# To Mars in 70 days: Expert discusses NASA's study of paradoxical EM propulsion drive

Discussion in 'Astronomy, Exobiology, & Cosmology' started by paddoboy, Dec 7, 2016.

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To Mars in 70 days: Expert discusses NASA's study of paradoxical EM propulsion drive
December 7, 2016 by Colin Poitras

EM Drive in forward thrust configuration. Credit: NASA Photo
After months of speculation and rumor, NASA has finally released its long-awaited research paper on the controversial EM Drive propulsion system. The paper was recently published in the American Institute of Aeronautics and Astronautics' peer-reviewed Journal of Propulsion and Power. If the electromagnetic technology proves sound, it could radically change the way humans travel in space, opening up the possibility of journeys to Mars in just 70 days. But there is no shortage of skeptics who are adamant that the drive is more science fiction than science fact. Critics are quick to point out that the drive violates one of the fundamental laws of physics, namely: for every action, there is an equal and opposite reaction. With the science world abuzz in light of the recent developments, UConn Today called on engineering professor Brice Cassenti, an expert in advanced propulsion systems, to help us understand what's happening.

The article continues with a series of questions of a NASA expert:
The final question and answer as follows.........

Q. Is there anything else you would like to share about the EM Drive to help us understand?

A. No, but over my professional life I have seen several of these exciting experimental or theoretical results reported in peer-reviewed literature. So far only the reality of black holes has come through. So, based on my experience, the probability of this holding up under further analysis and testing appears slim. But it's not zero.

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http://arc.aiaa.org/doi/10.2514/1.B36120

Measurement of Impulsive Thrust from a Closed Radio-Frequency Cavity in Vacuum

ABSTRACT
Choose Top of pageABSTRACT <<I.IntroductionII.ExperimentationIII.ConclusionsAcknowledgmentsReferences

A vacuum test campaign evaluating the impulsive thrust performance of a tapered radio-frequency test article excited in the transverse magnitude 212 mode at 1937 MHz has been completed. The test campaign consisted of a forward thrust phase and reverse thrust phase at less than 8×10−6 torr vacuum with power scans at 40, 60, and 80 W. The test campaign included a null thrust test effort to identify any mundane sources of impulsive thrust; however, none were identified. Thrust data from forward, reverse, and null suggested that the system was consistently performing with a thrust-to-power ratio of
1.2±0.1mN/kW1.2±0.1  mN/kW.

Last edited: Dec 7, 2016

5. ### Q-reeusValued Senior Member

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From the article linked to in #1: http://phys.org/news/2016-12-mars-days-expert-discusses-nasa.html#jCp
Make up your mind expert - last passage you claimed any violation would overthrow physics as we know it. Now it's just an approximate thing not worth worrying too much about?!
The truth is EM Drive violates conservation of momentum but never violates Newton's 3rd Law. A point I have made numerous times elsewhere on this subject.

7. ### rpennerFully WiredValued Senior Member

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Please don't misteach physics on the main science forums.

First Law: An object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
$\vec{F}_i = \sum_j \vec{f}_{ij} = 0 \Leftrightarrow \frac{d \; }{dt} \vec{v}_i = 0$

Second Law: The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object.
$\frac{1}{m_i} \vec{F}_i = \frac{1}{m_i} \sum_j \vec{f}_{ij} = \frac{d \; }{dt} \vec{v}_i$ (This is the formulation which is approximate)
Or
$\vec{F}_i = \frac{d \; }{dt} \left( m_i \vec{v}_i \right)$
Or
$\vec{F}_i = \frac{d \; }{dt} \vec{p}_i$ (This is the formulation which is preserved in special relativity, with a different formula for momentum)

Third Law: For every action, there is an equal and opposite reaction.
$\vec{f}_{ij} + \vec{f}_{ji} = 0$
or
$\frac{d \; }{dt} \sum_i \vec{p}_i = 0$

The EM drive allegedly produces a net force in a closed, isolated system, thus $\vec{F}_0 = \vec{f}_{00} = \frac{d \; }{dt} \vec{p}_0 \neq 0$ without any other object in play, so there is a claimed violation of momentum conservation and that violates Newton's third law because there is no second object that balances out the sum to zero as in a rocket. It's claimed to be a reactionless drive.

Last edited: Dec 13, 2016
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8. ### Q-reeusValued Senior Member

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It is you, not me that is in error and misleads. Newton's 3rd law can never be violated, in any circumstance whatsoever. Always, action and reaction are balanced. In the case of EM Drive, that balance is achieved dynamically: F + ma = 0. A thing called inertia has to be factored in. That it is termed a 'reactionless' drive refers to the absence of the usual application of Newton's 3rd Law requiring rocket exhaust. The EM Drive reaction is acceleration of associated mass.

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9. ### danshawenValued Senior Member

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You can derive thrust by means of installing a synchrotron inside a rocket bell / venturi / thruster, can't you? It doesn't break Newton's third law to derive thrust that way, really, does it? Same idea here, only with microwaves instead of a synchrotron, ion engine, or for that matter, a flashlight coupled to a gyroscope to keep the thrust directionally stable.

The more momentum you can impart to smaller and smaller particles or photons, the better.

Electrical power for longer than 5000 years using diamonds and nuclear waste is now a practical and safe reality, so this sort of low level thruster just got a boost in terms of practical application, even in deep space. Mars colonization just got a boost as well.

That thruster looks rather massive though, doesn't it? Likely it only flies in space. How long would it take something like that to leave orbit using only that kind of thrust?

Last edited: Dec 14, 2016
10. ### exchemistValued Senior Member

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Are you contending then that force is not necessarily the rate of change of momentum with time?

11. ### Q-reeusValued Senior Member

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Are you serious there Dan? Never mind.
The only reason to answer your post is to use it as excuse to correct a sign error in #5. With F representing the presumed thrust force of EM origin, the correct expression is F - ma = 0, since the inertial reaction force is against the sense of both F and a.
Must go.

12. ### Q-reeusValued Senior Member

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I just caught that before departing. Hope my corrective in #8 settles your question. Oh, I see what you probably mean - that ma is only the low velocity expression. Sure, more generally, in any frame F = - dp/dt where it's understood there the minus sign implies the inertial reaction of the accelerated mass, not the driving force generating dp/dt

My use of ma is always valid in the proper frame of the accelerated system, which was the context of my thinking in #5 & #8. The main contention of course was about whether an EM drive breaks the 3rd Law, and I maintain it logically cannot.

Last edited: Dec 14, 2016
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13. ### rpennerFully WiredValued Senior Member

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Newton's Second Law: $\vec{F}_0 = m_0 \vec{a}_0$
Q-reeus's claim about the EM Drive: $\vec{F}_0 + m_0 \vec{a}_0 = 0$

From these two statements, algebra allows us to rewrite the first as: $\vec{F}_0 - m_0 \vec{a}_0 = 0$

Likewise, algebra allows us to term-by-term add the two equations to get $2 \vec{F}_0 = 0$

Likewise, algebra allows us to term-by-term subtract one equation from another to get $2 m_0 \vec{a}_0 = 0$ .

Thus, in light of Newton's second law, claiming $\vec{F} + m \vec{a} = 0$ where all terms refer to the same body is tantamount to claiming the acceleration is zero.

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14. ### OceanBreezeRegistered Member

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If “whatever this thing is supposed to do” violates conservation of momentum, that is a capital offense, more grievous than any supposed violation of Newton’s laws. I don’t see any need to consider which NL is violated, 1st 2nd or 3rd, because conservation of momentum trumps all of them. I maintain that it logically cannot violate conservation of momentum, and if it does it is a load of horse manure.

I still believe any thrust that is seen results from interacting with the earth’s magnetic field, and not by pushing against a “quantum vacuum” by unknown means.

15. ### Walter L. WagnerCosmic Truth SeekerValued Senior Member

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About the only thing I can think of that is remotely similar is the Moessbauer Effect (https://en.wikipedia.org/wiki/Mössbauer_effect) in which the momentum is absorbed not by individual particles, but by an entire matrix of particles (crystal matrix). If this is 'pushing' against something, the 'something' would be the universe as a whole. It should, however, leave some detectable evidence. I doubt this is an explanation, and instead it simply is a mis-reading of information, not taking into account all variables.

16. ### billvonValued Senior Member

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Mars in 70 days! Quite a claim. Let's look at that:

To get to Mars in 70 days at its closest approach, you'd need to accelerate and decelerate at about .008 meters/second^2. Let's assume that the mass you need to get to Mars, land on Mars, take off again and make it back is 336,000 kg. (Basically twice the mass of the old Apollo third stage plus command module plus lunar lander.) That means with this drive you'd need 2.2 megawatts of power.

Where would you get it? That much solar would require hundreds of thousands of kilograms of solar panels, or a nuclear reactor. 2.2 megawatts isn't hard to generate here on Earth with a fission reactor, but in space you'd have to dump about 8 megawatts of thermal power somehow - and that means, again, at least tens of thousands of kilograms of radiators and coolant. Plus the weight of the reactor itself.

So even if it works, we're a long way from "Mars in 70 days." Indeed, we could probably get there much faster (and sooner) with more proven technologies like ion or plasma engines. Even nuclear pulse, which is probably closer (timewise) than this technology.

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17. ### Q-reeusValued Senior Member

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Who is being shown up here? It's at minimum expected of a high and mighty mod to at the least have read and properly and objectively taken into account ALL relevant posts before responding. You again choose a rather foolish tactic of selectively seeking out any slip on my part so as to play it up for all it's worth. Quite irregardless of the obvious corrective in #8 and as further clarified in #9.

That kind of petty churlish behaviour is not reflecting badly on me, but you. Just as in that other currently ongoing thread.

Your statement in #4 that a so-called 'reactionless' EM drive, if it works as claimed, would violate Newton's 3rd Law is simply wrong. Period. Petty attack as deflection tactic of that basic conceptual error is just childish. That among others the 'expert' quoted in #5 fell into the same conceptual error does not excuse or lessen that fact.

[Just to put this beyond further exploitation via petty nitpickery, here's the condensed version of #5 and essence of subsequent posts by me re correct application of Newton's 3rd Law:

Fem + Fibr = 0. Where Fem is the driving force presumed to be of EM origin, and Fibr = -dp/dt is the inertial back-reaction force directly opposing Fem. Fibr provided by the accelerated system mass (e.g. entire EM drive) undergoing a time-rate-of-change of momentum dp/dt. Hope that's sufficiently brief and 'legally watertight' for the unfortunate purpose needed here.
Actually here's another way of restating the 3rd Law: Push on something, and always get an equal push back. No magic allowed.]

Last edited: Dec 15, 2016
18. ### Q-reeusValued Senior Member

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I disagree. It's Newton's 3rd Law that cannot fail for what should be an obvious basic logical reason. Unless 'genuine magic' exists, and I think not. Whereas failure of conservation of energy-momentum (relativity requires they be combined) signifies a field/particle interaction hitherto unknown or overlooked. It's the latter, at least according to clear implications of certain long published solutions of the ME's I have seen. And as before, I'm not about to spill here what they are.
We discussed that in another thread and I pointed you to the data - does reported thrust amplitude follow a linear or parametric dependency on internal EM field amplitudes? Results are consistent with thrust being directly proportional to input RF power. Hence a parametric function of RF internal EM field amplitudes. That effectively knocks your speculation on the head. Get used to the 'new physics'. It won't be disappearing - only further confirmed. A prediction I made way back in a much earlier thread.

Last edited: Dec 15, 2016
19. ### Q-reeusValued Senior Member

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An understandable reaction but it's wrong - see my reply to OceanBreeze in #15.

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Since you so churlishly and childishly brought it up, the above is just another example of your total hypocrisy in the fact that in the "other thread" you dismiss science in favour of some magical spaghetti monster and ID, then use it here as an invalid means of dismissing this.
So yes, in essence, it certainly does reflect on you.
I'm beginning to believe that your continued indulgence in this hypocrisy, has now got to a stage where you are totally unaware of when you are doing it.

On the story, whatever the outcome, I don't believe any known laws of physics will be broken, whether it turns out as successful or a failure.
Worth sending it to space though to find out properly, one way or the other.....

http://aip.scitation.org/doi/full/10.1063/1.4953807

On the exhaust of electromagnetic drive

Action-Reaction seems to have been violated. We consider the possibility that the exhaust is in a form that has so far escaped both experimental detection and theoretical attention. In the thruster’s cavity microwaves interfere with each other and invariably some photons will also end up co-propagating with opposite phases. At the destructive interference electromagnetic fields cancel. However, the photons themselves do not vanish for nothing but continue in propagation. These photon pairs without net electromagnetic field do not reflect back from the metal walls but escape from the resonator. By this action momentum is lost from the cavity which, according to the conservation of momentum, gives rise to an equal and opposite reaction. We examine theoretical corollaries and practical concerns that follow from the paired-photon conclusion.

21. ### Q-reeusValued Senior Member

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Rave on brown-noser. Keep collecting Brownie points like a good little low-IQ sycophant. The low IQ bit confirmed below....
Repeating the same fool refrain I took you to task over back in another thread. Woefully ignorant of what just SR considerations alone imply re any EM drive success.
More stupid repetition from that other thread. I tore that junk article's logic apart back there and then but nothing useful gets through to the low IQ likes of you.

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I really don't need to "brown nose" as you put it, and also unlike yourself and a couple of other trolls, I don't whinge about actions taken against me by mods.

No I'm right again, as others told you in that thread, and you actually taking anyone to task after recent performances is actually hilarious, particularly with your apparently defunct anti GR and anti GW rants.
Anyway I know this will set you off again on your usual rage, so you have fun...not really interested in your hypocrisy in this thread anymore.