"The EmDrive Just Won't Die"

[DDE]

PopMech article here:

https://www.popularmechanics.com/space/rockets/amp33917439/emdrive-wont-die/

Old thread here:

 

[Guest]

Yeah, that sort of thing is why I'm worried about KSP2 featuring metallic hydrogen doing the same thing to that theory. Myths, especially too good to be true hypothetical technologies, die hard. Cold fusion still has its proponents, too (Stellaris fell into that trap, though luckily it doesn't sell itself as hard SF). This is a waste of taxpayer money, and a good example of bad science doing real harm.

[Entropian]

14 minutes ago, Dragon01 said:

Cold fusion still has its proponents, too

Don't even get me started on that...

14 minutes ago, Dragon01 said:

This is a waste of taxpayer money, and a good example of bad science doing real harm.

Well, I would expect the testing budget to be pretty low in terms of DARPA's overall spending.  I could be wrong though.  It may be bad science, but more testing never hurts.

[Guest]

A small waste is still a waste, it's wrong on principle, and harm may be small, but it's very much real. Even a small project has a staff that, if they weren't busy chasing bogus claims, could be working on real science. Bad science has to be pushed back against, hard, on every front. That sort of thing only lends it credibility. EM Drive was fine while it was a plausible hypothesis, but once it was disproved experimentally, it really doesn't need to take up any more time. Just like cold fusion or metallic hydrogen, time spent on that is wasted time.

[Entropian]

12 minutes ago, Dragon01 said:

disproved experimentally

It was?  I didn't hear of that.  Could you please post a link for that?

[Guest]

EM drives have been debunked... why is this still a discussion 

[Nuke]

i heard that woodward got an order of magnitude increase in thrust output from a mega drive. its probably still spurious and i haven't found any proof to back it up. but order of magnitude improvements are a sign that its going somewhere if in fact that's what he's getting. if its not, well then torsion pendulum micro-thrust measurement technology is getting really good as a result. 

though i have problems resolving the theory of operation of mega drive with gravity waves. the whole idea is based around exploiting natural mass fluctuation it the universe. however they seem to be trying to find their way in the dark. they always sweep a range of frequencies until they find a sweet spot and try to maintain that frequency, which the device does not make easy. but it seems you would want to sync up to known strong gravity wave sources. in practice such a drive would need a gravity wave observatory attached to it so you could monitor the gravity noise and use that to find a good setpoint for frequency and phase. 

 

[Guest]

Just now, Nuke said:

i heard that woodward got an order of magnitude increase in thrust output from a mega drive. its probably still spurious and i haven't found any proof to back it up.

It also hasn't been replicated... which in science makes any claim useless.

[Nuke]

5 minutes ago, The Doodling Astronaut said:

It also hasn't been replicated... which in science makes any claim useless.

it was fairly recent so i dont think hes had time to put out a paper for peer review yet. 

these things are more of a curiosity to me, though i remain skeptical. 

Edited September 12, 2020 by Nuke

[Nuke]

1 hour ago, Dragon01 said:

A small waste is still a waste, it's wrong on principle, and harm may be small, but it's very much real. Even a small project has a staff that, if they weren't busy chasing bogus claims, could be working on real science. Bad science has to be pushed back against, hard, on every front. That sort of thing only lends it credibility. EM Drive was fine while it was a plausible hypothesis, but once it was disproved experimentally, it really doesn't need to take up any more time. Just like cold fusion or metallic hydrogen, time spent on that is wasted time.

well think of it this way, if these people turn out to be quacks, do you really want them working on real science? 

then you got tajmar in dresden who is doing most of the peer review. he is more of a thrust balance guy than an em drive guy. i think he also tests low thrust ion engines as well. and these drives, even if they are snake oil, are helping him improve his field. getting the noise floor down on his instruments.

 

2 hours ago, Dragon01 said:

This is a waste of taxpayer money, and a good example of bad science doing real harm.

 

thats just the way the defence industry works. even if there is a snowball's chance in hell that the drive is real, that has major consequences in the defense space. its a good idea to stay ahead of these things than to fall behind. if you dont research the drive, and a potential enemy does, and it is real then it puts the military in a really disadvantaged position. this is why nuclear weapons were developed. not because they knew it worked, but because if it did work, it would have dire consequences if they did nothing. the powers that be will stop at nothing to maintain that power. even if that mean putting millions of taxpayer dollars into a burn pile. 

Edited September 13, 2020 by Nuke

[K^2]

6 hours ago, Dragon01 said:

Cold fusion still has its proponents, too (Stellaris fell into that trap, though luckily it doesn't sell itself as hard SF).

To be fair, muon-catalyzed fusion is a thing. It's not what people usually mean by "cold fusion," but it's close enough for me to give sci-fi a pass on that.

[Incarnation of Chaos]

29 minutes ago, K^2 said:

To be fair, muon-catalyzed fusion is a thing. It's not what people usually mean by "cold fusion," but it's close enough for me to give sci-fi a pass on that.

And there's been pretty exciting developments in Muon lasers recently....

Man i wish i could play with some of this stuff at some point; even though I'd imagine it would end up consuming more energy than it produced in the end xD.

But back to the actual topic at hand, NASA tested this thing in a vacuum chamber with some of the most sensitive instruments to date a few years back. They were able to get a force, but noted that when rotating the "Drive" into various positions it didn't seem to change direction (Or something like that). Their conclusion was basically some imperfection in the cavity was causing more heating than average, and thus producing a tiny force.

So that should've killed it, right there. But even if this thing worked, everyone ignores the simple fact that even the "designer" admits. The damn thing doesn't scale, and requires increasingly ludicrous amounts of energy to produce more thrust as you continue trying desperately to make it work. So even without the extra mass of propellant, it isn't this silver bullet to free humanity from the tyranny of the rocket equation. After a point; the weight of the generators completely dominates the thrust.

Oh and it violates one of the core laws of physics, so there's that minor detail also. Mind you; that would actually be fine if a sufficient explanation backed up by extraordinary evidence was provided and repeatable (One of the things that the "Well we should have an open mind" people seem to forget). But it doesn't....

Special and General Relativity were "Crazy" ideas for their time, but Einstein didn't just go lay down and say **** you haters. Nah, he sent teams to observe eclipses and measure the difference in the position of stars that could only be explained by the sun's mass bending the light around it. He also showed that the anomalies in Mercuries orbit were explained by his model, and even today GPS has to account for tiny amounts of relativistic drift for it's calculations. EMdrive hasn't showed anything similar, and instead has failed every test thrown at it.

Do i think that eventually, something will be found that's a departure from conventional physics? Absolutely, but EMdrive isn't going to be what finds it.

[Nuke]

orientation of gravity waves in the local frame might explain the directional thrust asymmetries and why thrust readings tend to vary from test to test or even changing orientations within the same test. especially if you have multiple gravity wave sources all at different frequencies and amplitudes and all interfering with each other. so if these drives (mega/em/cannae, assuming they are all different ways to do the same thing) are engaging the gravity waves in some way, then it can be thought of as a cosmic surf board of sorts. obviously you wouldn't be able to surf into the wave or you would wipe out. to test this you would need to find a known strong gravity wave source, match the drive to some resonant of the wave frequency. then see if you get any thrust. as a control, choose a vector perpendicular to that source, and you should receive significantly less thrust (though probably not zero as you might catch a component of some other wave source). 

the implications of traveling space along vectors towards gravity wave sources might be that to get maximum thrust output, you might need to take a much less direct route and navigate along gravity wave highways of sorts. it would be like sailing the cosmic trade winds, so future interstellar helmsmen better learn how to tack. 

Edited September 13, 2020 by Nuke

[Guest]

3 hours ago, K^2 said:

To be fair, muon-catalyzed fusion is a thing. It's not what people usually mean by "cold fusion," but it's close enough for me to give sci-fi a pass on that.

Honestly, "muon-catalyzed fusion" sounds far cooler and more SF-ish than "cold fusion", and doesn't run the risk for being mistaken for the bad science kind. 

[DDE]

10 hours ago, Dragon01 said:

Stellaris fell into that trap, though luckily it doesn't sell itself as hard SF

I think Stellaris strikes the right balance for accessible, soft sci-fi. It's a space opera simulator that occasionally dips into real science for inspiration (e.g. higher-frequency lasers are superior).

10 hours ago, Dragon01 said:

Myths, especially too good to be true hypothetical technologies, die hard. Cold fusion still has its proponents, too

Unfortunately, I don't think everyone here realizes just how this thing is being sold. Note the passage in the PopMech article describing it being used for liftoff.

The creator peddled it as a stealthy thruster with a reduced thermal signature for atmospheric and even water craft.

 

[Guest]

They don't, that's why myths can do so much damage. Especially when people start going into "it barely works now, but think what it might do in the future!" thing, based on a few technologies that did achieve that sort of growth. Inventors of such machines generally don't understand physics and thermodynamics, but neither does the general public, which makes them vulnerable to that sort of thing.

[DDE]

Frankly, @Dragon01, I believe the Pentagon/broader NatSec community may be entering a phase where it's once again willing to throw money and, more importantly, credibility at charlatans. Consider the recent UFO campaign, for example:

More plausibly, you have them trying to uss the railgun as a panacea, first for the USMC's coastal bombardment needs, then for anti-ballistic missile defence - hence the talk of putting it onto the proposed cruiser derived from a San Antonio-class LPD.

https://www.thedrive.com/the-war-zone/20160/heres-the-navys-vision-for-a-new-cruiser-to-replace-the-aging-ticonderoga-class

[Guest]

Yup, only in this day and age, they're throwing fuel onto conspiracy theorists' fires. At least the staring at goats thing was classified, as were the CIA's weirder projects. Now it's out there for all internet to see, and as we've all seen too many times, truth counts for little in eyes of most people on the internet.

At least the railgun really makes sense for these things, it's basically a really powerful, electrically powered gun. It can therefore be used for everything guns can be, which is a lot of things. Whether it's better at it than missiles remains to be seen, but you do get more shots from out of a railgun.

[Incarnation of Chaos]

2 hours ago, Nuke said:

orientation of gravity waves in the local frame might explain the directional thrust asymmetries and why thrust readings tend to vary from test to test or even changing orientations within the same test. especially if you have multiple gravity wave sources all at different frequencies and amplitudes and all interfering with each other. so if these drives (mega/em/cannae, assuming they are all different ways to do the same thing) are engaging the gravity waves in some way, then it can be thought of as a cosmic surf board of sorts. obviously you wouldn't be able to surf into the wave or you would wipe out. to test this you would need to find a known strong gravity wave source, match the drive to some resonant of the wave frequency. then see if you get any thrust. as a control, choose a vector perpendicular to that source, and you should receive significantly less thrust (though probably not zero as you might catch a component of some other wave source). 

the implications of traveling space along vectors towards gravity wave sources might be that to get maximum thrust output, you might need to take a much less direct route and navigate along gravity wave highways of sorts. it would be like sailing the cosmic trade winds, so future interstellar helmsmen better learn how to tack. 

I really, REALLY want you to sit down and write up a mathematical formula for how spewing Microwaves with a wavelength measured in the Centimeters into a copper cone could interact with....gravity waves. Especially at differing frequencies that would cause destructive interference(Since the frequency of the microwave source wouldn't vary much, unless constructed intentionally to do so), and then get up on the wake  and "Surf" on them, while also not falling off.

Things we've detected so far that create gravity waves are incredibly large collisions between massive compact objects such as black holes, neutron stars etc. Or other cataclysmic events, such as the Big Bang or Supernova. And we know their directions pretty well, and mind you if any of this was true then we would've seen some significant changes in thrust regardless (Since there's stronger GW sources in some directions than others, so just by pointing it in different directions you would've measured changes).

Also "Gravity Wave Highways"?....what? Like are we using Gravity waves as a stand-in for the Aether now? Even though that doesn't make any sense?

Like this highlights my post pretty exceptionally well; what about any of this is testable/already hasn't been busted? What defines the behavior of "Engaging gravity waves"? What would even make you think that the behavior is related to Gravity waves in any way? There's multiple detectors around the world, and they would've noticed any anomalies during the testing. So this ad hoc hypothesis doesn't even stand up to the most basic of scrutiny, and the explanation of microwaved copper is still valid.

 

[DDE]

40 minutes ago, Dragon01 said:

At least the railgun really makes sense for these things, it's basically a really powerful, electrically powered gun. It can therefore be used for everything guns can be, which is a lot of things. Whether it's better at it than missiles remains to be seen, but you do get more shots from out of a railgun.

Well, yeah, especially the 1000-mile Strategic Strike Cannon Artillery that was all the rage before INF was torn up and allowed straightforward neo-Pershings. The problem with the US artillery establishment is that they're so obsessed with range they're throwing everything at the problem: their recent craze are ramjet-powered shells.

I'm not sure they're going to get the cost savings that artillery is supposed to provide over pure rocketry if they keep cramming more and more sophisticated systems into each modestly-sized round. In fact, I think this should hang on their wall:

Spoiler

 

[kerbiloid]

To make the EM-drive work, you just need to use metallic hydrogen superconductors.

Spoiler

 

[Nuke]

6 hours ago, Incarnation of Chaos said:

I really, REALLY want you to sit down and write up a mathematical formula for how spewing Microwaves with a wavelength measured in the Centimeters into a copper cone could interact with....gravity waves. Especially at differing frequencies that would cause destructive interference(Since the frequency of the microwave source wouldn't vary much, unless constructed intentionally to do so), and then get up on the wake  and "Surf" on them, while also not falling off.

Things we've detected so far that create gravity waves are incredibly large collisions between massive compact objects such as black holes, neutron stars etc. Or other cataclysmic events, such as the Big Bang or Supernova. And we know their directions pretty well, and mind you if any of this was true then we would've seen some significant changes in thrust regardless (Since there's stronger GW sources in some directions than others, so just by pointing it in different directions you would've measured changes).

Also "Gravity Wave Highways"?....what? Like are we using Gravity waves as a stand-in for the Aether now? Even though that doesn't make any sense?

Like this highlights my post pretty exceptionally well; what about any of this is testable/already hasn't been busted? What defines the behavior of "Engaging gravity waves"? What would even make you think that the behavior is related to Gravity waves in any way? There's multiple detectors around the world, and they would've noticed any anomalies during the testing. So this ad hoc hypothesis doesn't even stand up to the most basic of scrutiny, and the explanation of microwaved copper is still valid.

 

its a known property of waves that when they interact with each other they can either cancel out, or stack up, scientists call it interference. this is likely true for gravity waves. considering that there are multiple sources in the universe at various frequencies and amplitudes, the universe is effectively a sea of gravity fields which are constantly in flux. sort of like the gravitational equivalent of radio static as a large number of radio sources interact in such a way as to create a chaotic mess. so its no aether, just a product of multiple wave interactions. 

enter mega drive, em drive's mechanical cousin. the real difference between the two is that the mega drive is built on a lot of peer reviewed science (from theory to device, while em drive attempted to go the other way). the wikipedia article is really out of date, but it does cover the theory of operation pretty well. the article describes the use of capacitors and inductors, but they have moved on to stacks of pzt disks, which are electrostrictive. the short explanation is that if you physically oscillate an energy storage device while simultaneously charging it up you should get some thrust. the claim is that it exchanges momentum with matter in the distant universe. now i have to admit that woodward and his team have been getting slammed hard in peer review in the past year or two. in part because em drive, and also because of the unfavorable outcome of tests of their thruster in dresden. and another guy from their team (rodal sp? i think) put out a paper that stated that mega would be impractical as a thruster. 

my idea was simply to find a relatively strong gravitational wave source, tune the frequency of the drive to match that of the gravity waves (it doesnt have to be 1:1, i figure you could hit a harmonic), point the drive at it, run the test and see if the results are any different. i dont think this would work for an em drive unless it was designed to hit a specific harmonic of the target gravity wave, which means making a custom cavity, but its possible that it could be tested in the same way with a one off test article. with the way that the mega drive is supposed to work, i was wondering if you could selectively use a single gravity source as the thing from which to borrow momentum, rather than 'the distant universe'. 

i should point out that i dont expect these drives to go anywhere, give me old boom boom any day, and i think that it may turn out to be quack science. but quacks doing quack science doesn't harm anyone (people arguing about it on youtube now, or worse using it to 'prove' some other wackjob ideology. thats more a symptom of general scientific illiteracy). wouldn't be the first time a scientist chased their own shadow. but you wanted me to play scientist, im out of my league there, so i dont have any equations for you. but there are woodward's equation from the wikipedia article. i need to better familiarize myself with the math behind gravity waves. since im making an assumption that gravity fluctuation + mass fluctuation = moar boosters. 

Edited September 13, 2020 by Nuke

[Guest]

TBH, riding a gravitational wave strikes me as impractical for one reason: they're really, really weak. Only recently have we figured out how to measure them, nevermind use them for something besides observing distant astronomical events. Not my field so I could be wrong, but I don't see this creating accelerations that would be significant on human timescales.

9 hours ago, DDE said:

Well, yeah, especially the 1000-mile Strategic Strike Cannon Artillery that was all the rage before INF was torn up and allowed straightforward neo-Pershings. The problem with the US artillery establishment is that they're so obsessed with range they're throwing everything at the problem: their recent craze are ramjet-powered shells.

Of course, remember that before INF treaty fell apart, missiles in that range category were very much verboten. Since the whole reason they were banned was because they were just so darn useful, everyone has been looking at a way to get a similar performance out of something else, if only because the Chinese were not bound by the treaty. Russia was in a hurry because of their (historically contentious) Chinese border, so they just went with missiles that had "growth potential", while US, being further away, decided to be more subtle.

[magnemoe]

1 hour ago, Dragon01 said:

Of course, remember that before INF treaty fell apart, missiles in that range category were very much verboten. Since the whole reason they were banned was because they were just so darn useful, everyone has been looking at a way to get a similar performance out of something else, if only because the Chinese were not bound by the treaty. Russia was in a hurry because of their (historically contentious) Chinese border, so they just went with missiles that had "growth potential", while US, being further away, decided to be more subtle.

Back then INF was written none though seriously about conversational 1000 km range missiles, they was nuclear weapons with the destabilizing effect that they was under lower level command and would have an use it or loose it setting in an conversational war. 
Today they are relevant for rapid key target strikes, its one of the weapon systems who are very nice to have if you need it but you will not use many of them. 
Something the same about stuff like ramjet artillery rounds, its not something you will use often but its nice to have if you need them and enemy have to take them into account. 

Germany's most effective capital ship during WW2 was Tirpitz, as I understand it never used their main guns against serious targets but they tied up multiple battleships and carriers as convoy escorts, one convoy who did not have capital ship escort had to break up as an battleship hitting it would be an wipe, most of the cargo ships was lost. Kind of like an queen in chess is primarily an threat  you have to counter 

[JoeSchmuckatelli]

If Elon Musk can throw a Tesla into space... why don't they just pack up one of these things with some kind of off-the-shelf brain and see if it does anything once in space.

 

If it does, drive it around for a bit to see if it handles, and if it doesn't call it a 'dummy payload'