EmDrive? woo or not?

coops · 9th February 2013, 06:25 PM

http://www.wired.co.uk/news/archive/...nd-cold-fusion
http://emdrive.com/principle.html

I just came across the following article describing a propellantless drive for space applications and wanted some opinions from those with more knowledge in the field than me on whether it is based in reality or not.

In the article they claim 'that with a couple of kilowatts of power they can produce 720 mN (about 72 grams) of thrust.'

That claim seems believable from a laymans perspective, but they then appear to go off the deep end with the following claim:

'By using superconducting apparatus, Shawyer says that the Q value, and hence thrust, can be boosted by a factor of several thousand -- producing perhaps a tonne of thrust per kilowatt of power. Suddenly it's not about giving a satellite a slight nudge, it's about launching spacecraft.'

So what are peoples opinions? Something to watch with interest or a scam for the gullible?

Brian-M · 9th February 2013, 06:50 PM

What the hell is a tonne of thrust? What's that in newtons?

casebro · 9th February 2013, 06:57 PM

And how to convert it to 'furlongs per fortnight'?

StankApe · 9th February 2013, 07:04 PM

Originally Posted by Brian-M

What the hell is a tonne of thrust? What's that in newtons?

We Americans measure torque in foot/pounds.... could he maybe mean 2000 foot/pounds of thrust? maybe?

coops · 9th February 2013, 07:05 PM

from http://emdrive.com/secondgenengines.html i get:

'At present, superconducting microwave cavities are restricted to high energy physics applications. An example is the European Tesla accelerator where 20,000 S Band niobium cavities cooled with liquid helium will form the basis of the main accelerators. Early production versions of these cavities readily achieve Q values of 5 x 109 (BAUER, S. et al ‘Production of Superconducting 9-cell Cavities for the Tesla test facility, Standford University and Forschungszentrum Rossendorf’ Accel Instruments GmBh). This would lead to a static specific thrust of 3.15 x 104 N/kW (3.2 tonnes / kW).

A second generation engine using similar technology would however be subject to equation 2, and the effect at these high values of unloaded Q is dramatic. An average velocity of only 0.1 m/sec will reduce the specific thrust to 0.93 Tonne / kW.'

Which means next to nothing to me but hopefully you can translate

StankApe · 9th February 2013, 07:06 PM

^^^ what he said

Pulvinar · 9th February 2013, 07:24 PM

Originally Posted by Brian-M

What the hell is a tonne of thrust? What's that in newtons?

1 Tonne-force = 9.80665 kN.

Myriad · 9th February 2013, 08:00 PM

From the Principle of Operation page:

Quote:

The inevitable objection raised, is that the apparently closed system produced by this arrangement cannot result in an output force, but will merely produce strain within the waveguide walls. However, this ignores Einstein’s Special Law of Relativity in which separate frames of reference have to be applied at velocities approaching the speed of light. Thus the system of EM wave and waveguide can be regarded as an open system, with the EM wave and the waveguide having separate frames of reference.

A similar approach is necessary to explain the principle of the laser gyroscope, where open system attitude information is obtained from an apparently closed system device.

Special Relativity says nothing of the sort. Quite the contrary: it says the laws of physics remain the same in any inertial reference frame. You can choose whatever frame is most convenient to assess the system, as long as you assess the wave and the waveguide with respect to the same reference frame.

Laser gyroscopes detect rotation, which is not movement in an inertial reference frame.

I suspect that the lengthy equation-filled pdf "theory paper" merely repeats in more detail the same basic misconception about reference frames. That is, it calculates the force at one end of the waveguide in one reference frame, the force at the other end in a different reference frame, and fails to notice (assuming everything else is calculated correctly) that once these forces are translated into the same reference frame there is no net force. However, I haven't gone through it in detail to verify that.

Respectfully,
Myriad

Brian-M · 9th February 2013, 08:55 PM

Originally Posted by StankApe

We Americans measure torque in foot/pounds.... could he maybe mean 2000 foot/pounds of thrust? maybe?

Originally Posted by Pulvinar

1 Tonne-force = 9.80665 kN.

Ah, that makes sense. I'm not used to seeing force described in units of weight. Looking it up, I did find a calculator for it... http://www.sengpielaudio.com/calculator-forceunits.htm

It looks like a ton of force can be any of three different values, depending on whether you're using short, long or metric units.

(I'm more used to seeing figures for power rather than figures for force.)

StankApe · 9th February 2013, 09:01 PM

Originally Posted by Brian-M

Ah, that makes sense. I'm not used to seeing force described in units of weight. Looking it up, I did find a calculator for it... http://www.sengpielaudio.com/calculator-forceunits.htm

It looks like a ton of force can be any of three different values, depending on whether you're using short, long or metric units.

(I'm more used to seeing figures for power rather than figures for force.)

I had never heard it described as newton/meters until I discovered the UK car show Top Gear. They use both measurements on there relative to the country of origin of the car I guess (as I reckon they use the printed stats and info released by the manufacturer in regards to performance)

coops · 10th February 2013, 02:33 PM

ok so junk science by the sound of it?

Disappointing but not unexpected really. I guess I'll just have to wait to see if they can pull off a working prototype and prove us all wrong then.

Mikemcc · 10th February 2013, 03:00 PM

Originally Posted by Brian-M

What the hell is a tonne of thrust? What's that in newtons?

1000 x 9.81 = 9810N. Pure BS.

Mikemcc · 10th February 2013, 03:02 PM

Originally Posted by coops

from http://emdrive.com/secondgenengines.html i get:

'At present, superconducting microwave cavities are restricted to high energy physics applications. An example is the European Tesla accelerator where 20,000 S Band niobium cavities cooled with liquid helium will form the basis of the main accelerators. Early production versions of these cavities readily achieve Q values of 5 x 109 (BAUER, S. et al ‘Production of Superconducting 9-cell Cavities for the Tesla test facility, Standford University and Forschungszentrum Rossendorf’ Accel Instruments GmBh). This would lead to a static specific thrust of 3.15 x 104 N/kW (3.2 tonnes / kW).

A second generation engine using similar technology would however be subject to equation 2, and the effect at these high values of unloaded Q is dramatic. An average velocity of only 0.1 m/sec will reduce the specific thrust to 0.93 Tonne / kW.'

Which means next to nothing to me but hopefully you can translate

Thes cavities are particle accelerators, so require reaction mass...

RecoveringYuppy · 10th February 2013, 03:06 PM

Originally Posted by Myriad

Special Relativity says nothing of the sort. Quite the contrary: it says the laws of physics remain the same in any inertial reference frame. You can choose whatever frame is most convenient to assess the system, as long as you assess the wave and the waveguide with respect to the same reference frame.

Got to wonder if you could ask those guys if they could meet us in our reference frame to discuss investment opportunities. The idea that two things might not share a reference frame is a big clue that you're hearing woo. One of the more amusing ones IMO.

Cuddles · 11th February 2013, 09:27 AM

Originally Posted by coops

'At present, superconducting microwave cavities are restricted to high energy physics applications. An example is the European Tesla accelerator where 20,000 S Band niobium cavities cooled with liquid helium will form the basis of the main accelerators.

The TESLA project has been defunct for nearly a decade, so using it in a paragraph beginning "at present" seems a little odd.

Other than that, yeah, it's nonsense. I think it's been discussed here before. I very nearly wrote a post noting that there was nothing wrong with the principle, since radiation pressure means shooting light out of a waveguide must produce thrust. Then I noticed that they're not actually talking about shooting light out of a waveguide, but having closed off at both ends and just bouncing light backwards and forwards. This absolutely will not produce any thrust. A closed system can't produce a net external force on itself. That's very basic conservation of momentum - if you don't shoot anything out the back, you don't go forwards.

Reality Check · 11th February 2013, 01:56 PM

Originally Posted by coops

http://www.wired.co.uk/news/archive/...nd-cold-fusion
http://emdrive.com/principle.html

...producing perhaps a tonne of thrust per kilowatt of power. Suddenly it's not about giving a satellite a slight nudge, it's about launching spacecraft.'

Other than the emdrive looking like woo, the last claim is dubious to say the least. The Saturn V rocket for example had a first stage thrust of 7,648,000 pounds-force (34,020,000 N) to deliver 260,000 pounds (120,000 kg) to LEO.
They are talking about a thrust of about 9810 N.

Reality Check · 11th February 2013, 02:07 PM

I can even make a wild guess at what they are actually measuring. They have a closed, tapered microwave guide. Maybe the narrow end is hotter than the broader end. If their apparatus is made of materials that can out-gas than there will be more out-gassing from the narrow end. So what they are measuring could be an actual thrust from their apparatus emitting gas.

CORed · 11th February 2013, 03:03 PM

Originally Posted by Brian-M

Ah, that makes sense. I'm not used to seeing force described in units of weight. Looking it up, I did find a calculator for it... http://www.sengpielaudio.com/calculator-forceunits.htm

It looks like a ton of force can be any of three different values, depending on whether you're using short, long or metric units.

(I'm more used to seeing figures for power rather than figures for force.)

"Tonne" (with that spelling) means a metric ton (10e6 grams) . Using it as a unit of force, rather than mass is non-standard.

CORed · 11th February 2013, 03:11 PM

Originally Posted by casebro

And how to convert it to 'furlongs per fortnight'?

Since thrust is force,rather than velocity, that's not possible,but perhaps we could convert it to whatever the unit of force is called in the fsf (furlong-stone-fortnight) system.

CORed · 11th February 2013, 03:29 PM

Originally Posted by RecoveringYuppy

Got to wonder if you could ask those guys if they could meet us in our reference frame to discuss investment opportunities. The idea that two things might not share a reference frame is a big clue that you're hearing woo. One of the more amusing ones IMO.

It works in the humberverse.

The Man · 11th February 2013, 04:15 PM

Originally Posted by Mikemcc

Thes cavities are particle accelerators, so require reaction mass...

Right, that's what I first noticed too. So unless you are accelerating the particles away from you (basically spitting them out the back) you won't get any trust. Certainly not propellant less and I'm not even sure if it reduces the amount of propellant all that much. Ion drives already electromagnetically accelerate charged particles away from you for trust.

GodMark2 · 11th February 2013, 07:28 PM

August 2005
November 2009
September 2012

Imma votin' woo. Again.

Brian Jackson · 11th February 2013, 08:28 PM

Originally Posted by GodMark2

August 2005
November 2009
September 2012

Imma votin' woo. Again.

Looks like it's gettin' about the same mileage as the Moller SkyCar.

GodMark2 · 12th February 2013, 05:45 PM

Originally Posted by Brian Jackson

Looks like it's gettin' about the same mileage as the Moller SkyCar.

No, the SkyCar has managed to actually hover (for a short time, while tethered) and has multiple working prototypes.

Brian Jackson · 12th February 2013, 06:42 PM

Originally Posted by GodMark2

No, the SkyCar has managed to actually hover (for a short time, while tethered) and has multiple working prototypes.

You are right. I was referring to the "seeking investors" part where a breakthrough is always just around the corner.

GodMark2 · 13th February 2013, 06:54 PM

Originally Posted by Brian Jackson

You are right. I was referring to the "seeking investors" part where a breakthrough is always just around the corner.

Well, by that definition, IBM is in the same boat.¹

The SkyCar has every chance of being possible: the basic principles work, and don't try to rewrite physics. Whether you can get an engine powerful enough and light enough and cost-effective enough all at the same time is just an engineering problem. Trying to get the DOT and FAA to agree on who gets to regulate it might take an act of Hank, though.

Achieving thrust by bouncing light around a sealed box, on the other hand...

¹Of course, their breakthroughs actually produce results, but there's always another one 'just around the corner', and they actually do provide dividends for investment, but they always like investors.

cjameshuff · 26th February 2013, 05:48 AM

Originally Posted by Cuddles

Other than that, yeah, it's nonsense. I think it's been discussed here before. I very nearly wrote a post noting that there was nothing wrong with the principle, since radiation pressure means shooting light out of a waveguide must produce thrust. Then I noticed that they're not actually talking about shooting light out of a waveguide, but having closed off at both ends and just bouncing light backwards and forwards. This absolutely will not produce any thrust. A closed system can't produce a net external force on itself. That's very basic conservation of momentum - if you don't shoot anything out the back, you don't go forwards.

Shawyer claims it's actually an open system because [insert content-free handwaving about laser gyroscopes here]. Of course, for it to be an open system, energy and/or matter must enter or exit the system somehow. It doesn't eject matter, so we can determine that, at best, it must be equivalent to a photon drive...which doesn't give anything like the performance claimed.

And what about laser gyroscopes? Simple: rotating frames are not inertial frames. Same fundamental reason any other gyroscopes work.

It's easy to show just how badly this thing breaks conservation laws, despite claims to the contrary. Shawyer put up an updated PDF a while back, 2Gupdate.pdf on the main page of his website. On page 6, amusingly titled "Energy Conservation", Shawyer equates it to a classical electric machine, accelerating when power is input and producing power when accelerated. It's pretty straightforward to see that simply standing an EmDrive on end on Earth's surface would make either an infinite energy sink or an infinite energy source, depending on orientation.

quarky · 26th February 2013, 12:50 PM

Thermo-dynamics is the morality of science.

Eventually, we can reject free energy because it is immoral.
It's against the law.

Brian-M · 27th February 2013, 01:08 AM

Originally Posted by cjameshuff

It's pretty straightforward to see that simply standing an EmDrive on end on Earth's surface would make either an infinite energy sink or an infinite energy source, depending on orientation.

No, you'd just be using it to change the velocity of the earth.

cjameshuff · 27th February 2013, 06:14 AM

Originally Posted by Brian-M

No, you'd just be using it to change the velocity of the earth.

While producing an endless stream of energy from nowhere in one of those cases, and making an unlimited amount vanish from the universe in the other. If you think it might somehow come from or go into the Earth's kinetic energy, just put an identical one on the far side to cancel any planetary accelerations. It's Earth's gravitational acceleration that's relevant to my argument...Shawyer doesn't seem to be aware of the equivalence principle.

It's even worse than that. He's claimed that the EmDrive works best when "stationary relative to its thrust". The "Future" section of his website makes clear what he means...his reactionless thruster works best if you don't let it move (you read that right), and its performance decreases as velocity increases. He suggests vehicles using EmDrive for lift and jet engines for forward propulsion, to "limit kinetic output". Throughout the whole thing, it's clear that he thinks velocity is some absolute universal quantity, completely missing the point of relativity. (In fact, he's assuming Earth is in an absolute rest frame...his claims require a geocentric universe.)

quarky · 27th February 2013, 12:22 PM

Originally Posted by cjameshuff

While producing an endless stream of energy from nowhere in one of those cases, and making an unlimited amount vanish from the universe in the other. If you think it might somehow come from or go into the Earth's kinetic energy, just put an identical one on the far side to cancel any planetary accelerations. It's Earth's gravitational acceleration that's relevant to my argument...Shawyer doesn't seem to be aware of the equivalence principle.

It's even worse than that. He's claimed that the EmDrive works best when "stationary relative to its thrust". The "Future" section of his website makes clear what he means...his reactionless thruster works best if you don't let it move (you read that right), and its performance decreases as velocity increases. He suggests vehicles using EmDrive for lift and jet engines for forward propulsion, to "limit kinetic output". Throughout the whole thing, it's clear that he thinks velocity is some absolute universal quantity, completely missing the point of relativity. (In fact, he's assuming Earth is in an absolute rest frame...his claims require a geocentric universe.)

Glad you're here.
New blood is good.

temporalillusion · 31st July 2014, 08:56 AM

A new development in this?

http://www.wired.co.uk/news/archive/...le-space-drive

Quote:

However, a US scientist, Guido Fetta, has built his own propellant-less microwave thruster, and managed to persuade Nasa to test it out. The test results were presented on July 30 at the 50th Joint Propulsion Conference in Cleveland, Ohio. Astonishingly enough, they are positive.

The Nasa team based at the Johnson Space Centre gave its paper the title "Anomalous Thrust Production from an RF [radio frequency] Test Device Measured on a Low-Thrust Torsion Pendulum". The five researchers spent six days setting up test equipment followed by two days of experiments with various configurations. These tests included using a "null drive" similar to the live version but modified so it would not work, and using a device which would produce the same load on the apparatus to establish whether the effect might be produced by some effect unrelated to the actual drive. They also turned the drive around the other way to check whether that had any effect.

How long until they just put one of these in space and see if it works?

phunk · 31st July 2014, 09:26 AM

Or test in a vaccuum chamber.

casebro · 31st July 2014, 11:33 AM

Would it work better in the nano- range? I'll have to take a Pico at the theory.

Hmmm, e=mc2, so the waves have mass? And radio waves sent in one direction should give equal thrust in the opposite direction? And since the velocity of radio waves is the speed of light, thrust would depend on the mass of Rock & Roll? Isn't classical music denser? Or is Country-Western the densest? .... Punk Rock?

The Man · 31st July 2014, 04:37 PM

Originally Posted by casebro

Would it work better in the nano- range? I'll have to take a Pico at the theory.

Hmmm, e=mc2, so the waves have mass? And radio waves sent in one direction should give equal thrust in the opposite direction? And since the velocity of radio waves is the speed of light, thrust would depend on the mass of Rock & Roll? Isn't classical music denser? Or is Country-Western the densest? .... Punk Rock?

I think jazz is admired particularly for its musical density.

Lensman · 31st July 2014, 04:43 PM

Originally Posted by casebro

Would it work better in the nano- range? I'll have to take a Pico at the theory.

Hmmm, e=mc2, so the waves have mass? And radio waves sent in one direction should give equal thrust in the opposite direction? And since the velocity of radio waves is the speed of light, thrust would depend on the mass of Rock & Roll? Isn't classical music denser? Or is Country-Western the densest? .... Punk Rock?

Nah - heavy metal is the densest.

Red Baron Farms · 31st July 2014, 06:10 PM

I found this: Anomalous Thrust Production from an RF Test Device Measured on a Low-Thrust Torsion Pendulum
and Net thrust measurement of propellantless microwave thrusters*

So it seems to me instead of "proving it is impossible" the onus is on physicists to explain the measured results. Maybe he has described how it works incorrectly. But that begs the question, how do you explain it?

Because you have the claim made by him, followed by 2 independent teams getting measurable thrust. So at this point it is not about proving it impossible, but instead figuring out the physics of the phenomenon.

casebro · 1st August 2014, 07:02 AM

Originally Posted by Red Baron Farms

I found this: Anomalous Thrust Production from an RF Test Device Measured on a Low-Thrust Torsion Pendulum
and Net thrust measurement of propellantless microwave thrusters*

So it seems to me instead of "proving it is impossible" the onus is on physicists to explain the measured results. Maybe he has described how it works incorrectly. But that begs the question, how do you explain it?

Because you have the claim made by him, followed by 2 independent teams getting measurable thrust. So at this point it is not about proving it impossible, but instead figuring out the physics of the phenomenon.

I thought I already did in my previous post:

Originally Posted by casebro

Hmmm, e=mc2, so the waves have mass? And radio waves sent in one direction should give equal thrust in the opposite direction? And since the velocity of radio waves is the speed of light, thrust would depend on the mass ...... (eta- quantity/ volume)

Matter is energy, energy is matter, waves have mass, equal and opposite reactions, recoil = thrust.

casebro · 1st August 2014, 07:04 AM

But I would think a system for use near-eaerth would need to push agaisnt the gtravity waves directly, rather than use the reaction thrust alone.

Red Baron Farms · 1st August 2014, 07:10 AM

Originally Posted by casebro

I thought I already did in my previous post:

Matter is energy, energy is matter, waves have mass, equal and opposite reactions, recoil = thrust.

And since it is equal and opposite reactions, and nothing is leaving this closed system, why don't they cancel each other out? and please go easy on me. It has been 35 years since university physics class for me.

9th February 2013, 06:25 PM	#1
coops Scholar Join Date: Feb 2008 Posts: 55	EmDrive? woo or not? http://www.wired.co.uk/news/archive/...nd-cold-fusion http://emdrive.com/principle.html I just came across the following article describing a propellantless drive for space applications and wanted some opinions from those with more knowledge in the field than me on whether it is based in reality or not. In the article they claim 'that with a couple of kilowatts of power they can produce 720 mN (about 72 grams) of thrust.' That claim seems believable from a laymans perspective, but they then appear to go off the deep end with the following claim: 'By using superconducting apparatus, Shawyer says that the Q value, and hence thrust, can be boosted by a factor of several thousand -- producing perhaps a tonne of thrust per kilowatt of power. Suddenly it's not about giving a satellite a slight nudge, it's about launching spacecraft.' So what are peoples opinions? Something to watch with interest or a scam for the gullible?
coops Scholar Join Date: Feb 2008 Posts: 55

9th February 2013, 06:50 PM	#2
Brian-M Daydreamer Join Date: Jul 2008 Posts: 8,044	What the hell is a tonne of thrust? What's that in newtons?
Brian-M Daydreamer Join Date: Jul 2008 Posts: 8,044	__________________ "That is just what you feel, that isn't reality." - hamelekim

9th February 2013, 06:57 PM	#3
casebro Penultimate Amazing Join Date: Jun 2005 Posts: 14,155	And how to convert it to 'furlongs per fortnight'?
	__________________ Great minds discuss ideas. Medium minds discuss events. Small minds spend all their time on U-Tube and Facebook.

9th February 2013, 07:04 PM	#4
StankApe Banned Join Date: Oct 2012 Posts: 4,628	Originally Posted by Brian-M What the hell is a tonne of thrust? What's that in newtons? We Americans measure torque in foot/pounds.... could he maybe mean 2000 foot/pounds of thrust? maybe?
StankApe Banned Join Date: Oct 2012 Posts: 4,628

9th February 2013, 07:05 PM	#5
coops Scholar Join Date: Feb 2008 Posts: 55	from http://emdrive.com/secondgenengines.html i get: 'At present, superconducting microwave cavities are restricted to high energy physics applications. An example is the European Tesla accelerator where 20,000 S Band niobium cavities cooled with liquid helium will form the basis of the main accelerators. Early production versions of these cavities readily achieve Q values of 5 x 109 (BAUER, S. et al ‘Production of Superconducting 9-cell Cavities for the Tesla test facility, Standford University and Forschungszentrum Rossendorf’ Accel Instruments GmBh). This would lead to a static specific thrust of 3.15 x 104 N/kW (3.2 tonnes / kW). A second generation engine using similar technology would however be subject to equation 2, and the effect at these high values of unloaded Q is dramatic. An average velocity of only 0.1 m/sec will reduce the specific thrust to 0.93 Tonne / kW.' Which means next to nothing to me but hopefully you can translate
coops Scholar Join Date: Feb 2008 Posts: 55

9th February 2013, 07:06 PM	#6
StankApe Banned Join Date: Oct 2012 Posts: 4,628	^^^ what he said
StankApe Banned Join Date: Oct 2012 Posts: 4,628

9th February 2013, 07:24 PM	#7
Pulvinar Graduate Poster Join Date: Aug 2009 Posts: 1,405	Originally Posted by Brian-M What the hell is a tonne of thrust? What's that in newtons? 1 Tonne-force = 9.80665 kN.

9th February 2013, 08:00 PM	#8
Myriad Hyperthetical Join Date: Nov 2006 Location: Pennsylvania Posts: 13,023	From the Principle of Operation page: Quote: The inevitable objection raised, is that the apparently closed system produced by this arrangement cannot result in an output force, but will merely produce strain within the waveguide walls. However, this ignores Einstein’s Special Law of Relativity in which separate frames of reference have to be applied at velocities approaching the speed of light. Thus the system of EM wave and waveguide can be regarded as an open system, with the EM wave and the waveguide having separate frames of reference. A similar approach is necessary to explain the principle of the laser gyroscope, where open system attitude information is obtained from an apparently closed system device. Special Relativity says nothing of the sort. Quite the contrary: it says the laws of physics remain the same in any inertial reference frame. You can choose whatever frame is most convenient to assess the system, as long as you assess the wave and the waveguide with respect to the same reference frame. Laser gyroscopes detect rotation, which is not movement in an inertial reference frame. I suspect that the lengthy equation-filled pdf "theory paper" merely repeats in more detail the same basic misconception about reference frames. That is, it calculates the force at one end of the waveguide in one reference frame, the force at the other end in a different reference frame, and fails to notice (assuming everything else is calculated correctly) that once these forces are translated into the same reference frame there is no net force. However, I haven't gone through it in detail to verify that. Respectfully, Myriad
	__________________ A zømbie once bit my sister...

9th February 2013, 08:55 PM	#9
Brian-M Daydreamer Join Date: Jul 2008 Posts: 8,044	Originally Posted by StankApe We Americans measure torque in foot/pounds.... could he maybe mean 2000 foot/pounds of thrust? maybe? Originally Posted by Pulvinar 1 Tonne-force = 9.80665 kN. Ah, that makes sense. I'm not used to seeing force described in units of weight. Looking it up, I did find a calculator for it... http://www.sengpielaudio.com/calculator-forceunits.htm It looks like a ton of force can be any of three different values, depending on whether you're using short, long or metric units. (I'm more used to seeing figures for power rather than figures for force.)
Brian-M Daydreamer Join Date: Jul 2008 Posts: 8,044	__________________ "That is just what you feel, that isn't reality." - hamelekim Last edited by Brian-M; 9th February 2013 at 08:56 PM.

9th February 2013, 09:01 PM	#10
StankApe Banned Join Date: Oct 2012 Posts: 4,628	Originally Posted by Brian-M Ah, that makes sense. I'm not used to seeing force described in units of weight. Looking it up, I did find a calculator for it... http://www.sengpielaudio.com/calculator-forceunits.htm It looks like a ton of force can be any of three different values, depending on whether you're using short, long or metric units. (I'm more used to seeing figures for power rather than figures for force.) I had never heard it described as newton/meters until I discovered the UK car show Top Gear. They use both measurements on there relative to the country of origin of the car I guess (as I reckon they use the printed stats and info released by the manufacturer in regards to performance)
StankApe Banned Join Date: Oct 2012 Posts: 4,628

10th February 2013, 02:33 PM	#11
coops Scholar Join Date: Feb 2008 Posts: 55	ok so junk science by the sound of it? Disappointing but not unexpected really. I guess I'll just have to wait to see if they can pull off a working prototype and prove us all wrong then.
coops Scholar Join Date: Feb 2008 Posts: 55

10th February 2013, 03:00 PM	#12
Mikemcc Graduate Poster Join Date: Dec 2009 Location: UK Posts: 1,610	Originally Posted by Brian-M What the hell is a tonne of thrust? What's that in newtons? 1000 x 9.81 = 9810N. Pure BS.

10th February 2013, 03:02 PM	#13
Mikemcc Graduate Poster Join Date: Dec 2009 Location: UK Posts: 1,610	Originally Posted by coops from http://emdrive.com/secondgenengines.html i get: 'At present, superconducting microwave cavities are restricted to high energy physics applications. An example is the European Tesla accelerator where 20,000 S Band niobium cavities cooled with liquid helium will form the basis of the main accelerators. Early production versions of these cavities readily achieve Q values of 5 x 109 (BAUER, S. et al ‘Production of Superconducting 9-cell Cavities for the Tesla test facility, Standford University and Forschungszentrum Rossendorf’ Accel Instruments GmBh). This would lead to a static specific thrust of 3.15 x 104 N/kW (3.2 tonnes / kW). A second generation engine using similar technology would however be subject to equation 2, and the effect at these high values of unloaded Q is dramatic. An average velocity of only 0.1 m/sec will reduce the specific thrust to 0.93 Tonne / kW.' Which means next to nothing to me but hopefully you can translate Thes cavities are particle accelerators, so require reaction mass...

10th February 2013, 03:06 PM	#14
RecoveringYuppy Philosopher Join Date: Nov 2006 Posts: 6,506	Originally Posted by Myriad Special Relativity says nothing of the sort. Quite the contrary: it says the laws of physics remain the same in any inertial reference frame. You can choose whatever frame is most convenient to assess the system, as long as you assess the wave and the waveguide with respect to the same reference frame. Got to wonder if you could ask those guys if they could meet us in our reference frame to discuss investment opportunities. The idea that two things might not share a reference frame is a big clue that you're hearing woo. One of the more amusing ones IMO.
	__________________ REJ (Robert E Jones) posting anonymously under my real name for 30 years. Make a fire for a man and you keep him warm for a day. Set him on fire and you keep him warm for the rest of his life.

11th February 2013, 09:27 AM	#15
Cuddles Penultimate Amazing Join Date: Jul 2006 Posts: 18,519	Originally Posted by coops 'At present, superconducting microwave cavities are restricted to high energy physics applications. An example is the European Tesla accelerator where 20,000 S Band niobium cavities cooled with liquid helium will form the basis of the main accelerators. The TESLA project has been defunct for nearly a decade, so using it in a paragraph beginning "at present" seems a little odd. Other than that, yeah, it's nonsense. I think it's been discussed here before. I very nearly wrote a post noting that there was nothing wrong with the principle, since radiation pressure means shooting light out of a waveguide must produce thrust. Then I noticed that they're not actually talking about shooting light out of a waveguide, but having closed off at both ends and just bouncing light backwards and forwards. This absolutely will not produce any thrust. A closed system can't produce a net external force on itself. That's very basic conservation of momentum - if you don't shoot anything out the back, you don't go forwards.

11th February 2013, 01:56 PM	#16
Reality Check Penultimate Amazing Join Date: Mar 2008 Location: New Zealand Posts: 20,136	Originally Posted by coops http://www.wired.co.uk/news/archive/...nd-cold-fusion http://emdrive.com/principle.html ...producing perhaps a tonne of thrust per kilowatt of power. Suddenly it's not about giving a satellite a slight nudge, it's about launching spacecraft.' Other than the emdrive looking like woo, the last claim is dubious to say the least. The Saturn V rocket for example had a first stage thrust of 7,648,000 pounds-force (34,020,000 N) to deliver 260,000 pounds (120,000 kg) to LEO. They are talking about a thrust of about 9810 N.
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11th February 2013, 02:07 PM	#17
Reality Check Penultimate Amazing Join Date: Mar 2008 Location: New Zealand Posts: 20,136	I can even make a wild guess at what they are actually measuring. They have a closed, tapered microwave guide. Maybe the narrow end is hotter than the broader end. If their apparatus is made of materials that can out-gas than there will be more out-gassing from the narrow end. So what they are measuring could be an actual thrust from their apparatus emitting gas.
	__________________ NASA Finds Direct Proof of Dark Matter (another observation) (and Abell 520) Electric comets still do not exist!

11th February 2013, 03:03 PM	#18
CORed Philosopher Join Date: Dec 2008 Location: Central City, Colorado, USA Posts: 7,199	Originally Posted by Brian-M Ah, that makes sense. I'm not used to seeing force described in units of weight. Looking it up, I did find a calculator for it... http://www.sengpielaudio.com/calculator-forceunits.htm It looks like a ton of force can be any of three different values, depending on whether you're using short, long or metric units. (I'm more used to seeing figures for power rather than figures for force.) "Tonne" (with that spelling) means a metric ton (10e6 grams) . Using it as a unit of force, rather than mass is non-standard.

11th February 2013, 03:11 PM	#19
CORed Philosopher Join Date: Dec 2008 Location: Central City, Colorado, USA Posts: 7,199	Originally Posted by casebro And how to convert it to 'furlongs per fortnight'? Since thrust is force,rather than velocity, that's not possible,but perhaps we could convert it to whatever the unit of force is called in the fsf (furlong-stone-fortnight) system.

11th February 2013, 03:29 PM	#20
CORed Philosopher Join Date: Dec 2008 Location: Central City, Colorado, USA Posts: 7,199	Originally Posted by RecoveringYuppy Got to wonder if you could ask those guys if they could meet us in our reference frame to discuss investment opportunities. The idea that two things might not share a reference frame is a big clue that you're hearing woo. One of the more amusing ones IMO. It works in the humberverse.

11th February 2013, 04:15 PM	#21
The Man Scourge, of the supernatural Join Date: Jun 2007 Location: Poughkeepsie, NY Posts: 11,971	Originally Posted by Mikemcc Thes cavities are particle accelerators, so require reaction mass... Right, that's what I first noticed too. So unless you are accelerating the particles away from you (basically spitting them out the back) you won't get any trust. Certainly not propellant less and I'm not even sure if it reduces the amount of propellant all that much. Ion drives already electromagnetically accelerate charged particles away from you for trust.
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11th February 2013, 07:28 PM	#22
GodMark2 Graduate Poster Join Date: Oct 2005 Location: Oregon, USA Posts: 1,963	August 2005 November 2009 September 2012 Imma votin' woo. Again.
	__________________ Knowing that we do not know, it does not necessarily follow that we can not know.

11th February 2013, 08:28 PM	#23
Brian Jackson Graduate Poster Join Date: Aug 2006 Posts: 1,112	Originally Posted by GodMark2 August 2005 November 2009 September 2012 Imma votin' woo. Again. Looks like it's gettin' about the same mileage as the Moller SkyCar.

12th February 2013, 05:45 PM	#24
GodMark2 Graduate Poster Join Date: Oct 2005 Location: Oregon, USA Posts: 1,963	Originally Posted by Brian Jackson Looks like it's gettin' about the same mileage as the Moller SkyCar. No, the SkyCar has managed to actually hover (for a short time, while tethered) and has multiple working prototypes.
	__________________ Knowing that we do not know, it does not necessarily follow that we can not know.

12th February 2013, 06:42 PM	#25
Brian Jackson Graduate Poster Join Date: Aug 2006 Posts: 1,112	Originally Posted by GodMark2 No, the SkyCar has managed to actually hover (for a short time, while tethered) and has multiple working prototypes. You are right. I was referring to the "seeking investors" part where a breakthrough is always just around the corner.

13th February 2013, 06:54 PM	#26
GodMark2 Graduate Poster Join Date: Oct 2005 Location: Oregon, USA Posts: 1,963	Originally Posted by Brian Jackson You are right. I was referring to the "seeking investors" part where a breakthrough is always just around the corner. Well, by that definition, IBM is in the same boat.¹ The SkyCar has every chance of being possible: the basic principles work, and don't try to rewrite physics. Whether you can get an engine powerful enough and light enough and cost-effective enough all at the same time is just an engineering problem. Trying to get the DOT and FAA to agree on who gets to regulate it might take an act of Hank, though. Achieving thrust by bouncing light around a sealed box, on the other hand... ¹Of course, their breakthroughs actually produce results, but there's always another one 'just around the corner', and they actually do provide dividends for investment, but they always like investors.
	__________________ Knowing that we do not know, it does not necessarily follow that we can not know.

26th February 2013, 05:48 AM	#27
cjameshuff Scholar Join Date: Feb 2013 Posts: 94	Originally Posted by Cuddles Other than that, yeah, it's nonsense. I think it's been discussed here before. I very nearly wrote a post noting that there was nothing wrong with the principle, since radiation pressure means shooting light out of a waveguide must produce thrust. Then I noticed that they're not actually talking about shooting light out of a waveguide, but having closed off at both ends and just bouncing light backwards and forwards. This absolutely will not produce any thrust. A closed system can't produce a net external force on itself. That's very basic conservation of momentum - if you don't shoot anything out the back, you don't go forwards. Shawyer claims it's actually an open system because [insert content-free handwaving about laser gyroscopes here]. Of course, for it to be an open system, energy and/or matter must enter or exit the system somehow. It doesn't eject matter, so we can determine that, at best, it must be equivalent to a photon drive...which doesn't give anything like the performance claimed. And what about laser gyroscopes? Simple: rotating frames are not inertial frames. Same fundamental reason any other gyroscopes work. It's easy to show just how badly this thing breaks conservation laws, despite claims to the contrary. Shawyer put up an updated PDF a while back, 2Gupdate.pdf on the main page of his website. On page 6, amusingly titled "Energy Conservation", Shawyer equates it to a classical electric machine, accelerating when power is input and producing power when accelerated. It's pretty straightforward to see that simply standing an EmDrive on end on Earth's surface would make either an infinite energy sink or an infinite energy source, depending on orientation.
cjameshuff Scholar Join Date: Feb 2013 Posts: 94

26th February 2013, 12:50 PM	#28
quarky Banned Join Date: Oct 2007 Posts: 20,121	Thermo-dynamics is the morality of science. Eventually, we can reject free energy because it is immoral. It's against the law.
quarky Banned Join Date: Oct 2007 Posts: 20,121

27th February 2013, 01:08 AM	#29
Brian-M Daydreamer Join Date: Jul 2008 Posts: 8,044	Originally Posted by cjameshuff It's pretty straightforward to see that simply standing an EmDrive on end on Earth's surface would make either an infinite energy sink or an infinite energy source, depending on orientation. No, you'd just be using it to change the velocity of the earth.
Brian-M Daydreamer Join Date: Jul 2008 Posts: 8,044	__________________ "That is just what you feel, that isn't reality." - hamelekim

27th February 2013, 06:14 AM	#30
cjameshuff Scholar Join Date: Feb 2013 Posts: 94	Originally Posted by Brian-M No, you'd just be using it to change the velocity of the earth. While producing an endless stream of energy from nowhere in one of those cases, and making an unlimited amount vanish from the universe in the other. If you think it might somehow come from or go into the Earth's kinetic energy, just put an identical one on the far side to cancel any planetary accelerations. It's Earth's gravitational acceleration that's relevant to my argument...Shawyer doesn't seem to be aware of the equivalence principle. It's even worse than that. He's claimed that the EmDrive works best when "stationary relative to its thrust". The "Future" section of his website makes clear what he means...his reactionless thruster works best if you don't let it move (you read that right), and its performance decreases as velocity increases. He suggests vehicles using EmDrive for lift and jet engines for forward propulsion, to "limit kinetic output". Throughout the whole thing, it's clear that he thinks velocity is some absolute universal quantity, completely missing the point of relativity. (In fact, he's assuming Earth is in an absolute rest frame...his claims require a geocentric universe.)
cjameshuff Scholar Join Date: Feb 2013 Posts: 94

27th February 2013, 12:22 PM	#31
quarky Banned Join Date: Oct 2007 Posts: 20,121	Originally Posted by cjameshuff While producing an endless stream of energy from nowhere in one of those cases, and making an unlimited amount vanish from the universe in the other. If you think it might somehow come from or go into the Earth's kinetic energy, just put an identical one on the far side to cancel any planetary accelerations. It's Earth's gravitational acceleration that's relevant to my argument...Shawyer doesn't seem to be aware of the equivalence principle. It's even worse than that. He's claimed that the EmDrive works best when "stationary relative to its thrust". The "Future" section of his website makes clear what he means...his reactionless thruster works best if you don't let it move (you read that right), and its performance decreases as velocity increases. He suggests vehicles using EmDrive for lift and jet engines for forward propulsion, to "limit kinetic output". Throughout the whole thing, it's clear that he thinks velocity is some absolute universal quantity, completely missing the point of relativity. (In fact, he's assuming Earth is in an absolute rest frame...his claims require a geocentric universe.) Glad you're here. New blood is good.
quarky Banned Join Date: Oct 2007 Posts: 20,121

31st July 2014, 08:56 AM	#32
temporalillusion Technical Admin Join Date: Jul 2006 Location: Canada's Texas Posts: 1,495	A new development in this? http://www.wired.co.uk/news/archive/...le-space-drive Quote: However, a US scientist, Guido Fetta, has built his own propellant-less microwave thruster, and managed to persuade Nasa to test it out. The test results were presented on July 30 at the 50th Joint Propulsion Conference in Cleveland, Ohio. Astonishingly enough, they are positive. The Nasa team based at the Johnson Space Centre gave its paper the title "Anomalous Thrust Production from an RF [radio frequency] Test Device Measured on a Low-Thrust Torsion Pendulum". The five researchers spent six days setting up test equipment followed by two days of experiments with various configurations. These tests included using a "null drive" similar to the live version but modified so it would not work, and using a device which would produce the same load on the apparatus to establish whether the effect might be produced by some effect unrelated to the actual drive. They also turned the drive around the other way to check whether that had any effect. How long until they just put one of these in space and see if it works?
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31st July 2014, 09:26 AM	#33
phunk Illuminator Join Date: Aug 2007 Posts: 3,530	Or test in a vaccuum chamber.
phunk Illuminator Join Date: Aug 2007 Posts: 3,530

31st July 2014, 11:33 AM	#34
casebro Penultimate Amazing Join Date: Jun 2005 Posts: 14,155	Would it work better in the nano- range? I'll have to take a Pico at the theory. Hmmm, e=mc2, so the waves have mass? And radio waves sent in one direction should give equal thrust in the opposite direction? And since the velocity of radio waves is the speed of light, thrust would depend on the mass of Rock & Roll? Isn't classical music denser? Or is Country-Western the densest? .... Punk Rock?
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31st July 2014, 04:37 PM	#35
The Man Scourge, of the supernatural Join Date: Jun 2007 Location: Poughkeepsie, NY Posts: 11,971	Originally Posted by casebro Would it work better in the nano- range? I'll have to take a Pico at the theory. Hmmm, e=mc2, so the waves have mass? And radio waves sent in one direction should give equal thrust in the opposite direction? And since the velocity of radio waves is the speed of light, thrust would depend on the mass of Rock & Roll? Isn't classical music denser? Or is Country-Western the densest? .... Punk Rock? I think jazz is admired particularly for its musical density.
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