EmDrive: Nasa paper has finally passed peer review | Hacker News Reader

EmDrive: Nasa paper has finally passed peer review

ibtimes.co.uk

87 pointsxbmcuser57 comments

TLDR: Now deleted forum comment by a scientist says that the paper "Measurement of Impulsive Thrust from a Closed Radio Frequency Cavity in Vacuum" has passed peer review and will be published in AIAA Journal of Propulsion and Power. A line of text was included that may be from the paper itself: "Thrust data in mode shape TM212 at less than 8106 Torr environment, from forward, reverse and null tests suggests that the system is consistently performing with a thrust to power ratio of 1.2 +/- 0.1 mN/Kw ()"

We have an ibtimes post referring a deleted comment on NASAspaceflight forum (not affiliated with NASA).

Guess it's best to wait for the actual publication.

What is a "Kw" ? Must be a typo?

1024 watts

You're thinking of the Kiwi, which is a base-2 measurement of watts.

It's obviously a typo

I suppose kW ?

Is that good thrust or not? I don't have a point of reference.

Depends on how well does it scale; here is some back of the envelope math:

If we take a Topaz reactor design and build a spacecraft say 10 times bigger than new horizons this gives us a mass of 5000 Kg.

We'll dedicated 2000 of those to the reactor and fuel, and 2000 of those to the instrumentation (this alone is 5 times the dry mass of New Horizons) and 1000 KG for the platform/chassis. A Topaz reactor weighs around 300KG, let's say ours weights 500 because we want to be able to swap fuel in and out and we want to make sure it generates 5KW of power. It can operate for about 5 years on 15 KG (12 in the original design) of fuel which in this case is UO2 gas (spent fuel might be used as propellant so we might be able to have a secondary Ion drive cycle to maximize the thrust we get but won't use that in our calculations) this means we have fuel for 100 years.

4 of our 5KW would be dedicated to our propulsion system which would give us a ~4.8N of force which at a mass of 5000KG means we get 0.00000096 m/s2 of acceleration.

Given V=V0 + at after one year or 31622400 seconds accelerating at 0.00000096 m/s2 we'll have a velocity of 30.357504 m/s after 50 years our velocity would be 1517 m/s or about 10% of Voyager 1 and 2.

So yeah not so great unless we can scale it much much better, that said if we do figure out the physics behind it we might be able to design more efficient emitters with considerable better thrust to power ratio.

[0]https://en.wikipedia.org/wiki/TOPAZ_nuclear_reactor

Did the math on a hobby plane. came out 21N/KW. about 10k times less powerful. of course a prop plane work in air and an emDrive changes physics.

I've been doing some reading on this recently, and as far as I understand it, this paper is not going to settle the matter one way or the other. IANAP so take these notes with a grain of salt.

There was an experiment done by a Chinese lab a few years ago, which seemed to support the effect, but when they re-did the experiment using an on-board battery instead of a power cable, the effect disappeared.

So far noone has publically replicated this condition (i.e. battery instead of power cable), and either confirmed or disconfirmed this null-result, and I do not think this new paper will report any experiments using this condition either.

There are however efforts underway to actually put one of these things into space in the form of a tiny satellite, and see if any thrust is produced there, which seems like the perfect experimental setup.

All in all I think it is going to be years before we know what is what in regards to this technology.

> There are however efforts underway to actually put one of these things into space in the form of a tiny satellite, and see if any thrust is produced there, which seems like the perfect experimental setup.

Wouldn't this have the problem that the object will constantly being hit by particles (and the distribution of particles will not be random) and accelerated by these?

yes but they can use data from pioneer to correct for it, especially if they are far enough from earth, also if the drive can be cycled, they can measure against the condition at rest.

"...There are however efforts underway to actually put one of these things into space in the form of a tiny satellite..."

Neat. Got a link for that?

The Cannae Drive is another implementation of the same idea. They say they'll launch a cubesat in a couple of years to demonstrate the drive. Their website doesn't have much information about it but here are some links:

1. http://cannae.com/cannae-is-developing-a-cubesat-thruster/

2. http://cannae.com/press-release-from-cannae/

3. http://cannae.com/cubesat/

This paragraph made me laugh.

> Eagleworks is an experimental lab that is to Nasa essentially what the secretive Google X "moonshot" R&D lab is to Google/Alphabet

So Google is the gold standard for R&D now?

Not to mention that NASA made the first ever "moonshot" actually happen.

A term that's since been cheapened for the purposes of good PR.

That was the bit that made me really facepalm. It's one thing to compare to something more familiar but it's sorta sad when you need to use Google or something like that to explain what a "moonshot program" is in reference to NASA.

An Stanford/Thurman not Google created the autonomous car. I don't really call commercializing an existing technology innovation. Don't get me wrong introducing an autonomous vehicle to market will be a great achievement but still not "put people on the moon using a government bureaucracy" kind of jaw dropping.

An older discussion on HN about an experiment that was unable to replicate the effect when using batteries

https://news.ycombinator.com/item?id=12007877

Couldn't you connect the battery by the cable and get the effect back?

Almost as interesting, its reported/discussed that light entering the EmDrive chamber via laser appeared to have travelled superluminally thought to be due to some distortion of the light cone inside the chamber.

Thread: http://forum.nasaspaceflight.com/index.php?topic=36313.1860

FTFA :

"The work we're doing is difficult and expensive and the people paying for it don't necessarily want to give it away to the rest of the world, but EmDrive will make a huge impact and a lot of people have thought of a lot of things to apply it to," he said.

I hate this world sometimes...

The approach and the lack of (yet) a convincing theory reminds me of the E-Cat http://www.e-catworld.com/

In the end what matters most is if they work. For the EmDrive to succeed it's enough to be a better fit for some use cases than other engines.

At least E-Cat didn't initially claim to violate any fundamental laws of physics. The unnamed "aerospace company" he says he is working with will never see their money again.

Old-style science is apparently dead. Imagine if Einstein created General Relativity today, but (in keeping with the times and contrary to everything we know about Einstein) realized the commercial potential of the ideas before submitting his paper for publication.

Or the quantum theorists of the 1920s -- imagine that they somehow foresaw all the commercial potential of these ideas, before publishing the broad outline of theories that essentially define modern times.

This is not to suggest that the EM Drive will necessarily pan out as some of its adherents are claiming, only that the old, pure-research tradition of publishing everything in advance of any consideration of applications seems to be dead.

Old-style science was not as expensive as new style science. If a team does something for commercial gain then it becomes publically accessible 20 years later when the patents expire. Probably sooner if people ignore the patents or find a way round them. The worst case scenario is that they sit on their invention and do nothing about it. The best case is that they create a new viable industry. Either way, eventually the technology will become available to everyone for free. If there was little incentive to develop these ideas then fewer people would bother and this tech may only have been invented in 100 years time.

"it becomes publically accessible 20 years later when the patents expire" I'm about 90% sure this is the opposite of how patents work. You describe the methods in the patent, and in exchange you get to use or license it for the duration of the patent. It's publicly accessible but not usable, which is a useful distinction. Without patents there wouldn't be an incentive to disclose.

The theoretical ideas are still out here. It'd be more if someone figured out a way to do GPS (with relativity issues solved) and decided to keep that secret.

Bit of a devil's advocate for patents too. Sure, you can't build the exact same thing for a while, but at least the principles are revealed.

There were many inventors/scientists in that era who developed things in secret or patented the heck out of their work, such as Edison or Tesla.

The analogy is not quite right for General Relativity, but this EmDrive thing is not at the same level either.

"People think it's black magic or something, but it's not. Any physicist worth his salt should understand how it works, or if they don't, they should change their profession."

This got me thinking about The Emperor's New Clothes. Be it that I'm not that bright to fully grasp how the RFRCT might actually function, the king is still naked to me.