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Casimir WHAT? Are you high?
You heard me. The Casimir Effect is one of the most interesting and potentially powerful phenomena known to modern science.
Allow the One True Wiki to explain.. well... let me paraphrase the introduction (it's technical):
An immense amount of latent energy is bound up in every cubic centimeter of space-time in the universe. Most of the cosmological constants - things like this l'il thing here, The Planck Constant, are defined by the interplay of forces, effects and particles that, aside from the most excellent Higgs Irish Setter, I mean, boson (Sorry, my one Mitt Romney joke of the night), are all pretty much locked down.
Yet all that means is we have taken inventory of the Lego blocks of reality...and there are a frackin' whole lot of them, and almost all of them come in multiple flavors that interact with themselves, (even if Rick Santorum thinks it's a sin especially if it's self-interacting dark matter). Sorry, had to get that out of the way as well.
Back to topic. The so-called zero point energy of the cosmos is immense. And it can be tapped simply by pressing two plates really, really close together. (Srsly! You Can Haz Powurz!)
The idea is that fluctuations have wavelengths.. and once the plates in question are shorter than the ambient wavelength...weirdness ensues. Specifically, the plates depending on their orientation, either press apart or start pressing together.
The closer they get - and they can get damn close - the more powerful the pressure generated. Keep in mind what you could be pressing against at this point - the expansion of the universe itself.
From the Casimir Effect Wiki article:
I tossed together a spreadsheet building off of equations on Wiki a few months back. Just today I went surfing and found a very interesting pdf, by two scientists, G. Jordan MacCay and one of my favorite science fiction authors - Robert L. Forward.
Because the strength of the force falls off rapidly with distance, it is only measurable when the distance between the objects is extremely small. On a submicron scale, this force becomes so strong that it becomes the dominant force between uncharged conductors. In fact, at separations of 10 [nanometers]—about 100 times the typical size of an atom—the Casimir effect produces the equivalent of 1 atmosphere of pressure (101.325 kPa), the precise value depending on surface geometry and other factors.
The piece in question was published in 2003 - two years after Forward's death of cancer. It has the interesting title "A Gedanken spacecraft that operates using the quantum vacuum (Dynamic Casimir effect)". In it the two men discuss, well, pretty much every imaginable variation of a Casimir Drive, concluding that, given what they deemed viable best-scenario assumptions, this wasn't going to work. Not anytime soon.
Now, at the scales they work on.. my spreadsheet checked out in terms of the potential energy output: not much. Accelerations on the order of billionths of gees. That's just plain pitiful. (My concept went a different way but more on that later.)
Still... they left the door open a crack. After all, there's a lot we don't know about quantum fluctuations in the electromagnetic field but what we do know is there is a LOT of power to tap. MacCay and Forward tried mainly one way: Vibrating two plates with what, to them, were best-case realistic tolerances to vibration frequencies, to generate unidirectional photon radiation by something they called the "Dynamic Casimir Effect".
The premise was that accelerating a boundary through a vacuum in this fashion would create photons (if I understand it rightly, by forcing some small portion of virtual particles to choose a "real" state). The faster the vibration, the more such photon radiation. (For giggles, the two scientists assumed it all went into modest but useful work propelling the spacecraft.)
This was their best-guess at a realistic proof-of-concept exercise to show that the Casimir Effect could be used to tap vacuum energy. And while they were dissatisfied with the performance but satisfied that they'd shown the principle was sound, even with conventional materials.
Then they launched into some speculation on something that did not exist 10 years ago but exists today Metamaterials.
We are now entering an age where we will be able to customize artificial materials to heretofore impossible physical specs (for example, negatively refractive materials or, taken to extreme, materials that are negatively refractive to not just visible light but hard radiation).
MacCay and Forward speculated that such materials could make a Casimir space drive much more powerful by virtue of handling much higher vibration frequencies - perhaps on the order of thousands or millions of times more durable. More vibrations, more propulsive radiation, compliments of the fabric of space-time itself. In theory, very high accelerations would be possible, even for large payloads.
From where I'm sitting, I'm skeptical physical matter of any kind can bring home the bacon in this respect. Then there is the matter that, ahem, matter has mass. It weighs something. Also, based on the lower range of potential vacuum energy, a LOT of space has to be tapped - first to get the energy, straight up, to run the propulsion array, then another array to manifest reaction mass - in the MacCay/Forward model, photons (which have momentum not mass but, hey, the math works and it's been validated in lab experiments).
Ah, but fear not. MacLay and Forward venture, albeit briefly, into the possibility that the Casimir generator elements could be constructed out of coherent sheets of force or plasma which, in theory, could be tuned up to any vibration frequency. They concede that any manipulation of energy would probably reduce the available vacuum potential energy (some of it would be in essence "assigned" to produce the boundaries used to actuate a Casimir Effect in the first place). But on the other hand it's easier to manipulate energy states than construct physical arrays. The loss of efficiency would be more than made up by gains elsewhere - including the potential to propagate the array to any size up to the limits of available energy.
So, if you could assemble such a toy, physical or energy-based, we go from talking about a concept that could, maybe, get a space probe up to Earth escape velocity in about ten years to a space drive that could punch a large starship up to near-light speed in a very short time.
And that, my friends, would be really, really cool.
Oh, I did say I would tell you my variant.
For, you see, space is never empty. It's more than a source of vacuum energy but a medium full of supplemental reaction mass - micrometeoroids, interplanetary (and interstellar) dust, hydrogen, supernova-fabricated heavy ions and the occasional piece of space junk. The faster you go, especially close to light speed, the more free reaction mass you have to play with.
Why not use Casimir effect 'jets', very truncated open-ended hourglass shapes, built at nanometer-scale, replicated to very high densities and cast as sheets across large planes of space perpendicular to the longitudinal axis of the spacecraft. Most of these structures would be invisible. Close in to the hypothetical projectors of these force-forms, they might resembles sails... or wings, glowing in various plasma colors ... red, purple, orange and gold, like our own Sun's prominences.
There would be two sets of these 'sails' - one to gather energy to support the forms, the other to accelerate whatever reaction mass the ship brought (some would be needed to kick-start the expedition) and whatever it collected as it accelerated - first slowly, then faster and faster until its operating maximum and mass gain from approaching near-light speed tapered off its acceleration.
A single 10-nanometer wide channel, 10 nanometers long, would impart negligible thrust to a 100-ton payload: try roughly 10^-21 meters/second squared.
Populate a 100 meter radius circular shield of such elements, at 50 million elements per square meter, and you'd get a mighty 10^-10 gees oomph. Meh. Not so great still.
We know that smaller channel width gets more juice so lets close the channels to 1 nanometer. That gets us to 10^-9 gees
And let's extend the reaction tracks to, oh, 100 nanometers, so there is more time to accelerate the reaction mass. This is trickier and more energy-intensive so we can't go too crazy with this.. and the more energy is utilized to make the shapes, the less efficient the drive. Let's just say this is the practical maximum for our purposes tonight. Now we're at 10^-8 gees. Still pretty light
So now we have to expand the array - this we can do, to the limits of our ability to propagate energy collection arrays and regulate the accelerator elements. We're already at a 100 meters... but we can go much further. Let's say... 100 kilometers, once we're really cooking.
And at that point you are talking roughly 3% gees acceleration. That's not much weight in once sense.. but in another you might as well be talking about warp drive.
It would take such a ship a matter of hours to go from low Earth orbit to Earth escape velocity. Yes, it would be a slow start and, once you got going, cruising up to near-light speed with tau factors in the thousands (one day onboard ship, a few years back home, a few light years down the road) we would have cosmic sails, wings to take us - well, some of us, anyway - anywhere we could imagine going.
From such ugly cignets as the spacecraft of today, beautiful golden swans will be born.
I think some of us, the youngest, will see the first of these ships take flight.
And that would be something worthy of Top Comments to diary about.