British, Chinese and now NASA teams seem to validate fuel-less microwave space drive...

Nevin73 wrote:

We combine this with cold fusion, a microwave, and powdered creamer to get warp travel?

Toss in a higgs boson and it will warp time as well!

Yonder wrote:
Nevin73 wrote:

We combine this with cold fusion, a microwave, and powdered creamer to get warp travel?

Toss in a higgs boson and it will warp time as well!

You forgot the jump to the left.

Well that is all together more compelling. I'll try to read the paper today for some more verification, but my criticisms of the first article have been handled.

My biggest concern before was the fact that the articles were saying that NASA's negative control gave a positive result, but that was just a mistake in the reporting. According to this there were three devices, the actual negative control, which gave the expected negative result, and then two devices that both gave thrust, one of which was described in many articles in a way that made it seem like it was supposed to be a negative control.

It looks like NASA did this with multiple people at multiple locations as well.

So at this point I've gone from "this is incredibly unlikely" to "this looks reasonable, but it still seems too good to be true so I'm only slightly leaning towards true until more evidence is collected."

Conceptually, it looks brilliant, presuming you don't summon horrors from the "other side" or something.

Hey, Big Bangs have to happen somehow.

In addition to future hoverboards, I'm guessing we can finally get thrusters for our Iron Man suits. Now we just need sufficient power sources.

I don't understand the science but the answers in that Wired piece seem to indicate that this could very likely be legit.

Malor wrote:
Conceptually, it looks brilliant, presuming you don't summon horrors from the "other side" or something.

Hey, Big Bangs have to happen somehow.

That goes along with my rule to never believe in anything that violates the conservation of energy.

1. If someone claims to be violating conservation of energy they are wrong.
2. No, they're just wrong.
3. I said they are wrong.
4. Ok, fine, they are getting energy from nothing. STOP DOING THAT PLEASE. It just has to be coming from somewhere doesn't it? Like, somewhere? Another time, another place, another plane, another universe? Maybe? They are going to be angry. Please stop.

But conservation of momentum is cool with me!

In that "10 questions" article I didn't understand the paragraph about Mars missions. Can anyone explain what they are saying?

UCRC wrote:

In that "10 questions" article I didn't understand the paragraph about Mars missions. Can anyone explain what they are saying?

The weight of fuel is a limiting factor in long distance space voyages so missions have to be planned accordingly to find the most optimal route that uses the least fuel. Since the new drive doesn't use conventional fuel, many of the normal limitations that have to be taken into account don't apply. For instance, a mission using a conventional engine would only be accelerating for a short period immediately after leaving Earth, and would essentially "coast" the rest of the way to Mars. The new drive could theoretically be accelerating the entire trip (or at least until it needs to start decelerating to enter orbit), which would dramatically shorten the time it takes to get there.

It's actually a larger step even than Ruhk is saying. We already have engines that can burn all the way to Mars, just sipping fuel the entire time. There are several variants on ion thrusters and spacecraft that have used them for various purposes. My favorite is one of the early test beds, the Artemis [/i]It was launched with an experimental ion engine to provide brief corrective station-keeping burns. Its launch vehicle malfunctioned and it was sent into an orbit that was too low. A year and a half of near continuous thrusting the little engine had pushed it up where it was supposed to be.

So while we already have engines that could run the entire way to Mars, these new Momentum Tea-bagging (that's the scientific term) engines are actually significantly more powerful than current ion engines. So not only are they using zero fuel instead of a tiny amount of fuel, they are also using less power to create more thrust.

If these things actually work we may never use another ion engine again.

Edit: The sentence in that section "The new drive provides enough thrust to overcome the gravitational attraction of the Sun at these distances, which makes manoeuvring much easier" is pretty much meaningless btw.

Yonder wrote:

If these things actually work we may never use another ion engine again.

Aww. But "ion drive" is such fun to say!

As a side note, even if this turns into a working drive technology down the road, the main effect seems to be saving fuel (which is, admittedly, a big thing when you have to bring it into orbit with you) not some magical warp technology that will let us visit other stars in person. Big boost for local travel around the solar system and unmanned probes, though.

I assume someone has already made a mod for Kerbal Space Program.

I unfortunately haven't been able to read the NASA paper yet, my work doesn't subscribe to that journal unfortunately. I read around on the www.emdrive.com site for some info. (Note that the recent NASA test wasn't an Emdrive, it was a similar Cannae drive, but I believe NASA took a preliminary look at the Emdrive as well). Interestingly the Emdrive site specifically says that the engine doesn't violate the conservation of momentum, because they are lessening the momentum of the microwave field. I don't really understand how that works, however, given that the microwave field is being carried along with the drive. Electromagnetics isn't my strong suit though.

plavonica wrote:

If this thing pans out and NASA can make a working thruster from it... I would love to see a large version of it strapped onto a huge nuclear reactor, a bunch of cameras and sensors, and launch it at the nearest 'earth-like exoplanet' or star. One way trip with no decelerating, just get out there and send back some pictures and data.

So basically you are looking to start the first interstellar war?

Re: getting to Mars. Thanks for answers. Is the whole conversation then "in the future we think we can scale this up to a point where it is useful" or they already know that the output is big enough to power spacecraft? I know nothing about space travel, so the numbers quoted are meaningless to me.

UCRC wrote:

Re: getting to Mars. Thanks for answers. Is the whole conversation then "in the future we think we can scale this up to a point where it is useful" or they already know that the output is big enough to power spacecraft? I know nothing about space travel, so the numbers quoted are meaningless to me.

technically any sort of sustainable acceleration is usable for non manned spacecraft (mostly because of the long time frames involved). The longer the flight the better a lightweight but not very powerful drive is. Faast changes in energy make the heavy and fuel dependent motors more attractive.

More in detail, my question is, with the numbers we are talking here, what kind of spacecraft at what distances/timespans would use such drive. Manned missions to Mars? New generation of Voyagers travelling to Alpha Centauri? What does it add up to?

I don't think any of us knows yet. If it actually does work, we know that it will have a very low thrust-to-weight ratio, probably nowhere near as good as an ion drive (which is already dismal, just a tiny bit of thrust from a lot of weight), but the fact that it won't run out of fuel as long as it has energy will make it usable for long-duration missions that require gigantic amounts of delta-V. A small thrust for a long time can add up to one heck of a lot of speed.

It probably won't be too useful for manned missions, because those all have such sharp time limits, but it could make things like asteroid mining much more feasible.... we'd be able to go get asteroids and bring them back to either Earth or Lunar orbit fairly easily. Decelerating mined packages to drop raw materials to Earth would also be relatively easy. (Of course, then you have the environmental lobby screaming about 'dropping rocks on our heads' and such.)

tl;dr version: it could be a big step into space for robots. For us, probably not.

Yonder wrote:

Interestingly the Emdrive site specifically says that the engine doesn't violate the conservation of momentum, because they are lessening the momentum of the microwave field. I don't really understand how that works, however, given that the microwave field is being carried along with the drive. Electromagnetics isn't my strong suit though.

What that implies to me is that without a continual addition of energy to the microwaves, the field will simply reduce in energy down to nothing, which of course does not violate any laws.

Malor wrote:

If it actually does work, we know that it will have a very low thrust-to-weight ratio, probably nowhere near as good as an ion drive (which is already dismal, just a tiny bit of thrust from a lot of weight), but the fact that it won't run out of fuel as long as it has energy will make it usable for long-duration missions that require gigantic amounts of delta-V. A small thrust for a long time can add up to one heck of a lot of speed.

From the article:

The Nasa paper says "the expected thrust to power for initial flight applications is expected to be in the 0.4 newton per kilowatt electric (N/kWe) range, which is about seven times higher than the current state of the art Hall thruster in use on orbit today."

The Hall thruster is an ion thruster, so this is a very large improvement over that. The Hayabusa and Dawn spacecraft used Hall thrusters successfully for long-distance travel. It's estimated that a Hall thruster based ship could travel to Mars in about 2.5 years. I'm guessing that 7 times the acceleration could reduce that to less than 6 months...

Basically, it's nearly an order of magnitude improvement, and the type of mission doesn't make a difference to the thruster, or vice versa, if it can generate enough velocity quickly enough to be of use.

the expected thrust to power

Note that that's thrust to power, not thrust to weight.

Regardless, any fuel-less thrust is a big deal.

I haven't seen actual masses of the experimental assemblies, but from looking at the pictures of the devices and what the do, they seem like they will be lighter than ion engines, certainly not much heavier. If these things actually work they will blow any of our current low-thrust options out of the water.

UCRC wrote:

More in detail, my question is, with the numbers we are talking here, what kind of spacecraft at what distances/timespans would use such drive. Manned missions to Mars? New generation of Voyagers travelling to Alpha Centauri? What does it add up to?

I've had the chance to do some math now and I can answer this question in more detail.

At this point it looks like this (I am looking at the Emdrive model here, which seems to be superior to the Cannae, and there is more information available) thruster would be the method of choice for every application other than lifting off from a planet or large moon's surface. It's that much better.

Wikipedia has a very nice article on Ion Engines, and its comparison table has information on a variety of different Ion Engines, both theoretical and in real world use. If you divide their thrusts by the power required you'll see that their specific thrusts vary from 8 to 40 mN/kW. Pushing things out really fast requires tons of power, so typically the more energy efficient drives are significantly less fuel efficient and vice versa. They pay for their higher ISP with higher energy use.

The very first Emdrive allegedly had a specific thrust of 18.8 mN/kW, so they are already in the right ballpark. Since then SPR claims to have developed an engine with a specific thrust of 326mN/kW, which is obviously far, far superior to any of the ion engines. The Chinese model attained 288 mN/kW, and the NASA one (they tested both a Cannae drive and a very small and anemic Emdrive) at 6.8 mN/kW. That number is far far lower because the drive was designed to be a very small and low-powered one, and at that level the effect is much less efficient. I don't know why that was chosen. Eagleworks, the lab that tested that small device, is now building a more effective device that should be in the 100mN/kW range, they will test it, and then bounce it around to Glenn Research Center, JPL, and Johns Hopkins so they can all try to verify it.

But there is a bit of a weird thing about this drive. All of those numbers are for static thrust, as in, thrust while the device isn't moving. The explanation of this is pretty much what makes me call bullsh*t on this whole thing. Or at least, it would, if independent people hadn't started preliminary verification.

Ok, so I'll try my best to describe this. It's similar in mathiness to the Oberth Effect. Basically, the faster it is that you are going, the more energy it takes to increase your speed further. This is due to conservation of energy.

The kinetic energy of a body is 0.5 * mass * velocity^2. Lets take a little two kilogram space ship. It starts at 1 m/s, and then it accelerates to 2 m/s. That means that it's gone from a kinetic energy of zero joules to a kinetic energy of 1 joule. (No the mass didn't change, we are looking at just the mass of the spaceship, not the fuel, we'll get to that in a second.).

But lets say instead that he started at 4 m/s, and did that same thing. Well he did the exact same thing, so he should have gotten one joule of energy, right? But no, by going from 4 m/s to 5 m/s he went from 16 Joule to 25 Joules, he gained 9 Joules!

Now why isn't this like a huge deal? Why don't we hear about all of our spaceships getting crappier and less responsive the faster they go? Also who the heck decides whether a spaceship is going zero or 4 or ten thousand m/s anyways? Well, in a reaction drive none of this matters! (except for some small special cases like in an Oberth Maneuver) It doesn't matter because the exact same thing is happening to the propellant you are spitting out. The faster you go, the more energy it takes you to go faster, but the more energy you get from changing the speed of your propellant (which is also moving faster) so it all works out to be exactly the same regardless of the frame you are looking at. For example, your rocket doesn't magically change in properties as it leaves Earth's influence and its most relevant and useful frame changes from it having a velocity of zero to a velocity of 32 m/s.

But, at least according to the theory paper (pdf) on the emdrive site that doesn't work with a these microwave resonance drives because something something special relativity something something their frames are different.

Yonder, big thanks for the answer, I missed that post initially.

I understood what you were saying about principles in traditional spacecraft. But what about Emdrive case? Were you saying that it's somehow better off, somehow worse or we just don't know?

Thanks once more for such long post.

Yonder, doesn't the paper acknowledge that they are in a new situation, and their explanation is from first principles? Wouldn't it be expected to behave differently from reaction engines?

No problem, I'm glad it was useful to you!

Before I answer your question, I finally got access to the actual NASA paper! The biggest misconception that I found in it is that the tests were NOT done in a vacuum. The test chamber that they used is a vacuum chamber, and they (confusingly) go into detail in one paragraph on its vacuum capabilities, but it becomes clear at the end that they couldn't actually evacuate the chamber, because the electrolytic capacitors they used to test the devices need air to operate. The next version they are building will rectify that.

That said, from the charts of the forces they show it doesn't look like atmospherically effects caused a substantial amount of the force, because if that was the case I would expect the force to lag the power increase as it took time for the device to heat/cool and air currents to form/dissipate, and that didn't happen.

Now, to go back to the force/power required by these drives at velocity. Like I mentioned before, when you are carrying propellant that you are sending out behind you, that propellant gains energy with you, so is worth more energy when you spit it out, the faster you go. It's not very intuitive, but it's the result of looking at the spacecraft in an unintuitive frame. However, according to the theory that the SPR people used to design the Emdrive, because of something something special relativity you can't look at the microwave field in the resonance chamber and the rest of the engine in the same frame, which is key to the force being produced. That means that as your spacecraft goes faster and faster, the kinetic energy of field is not increasing, so you aren't getting that "free" energy anymore. So the rest of that energy must be coming in as an extra power draw from the engine.

If this is accurate it would be a downside of the device. For a normal rocket it is an identical operation to accelerate from 5 to 6 m/s compared to accelerating from a standstill to 1 m/s. For the Emdrive it is apparently more expensive to do the former.

The bigger problem, however, is that this seems to be impossible. Who is measuring the speed? Once you have a velocity term in your equations that goes from "meh whatever" to something that you absolutely have to know, and that's impossible to know! Lets say we are leaving Earth to go to Mars, as we transition from the Earth's sphere of influence to the Sun's sphere of influence the easiest/best frame of reference to work with changes, and thus the ship's speed changes. Let's say from 2 km/s to 34 km/s. That's a pretty enormous jump, but obviously the engine isn't going to suddenly start using 17 times as much power just because it passed over some invisible, arbitrary, and artificial dotted line.

This discrepancy means that the theory is obviously incomplete or flat out wrong. And the whole theory paper sort of has that feeling, that things are being misapplied in invalid ways (which is fine, if the theory was completely correct it would still feel that way, because the result is unexpected). If a couple people hadn't already started to experimentally verify the devices in a rudimentary way I wouldn't be giving the thought the time of day. And it's important to note that the early testing that has been done, while positive, is very much incomplete. I wouldn't be surprised at all if the next model being built is invalidated and we find out that experimental error had led to these devices.

The weak/controversial theory is why the Eagleworks (the NASA group) paper isn't touching the theory with a ten foot pole. They are looking only at the devices and their thrust, which is the right thing to do in this case, because even if the devices work, I'm guessing that the math for some of the effects (this one here) will be substantially different or better described than SPR currently does.

The other most eye-raising thing on the current theory is the Emdrive FAQ which states that the drive supposedly conserves momentum. Unless I am very, very, very much mistaken (which is entirely possible, something something special relativity) that's just flat out not true. They state that momentum is conserved because the increase in momentum in the waveguide (engine) is matched by a decrease in momentum from the electromagnetic field. This is true. But that momentum had to get into the electromagnetic field in the first place, that's where the momentum appears to have been created from nowhere. Because if the momentum was imparted by the microwave emitter (which is carried on the ship) and the momentum of the microwave emitter (carried on your ship!!!) decreases... Well, you don't have an engine as much as you have a spring.

So yeah, the whole thing just smells weird, and I have no idea how it hasn't been debunked yet. But it hasn't. We'll have to see if we can say the same thing in a year.

Robear wrote:

Yonder, doesn't the paper acknowledge that they are in a new situation, and their explanation is from first principles? Wouldn't it be expected to behave differently from reaction engines?

Yes, it is possible that everything is correct, and the development that needs to be made is a definition for how to determine the "correct" frame to do all of your math and stuff in. (Which you'll be able to verify by flying around and measuring how your power draw changes with your thrust and making sure it matches.)

It just... seems really unlikely that that's the way the universe works. It seems like that would disprove most of what we know about reference frames (or maybe not, maybe something something special relativity means everything is fine and I'm just confused).

I've seen reference - Wikipedia? - to at least three different theories on how the devices operate, so it's obvious that the researchers are groping.

I guess my question to Yonder is, what relationship do they claim between power and kinetic energy? That's what's not clear to me. What leads you to conclude that the kinetic energy of the system is *not* increasing?

Robear wrote:

What leads you to conclude that the kinetic energy of the system is *not* increasing?

If the energy of the electromagnetic field was increasing as the ship gained speed that would itself violate conservation of energy.

The way this device (allegedly) operates is by decreasing the energy of the field to increase the kinetic energy of the engine. If the energy of the field increased along with the kinetic energy of the engine, so that the field had more energy to match the greater energy costs of higher speeds, well then nothing is losing energy anymore, everything is increasing its energy.

But if the particles used for acceleration are appearing at a particular velocity and immediately used, wouldn't that meet the requirements of their frame?

Robear wrote:

But if the particles used for acceleration are appearing at a particular velocity and immediately used, wouldn't that meet the requirements of their frame?

I wouldn't try to use the various handwavy theories about quantum foam and whatnot at this point. The devices are using pretty basic electromagnetic principals when you get right down to it, there aren't any particles teleporting in or anything like that in the basic theory paper, just electromagnetic fields coming from a microwave resonator, bouncing around in a copper box.

What you are describing violates conservation of energy as well, incidentally. If a device is powered by particles which spontaneously appear in the device, are manipulated to perform useful work, and then vanish the you're once again creating energy from nothing. Or siphoning it from the bonds which secure an extradimensional demon or something.

A thought comes to mind from the discussion on not accelerating your fuel with you; that whole reference frame idea is really screwy, because if particles are popping up out of nothing and you're pushing on them, it seems to me that's implying an absolute reference frame, that they have to be at zero velocity with regard to something.

Since physics seems to go through any contortion required to maintain all frames as equally valid, and that rules out, to my understanding, any kind of universal frame, that would imply that this drive simply will not work, that virtual particles, if they do exist, can't be something you can push against, because that would imply an absolute frame they're related to. They would have to be at zero velocity for every frame simultaneously, and if any frame can push on them, that would be violated.

I'm sure I'm not fully grasping this, but it sure looks like it directly contradicts an awful lot of what we think we know.