NASA Confirms The Plausibility of Reactionless Drives??!!

Ace of Spades HQ ^ | 8-1-2014 | Ace

[GeronL]

Fire the wave motion gun!

....

from my viewing/reading of that anime... they told us how to make the propulsion system and humans devised the way to make a weapon from it

[cripplecreek]

'Impossible' Space Engine May Actually Work, NASA Test Suggests

[GeronL]

and then they will pooh-pooh the next idea

[GeronL]

Like an Ion engine it probably takes forever to build up speed

[RebelTex]

Vendome, you are the only one I know that can find a space bar while still in orbit.

;^D

[Kirkwood]

If I had a long enough extension cord, I could fly my microwave oven to the moon!

[FredZarguna]

I believe it is possible, does not violate the laws of motion or thermodynamics, and is relatively straight forward. Does that make me a barking moonbat?

No, it makes you correct. The author of this blog-post is confused.

The law of conservation of momentum in three dimensions only holds approximately, because classical physics is only an approximation. In relativistic physics, conservation of momentum hold exactly, and is four dimensional. The fourth component of momentum is energy, and the laws of conservation of energy and conservation of momentum are one law in relativity.

In Lorentz invariant terms: p^μp_μ = m². [in a system of units where ħ = c = 1.]

In practical units and more familiar terms: ]

As long as you can convert some mass -- usually binding energy from a chemical or nuclear bond -- into momentum/energy, you don't need "reactive mass." The article has been wrong since 1906.

There is nothing new here. Please move along.

[stig]

I stopped reading after “NASA a major player in spaceflight” then realized it must be fiction

[Boogieman]

Ah, I found some “meat” about how the drive works, and it seems to work basically how I speculated it might. It directs the photons to impact one side more than the other, but instead of using a containment system, it relies on a relativistic effect to achieve this:

“The device uses a magnetron producing microwaves directed inside a specially shaped, fully enclosed tapering high Q resonant cavity whose area is greater at one end, upon which radiation pressure would act differently due to a relativistic effect caused by the action of group velocity in different frames of reference.”

“Roger Shawyer’s idea is to try to design a microwave cavity as a conical frustum in such a manner that forces due to radiation pressure on one side are greater than the other.

Cullen showed the propagation rate of electromagnetic waves in space (group velocity) and the resulting force it exerts can be varied depending on the geometry of a waveguide within which it travels.[32] The increasing confinement of a narrowing waveguide (convergent) leads to a widening wavelength and a decrease of the group velocity (lower momentum transfer). Conversely, a widening waveguide (divergent) leads to a narrowing wavelength and an increase of the group velocity (higher momentum transfer).[35]

Shawyer states that if the electromagnetic wave travelling in a tapered waveguide is bounced between two reflectors, with a large group velocity difference at the end surfaces, the force difference resulting from the radiation pressure difference will give a resultant thrust to the waveguide linking the two reflectors, in the direction of the larger surface.”

http://en.wikipedia.org/wiki/EmDrive

Jesus, if this works, it is genius. Using simple geometry of the cavity to force the waves to transform their momentum into wavelength in order to control the direction of thrust. That’s a sublime solution if ever I’ve seen one.

[FredZarguna]

The science is settled. It was settled by Einstein in 1906. The "paradox" here is caused by 1) NASA over-hyping a technology that is very well understood [see previous post.] and 2) a blogger who doesn't know what he's talking about.

[FredZarguna]

The science behind it is not new and has been known for over 100 years. See post #14.

[Boogieman]

I think the novel part here is what they are converting to achieve the effect. They set the photons oscillating in a chamber which forces the wavelengths to change as the photon goes from one end to the other. This alters the group velocity of the photons, which changes the radiation pressure as the photons strike each end of the cavity.

So the conversion seems to be between the forward group velocity and the lateral oscillation, which is immaterial as it pertains to the desired effect of the drive. The photons don’t lose any energy before hitting the other side, they are just reconfigured so that they will impart energy less efficiently before they hit that side.

[fedupjohn]

My engineering education thoughts, exactly!

[cripplecreek]

Baby steps. We haven’t even invented the wheel when it comes to space flight but there are a lot a lot of interesting technologies that are off the table for political and financial reasons.

The Orion drive could get us to the nearest stars within a matter of a few decades but cost trillions of dollars not to mention launching a crapload of nuclear bombs into orbit.

Project Deadelus was another interesting concept for getting to the nearest stars in a few decades.

In any case, baby steps are cool as long as they’re steps forward. I’m thinking moon base, Mars base, asteroid mining to printing large ships in space with ores mined from asteroids.

[fedupjohn]

lol!

[Boogieman]

That all depends on scale of the drive. These demonstration models probably wouldn’t budge a Prius, but if you have a big enough magnetron and nuclear reactor to power it, the acceleration should be much greater.

[fedupjohn]

Where does the electricity come from? At best perfect nuclear conversion of mass to energy.

EXACTLY! Thank You!!!

[Vendome]

[DManA]

Everything Robert Goddard was completely theoretically possible. And had been understood, theoretically, for a couple of hundred years.

[FredZarguna]

The "novel part" of the theory, that a closed waveguide [of any shape] can produce a net momentum is almost certainly wrong.

It's pretty clear that most of the Wiki article was actually written by the inventor of the drive, who does not really address his critics, and who did not originate the theory himself [whihc may or may not be applicable to his drive.]