"EMDrive Works" Topic

Appears a number of independent studies seem to verify original claims that EMDrive works:

link

I certainly hope they're right, since I'd like to see a bit more space exploration in the near future.

That really is fascinating. I hope it proves correct--and practical!

I'll believe it when the Discovery arrives in Jupiter orbit. If it works, build a practical demonstrator and test it.

If you dig through the links in the linked article there is a link to an article about work done by at Plymouth University which is the first good theory on how this is actually working. Still skeptical but interesting stuff.

-Will

Encouraging! This and the Canae Drive seem to keep passing tests and scrutinies set by skeptical minds. They must do so, of course, before someone can ever sign off on a spaceborne test. But I think that is coming ever closer…

I'm quietly giggling at the stuck-in-the-muds that keep screaming that reactionless drives are: A. Impossible B. Heresy C. The work of Satan himself. And yet it moves, people.

I can hope that a certain blogger, who refuses to acknowledge drive tech has moved beyond the Tom Corbett atomic zoominator 5000, will be melting down with spluttering denial sometime soon… ;)

But why is this in the Science FICTION forum?

Doesn't fit on the Ultramodern boards. Full of Tango's rage-bait.

This sent me of on some google work (I'd never heard of Unruh radiation, but it appears to be a (theoretical) thing: link . Also the "flyby anomaly": link )

I found this, somewhat more sober-minded article as well: link

So while, yes, this theory has enough real physics in it to be plausible and worth examining, it's not the end of the question, nor is the movement effect completely unattributable to measurement or apparatus error. It's just too early to declare "it works!"

But it's also too early to declare "no, it doesn't!"

There is a Science Board.

Yes, but many interested TMPers probably avoid it, due to the continued political squabbles that invariably erupt on it.

Of course, a fuel-less space drive on the order of Star Trek's "impulse engines" is a staple of science fiction, and thus a perfect point of entry dor this topic. Not to mention that such a drive could be a ready weapon system ("Any sufficiently advanced technology is indistinguishable from a really big gun."— Howard Tayler, Schlock Mercenary schlockmercenary.com ). SO one can certainly extrapolate from the science to the SF wargaming possibilities.

After all, the board is "Science Fiction."

I remain skeptical, but am more than willing to crack open a bottle of my finest if they can make this work.

As far as being on a science fiction board…

Most true science fiction attempts to take modern science and technology and extrapolate it forward.

As opposed to Science Fantasy, where stuff works because it allows Luke to leap over tall buildings in a single bound.

IF this adds to our current understanding of science and technology base, it now resets the point of extrapolation forward.

For instance… some games out there actually use reaction mass spewing engines on their futuristic designs.

If (and it's a big IF) EM drive works, it's almost absurd to think anyone would be using reaction-mass engines 300 years from now.

This is so far from any practical application it is, almost, unremarkable.

> If (and it's a big IF) EM drive works, it's almost absurd to think anyone would be using reaction-mass engines 300 years from now.

Efficiency – this drive may work but unless it works better than existing drives it will not be used. So what if it does not require reaction mass but requires an "engine" 100x larger. Heck, solar sails have been proven to work (and are in effect reactionless, yeah yeah, I know) but are limited in application.

Yes, this belongs under science fiction since if the drive works (still a big if) then it will inform possible speculative fiction.

I'm still skeptical since there hasn't been tests to rule other sources of the thrust (like copper ablation), and until the article from Plymouth U. no one had really put forward a plausible reason as to *why* it worked (and not everyone agrees with that article). I'm also skeptical since the Chinese study keeps getting cited as proof, but my understanding that other than *also* producing apparent thrust nearly none of the other results matched.

All that said, there's been no smoking gun to show that the thrust measurement is erroneous. So testing must continue.

-Will

???!!!??? Dynaman ???!!!???

It's a propellant-free drive.

The single biggest issue in space propulsion is mass. A rocket not only must push the mass of the ship and the payload, it must also push the mass of its own fuel— specifically, propellant, which is mass that it is essentially THROWING OUT THE BACK in order to move! That's how you get thrust in a rocket— you take some stuff and throw it out the back of the rocket. The greater the mass and the greater the velocity at which you can throw it, the more thrust you get. BUT most of that thrust is being used just to move the mass of propellant you are going to throw out later! And once you run out of stuff to throw out, you can't accelerate any more (except by gravity).

But the EM drive, assuming it actually works as advertised (a big if), DOESN"T require the ship to carry ANY propellant (aka "reaction mass") AT ALL. The only thing it requires is a power source to generate electricity for the drive. As long as it has power, it can accelerate FOREVER, limited only be relativistic effects. And all it has to move is itself and the payload. So for the drive you have the drive itself— which is essentially a big engine nozzle with some electronic component— and the ship's power plant, which you need anyway. I don't know where you get the idea this all has to mass 100x the mass of standard reaction mass rockets (even nuclear ones), but there's little reason that it would. Plus, with a standard reaction mass rocket, the further you want to go, the more reaction mass you have to add at the start. You wouldn't have to add any for an EM drive. Power plant fuel (whatever it is), maybe, but that's a lot less potential mass than any meaningful amount of propellant.

As for solar sails, they are very mass restricted on payload, plus there is a fall-off of acceleration as the sail moves away from the sun (or any star)— the farther away from a star a sail is, the fewer photons strike the sail. By the time a solar sail reaches Jupiter, the photon pressure is about 1/4 of the photon pressure around Earth. Any interstellar solar probe is strictly that— a probe. Manned solar sailing beyond our solar system (or even as far as Saturn's orbit) is highly unlikely. But an EM drive could easily go interstellar.

Of course, as it stands now, I don't think an EM drive is going to give you any "zippy" maneuverability or a quick start. For that, I suspect some sort of reaction mass propellant would be necessary, should any rapid course adjustments be ordered. But space travel isn't about jackrabbit starts or sharp turns; it's about going a very long way at very high velocities over a very long time. In this case, slow and steady really does win the race.

This is so far from any practical application it is, almost, unremarkable.

> If (and it's a big IF) EM drive works, it's almost absurd to think anyone would be using reaction-mass engines 300 years from now.

Efficiency – this drive may work but unless it works better than existing drives it will not be used. So what if it does not require reaction mass but requires an "engine" 100x larger. Heck, solar sails have been proven to work (and are in effect reactionless, yeah yeah, I know) but are limited in application.

The caveat on all this is IF it works…

Note the point where I said 300 years in the future… if we can even prove the concept is viable now… in 300 years this or something else will have replaced reaction drives for in-space applications.

As far as 'efficiency' – well that depends on your definition.

If you accept:

Efficiency = (Total Delta V) / (Mass of Propellant and Fuel used)

You can see that reducing Propellant to zero and fuel to very little (a couple of grams of Uranium) would send your efficiency skyrocketing. [Pun intentional]

In the end, if it can produce really ANY net thrust without use of propellant, it would make reaction drive obsolete for just about anything except for reaching orbit.

Not to mention that since this effectively 'breaks' the current understanding of physics, proving it works might open the door to all sorts of amazing (and potentially frightening) stuff.

Nothing (even in the vacuum of space) works in a vacuum. If the drive is not efficient enough to overcome gravity it is worthless. Over a long enough trip a reactionless thruster always wins, but if it takes 20 years to start moving an object at 10 miles an hour vs where it started it is not much more than a curiosity.

> In the end, if it can produce really ANY net thrust without use of propellant, it would make reaction drive obsolete for just about anything except for reaching orbit.

Only if it gets stuff to other places in a reasonable amount of time. Sure it never stops but if it barely goes in the first place. Most of the fuel for getting anywhere in the solar system currently is for getting off the planet. Use up that much more to get a possibly massive engine up in space may very well be a waste.

Repeat experiments are good sign, but there is a spectrum of possabilities to all this:
1)Its probablem with the experiment, though that possibility is getting smaller the more experimental work is done
2)Its a bench-top anomaly, which appears resistant to scaling up and real world application, becoming an esoteric oddity for some bored theoretical physist waiting for machine time at CERN Mk3 to figure out in the bathroom…
3)Its works, but has fairly serious theoretical or engineering limitations – like only useful for low thrust applications such as probes or keeping satellites in there orbital tracks.
4) It's a fully scalable reactionless drive, but I'm still not happy, where's my 'warp' drive!

Dynaman, we seem to be miscommunicating here.
Rocketry is all about the concept of specific impulse
The "specific impulse" of a rocket engine is the total amount of momentum change per unit of propellant consumed. The higher the specific impulse, the more efficient the rocket.
Here's the deal with the EM drive as presented: it consumes no propellant. Thus, its efficiency is effectively infinite.
Furthermore, the change in momentum is acceleration, which means the velocity is constantly building up.
Our current rocket systems— all of them— rely on throwing a lot of mass out the back over a very short time and then, essentially, coasting the rest of the way, saving a smaller amount of rocket mass to slow down once we get where we're going. It's like getting in your car, pointing it towards you destination, slamming on the gas as hard as you can for ten seconds… and then taking your foot off the gas, and letting the car roll the rest of the way. Granted, you're not slowing down (much), but your top speed is your top speed, and you gain it very very quickly… and then can't change it at all for days, months, or years, depending on how far you're going.
But a propellant-free drive is like getting in a car, and very gently, very slowly, pushing down the gas pedal… and never stopping to continue that very slow pushing. Let's assume you have a meager acceleration of 1m/s^2— a tenth of Earth's gravity. In the first second, you move 1 meter. In the second second, you move 2 meters, in the third, 3 meters, in the fourth, 4 meters, and so on. One hour after starting, you're travelling 12,960 kph (over 8,000 mph, roughly 1/2 of what's needed for LEO, btw) AND YOU CONTINUE TO INCREASE AT THAT SAME EXPONENTIAL RATE, without EVER having to take your foot off the gas. By the time you reach midway to your destination, you're far exceeding the speed of the "stomp the gas and coast" guy, and have left him way back in the cosmic dust.
Space is very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very… very big. And that's just to get to the Moon. The problem actually isn't so much in getting to orbit— we know how to do that. The problem is getting to someplace interesting in a reasonable amount of time. (And, of course, minimizing that same time for health reasons, as reducing the chance of being caught in a solar flare, etc., etc..) So a propellant-less drive isn't about getting to Earth orbit, it's about getting to other planets and even other stars as rapidly as possible. Our current "get us to orbit" rockets can barely do the former (a manned Mars mission could potentially take years), and cannot possibly do the latter AT ALL.

(By the way, in the thought example above, if the car were a spaceship, with an acceleration rate of a measly 0.1g (1m/s^2), it could be halfway to Mars orbit in about 5.5 days, and arrive at the planet* (assuming deceleration) in a little over 11 days total. On a flyby, it would zoom past Mars orbit in a little over a week.)

*I'm using the average orbital distance and ignoring orbit location, matching orbital velocities and such, which for the purposes of this general calculation and the acceleration rate of our carrocket aren't significant.

I'll put it another way, if this thing gives off such a small amount of thrust that it may very well be nothing more than an error in the instruments then it most likely does not have enough power to be practical as an engine – even if it does not require reaction mass.

That's two different things.

If it's an error in the instruments then Newton still rules and all remains boring.

If it's a tiny thrust, no matter how slight, the impact on physics WILL be HUGE. Even a tiny thrust would make it the first feasible interstellar engine.

What you seem to keep missing is that current flight profiles for ANY interstellar mission are on the order of decades. Having an engine that could produce even minuscule thrust for decades instead of a high thrust for days would be revolutionary.

Doesn't matter how you put it, Dynaman, your understanding is flawed. You're thinking in terms of constant velocity, when what is relevant is constant acceleration.

Let's get down to some brass tacks, here:
Mass of empty Space Shuttle: 75 metric tons
Mass of Shuttle fuel at launch: 1717 metric tons
Burn time to empty: Around 6 minutes.
Max velocity (LEO): around 17,000 mph.

Mass of current "truck bed" nuclear power plant, 30MWe range: 100+ tons
Operational life before refueling: 10-25 years
And of course we don't need that kind of wattage output to power our drive or our craft's systems! In fact, we already have concepts for nuclear fission plants for spacecraft, and small ones have been used in the past.
So, effectively, our hypotheical 0.1g "EM" drive hooked up to one of these things could fly with non-stop acceleration, and reach LEO speed in less than two hours… and then continue accelerating.

Now, the lab model is around 100µN, or 0.0001 Newtons of force, which is roughly 0.00001g. Yeah, that's damn faint, as forces go.
Effectively, it's 0.0001 m/s^2, or 0.1mm/s^2. But it's still acceleration.
At one hour, it's going 1.296 kph. At ten hours it's going 12.96 kph. At 100 hours (4 days or so) it's going 129.6 kph. At 1000 hours (about a month and a half), it's going 1,296 kph. At 10,000 hours (a year and a third, give or take), it's 12,960. At 10 years (the low-end fuel life of a fission plant), that would be 113,604 kph— That's just the bench-top, lab scale model!
Now, let's say they can get the force up to 10µN. Still faint, but now it's 1 hour=129.6 kph, 10 hours=1,296 kph, 100 hours=12,960 kph, 1000 hrs= 129,600 kph… Go up another factor of 10 to a full micronewton and you get the same enhancement.
So, yeah, it's a BIG HAIRY DEAL on the rocketry side of things, if this thing actually works (big if).

The proposed theoretical framework at the very least seems to be leaving critics unimpressed, to say the least:
link

Mathematicial physicist John Baez was less diplomatic at his g+ feed and can be quoted saying that

this paper is a stew of nonsense served with a hefty helping of warmed-over baloney

Still not too keen to hold my breath until I can book a tourist flight to Alpha Centauri.

John Baez has been a long time critic of the EM drive – so is unlikely to be swayed. I also note he seems best known for his internet presence rather than his science.

And Mike McCulloch appears to have hitched the EM drive to a personal hobby horse, though his paper is peer reviewed, which looks somewhat left field. My gut instinct is it may well be cobblers, not every scientist 'battling' the mainstream turns out to be right, on the other hand I'm no physicist!

There appears to be a bit of an issue that the experimentalsists are finding it difficult to publish observations in peer reviewed journals in the abscence of theoretical underpinning – And I can't help but wonder whether some of the critism from theorists is down to them usually making the running with experimentalists confirming their theoretical models rather than them having to come up with something to explain the observations of experimentalsists….

Also funding appears to be issue, which will only really cease once a crtical mass of positive data has been accrued.