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Sunday, August 08, 2004

Using Quantum Entanglement for Space Propulsion

Spooky Spaceflight: "Once derided by Einstein as "spooky action at a distance", quantum entanglement could hold out the promise of a novel means of space propulsion, perhaps even making interstellar travel feasible."

Here is the core of his proposal:

"While quantum entanglement and quantum teleportation experiments have to date been confined to entangled specimens of materials within the same laboratory, there is no theoretical limitation on how great a distance quantum entanglement can operate across. In other words, once two groups of atoms have been entangled, that entanglement would still be in effect were one of the entangled specimens moved to the other side of the earth.or the solar system.

Therefore, were two specimens of cesium (to take one example; other materials would also work) to be entangled on earth, then one of the specimens lofted into space, exciting the earthbound cesium sample to produce ions would result in the space-traveling cesium sample becoming energetically excited and producing ions like its earthbound counterpart. A resulting ion stream, produced without the benefit (or hindrance, for that matter) of any form of internal engine system onboard the spacecraft, could propel the craft through space. It would be a kind of engineless drive system, which I am calling the teleportation drive. The actual engine and, even more importantly, its power source-a nuclear reactor, a solar array, or other form of power generation-would remain on earth along with the earthbound, entangled fuel sample.

He then goes on to describe another interesting idea using quantum enablement for space drives, something he calls a Photon Drive:

"There is another propulsion application for quantum entanglement which, while probably requiring more R&D investment than the teleportation drive, would have even greater (as in, several orders of magnitude greater) speed benefits for a spacecraft: applying quantum entanglement to produce the first viable photon drive. A photon drive system uses nothing but a beam of photons (a beam of light if the photons fall in the frequency spectrum of visible light) to propel a spacecraft. The photon drive is a theoretical possibility that has been talked about for decades but has never been practical due to the immense power requirements it would take for such a drive to generate sufficient thrust to propel a spacecraft."

Can anyone report on how credible this idea is? Sounds interesting to me, but IANAP (I Am Not A Physicist).

If what he is saying is true, then hasn't he invented a credible way to teleport energy without wires and without any loss? It seems to me that this could revolutionize energy transmission, including transmitting energy to small devices; it effectively decouples the client of energy from needing to generate its own energy.

He goes on to discuss distributed energy generation, especially solar power satellites in spaces and how his possible idea might make them viable:

"However, aided by advances in solar cell technology, much smaller solar arrays could today be placed in orbit around the sun, perhaps within the orbit of Mercury (naturally the arrays would need to be designed to withstand intensive bombardment by heat and radiation; the upside would be that the proximity to the sun would also allow for greater power collection). A resulting microwave beam generated with the energy collected could be quantum-teleported directly to the earth's surface. Aside from the obvious immediate benefits of such an efficient power generation system, these satellites could also provide the power input for a telephotonic or entangled laser fusion drive. Thus quantum teleportation could provide an "end-to-end solution" for propelling a craft up to near-light speeds."

In the September, 2004, edition of Discover magazine
( the entire issue is dedicated to Albert Einstein)
it explains his theories and thoughts about quantum physics and the speed of light ... it is fascinating!
First section: I don't think entanglement works that way. You can't ionise one entangled atom and have that *cause* ionisation of the other. So I don't think there's a way to transmit *power*, only information (AFAICS).

Second section: photon drive is a perfectly valid propulsion system, just not powered via a remote ion generator. As I understand it, the main problem with a photon drive isn't the power requirement -- it's *the* most efficient drive possible -- but the very low thrust generated, maybe about one-thousandth of a gee. As such, it's only useful for long slow journeys well away from gravity wells. So no good for transport to the Moon, or Mars, but maybe to drive a 200-year sleepership to Alpha Centauri.

A possibly-better alternative is described in Robert L. Forward's "Flight of the Dragonfly", where a *big* laser in solar orbit is used to push the ship to Barnard's Star; the ship thus carries only a solar sail, and not the mass of the main drive.

Third section: for an example of a device powered by incoming radiant energy, just look at RFID tags. They have no battery; the incoming radio pulse from the transponder also provides enough power to run the on-tag circuitry. Once again, "Flight of the Dragonfly" has an extrapolation from this, with a "robot" made of a multitude of tiny units, which transfer information *and power* among themselves by laser.

Finally: if we put solar collectors around Mercury, why do we need to "teleport" the energy back to Earth? Why not just use a conventional coherent beam (e.g. maser) back to an Earth-orbit transfer station? (I think this scheme featured in one of Asimov's early "Robot" stories, "Belief" IIRC).

Well, that's my take on the story, anyway. I'm not a physicist either, but I did use to be "Keeper Of The Units" on a.d.t.e :-)
I think he may have 'Ion' and 'photon' confused. If energy was applied to the Earth-based atoms, the information for the energy, and thus one half the energy (since you cannot just create energy from nothing), should be transferred to the space-based atoms. The space-based atoms would then emit photons, which if the wavelength were high enough (ie. UV), should be able to power solar panels, which would be able to create ions.
Thought you might enjoy reading this:

Quantum Entanglement

Explains QE with pictures, analogies, but without math.

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