Mustafa's Space Drive: An Egyptian Student's Quantum Physics Invention | Hacker News Reader

Mustafa's Space Drive: An Egyptian Student's Quantum Physics Invention

fastcompany.com

49 pointsmikeleeorg23 comments

This appears to be another reactionless drive [1] that sci-fi authors and crackpots come up with every few years. There are many variants of these designs [2] and a drive based on the Casimir effect is just one of them. However, they all tend to violate a critical law of physics or depend on a custom theory of physics [3]

BTW, the original article at http://www.onislam.net/english/health-and-science/science/45... goes into slightly more detail about her invention and mentions that it's related to a differential sail.

[1] http://tvtropes.org/pmwiki/pmwiki.php/Main/ReactionlessDrive [2] http://en.wikipedia.org/wiki/Breakthrough_Propulsion_Physics... [3] http://en.wikipedia.org/wiki/Inertialess_drive

There's also some variants that do work, or at least could work in theory, which turn out to simply be highly inefficient photon drives. For instance, one recurring one that seems to get reinvented every few years is one where you put two electromagnets some distance from each other, and use the speed of light delay and some moderately clever polarity flipping to make it so the magnets always attract or repel each other in one direction, providing thrust. There's no reason why this won't work... except that also shoots huge amounts of defocused radio waves out the back, which is where the equal & opposite momentum is "coming from", and it's wildly less efficient in every conceivable way than simply shooting a conventional laser in the opposite of the direction you want to thrust. (And there's some other caveats too when you really get down to the engineering task of trying to flip the polarity of really powerful magnets at the necessary rate of speed. But it is conceivable that using real physics, you might be able to build something with this principle that could generate vanishing fractions of a Newton without necessarily blowing up....)

Based on the link you provide, and guessing what the QM equivalent of the differential sail (this thing, I think: [1]) would be, it seems to me this could fall into either class, something that simply won't work or something that will turn out to be another variant of inefficient electromagnetic radiation drive, once the full set of interactions is taken into account. (It's pretty easy to miss some of the more subtle ways of creating electromagnetic waves.)

[1]: http://www.daviddarling.info/encyclopedia/D/differential_sai...

Conservation of momentum has been one of the most unshakeable laws of physics. Reactionless drives violate conservation of momentum. The likelihood that this is flawed is infinitely greater than the likelihood that conservation of momentum has been overturned. End of story, as far as I'm concerned.

Anyone remember the EmDrive debacle? http://en.wikipedia.org/wiki/EmDrive

I don't think conservation of momentum is under fire here - the vacuum fluctuations (due to second quantization, quantization of electron, quark, etc. fields) might pick up the difference... although I don't really know enough QFT to be definite. Not that I believe any of this though, haha, seems like complete bullshit. The original article, especially. None of the physics seems to make any sense.

Does anyone find the reporting horrible? It's like reading a press release with all the buzz words and jargon thrown in. "Dynamic Casimir effect" that produces a net force? Yeah, the net force is the opposing forces squeezing the two plates together from outside. It produces zero directional net force. I don't see how it can move an object in space.

As far as I am aware, dynamic casmir is achieved by moving a virtual mirror at relativistic speeds to create photons, so I am assuming that if the photons are preferentially directed, there would be a small net force in the opposite direction.

And what is a virtual mirror, I ask?

In the report I read they were using SQUIDs to make the effect of a mirror that operated in the microwave range.

[edit] you could also use a real mirror, is just very hard to move it that fast.

Sounds a lot like some of the ideas in this NASA-produced survey of possible drives- http://www.grc.nasa.gov/WWW/bpp/1997-J_AIAA_SpaceDr.pdf

NASA does have some research folks working on pretty esoteric space drive concepts. http://www.nasa.gov/centers/glenn/technology/warp/ideachev.h...

I predict with very high confidence that this does not work.

It is a patent. Who say a patent has to work? It just describes some methods dreamed up by someone. The hardwork of finding out and getting it to work is left to the engineers. And payment is due to the idea guy if it ever works.

"Lisa, in this house, we obey the laws of thermodynamics!"

--Homer Simpson

Plus, "space drives" violate the conservation of momentum.

Still waiting for the very excited paper on zero point energy that explains it in non-leagalise. If she figured this out, why not use it to run a generator? They again, who wants to get power off the heat death of the universe -tanstaafl -3rd law of thermodynamics

The only space drive that actually can work is the transmission of information, not of mass. But you'll need a receiver that is capable of acting on that information. Hopefully, such receivers can be made very small and then "seeded" through the galaxy.

TLDR: It's like a solar sail, but instead of being pushed by energy from a star, it manipulates local quantum particles to create a small force that propels the vessel.

Eg, not warp or hyperdrive, but still very clever.

No, more like "Thrusters" in Larry Niven's "Known Space" universe. It's still fantastical because it doesn't need to expend reaction mass, hence it's not subject to the rocket equation.

http://www.larryniven.net/kzin/worlds.shtml

It's not like a solar sail. You don't need energy to use the sail, you need energy here. This idea is not going to change space propulsion.

Huh? It's "only" a >reaction-less< drive. That's only a science-fiction conceit to allow compact little spacecraft to zip all over a solar system with mass fractions that are actually sane.

If the guy has invented a science fiction conceit in real life, I think he deserves some praise.

The student is female, Mustafa is her surname.

You need energy to move the mirror that is used to create the photons.

In the report, it isn’t clear if the photons are released or not. If they are release it is not a reaction-less drive, it only throws a photon jet instead of an atomic jet. If the photons remain inside the cavity, the device violates the physics laws, and after building it they will find that they forget to include some little detail that makes the device not useful.

It is important to remember that quantum mechanics is strange and the Casimir effect is very strange, but none of them violates the conservation of momentum law. The problem with the conservation of momentum law is that to prove it, you only have to suppose that the space is invariant under translations (if you "move" the universe 1 foot to the "right", the physical laws don’t change), so any sensible physical theory comply with it.

This is the Quantum Ram Jet in Artur C. Clarks "Songs of a Distant Earth" from 1985 http://en.wikipedia.org/wiki/The_Songs_of_Distant_Earth. It is based on the Dynamical Casimir Effect which is thought to have been observed, http://www.technologyreview.com/blog/arxiv/26813/

One thing I like about Fast Company's article is that it's not revealed (name aside, for those familiar with it) that the student in question is female until the last paragraph or so.

You can just imagine a TV reporter, breathlessly:

"It's a new space invention, from a student. And a female as well!"

Well, this is awkward

It's apparently relying on the 'dynamic Casmir effect' but what exactly is doing is not clear

I assume photons created by accelerating a plate have zero angular momentum (the sum of all them) unless maybe if you have a plate near it then it isn't? (and by 'near' I mean 'Casmir near')

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