed to pass through? If so, then a high-energy laser in the visible spectrum would pass through as well. Thoughts?

[Patroklos]

There are some pretty famous examples of science fiction authors taking this pretty seriously and deciding no, visible light would not pass through a field whose entire reason for being is stopping electromagnetic radiation. Niven's Langston Field from Mote in God's Eye and related material being a very good and well know example. The energy from this field, as it happens, also makes it a good physical projectile defense in universe if I remember.

I fight with this issue when thinking about scifi. Having blind ships stumble around blindfolded wacking at each other piñata style, peeking out momentarily if they dare, can make for a good story but unfortunately the same story. Like the FTL handwave I generally accept the "we will let THIS radiation through" handwave for artistic purposes.

Sensors are also something that bother me with this issue. visible light is pretty low energy most of the time, but what about these magic sensors that can observe huge volumes of space instantaneously? Or communications?

[Lord Revan]

one possibility would be that a shield has an intensity threshold so that if they light source is intense/focused enough to harm the ship it will be blocked but something like visible light passes cause it's not very intense.

[Elheru Aran]

There is the potential for 'flashbang' type weapons-- creating an extremely visually intense explosion in the field of view of the crew to temporarily blind them and/or mask sensors for some time. This could be interesting, but I suspect something along the lines of blast shutters would be called for. Or simply enclosing the ship entirely and using redundant networked cameras for external view-- if one set gets burned out by such an explosion, bring the other set online.

[Meest]

What about linking or getting data from outside the shield with probes/drones or escort craft, using neutrinos/tachyons to carry data, can you even jam those particles? Maybe it depends on range, why would you need to see outside even at the ranges we see on screen. Poke some telescopes outside the shield barrier once in awhile and update your virtual theatre view.

[Sea Skimmer]

There is the potential for 'flashbang' type weapons-- creating an extremely visually intense explosion in the field of view of the crew to temporarily blind them and/or mask sensors for some time.

Before the Protocol on Blinding Laser Weapons passed the US and China were apparently working on devices exactly like that, except remove the temporary clause. More or less they worked like the chemicals of a chemical laser in a bomb, so they'd mix inside a spinning artillery shell and then burst with an enormous flash of UV and visual light but without the focusing optics of a laser beam. In principle such a device could be bright enough to burn people to death at close range were it big enough. Even a very small one could cause blindess though, and it appears to be weapons like this as much or more then directed beam lasers that really motivated the 1997 agreement.

Throw hand grenades were also being worked on, not just large artillery and aircraft weapons.

This could be interesting, but I suspect something along the lines of blast shutters would be called for. Or simply enclosing the ship entirely and using redundant networked cameras for external view-- if one set gets burned out by such an explosion, bring the other set online.

Physicals shutters would be too slow moving in realistic, though they might close up to be a second line of defense against heavy attacks. However this topic has been addressed in real life for protecting pilots from nuclear flash, in the simplest forms gold coated glasses provide significant protection from visual and near IR light, but in more elaborate forms powered polarization devices which are by default opaque and made clear by an electrical charge. The other way around also works, but is slower reacting.


Like this, EEU-2A/P goggles for the FB-111. They had service problems, but the basic protective technology worked.

I've also just recently come across some research from a decade ago on 'Molecular Photonics of supra Nonlinear Liquid Crustals' for laser protection, which amounted to a form of crystal matrix in which and array of flanking microlaser beams are used to selectively change the refraction value of the crystals. This allows for actually selectively turning stuff opaque within the material, and deflecting the incoming light to the sides, allowing for a much larger energy absorption area. It was all lab bench stuff, but allowed in principle to filter out almost all of a laser beam, and all glare from the beam dispersion, while still maintaining almost all of the background scenery image.

The science of the above is beyond me, but it appeared to be about as close as a sci fi shield as any real technology has ever gotten to date even in principle, though working a bit more like a powered armor then a force field. Naturally such a device would have limits to how much energy it could absorb before overheating, but science fiction being not limited to real materials might make that value very high.

Realistically a space warship would have no conventional windows because of the need to shield against hard radiation if nothing else, but camera positions would still need protection against nuclear flash and laser attacks anyway. It'd just be less critical on how strong the protection is. Nuclear flash or high power lasers at long range(with resulting wide beam) could 'rake' the entire side of a ship, so you wouldn't really want to rely on pure redundancy. It'd also depend on how mass critical the ship design AKA tech base is.

[Sea Skimmer]

What about linking or getting data from outside the shield with probes/drones or escort craft, using neutrinos/tachyons to carry data, can you even jam those particles?

If you can generate them, and you can pick them up, then by default someone can jam them!

However if the jamming would be effective/realistic in actual operating conditions is a different story and would be highly dependent on how the technology actually worked.

[The Romulan Republic]

There are some pretty famous examples of science fiction authors taking this pretty seriously and deciding no, visible light would not pass through a field whose entire reason for being is stopping electromagnetic radiation. Niven's Langston Field from Mote in God's Eye and related material being a very good and well know example. The energy from this field, as it happens, also makes it a good physical projectile defense in universe if I remember.

I fight with this issue when thinking about scifi. Having blind ships stumble around blindfolded wacking at each other piñata style, peeking out momentarily if they dare, can make for a good story but unfortunately the same story. Like the FTL handwave I generally accept the "we will let THIS radiation through" handwave for artistic purposes.

Sensors are also something that bother me with this issue. visible light is pretty low energy most of the time, but what about these magic sensors that can observe huge volumes of space instantaneously? Or communications?

Couldn't you have some means of detecting things outside the shield? Like detecting their gravitational effects? Or, since this is science fiction, having psychics on board to tell you where to fly and shoot?

[Borgholio]

having psychics on board to tell you where to fly and shoot?

WH40k does this.

[GrandMasterTerwynn]

There are some pretty famous examples of science fiction authors taking this pretty seriously and deciding no, visible light would not pass through a field whose entire reason for being is stopping electromagnetic radiation. Niven's Langston Field from Mote in God's Eye and related material being a very good and well know example. The energy from this field, as it happens, also makes it a good physical projectile defense in universe if I remember.

I fight with this issue when thinking about scifi. Having blind ships stumble around blindfolded wacking at each other piñata style, peeking out momentarily if they dare, can make for a good story but unfortunately the same story. Like the FTL handwave I generally accept the "we will let THIS radiation through" handwave for artistic purposes.

Sensors are also something that bother me with this issue. visible light is pretty low energy most of the time, but what about these magic sensors that can observe huge volumes of space instantaneously? Or communications?

Couldn't you have some means of detecting things outside the shield? Like detecting their gravitational effects? Or, since this is science fiction, having psychics on board to tell you where to fly and shoot?

You could have antenna sticking up out of the shield somewhere (or places where your shields don't offer full coverage) with your data coming in from drones, your fellow ships that might not be under vigorous attack, or some sort of AWACS-type ship that's trying to stay out of range of your enemy's weapons. Or even some sort of towed sensor array. Of course, anything sticking out of the protection of the shields is fair game; like those antennae, towed arrays, or drones. Of course, if you've got drones with sensors aboard them, you could also bolt nuclear warheads onto them, and lob missiles at shielded ships that would have a harder time intercepting them.

Of course, there are lots of stories one can write around limitations like that. Either they don't like fighting, and do everything to avoid it; because you'll just end up flailing about blindly when it comes down to shooting. Or else, they develop a lot of tactics and strategies that revolve around trying to catch enemy ships off-guard, so you get the first shots in before anyone can get their shields up ... either killing them quickly, or forcing their surrender because you can keep their shields loaded, robbing them of their ability to see (while you can strike at them with impunity ... at least until their reinforcements show up.)

[Guardsman Bass]

I like the idea of "flickering" shields. You flip your shields up and become nearly invisible and secure, but also blind to stuff happening outside the shield. You drop them temporarily to have your telescopes look for anything, and possibly ping any potential targets with radar - then pull the shield back up hopefully fast enough so as to be secure.

[Simon_Jester]

This is interesting. It is also problematic if you can't tell when you're being shot at, unless you have some other defense that will protect delicate ship components (like your telescopes and radar antennae) while the shields are down.

It's also problematic when under fire from continuous beam weapons.

[GrandMasterTerwynn]

I like the idea of "flickering" shields. You flip your shields up and become nearly invisible and secure, but also blind to stuff happening outside the shield. You drop them temporarily to have your telescopes look for anything, and possibly ping any potential targets with radar - then pull the shield back up hopefully fast enough so as to be secure.

One can also posit that the shields might need to have "portholes" opened in them, because anything that's really good at keeping outside laser fire from getting in might also be really good at keeping inside laser fire from getting out. So you might open momentary weak spots in your shields to take shots at your enemies (and also, maybe, get some idea of what's going on outside the shields.)

Of course, there is always the chance that your enemy will happen to be firing at the same region of shield that you're opening your portholes in, at the same time the porthole happens to be open. But, then again, if your enemy can shoot into your shields like that ... you can do the same thing to him.

[Patroklos]

It was postulated a LONG time ago that SW shields flickered like most fields. If that's the case you can shoot turbo lasers through them like a timed WWI biplane machine gun through its propellers.

In the case of beam weapons if you are using real world rules it actually isn't necessarily advantageous to have then be a continuous beam. When this beam hits the target material it vaporizes degrades the follow on beam dwell and decreases damage. What you often want to do is pulse your laser ever so minutely to let vaporized material escape. That pulse could be combined with the shield flicker to allow your weapons to exit to the target. You could similarly line your signal based sensors to do the same and have your visual sensors link some sort of frame rate speed to that as well. Alternate the flicker of your shields (and also your sensors and weapons) ever so often and the enemy might get a laser pulse in by lick here or there but largely will be out of tune with your shield flicker and stopped.

No that I think about it that sounds a lot like mechanics of shield frequencies in Star Trek, if not in technobabble then in practical application.

[biostem]

If you could open tiny apertures in your own shields, then you could conceivably have several small sensor clusters scattered about your ship, and you just open these small apertures as needed, so these sensors can see through. If you have the ability to adjust the shield's permiability to different forms of radiation, then you could have sensors that can "see" in various wavelengths - like alternating from IR, to UV, or X-Ray, etc.

[Lord of the Abyss]

I recall reading many years ago about a synthetic crystal that stopped laser light but let visible light through. IIRC, the coherent nature of laser light set up a resonance in its electromagnetic bonds that changed the nature of the crystal enough to render it opaque, while incoherent normal light didn't. Something similar could be how an invisible shield blocks laser light.

Or is the visible light wavelength of the spectrum allowed to pass through? If so, then a high-energy laser in the visible spectrum would pass through as well.

That's actually how it works in the Starfire setting. Their electromagnetic shields stop impacts like nuclear explosions, but lasers will just ignore them.

[puskas78]

In Babylon 5, the Third Space aliens use energy shields. One site says that the shields don't work against lasers.
http://babylon5.wikia.com/wiki/Thirdspace_Alien
http://efni.org/Damocles1.htm (how canon is this? Is this fanfic or EU material?)

I recall reading many years ago about a synthetic crystal that stopped laser light but let visible light through. IIRC, the coherent nature of laser light set up a resonance in its electromagnetic bonds that changed the nature of the crystal enough to render it opaque, while incoherent normal light didn't. Something similar could be how an invisible shield blocks laser light.

The beam of a dye laser is less coherent. http://en.wikipedia.org/wiki/Dye_laser

[Adam Reynolds]

Interestingly, the Star Trek TM described their shields as bending light 90 degrees before it hits the ship, which would obviously make lasers useless. How this fails to make the ship invisible is left as an exercise for the reader*.
* This was pointed out by Lawrence Krauss in his Trek book.

[Eleventh Century Remnant]

What I want to know is how a gravity field intense enough to do that, when stellar masses only manage to bend light by fractions of a degree, can be,
a), generated, and
b), not destroy the ship they're supposed to be protecting with tidal spaghettification? Inquiring minds need to know...

Frankly bending light with gravity, to this extent, makes significantly less sense than nuclear explosive reactive armour. At least that would only likely kill you when it actually takes a hit.

(Oh, and as far as a) goes, this is only a couple of orders of magnitude ((wild ass guess)) short of the intensity of the warp field, and at a gut guess the warp field is the deflector field also, make the thing do double duty. Means the shields also take you into a blind pocket universe- hey, that looks like Square One over there. Hm.)

Lord of the Abyss, you don't happen to remember anything about the mechanical properties of that crystal? Such as whether it could be used as armour or radiation shielding, whether it has any additional function that might make it worth eating the mass allowance for?
(added- isn't that the same stuff that Sea Skimmer is describing, " 'Molecular Photonics of supra Nonlinear Liquid Crystals' "?)

As far as I recall, not actually Niven and Pournelle's idea- Steven Barnes, I think, a friend of theirs and playing in the same universe- about the Langston Field is that you can detect when energy impinges on the field- you have to manage the dispersion of it for a start- so you can basically use your own shield management hardware as a synthetic aperture telescope. Not blind; vague and fuzzy as hell, but not blind.