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Captain Shatner January 17 2013 02:42 AM

Shields Down!
 
In all my reading about the Physics of Trek, never once have I seen an explanation for "shields." Think about it for a minute. "Shields" are a hallowed Sci-Fi convenion, Star Wars also making extensive use of shields. But what exactly are they? Are they pure energy? If so, what keeps them from dissipaiting, as opposed to mainting a rigid structure conforming to the ship?

Melakon January 17 2013 02:59 AM

Re: Shields Down!
 
Shields are basically forcefields. Here's the Memory Alpha explanation:

http://en.memory-alpha.org/wiki/Deflector_shield

Tiberius January 17 2013 03:14 AM

Re: Shields Down!
 
We saw them in action in "The Hunted".

Gary7 January 17 2013 03:39 AM

Re: Shields Down!
 
Deflector shields had two main purposes: protecting the ship from debris and from attack.

I wonder if deflector shields weren't covered in the book because they didn't make much sense. An energy field might dissipate some forms of energy attacks, but the amount of power you'd need would be enormous. And of course, why bother... because all an enemy vessel would have to do is resort to hard missile weapons if you put your shields up. ;)

Warped9 January 17 2013 04:56 AM

Re: Shields Down!
 
I've got a book on my shelf somewhere (not Trek related) that explains what kind of forcefields (or shields) you could have with sufficiently advanced science and technology. From what I remember some of it was pretty wild and rather effective. I'll try to find it.

Now if you can manipulate gravity (which Starfleet seems able to do on some levels) than a sufficiently powerful antigravity field could be a quite effective shield since you could repel physical objects (such as missiles) and even deflect energy beams. If the antigrav field weakens then things start too get through.

But there is some suggestion in TOS that the deflector shields seem to absorb/dissipate energy and successive hits can eventually weaken the field. That doesn't really sound like a "deflector" shield or screen whereas an antigrav field would indeed be a "deflector."

jayrath January 17 2013 06:08 AM

Re: Shields Down!
 
This and similar threads I've seen on other boards might be better in Trek Tech, which is a fascinating board in its own right. I strongly recommend it, but be ready for serious discussions of real and theoretical physics. It makes my head spin.

Anyway, TMOS and one of the TNG DVD extras make clear that deflectors are different from shields. The former sweeps way, way ahead of a ship, to (appropriately) deflect even dust that could pierce the hull at hyper-light speeds. I agree that they are likely something like tractor beams, but in reverse.

We can assume that deflectors are fairly weak. But they're critical -- they're in action anytime a ship goes to warp (and perhaps even at high rates of impulse).

By contrast, shields are raised only periodically, and we've seen that they're real energy hogs. (Besides canon, why not otherwise run around with shields engaged all the time?)

To make matters more complicated, we've seen and heard on-screen that shields are both a sort of skinfield, right next to the hull, and also a sort of shell surrounding a ship at some distance. TOS, which I know best, made it even more complex, by having different, numbered shield zones, which could be moved to cover each other.

As for what shields and deflectors are and what they can do, thanks to TNG we know that Geordi can reconfigure them to ward off pretty much anything but a frown or rainy day. I doubt if we'll ever be able to come up with a Treknical explanation.

Dale Sams January 17 2013 07:25 AM

Re: Shields Down!
 
My fanwank explanation for skintight fields versus bubble ones...was that the skintight ones were more efficient. So if you're the E-D, and still basically an exploration ship...you'd be carrying the bubble shield.

But later with the E-E...they're at war, and it's pretty much a war vessel.

Timo January 18 2013 02:58 PM

Re: Shields Down!
 
We know that making shields bigger weakens them ("Mudd's Women" already established this), so this might make bubble shields less desirable than skintight ones. On the other hand, it would be easy to argue that stretching the shield over the complex shape of a starship will weaken it.

Quote:

we've seen that they're real energy hogs. (Besides canon, why not otherwise run around with shields engaged all the time?)
This is the great mystery about shields: starship skippers will do just about anything within or without reason to avoid raising shields until the very last second. Yet once up, the shields don't seem to require shutting down within minutes; sometimes they can take hours of constant punishment. And we never actually hear of the shields consuming power when they are not being subjected to some sort of an attack, say, enemy fire, the crushing pressure of an atmosphere or a divine hand, the radiation of a star's outer layers...

Timo Saloniemi

MarsWeeps January 18 2013 03:01 PM

Re: Shields Down!
 
And then we have "screens" which are another name for shields I guess. I think they went back and forth before finally settling on "shields."

I never understood why, when danger appears and time is of the essence, the Captain has to order someone else to "raise the shields"...often numerous times before someone gets around to raising them. Why can't the captain just hit a button on his chair? Or better yet, why can't the computer automatically raise them under certain conditions?

Timo January 18 2013 04:02 PM

Re: Shields Down!
 
The computer does automatically raise shields in several TOS episodes and in early TNG. The reason this is not allowed to happen more often might be directly tied to the reason shields are not being kept up by default.

If it's not power consumption, what could it be?

- Unthreatening posture? This is a smart initial move in a universe where most opponents have divine powers and could smite the starship if angered, regardless of whether shields are up or down (that is, the TOS universe). It is also a smart move in a universe where most opponents have learned that trading of blows will quickly escalate into a war they can't afford, and that a Starfleet vessel with shields down is offering them an honorable way out of the week's dilemma, and not being either suicidal or insulting (that is, the TNG universe).

- Sensor troubles? If shields prevent accurate sensing, then the better way to prevent the enemy from sucker-punching you is to keep shields down and see him before he sees you. We don't have much in the way of dialogue to support the idea that shields hamper combat, but it's a possibility.

- Stealth? Shields sound like something that would glow on the enemy's sensors more brightly than the local star, whereas we know that it's basically impossible to spot starships in space if they refrain from activating their high energy systems. Indeed, it might be that raising shields makes it significantly easier for the enemy to target you, except at point blank ranges - so it's sensible to keep shields down even after spotting a distant enemy on approach.

Timo Saloniemi

Melakon January 18 2013 04:17 PM

Re: Shields Down!
 
Quote:

MarsWeeps wrote: (Post 7553677)
. . .I never understood why, when danger appears and time is of the essence, the Captain has to order someone else to "raise the shields"...often numerous times before someone gets around to raising them. . .

I suspect the producers felt it more dramatically exciting this way, and reinforced the idea of Kirk in command.

Timo January 18 2013 04:33 PM

Re: Shields Down!
 
...And even more prominently so when Kirk chooses not to raise shields when the supporting cast already makes panicky requests for being allowed to do so. It's stupid bravado that achieves nothing; a skipper free of self-esteem problems would have no trouble raising the shields well in advance of meeting the threat. But playing chicken looks manly.

Timo Saloniemi

Dale Sams January 19 2013 06:02 AM

Re: Shields Down!
 
Now what the hell is going on in the DS9 battles at the end of the series when it appears almost every ship but the Defiant has no shields...I have no idea.

UssGlenn January 19 2013 06:15 AM

Re: Shields Down!
 
Quote:

Timo wrote: (Post 7553668)
We know that making shields bigger weakens them ("Mudd's Women" already established this), so this might make bubble shields less desirable than skintight ones. On the other hand, it would be easy to argue that stretching the shield over the complex shape of a starship will weaken it.

My guess is that the 2 styles are a result of 2 ways to generate the Shields. Bubble shields come from large generators mounted centrally inside the ship, better protected but when damaged most or all of the shields drop. Skintight shields are generated from smaller emitters distributed throughout the outer hull. That way only small sections of shields can be taken down at a time from enemy fire, unless the take out the power supply.

Melakon January 19 2013 06:50 AM

Re: Shields Down!
 
Quote:

Dale Sams wrote: (Post 7558399)
Now what the hell is going on in the DS9 battles at the end of the series when it appears almost every ship but the Defiant has no shields...I have no idea.

At one point in the final arc, the Breen have a weapon that drains all power from ships. The Klingons are able to develop a defense after a disastrous battle that requires adjusting their engines, but it doesn't work for the Federation and Romulans.


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