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Emdrive (electromagnetic microwave reactionless drive) ?

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Bjørn

Mon Sept 11 2006, 02:44AM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

So you don't believe in solar sails either? Or that photons carry momentum?

I do believe in those, but I don't believe that shining a laser on a small 1 kg aluminium cone will make it escape gravity unless there is air present.

If someone puts it into orbit first, it will work, slowly, very slowly.

AndrewM

Mon Sept 11 2006, 04:18AM

Registered Member #49 Joined: Thu Feb 09 2006, 04:05AM
Location: Bigass Pile of Penguins
Posts: 362

yeah i'm with you, just didn't understand we were talking in the 1kg regime. I thought the cones they lifted were made of foil, a couple grams tops.

Bjørn

Mon Sept 11 2006, 04:33AM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

They were fairly solid and spun up at high speed using compressed air to make them stable. The current idea is to get it to orbit using a 1MW laser and liquid hydrogen to source the plasma explosions during the part of the flight where there is not enough air. Since their best attempt is 80 meters I suspect it is not going to happen soon.

Bored Chemist

Mon Sept 11 2006, 05:54AM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

"I didn't actually bother reading that article
It shows.

Marko

Mon Sept 11 2006, 11:03AM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

What a BUNCH of CRAPOLA!

Firstly, look at the website . . .

I would think someone that is the brainchild of the next evolution of spaceflight, backed by academics and governments (as stated in the article), would be able to afford an AD-free web provider. Also, the AOL address is pretty lame as well.

Plus, his company, SPR Ltd - if you do a search on it via the UK company register, it states it is bankrupt. Hardly something i would expect from the scientific invention of the millenium.

"I didn't actually bother reading that article
It shows.

Well the former was reason why I quit after first few rows

I came to the Q factor thing and when I looked around the page it looked just silly.

As andrew sadi you always need a some kind of 'exshaust' to propel something in a direction (and with very, very low force).

If there is a cavity wich uwaves don't exit anywhere, no matter of it's shape radiation 'pressures' will cancel themselves out and net force will be zero in any directions.

Otherwise our MO's would be flying around when plugged in.. (my $0.002 understanding at last (discovering hot water), sorry for off-topicish comments up there

)

from wiki:

'factual accuracy of this articl is disputed'

Bored Chemist

Mon Sept 11 2006, 05:16PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

Well, there's always the caveat that, if it looks too good to be true, it probably is.
On the other hand, New Scientist doesn't often publish rubbish and, more importantly, the prototype seems to deliver a real force. OK 88mN is not going to knock any dams over, but it's a bit big for an experimental error. Perhaps nobody thought to make a conical microwave oven.

Ben

Mon Sept 11 2006, 05:55PM

Vigilatny
Registered Member #17 Joined: Thu Feb 02 2006, 02:47PM
Location: NL
Posts: 158

This is nothing special. Q might increase the efficiency, but it's not going to multiply the force produced by expelling photons. That being said, I didn't read the article. New Scientist, in my opinion, is not a reliable source of scientific truth.

Conundrum

Mon Sept 11 2006, 06:46PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

Apparently particle accelerators actually do experience this force, and are designed to withstand it.

its one of those obscure "yes we are aware of it and design around it" issues that has probably never been considered as a realistic means of propulsion.
sometimes real discoveries are made that way, take Superglue (ruined prisms) and vulcanised rubber.

I'm convinced there are new discoveries "out there" but almost certainly they will be found when looking for something similar.
-A

Bjørn

Mon Sept 11 2006, 09:40PM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

This is nothing special. Q might increase the efficiency, but it's not going to multiply the force produced by expelling photons.

It does not expel anything, it bounces microwaves in a closed cavity. Since the group velocity is higher in one end than the other there is a directional force, increasing Q will multiply the force since the waves will bounce several times and deliver the force several times.

Nik

Mon Sept 11 2006, 11:29PM

Registered Member #53 Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638

I don't think this one will work and heres what lead me to this conclusion.

The suposed thrust is in the direction "A". "B" and "C" are the thrust caused but the microwaves bounceing off the sloped sides of the narrower end. (its a triangle for simplicity but the same will aply to cone) "B" and "C" are made of components int eh x and y direction (this is what most people dont seem to think about) and the sum of "B1" and "C1" will add up to be exactly the oposite of "A". Also "B2" and "C2" will cancle eachother out leaving the device with 0 thrust.

Im sorry if this is a little muddled up.

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