The EmDrive just won't die

Almost certainly, but maybe the type of valuable thing NASA scientists and engineers learn 100 times a year rather than once in a century.

If we're lucky. Sometimes it's just a loose cable. https://en.wikipedia.org/wiki/Faster-than-light_neutrino_ano...

Part of the problem with “cold fusion” was the claim that it was fusion, which it pretty clearly wasn’t. If the claim was merely that they’d observed apparently unexplained release of energy, or even that they believed they’d detected fission byproducts down near the limits of their instruments, it would have been more palatable. If they’d decided to release their ‘results’ in a peer-reviewed journal instead of in a press conference where they kept the details secret, they might have been treated better by the community. The problem with Cold Fusion wasn’t that it was bad science—-it was that it wasn’t science.

The Em Drive lacked the snake-oil showmanship of Cold Fusion, so it got treated better. It was also described well enough for the experiment to be replicated, and a few confirmations make it interesting enough to explore.

I think this is most likely to turn out to be experimental error, not a cause a revolution in electromagnetic theory, but it is worthy of the investigation, which Cold Fusion never was.

Momentum is still conserved in quantum mechanics. This breaks the laws of physics regardless of whether or not it needs a constant energy source.

> that very scale and effort seems to be problematic when it comes to reproducing the results of experiments

First of all, LIGO is 2 observatories so every result out of LIGO was observed by at least two locations.

There is also an independent project called Virgo which is making gravitational wave observations, and the results are being correlated with LIGO. They have made a number of overlapping observations, which further moves us towards reproducibility.

Future observatories are also planned (like LISA), which will be another opportunity to further validate events.

> How would we ever know?

That is why they built two of them in two different locations, one in Washington and one in Louisiana. Only results that are measured by both are considered actual signals.

This is in large part why we consider measurements probabilistically too.

LIGO could be wrong, sure, but that's why it's measured twice. The results fit numerical predictions by general relativity that we think the probability of it being wrong is very low. It might not be, but we could be inside a Boltzmann brain too.

I believe there have been visual/radio detections correlated with LIGO detections. I couldn't find a more authoritative source, but did find at least one reference in a Popular Mechanics[1] article.

[1]: https://www.popularmechanics.com/space/deep-space/a28631/neu...

Does it violate the conservation of energy though? I don't think that was proposed.

Orbit is actually a very dynamic and variable place. The Earth’s gravitational fields varies due to asymmetric mass distribution of the continental shelves, mountain ranges and features below the crust. Our atmosphere has an affect on satellites at even thousands of km altitude. The magnetic field is constantly shifting and can affect the orbits of metallic satellites. Then there’s the solar wind. This is why a lot of satellites need station keeping thrusters. Decent thrust would be observable, but very small rates of thrust that are hard to measure at all in the lab could be swamped by these effects and just as hard to measure in orbit, if not more so.

My understanding is running this experiment in space would cost >$10m, a very pricey experiment when the expected outcome is negative.

Why not just teleport to where you want to be?

Wouldn’t that much energy melt whatever you are bouncing it around in?

What is gravity shielding?

Falcon 9’s engines combined produce ~7,500,000,000 millinewtons of force (at sea level) per SpaceX’s website (converted from their figure of 1.7M lb/foot of force).

So doing some napkin math with the article’s 12mN/kW, that’s close to a terawatt. For reference, I think worldwide electrical power generation capacity is around 10x that.

edit: made the math more explicit due to child comments and fixed spelling error

Maybe it will require 1.21 gigawatts and travel through time.

That's easy. It mostly goes into heat. Eddy current heating of the copper tube should be the largest part. Wires, waveguides, a microwave generator aren't 100% efficient too. Small part of energy is lost as electromagnetic radiation.

What's mysterious is where the energy and the impulse are going if thrust is real. We can point the drive in such a way that it slows rotation of the earth, so the earth's rotational energy and angular impulse are decreasing. Where should they be going? I don't know.

you seems to be conflating thrust(momentum) and energy a bit - linear on speed vs. quadratic on speed in classic case. It is very similar to photon drive - a lot of energy carried away by the photons while they generate too little thrust.

If there is a genuine effect, and as EmDrive generates more thrust than photon drive for the same energy, it would mean that EmDrive does eject some small mass at large speeds (kind of like super ion thruster) - whether it is some mass chipped from the EmDrive (i'd bet it is the case) and/or created using the spent energy (say some smaller mass boson interaction with some field which looks less probable to me) - that we don't know yet.

I think you didn't read the second half of the sentence he quoted.

Some napkin math.

How long would it take a nuclear powered EmDrive to push a fully loaded semitrailer from 0m/s to the speed of the interntional space station?

The maximum mass for a semi-truck fully loaded is 36000kg. The EmDrive generates 12millinewtons per kw. 1n = 1kg*(1m/s^2). Leo ~=7.66km/s^. A nuclear reactor produces ~1gw. We would need 275760000N to accelerate a semi truck to leo speeds. A nuclear powered EmDrive would take ~265 days to push a semi truck to low earth orbit speeds.

The escape velocity of Earth's orbit is 11.19 km/s, and if you were going to take humans on the trip you'd need much more cargo than 36000kg. Granted, you wouldn't have to move the craft from 11.19km/s to 0km/s and then 0km/s to 11.19 km/s every time you entered and left orbit, but it would be a slow ride regardless.

If we could put a nuclear reactor in space large enough for this to be useful, we could use the reactor to boil water and get vastly more thrust. Or run an ion drive and get more thrust. Or just let the fission fragments out the back and get more thrust.

What this would be useful for is (by no coincidence) also the exact reason why it is considered crank science: you could use it to build a perpetual motion machine because it violates conservation of energy/momentum laws.

Ion thrusters already do this though. Even with conventional rockets once you're in space finding new fuel shouldn't be a big deal. It's just a matter of building the infrastructure. Right now leaving earth is still the biggest problem.

Then it'd probably be called a space port or something instead of a launchpad?

When you do the math, in order to extract infinite free energy as per OP's argument, you have to get the drive up to a certain speed (think of a y=x line intersecting with a y=x^2 parabolic curve). The required speed depends on the performance of the drive (i.e. the N/kW figure), with a higher performance drive meaning a lower required speed before you can start extracting energy. For a photon drive, the speed you need to reach to extract infinite free energy is... the speed of light. Which you can't get to. So OP's argument only applies to drives which perform better than a photon drive, which naturally includes the EmDrive.

Kinetic energy is relative to some inertial reference frame. You can pick any reference frame you want and each will give you different numbers, but conservation laws should still hold in each.

Addition of kinetic energy is pretty unintuitive in this regard, e.g. when throwing a ball, the "work" done by your muscles depends on the reference frame that you pick to analyze the event.

In empty space yes, but space is a vacuum (mostly) but not empty.

If you are in orbit you can measure your speed relative to something else, the only that doesn't work is a privileged frame.

Because if emdrive works where science says it shouldn't be possible then it becomes difficult to predict it's characteristics.

I thought that was implied by the description of the EM drive of "X kilowatt for Y newton". But I guess the effect could indeed depend on your speed relative to some special reference frame, like that of the microwave background.

If that's the case, then we can do something like the Michelson–Morley experiment, to check whether the effect is different depending on the direction the Earth is moving in its orbit.

The force cannot possibly depend on the drive's kinetic energy, because the kinetic energy is based on the velocity, which is relative to the frame of reference you use to measure it. If your frame of reference is the drive itself, then the kinetic energy is always zero, and conversely it's always possible to use a remote galaxy as a frame of reference, which makes the kinetic energy (and velocity) absurdly high.

So traditional thrusters, which also convert energy into momentum, shouldn't work either?

Conservation of momentum only applies to mechanical processes, such as force and collisions. Converting energy breaks out of those bounds, and so it no longer applies - and the emdrive breaks no physics.

At least, that's how I've always understood it.

It can often be considered closed for the purposes of the phenomenon that we want to describe. To be specific, masses like galaxies, stars and planets accelerate all parts of our tiny rocket the same way. Yes, there are differences, but they are usually so small that they can be neglected. Our rocket works mostly the same no matter how it is oriented to these sources of gravity. Of course, as it gets closer to such masses, these forces (called tidal forces) start to matter and will eventually rip it apart, given that it doesn't burn up or collide first.

Rockets, differently to balloons, do not depend on an interaction with a gravitic field for their operation. They work by ejecting reaction mass opposite to the flight direction and relying on Newton's third law of motion. Most of the time, the energy to eject the reaction mass is generated by combustion, but it doesn't really matter. Rockets can also be driven by the reaction mass's pressure inside its tank.

In general, any system can be turned into a closed system by including all sources of force in the description. Of course, the more forces are included in our model, the less useful it gets. Therefore, physicists and engineers must decide which forces can be ignored. Else, even experiments would become useless because without a model, the experience gained from experiments cannot be generalized.

As to your first question, distant gravitational fields can be ignored as per theory of relativity - if you're looking at an experiment in a black box (e.g. in an EmDrive) then an otherwise closed system in freefall in gravitational field is absolutely indistinguishable from a system at rest without that field, any experiment would give exactly the same results.

And for the second question, mass is energy and energy is mass (as per relativity). Adding or removing energy from a system makes it respectively heavier or lighter; if you heat up an object so that afterwards it has exactly the same atoms but just more internal energy, then it will be slightly heavier than when it was cold - the difference is very small (m=E/c^2, and c^2 is large) but nonzero.

If you're looking from outside at the behavior of an isolated black box, it's impossible to detect if inside it some mass is "lost" in a nuclear reaction i.e. converted to energy, as both the inertial and gravitational mass of a system is equivalent to the sum of both rest mass and energy, and that total is conserved. If that box pushes out energy/mass to outside or gains energy/mass from outside, then of course it is not a closed system. But converting rest mass to energy and vice versa in a chemical or nuclear reaction would not make it a non-closed system as long as all the inputs and outputs stay in the system, as the total gravitational effect of the system before and after the reaction would be exactly the same.

Also heat, they talk about 1kW energy. Some heat has to go away, or the whole thing would glow and melt soon.

It’s certainly cheaper than funding the research and the cost to send stuff to space has gone down and continues to go down

>Entanglement is not mediated by a medium. If it was, it would have speed of light limitations.

This medium is that in which all energy is embedded. Two particles becoming entangled does mean they're highly correlated with each other. But what enables this correlation? I don't see this question as answered, because wave function collapse is actively disputed.

While my view of quantum entanglement is limited, I don't fully understand how entangled particles can be strongly correlated but can't transmit information FTL. Is it correct to say that two separate entangled particles are now one-and-the-same? I suppose you then get into a philosophical question of whether all parts of a system can ever observe the exact same thing at the exact same time. If this statement is false, then information must be transmitted, no?

>unknown type of matter that enables statistical correlations to exist

Matter and energy are one and the same. Why can't other types of energy exist which we don't fully understand? For example, how does dark "matter" work? We only have incomplete theories thus far, and I know of no paper that discusses physical manipulation of dark matter.

The ether as a concept existed because people didn't understand the vacuum of space. But perhaps the zero-point field is a more accurate rendition of what etherians were trying to communicate.

> Project Orion

Here is some declassified test footage of Project Orion. I don't believe any of the test crafts used nuclear explosions, but you'll get the idea from this footage (on why it's a terrible idea that could only exist in the 40s or 50s)

https://www.youtube.com/watch?v=Q8Sv5y6iHUM

The physical theories that prevent the EmDrive (conservation of momentum) are centuries old, and utterly fundamental to our university of reality on every scale from black holes merging to atoms radiating. A violation of this principle would involve radically altering the very foundations of modern physics, on a level more profound than anything that has ever happened in the history of the field.

I think the objection is that those are large error bars compared to the force measured. And that even a modest source of experimental error could put this at zero real output.

ETA: and since “non-zero real output” implies that virtually all of our physics is incorrect, and needs to be rebuilt from the ground up, the bar for measurement error needs to be exceptionally small.