Spaceship Engine “EmDrive” Actually Works, Leaked NASA Report Reveals | Hacker News Reader

Spaceship Engine “EmDrive” Actually Works, Leaked NASA Report Reveals

thedrive.com

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This is now two layers of garbage clickbait.

The article links to:

http://www.nextbigfuture.com/2016/11/new-nasa-emdrive-paper-...

which links to:

https://drive.google.com/file/d/0B7kgKijo-p0ibm94VUY0TVktQlU...

which is a year old and basically says "more work is needed to rule out mundane sources of error like thermal expansion".

If there was a new published paper anywhere, it would be significant but there isn't. This is just a work in progress with any number of corrections to be made (NOTE: in 12 months, no one has submitted this leaked paper).

Even if it does work, it's less propulsion than an ion drive.

Your final sentence puzzles me. If it works, then it's new physics. That's tremendously exciting, no matter how little thrust it produces. Especially since this is a device built without the slightest clue of how it actually works, so thrust could no doubt be increased dramatically once there's a good theoretical foundation behind it.

Of course, the fact that it represents new physics is also why the smart money is on it being some sort of measurement error.

I'm confused how this was presented by someone 10 years ago, and with all the researches out there, no one has yet replicated or refuted his work, and NASA is the only one doing it... 10 years later?

The supposed effect is so small that it's extremely difficult to distinguish it from potential confounding forces, like air currents or magnetism. Sufficiently precise experiments require sophisticated equipment, so not many researchers can try it. Even with really good equipment, it's hard to tell if the measured force is real. The work has been replicated and refuted many times, but never conclusively.

Leaked from fall of 2015. I feel like we've already discussed this since then.

The fact that it works is surprising (and I'm still not convinced until we are actually in space testing it), but also, 1.2 newtons per megawatt is... not a lot of thrust. But the fact that it works at all still the shock.

"1.2 newtons per megawatt is... not a lot of thrust"

If I recall the previous conversations correctly - the amount of thrust is irrelevant, because in space you continually apply that thrust over time, and eventually reach ridiculously high speeds?

The amount of thrust is relevant if something like ion drives gives you more thrust for the same power.

Of course, with something like an ion drive, you're throwing mass out the back, and eventually you run out of mass. (On the other hand, eventually you run out of the ability to generate power, too...)

[Edit: The bigger picture is that, for this to work at all, there probably needs to be some kind of new physics here. If there is, this device probably only exploits it by accident (no matter how much the inventor may think he knows what's going on). Once we figure out what the new physics is, newer devices may be much more efficient.]

If you're generating multi-MW in space, you have to do something about all that heat anyway so I'm not sure this is an improvement over an ion drive.

That said, yes, the important thing is that this potentially indicates new science, which is exciting. When we understand it, we can likely improve the efficiency greatly. Assuming the effect is real.

Since there's no drag the thermal system isn't as constrained in space as it would be for a car or aircraft. If you assemble the final spacecraft in orbit, all that matters is mass so you can create very high surface area radiators that are extremely efficient as long as they're a few AU from the nearest star (or pointed in different direction). It'd probably be as big or bigger than a solar sail but it would use the sails to emit photons instead of absorbing them and itd work far from any star.

That's actually really clever!

Isn't the important thing from a practical perspective (agreed that the new science aspect is more interesting) that if proved this has near infinite specific impulse? (As bizarre as that sounds)

From an interstellar transport standpoint, that would seem a game changer. At minimum, slipping the bounds of the rocket equation and being able to accelerate an endlessly looping hulk to closer-to-c velocities seems fascinating. I'm curious what the specific impulse numbers look like given the hypothetical conversion rate on this powered by pure fusion.

It's an order of magnitude higher than a laser sail which is part of NASA projects for some missions. So that already makes 1.2 N/MW pretty good.

Also, remember that the EM drive doesn't need to carry combustible fuel to work, it could do with a fusion reactor in the future and that would save a lot of mass in the spaceship.

How about the ability to dissipate that much heat? I imagine it would be an issue in vacuum, but I don't know much about space technology, just a guess.

Allow me to introduce you to the intergalactic crock pot. The most tender roast beef you'll ever taste, by the time you exit the solar system.

I'd imagine if it is real we'd be able to increase the effieciemcy. It seems unlikely we stumbled onto the optimal design.

Wouldn't really help to test it in space unless you can do a better job in space of controlling error than on the Earth. It seems unlikely you'd be able to control for error better when you don't even have physical access to the experiment item. There are myriad of forces acting on objects in orbit, even interplanetary. Remember the Pioneer anomaly?

NASA haven't validated this http://blogs.discovermagazine.com/outthere/2014/08/06/nasa-v...

Everyone go back to something meaningful.. like the election :p

The paper in question: https://drive.google.com/file/d/0B7kgKijo-p0ibm94VUY0TVktQlU...

The leaked report:

https://drive.google.com/file/d/0B7kgKijo-p0ibm94VUY0TVktQlU...

Garbage article. Just a clickbait review of the article over at http://www.nextbigfuture.com/2016/11/new-nasa-emdrive-paper-....

Garbage article. Just a clickbait review of the paper over at https://drive.google.com/file/d/0B7kgKijo-p0ibm94VUY0TVktQlU...

So, someone more clever than me do the math: Can I take some solar panels, and a few of these babies and head on over to Mars? Or is this still impractical given the "micronewtons per kilowatt" levels we're talking about?

Assuming you and your ship weights 1kg, it would take 9.8 gigawatts just to get it to hover in Earths gravity.

This is roughly half the solar output of Germany at noon or about the same energy as the Space Shuttles boosters. Basically, if these engines prove out, they will only be used in space.

Its only usable outside of any serious gravity wells, e.g. for interplanetary and possibly intersolar travel. They would replace uses currently postulated for solar sails. Not sure, but it may also be suitable for use-cases currently postulated by small ion-thrusters as well (especially where weight is critical).

It would be useful once you're in orbit, even deep in gravity wells, if you're patient. For example, a geosynchronous satellite with a drive like this could be launched on a rocket just big enough to get it to low-Earth orbit, and then it could gradually take itself the rest of the way. But it won't be replacing traditional rockets for that initial launch unless it's possible to increase its thrust by many orders of magnitude, and that initial launch is really the hardest part of doing space.

So you're saying it's possible then?

And yes, I mean after I pay SpaceX a large sum of money to get me up into orbit. Hovering with these would definitely be a bit overbudget. I guess my question is whether a few micronewtons per kw adds up to a viable means to travel in space, or is it more like just enough to keep the satellite in orbit indefinitely?

Once you have your spacecraft in orbit around Earth, you only have to overcome the the remaining drag of the upper atmosphere, the solar wind in case you are going towards the sun and maybe a couple of other [small] effects I am missing. But once you have enough trust to not slow down due to those effects, it just becomes a matter of time. Keep circling Earth, accelerating with whatever tiny surplus trust you have available and eventually you will reach escape velocity and off you go.

The papers [1] says on page 33 that the measured performance is more than two orders of magnitude better than light sails. Given that light sails are more or less considered a viable technology, it seems quite reasonable that you could get this working if you could manufacture huge and light enough solar cells.

But I personally would not hold my breath - if I had to decide between quite radical new physics and measurement errors, I would certainly pick measurement errors. It seems way more likely that this is a case of faster than light neutrinos than the key to interplanetary or even interstellar travel.

[1] https://drive.google.com/file/d/0B7kgKijo-p0ibm94VUY0TVktQlU...

I vaguely remember the inventor's theory on how it worked. It's an artifact of the speed of light being constant in all reference frames. If there is a pressure inside the chamber, intuitively the outside net force would be zero. But with light it's different due to the constant velocity. If the pressure was caused by little particle bouncing against the chamber walls, their velocities would counter each other as they bounced the chamber around. Velocities with light don't add that way.

I may have gotten some of it wrong, but that's how I recall it.

Reported thrust to weight ratio is 360 times raw photons:

http://www.wolframalpha.com/input/?i=(1.2+mN%2FkW)%2F(1%2F(3...)

I spent a little time evaluation some form of quantum resonant enhancement of pair production as an explanation, but not enough to make any claims. The pilot wave / ether theories suggested in the conclusion seem highly unlikely. I'm also still holding out for weird RF coupling - those Q factors are so high.

I love this type of science. It's completely, totally impossible... until we learn about how it works and the mechanics behind it. Maybe this type of drive just previews a new discovery?

For most results like this, it turns out to be an experimental mistake. That's how the phrase "extraordinary claims require extraordinary proof" came about.

I'll believe it when I see a small spacecraft propelled by it (even if the entire spacecraft is the engine), but I think it's an experiment that should (and could) be done soon.

Seem like it's already in motion by USA and China

http://www.ibtimes.co.uk/space-race-revealed-us-china-test-f...

What "leak"? It's on the NASA Eagleworks Facebook page and there's a press release.[1] NASA has an in-house fringe science operation in case something actually works.

[1] https://www.facebook.com/eagleworksnasa/

Technology presentation: https://vimeo.com/channels/Emdrive

Inventor website: http://www.emdrive.com/

I wanted to understand the context. Does my analogy correctly approximate the claims?

The power of 100 100 watt bulbs applied towards pushing a 1 kg object 1.2 millimeters.

It says 1.2mN of force per kW. One kW would be 10 100 watt bulbs. So for as long as you apply that amount of power, you get that amount of force. And because force = mass times acceleration, your 1kg object would be accelerated at 1.2mm/s^2 - meaning its velocity would increase by 1.2 millimeters per second, each second, for as long as the force is applied. So, run it for 10 seconds and then turn it off, and the object would be moving at 12mm per second, for instance.

That is in absence of any counter-force, such as would be applied by friction or air resistance. Practically those would overwhelm the tiny force from this drive, which is why it's only really practical in space.

Thank you for catching my conversion mistake. Also the helpful description

I recall that some group was planning to put one on a cubesat and see what happens.

Take that, physics!

The going theory for why this works involves physics of the ether, something science has pushed into a corner and forgotten over the last century. Louis de Broglie would likely be disappointed it took us this long to realize what he postulated so long ago. I would also note that Faraday was running experiments late in life trying to dig up some experimental evidence for this hypothesized force, albeit by dropping bismuth chunks from a tower into a pillow.

http://www.helsinki.fi/~aannila/arto/emdrive.pdf

The PDF you linked to looks like crackpot work to me. I just skimmed it but it is written in a style very different from serious [physics] papers.

Sorry to crush your dreams bud:

https://en.m.wikipedia.org/wiki/Michelson–Morley_experiment

Don't speak for my dreams. I made zero comments regarding whether I think this is true or not and only provided as much info as I had on it. To have you comment in this way with some lame ass link is likely a sign of conflict within yourself.

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