Author Topic: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive  (Read 199286 times)

Offline Raj2014

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #460 on: 05/16/2015 05:30 PM »
What are they planning to do next with the EM Drive?

Offline Mulletron

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #461 on: 05/16/2015 07:21 PM »
http://www.ibtimes.co.uk/emdrive-warp-drive-are-two-different-things-nasas-still-working-emdrive-1501268

I'm linking to this because it mentions us, is mostly accurate (not completely) and is fair and balanced. It has lots of quotes from Shawyer himself. The final comment from him about the West has me extremely unnerved.
« Last Edit: 05/16/2015 07:44 PM by Mulletron »
Challenge your preconceptions, or they will challenge you. - Velik

Offline Star One

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #462 on: 05/16/2015 08:16 PM »

http://www.ibtimes.co.uk/emdrive-warp-drive-are-two-different-things-nasas-still-working-emdrive-1501268

I'm linking to this because it mentions us, is mostly accurate (not completely) and is fair and balanced. It has lots of quotes from Shawyer himself. The final comment from him about the West has me extremely unnerved.

That was posted to the main thread a few days back. It seems a bit of an odd mix material as it sounded like the interview quotes might have been recycled from an article from last year.

Offline Nilof

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #463 on: 05/16/2015 11:28 PM »
I'd say both the article above and several of the commenter above clearly have the wrong idea about which Eagleworks project is more likely to pan out into anything.

A warp drive does not break any obvious laws of physics, and is merely an esoteric construct that happens to require yet undiscovered forms of matter, but is clearly allowed by GR if these forms of matter are allowed. The Alcubierre metric is straightforward enough to show up as a source of homework exercises in general relativity courses.

The EM-drive on the other hand does break some rather important laws of physics, and otherwise should set off enough red lights that calling it a cargo cult is warranted.
« Last Edit: 05/17/2015 09:18 AM by Nilof »
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline KelvinZero

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #464 on: 05/17/2015 02:13 AM »
All the warp drives I have heard of concern FTL and allow time paradoxes. There apparently are all sorts of theoretical issues (eg energy conditions, whatever they are) with negative mass and paradoxes are probably an indication of trying to do something silly.
http://en.wikipedia.org/wiki/Negative_mass

Interestingly if you only warp space with positive mass you could travel approaching lightspeed for no cost... for example if there was a big rod-shaped cloud of dark matter between here and alpha centauri you would gain great speed falling into it and slow down at the other end.

Also the fact that we can imagine sending a digital description of ourselves and a machine reconstructing a copy at the other end makes it clear that physics does not exclude the basic concept of travel at light speed in some more analog fashion.

I have often thought that these sort of non-causality-violating ideas are highly underrated. I mean they would still be amazing while not containing glaring indicators that they have codependent relationships with unicorns.
« Last Edit: 05/17/2015 02:23 AM by KelvinZero »

Offline Star One

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #465 on: 05/17/2015 11:10 AM »
I'd say both the article above and several of the commenter above clearly have the wrong idea about which Eagleworks project is more likely to pan out into anything.

A warp drive does not break any obvious laws of physics, and is merely an esoteric construct that happens to require yet undiscovered forms of matter, but is clearly allowed by GR if these forms of matter are allowed. The Alcubierre metric is straightforward enough to show up as a source of homework exercises in general relativity courses.

The EM-drive on the other hand does break some rather important laws of physics, and otherwise should set off enough red lights that calling it a cargo cult is warranted.

I wonder if people even know what that phrase "cargo-cult" means as the way it's banded about would seem to indicate they don't especially in application to this topic.

It's fair enough to criticise the whole endeavour but at least do it in appropriate terms.
« Last Edit: 05/17/2015 11:15 AM by Star One »

Offline Raj2014

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #466 on: 05/17/2015 02:00 PM »
Assuming the EM drive has passed peer review and has had many tests done to verify it works. What will be the next step?

Offline kdhilliard

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #467 on: 05/17/2015 04:29 PM »
With no trouble at all. That is why the EM Drive stops at two-thirds of the speed of light.

Similar rules apply to cars, only with lower top speeds.

I don't think you're following me.

Shawyer's FAQ #18 deals with terrestrial applications:
Quote
The second generation engines will be capable of producing a specific thrust of 30kN/kW. Thus for 1 kilowatt (typical of the power in a microwave oven) a static thrust of 3 tonnes can be obtained, which is enough to support a large car. This is clearly adequate for terrestrial transport applications.

The static thrust/power ratio is calculated assuming a superconducting EmDrive with a Q of 5 x 109. This Q value is routinely achieved in superconducting cavities.

Note however, because the EmDrive obeys the law of conservation of energy, this thrust/power ratio rapidly decreases if the EmDrive is used to accelerate the vehicle along the thrust vector. (See Equation 16 of the theory paper). Whilst the EmDrive can provide lift to counter gravity, (and is therefore not losing kinetic energy), auxiliary propulsion is required to provide the kinetic energy to accelerate the vehicle.

This reduction in specific thrust is important to public acceptance of Shawyer's claim because otherwise his device would be more easily recognized as a free energy machine.  His attempt to enforce energy conservation is not invariant under Galilean transformation (more on that in a later post), but that's a point lost on the layman who doesn't understand the issues raised by a reactionless drive.

What we should all be asking after reading this interview is, if specific thrust drops so rapidly upon acceleration along the thrust vector that his proposed flying car can be levitated by EmDrive but requires auxiliary engines for propulsion, then how is it able to accelerate a spacecraft to 2/3 c in 10 yr.?  Let's crunch some numbers and figure out what kind of power density he is envisioning for its power source.

He addresses the reduction of specific power (thrust per unit power = T/P) with velocity (due to acceleration along the thrust vector of the EMDrive) starting on page 8 of his Theory Paper.  Combining equation (16) with his formulas for thrust and taking the limit on Q gives (T/P)max < 1 / v, with the maximum specific thrust approaching the inverse of the velocity as Q increases without bound.  Figure 3.2 plots the specific thrust against Q for a velocity of 3 km/s and shows it maxing out at 333 mN/kW.

Assume that our spacecraft of mass m and power P starting from rest is somehow able to achieve its maximum permitted specific thrust at all times.   Combing T/P = 1/v and T = m v-dot (where v-dot = dv/dt, acceleration) yields the differential equation v-dot = (P/m) v-1 with the initial condition v(0) = 0 and solution v(t) = sqrt(2Pt/m).  Plugging in v(10 years) =  2/3 c and solving for power density gives P/m = (2/90) c2 / yr = 63.3 MW / kg.  But that isn't even taking relativity into account.  2/3 c is not highly relativistic, but it does yield a Lorentz factor of 3/sqrt(5) = 1.34, so doing the calculations relativistically reveals a required power density of 97.3 MW / kg.  Accounting for electrical losses, payload, and the mass of the EmDrive itself will further increase the required power density of the spacecraft's power source.

Proponents of VASIMR driven 39 day trips to Mars are rightly taken to task for not pointing out that their plan requires a power source capable of generating an astounding 1 kW / kg.  Shawyer's zero to 2/3 c in 10 years spacecraft needs a power source with five orders of magnitude greater power density.

~Kirk

Offline Peter Svancarek

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #468 on: 05/17/2015 07:14 PM »
With no trouble at all. That is why the EM Drive stops at two-thirds of the speed of light.

Similar rules apply to cars, only with lower top speeds.

I don't think you're following me.

Shawyer's FAQ #18 deals with terrestrial applications:
Quote
The second generation engines will be capable of producing a specific thrust of 30kN/kW. Thus for 1 kilowatt (typical of the power in a microwave oven) a static thrust of 3 tonnes can be obtained, which is enough to support a large car. This is clearly adequate for terrestrial transport applications.

The static thrust/power ratio is calculated assuming a superconducting EmDrive with a Q of 5 x 109. This Q value is routinely achieved in superconducting cavities.

Note however, because the EmDrive obeys the law of conservation of energy, this thrust/power ratio rapidly decreases if the EmDrive is used to accelerate the vehicle along the thrust vector. (See Equation 16 of the theory paper). Whilst the EmDrive can provide lift to counter gravity, (and is therefore not losing kinetic energy), auxiliary propulsion is required to provide the kinetic energy to accelerate the vehicle.

This reduction in specific thrust is important to public acceptance of Shawyer's claim because otherwise his device would be more easily recognized as a free energy machine.  His attempt to enforce energy conservation is not invariant under Galilean transformation (more on that in a later post), but that's a point lost on the layman who doesn't understand the issues raised by a reactionless drive.

What we should all be asking after reading this interview is, if specific thrust drops so rapidly upon acceleration along the thrust vector that his proposed flying car can be levitated by EmDrive but requires auxiliary engines for propulsion, then how is it able to accelerate a spacecraft to 2/3 c in 10 yr.?  Let's crunch some numbers and figure out what kind of power density he is envisioning for its power source.

He addresses the reduction of specific power (thrust per unit power = T/P) with velocity (due to acceleration along the thrust vector of the EMDrive) starting on page 8 of his Theory Paper.  Combining equation (16) with his formulas for thrust and taking the limit on Q gives (T/P)max < 1 / v, with the maximum specific thrust approaching the inverse of the velocity as Q increases without bound.  Figure 3.2 plots the specific thrust against Q for a velocity of 3 km/s and shows it maxing out at 333 mN/kW.

Assume that our spacecraft of mass m and power P starting from rest is somehow able to achieve its maximum permitted specific thrust at all times.   Combing T/P = 1/v and T = m v-dot (where v-dot = dv/dt, acceleration) yields the differential equation v-dot = (P/m) v-1 with the initial condition v(0) = 0 and solution v(t) = sqrt(2Pt/m).  Plugging in v(10 years) =  2/3 c and solving for power density gives P/m = (2/90) c2 / yr = 63.3 MW / kg.  But that isn't even taking relativity into account.  2/3 c is not highly relativistic, but it does yield a Lorentz factor of 3/sqrt(5) = 1.34, so doing the calculations relativistically reveals a required power density of 97.3 MW / kg.  Accounting for electrical losses, payload, and the mass of the EmDrive itself will further increase the required power density of the spacecraft's power source.

Proponents of VASIMR driven 39 day trips to Mars are rightly taken to task for not pointing out that their plan requires a power source capable of generating an astounding 1 kW / kg.  Shawyer's zero to 2/3 c in 10 years spacecraft needs a power source with five orders of magnitude greater power density.

~Kirk

Shawyers equations are in my opinion rubbish. If you can float a car, that means you can accelerate at the rate of at least 10 m/s^2 (1g is 9.8m/s^2). If you can do this then you can slowly float higher and higher and accelerate as gravity grows weaker and acceleration wouldn't change from 10m/s^2...
2/3c looks like someone doesn't know what it means relative velocity. You can fly 99.99c but you are effectively staying at the same place, unmoving. You can walk around your hypothetical rocket and it would look like it isn't moving at all... You can look at it like the space is moving around yourself.
« Last Edit: 05/17/2015 07:16 PM by Peter Svancarek »

Offline kdhilliard

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #469 on: 05/17/2015 09:33 PM »
Shawyers equations are in my opinion rubbish. If you can float a car, that means you can accelerate at the rate of at least 10 m/s^2 (1g is 9.8m/s^2). If you can do this then you can slowly float higher and higher and accelerate as gravity grows weaker and acceleration wouldn't change from 10m/s^2...

His distinction between hovering (unlimited) and accelerating horizontally at 9.8 m/s^2 (limited due to reduction in specific thrust) would appear to violate the equivalence principle.

~Kirk

Offline Peter Svancarek

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #470 on: 05/18/2015 09:13 AM »

His distinction between hovering (unlimited) and accelerating horizontally at 9.8 m/s^2 (limited due to reduction in specific thrust) would appear to violate the equivalence principle.

~Kirk

Yeah, and not only that. It is said that mathematics is a servant of physics. But if you instruct your servant poorly, you will end with ill results.
« Last Edit: 05/18/2015 09:14 AM by Peter Svancarek »

Online WBY1984

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #471 on: 05/22/2015 04:08 PM »
Shawyer's a nut. That whole The West is slowly dying, and that's all for the good' business is wild speculation. His math has been shown to be nonesense by many people smarter than him, and the boffins in the other thread are closing in on more conventional and mundane explanations for EMDrive thrust.

End of.

Offline Star One

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #472 on: 05/22/2015 07:31 PM »

Shawyer's a nut. That whole The West is slowly dying, and that's all for the good' business is wild speculation. His math has been shown to be nonesense by many people smarter than him, and the boffins in the other thread are closing in on more conventional and mundane explanations for EMDrive thrust.

End of.

What are you defining as mundane?

Offline cometo

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #473 on: 06/09/2015 03:08 PM »

http://2.bp.blogspot.com/-C1cgolGV6r0/VUCw2IWncwI/AAAAAAAACWQ/8RhssZGNGKA/s1600/22.JPG


Your schematic is wrong. If you put 500kg in the 50x side, then you need 500x50 = 25.000 kg in the small jack, not 10 kg.

Regards.
« Last Edit: 06/09/2015 03:11 PM by cometo »

Offline JasonAW3

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #474 on: 06/09/2015 08:00 PM »
Regardless of how one feels about the EM drive, something IS happening, it is repeatable, not only by those who came up with it, but by many others using the same or very similar rigs.  Be it real or some sort of measuring error, calling it some sort of "cargo cult" thing is both misleading, if not more than a bit insulting.

     I don't know what is happening, I know what I hope is happening, but tests thus far have been mostly inconclusive.  If this IS a real phenomena, then I have some ideas, far fetched though they might be, of what MAY be happening, but again, the evidence is inconclusive.

     At worst, one could say I am skeptical, but hopeful.  I am trying to keep an open mind about this, but am tempering it with a large measure of skeptisism.

     If this does turn out to be a real phenomena, then we will have to rexamine some of our fundemental laws of physics, but I'm not quite ready to do that just yet.
My God!  It's full of universes!

Offline dustinthewind

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #475 on: 06/09/2015 08:05 PM »
I'd say both the article above and several of the commenter above clearly have the wrong idea about which Eagleworks project is more likely to pan out into anything.

A warp drive does not break any obvious laws of physics, and is merely an esoteric construct that happens to require yet undiscovered forms of matter, but is clearly allowed by GR if these forms of matter are allowed. The Alcubierre metric is straightforward enough to show up as a source of homework exercises in general relativity courses.

The EM-drive on the other hand does break some rather important laws of physics, and otherwise should set off enough red lights that calling it a cargo cult is warranted.

No real world device breaks the laws of physics.  It obeys the rules of the universe perfectly.  It is only our understanding that is limited.  Therefore we are looking into the physics of it to fully explain what is going on.  Until what is happening can be fully understood "satisfactorily" the search will continue.  If we can understand it in our framework of physics (convection propulsion maybe) then not much will change other than our improved ability to solve problems.  If we can't make a law to explain it then it will remain a mystery to be solved.  If we can explain it via a new hypothesis then it is possible the new hypothesis may become a law over time.  It is also possible a new and useful use of already known physics can be found. 
« Last Edit: 06/09/2015 08:25 PM by dustinthewind »

Offline cichy

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #476 on: 07/31/2015 12:54 PM »
Are the scientists absolutely sure that the thrust does not come from the interaction between test article and the Earth's magnetic field?

Offline michael.suede

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #477 on: 11/05/2015 09:28 PM »
From the article:

Quote
One possible explanation for the optical path length change is that it is due to refraction of the air.  The NASA team examined this possibility and concluded that it is not likely that the measured change is due to transient air heating because the experimentís visibility threshold is forty times larger than the calculated effect from air considering atmospheric heating.

This sounds like plasma self-focusing.  Someone should look into that.

Offline Trevor Aiden Kirkwold

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #478 on: 02/09/2016 02:18 PM »
I'm just a student in high school, but couldn't you possibly apply the Internet of Things to increase efficiency? This, along with an advanced magnetic fusion core, could possibly increase the efficiency of this "warp" drive, couldn't it?

It could also be possible to attach solar glitter "wrapping" in to certain parts of the hull to increase power output.
« Last Edit: 02/09/2016 03:26 PM by Chris Bergin »

Offline D_Dom

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #479 on: 02/09/2016 03:49 PM »
Welcome to the forum Trevor! You asked a good question, let me attempt a reasonable answer...
When I think of "internet of things" it breaks down into two distinct areas, sensors and actuators. I want to know what is going on within various areas of interest, be it astronomical, microscopic or somewhere in between. Sensors provide that information. I also want to be able to control various aspects of these interesting areas, sometimes as an experiment when I am not sure of the result, sometimes as part of an industrial process when I know exactly the desired result.
 FYI, I am in the rocket launching business, when I say exactly I mean within "advertised parameters". Say for the sake of argument, a six ton satellite, launched from W-154 degrees on the equator, into a geosynchronous orbital slot one mile wide on E-120 degrees providing coverage of Asia and Australia.
I use a lot of sensors to monitor what is happening during this launch. I use a lot of actuators to control the rocket and ground support equipment. All these systems communicate via computer networks, "the internet of things". For the EM drive experiments it is important to keep in mind we are talking about experiments where the outcome is not well understood. We use various sensors to monitor the experiments in an attempt to better understand the results. We have various control inputs, frequency, power, dimensional aspects of the frustum etc.

I am not sure how you mean to increase power output by applying glitter wrap.
Space is not merely a matter of life or death, it is considerably more important than that!

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