Wednesday, July 01, 2009

Recipe for a Force Field

We don't yet have flying cars, much less jet packs. I like our Roomba, but domestic robots still have far to go before they can whip up an omelet, set the table, and pour the coffee. In these and many other areas, technology continues to lag behind the rosy sci-fi scenarios of my youth. Allow me, then, to give the future a little kick in the pants by describing how to build a long anticipated and long overdue technology: The force field.

Start with a phase conjugate mirror. A conventional mirror simply reflects light, bouncing it off at an angle in the same way that the bumper on a pool table redirects the motion of a ball. A phase conjugate mirror, in contrast, reflects light in exactly the reverse direction and form as the light comes in. Banking shots would be impossible on a pool table with "phase conjugate" bumpers, as balls would always bounce back in exactly the same direction whence they came.

Add to the phase conjugate mirror this additional ingredient: pumping beams that create a amplified reflection of the incoming wave front. (Read the bit under "phase conjugate mirror" at this source for more details.) To recur to the pool table example, it would be as if you gently tapped a ball at a bumper and it came speeding straight back at you.

Lastly, top off the amplified phase conjugate mirror with an illumination beam—a laser that rapidly scans the protected area, say. This illuminating beam can operate at relatively low power levels, given that it serves only to bounce a few photons off of the target. When some of those illuminating photons find their way from the target to the amplified conjugate phase mirror . . . BAM! Out flashes a blast of electromagnetic energy, automatically aimed on-target.

To better understand how the force field works, consider a ready application: Protecting spacecraft from orbiting debris. A scanning laser would rapidly sweep the area from which space junk would most likely approach the protected craft. Most of the time, of course, that beam would dissipate into empty space and the force field would remain quiet. When the scanning laser illuminated an approaching threat, however, the phase conjugate mirror would bounce a beam of electromagnetic energy right back at the debris (or, what would in practice amount to the same thing, given the speed of light, at the location the debris occupied an flash earlier). With enough amplification, the phase conjugate mirror could alter the trajectory of the approaching junk, directing it away from the spacecraft. With more amplification, the force field could simply vaporize the threat.

I could say more, but readers who have read this far can probably work out other interesting applications of the force field, as well as the problems introduced by non-reflective or highly reflective targets and the remedies afforded by using different frequencies for the scanning and amplified beams. Some readers might quibble that, regardless of its merits, I've not really described a force field, but rather only something that appears to function like one. Given that sci-fi authors don't typically explain how force fields work, though, I don't feel too bad about borrowing the label.

I don't claim this recipe for a force field as any sort of breathtaking innovation, granted. Once you get your head around phase conjugate mirrors, the rest of what I've suggested falls into place pretty quickly. I guess you could call it obvious to one reasonably skilled in the relevant arts—dynamic holography—and, thus, unpatentable. Still, though, I've yet to find any references on the 'net about this method of creating a force field.

Given that I make my living as a law prof, rather than a non-linear optical scientist, you might wonder why I dabble in these topics. It turns out that I've long had an interest in holograms. I set up a home lab to make them when I was in high school, and later developed a holographic information processing system that, in theory at least, answered a challenge that a hero of my youth, Douglas Hofstadter, put to me personally. His response left me so disillusioned that I abandoned my plans to pursue a degree in AI, but that is another, much longer story.


BrendelConsulting said...


Actually, it's probably more accurately called an 'automatic defence shield'.

But anyway, the only two way to break through this then is to (1) either cover yourself with a mirror for the right wavelength of your amplified laser, so that it just gets reflected.

Or (2), avoid detection in the first place. Like with a cloaking device, for example.

Very nice!

Archer said...

Wow, that sounds cool, Tom! You really caught my imagination when you moved away from the pool table into the vacuum of space.
I will not quibble, although I immediately decided you better reinforce the phase conjugate mirror with some high tensile materials. (You know, forces are equal and opposite.) Wouldn't want a lot of glass fragements floating around...


Tom W. Bell said...

BC: Yes, the mirror would help to fight off the conjugate beam but--here's the part I love!--it would tend to make the target more visible to the illumination beam. And, of course, going for a black-body finish would impose trade-offs running the other way, lowering detection but increasing damage. The defender can, moreover, work around these problems to some degree by varying the frequency of the illumination and conjugate beams. You might, for instance, use visible light to detect a mirrored target and then blow it away using x-rays.

Archer/Dave: Yeah, there are a few complications raised by the use of high-powered conjugate beams. The force field might, for instance, push the space craft out of orbit! But, hey, I'm an ideas guy; a good engineer could surely fix those details.

Will Bendick said...

When can we expect the much longer story?

Tom W. Bell said...

WB: No time soon, I'm sure. It's not all *that* interesting (though it mattered a lot to me at the time) and probably would not reflect well on me *or* DH.

Archer said...
This comment has been removed by the author.
Archer said...

Tom, you certainly sparked something - it sure got my creative juices flowing... so speaking of cloaking devices, here's my take on a

Low Tech Stationary and Wearable Cloaking Device

Tom W. Bell said...

Brilliant, Archer! It makes me wish I'd have drawn some pictures, too. I could have had zooming spaceships and zapping rays . . . just like the cover of an old Heinlein paperback.

Anonymous said...

"But anyway, the only two way to break through this then is to (1) either cover yourself with a mirror for the right wavelength of your amplified laser, so that it just gets reflected.

Or (2), avoid detection in the first place. Like with a cloaking device, for example."
Or to be an heavy, high speed iridium-style slug with a very narrow face and a polished exterior. Retaining mechanical strength at over 1600c, the slug should be able to survive anything but a very powerful and concentrated blast, and the faster it goes the less time it spends in the cooking beam. On top of that, when it hits it's going to be superdense and still relatively hard/strong. Very difficult to stop with a field of this design. But an interesting idea nonetheless.

A mixture of cold plasma and magnetic fields seem to offer some 'forcefield' like properties. Heck, if you could get your hands on some antimass and neutronium you could make some godawful super armor out of it. This, of course, is far more speculative than yours.

Unknown said...

In reference to force fields, I actually started reading into Scalar Energy which randomly came from a friend of mine showing me this piece of glass (been energised with "scalar") that could take all the bad stuff out of water. Whether it really worked who knows, it did actually taste different. Back to what I was initially talking about...After researching what Scalar Energy was it seemed to point into the direction of force fields. I am not a professor of any kind just interested in the subject:)