NASA Confirms The Plausibility of Reactionless Drives??!!

Ace of Spades HQ ^ | 8-1-2014 | Ace

[servo1969]

Let me geek out on you (I love science) and explain to you the science (I love science) and why this had previously been confined to the pages of science fiction (I am a nerd; and oh Dear Sweet Bunsen-Burner Lighting Lord, do I love science).

So it's a pretty firmly established principle that every act causes, and requires, an equal and opposite reaction.

If I understand this right (did I mention I love science?), this means that any space vessel will have to carry with it an enormous amount of reaction mass.

You can't -- we think, or thought -- just push energy out the backside of a spaceship and make it go voom. (Voom is a term that we who love science use.)

You have to actually impart momentum to physical mass -- a gas, for example. You spurt the gas out of the back of the spaceship. The gas is going backwards quickly, which makes the spaceship go forwards.

Without actually ejecting mass in the opposite direction you want the spaceship to go, we think -- or thought (those of us who think about science because, oh right, we love it) -- you have no propulsion at all.

So this means that the various spaceships you see in movies are all wrong. (All wrong is a scientific term.) A real spaceship should have tremendously large tanks of reaction mass, which it uses in flight to propel it. The proportion of "tank" to actual ship should be enormous -- the actual ship part of the ship would be tiny.

Basically a real spaceship would be an enormous series of gigantic tanks, with a tiny little cockpit/living space somewhere on it like a pimple. (Pimples are small oil-filled sacs in the epidermis -- That's science!)

Not only does this look goofy, thus destroying our dreams of sleek spaceships, but it imposes considerable, considerable engineering challenges on spaceship design, as the ship would be something like 90% reaction mass.

You'd have to carry around that much mass-- and when you tried to propel yourself, you'd have to accelerate that much mass, and of course all that mass doesn't wish to be propelled and will resist you. (We call that resistance-of-mass-to-acceleration "inertia" -- now there's some deep Science for ya.)

All told, it would be so, so much easier if we were disburdened of this very inconvenient law that only a mass being ejected from the rear of the ship could propel the ship forward.

This is why science fiction often postulates "reactionless drives." The term describes a hypothetical, fanciful drive system which does not require mass to be ejected from the ship, but instead just pumps out energy.

Or something. Writers are rarely detailed about it because it's just silly.

This is -- or was -- widely believed to be simply impossible and a very silly, if nonetheless pleasing, background conceit of science fiction.

Or science fantasy, really, when you take into account a reactionless drive is physically (or should I say physics-ally) impossible. (Did you see that? That was a science joke.)

But is it impossible?

Short answer: Yes, it's impossible.

Long answer: But maybe not.

Nasa is a major player in space science, so when a team from the agency this week presents evidence that "impossible" microwave thrusters seem to work, something strange is definitely going on. Either the results are completely wrong, or Nasa has confirmed a major breakthrough in space propulsion.

British scientist Roger Shawyer has been trying to interest people in his EmDrive for some years through his company SPR Ltd. Shawyer claims the EmDrive converts electric power into thrust, without the need for any propellant by bouncing microwaves around in a closed container. He has built a number of demonstration systems, but critics reject his relativity-based theory and insist that, according to the law of conservation of momentum, it cannot work.

...

[A] US scientist, Guido Fetta, has built his own propellant-less microwave thruster, and managed to persuade Nasa to test it out. The test results were presented on July 30 at the 50th Joint Propulsion Conference in Cleveland, Ohio. Astonishingly enough, they are positive.

Now I gotta tell you: Frankly, I think this is all an error, and it will soon be disproven. I think there's some artifact going on here, something no one is checking.

I think it is true, and will remain true, that you have to shoot propellant out your rear to go forward.

But this does have one nice effect:

You can now read science fiction stories postulating reactionless drives and consider them plausible, rather than fantasy.

For now.

Until they disprove it all.

Thanks to various members of the blog's I Love Science/I am a Nerd team, @conarticritic, @rdbrewer4, and @comradearthur.

[DManA]

A better example would be the Wright Brothers. There actually was some theoretical debate about whether heavier than air flight was possible.

They actually pushed the boundaries of science and practically invented the science of aerodynamics.

[FredZarguna]

Yeah, these kind of comments, like the well-known claim that Bumble Bee flight “violates the laws of aerodynamics” drive me nuts. The Chinese had rockets as far back as the 7th century, and rockets have been used in warfare for nearly a thousand years. Nobody thought Goddard’s ideas were kooky in the least.

[Johnny B.]

Nobody seems to be bothering reading the actual paper:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140006052.pdf

Among the interesting facts from the paper: The measured thrust was only about 0.0001 ounces. They put the device in a vacuum chamber, but never bothered to actually test it in a vacuum. Most significantly, they build a "null" device, intentionally built to not produce any thrust, but that also appeared to show thrust. This is a strong indication that there is a systematic measurement error in their setup.

[DaBeerfreak]

Clarke’s Three Laws are three “laws” of prediction formulated by the British writer Arthur C. Clarke. They are:
1.) When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.
2.)The only way of discovering the limits of the possible is to venture a little way past them into the impossible.
3.)Any sufficiently advanced technology is indistinguishable from magic.

Nothing is “impossible”, there’s only stuff we haven’t tried yet....

[Pontiac]

Where does the electricity come from? At best perfect nuclear conversion of mass to energy.

Really nuclear power has been used in powering satellites for decades but are low powered reactors in the 10 top 500 kWatt range.

The problem that will have to be dealt with for a nuclear power plant to power such an engine is waste heat. The small size of the past and present space reactors made the waste heat easy enough to deal with.

The only method of disposing of waste heat in space is radiant heat. Some sort of enormous heat radiator will have to be developed.

[reed13k]

I’ve always wondered if instead of requiring a large reactive mass by pushing, instead we tried to pull and push. What I mean by this is have a collector up front that pulls in light, particles, background radiation energy like a vacuum... it could be partially or wholly passive and then funnel it through a nozzle on the back end.

This should create a positive force in the forward direction though incremental energy pressure differential, but it would have the potential of limiting or eliminating the mass required to be carried for fuel.

There may also be a means of attraction through gravimetric force if willing to add significant mass to the vessel to increase attraction of particles - diverting them from the mass and aft of the vessel.

I see from some of the latter posts the geometric ideas in this proposal and see a similarity with lift on wings.

[RebelTex]

ROTFLOL

Captain, the tribble with troubles (hic) is they drank all me scotch.

[60Gunner]

Ah, Space Battleship Yamato...

[publius911]

Most significantly, they build a "null" device, intentionally built to not produce any thrust, but that also appeared to show thrust. This is a strong indication that there is a systematic measurement error in their setup.

I always regret that the non-technically leaning readers will miss the significance of that statement.

This is an example of true classic science. An essential part of true science demands a second step; try to devise ways to explain or disprove the original theory.

[sten]

I’m not a physicist, but what if you had two microwave emitters mounted opposite sides of a box pointing to a front panel and emitting opposite waves. each wave would bounce towards the other emitter and get cancelled... but the bounce point would receive the energy.

if that worked, then just have loads of paired emitters on the inner walls to increase the force on the front wall.

I believe this would eliminate the opposite reaction when the bounced waves would normally hit the back wall, nullifying the forward momentum. if so, then the forward momentum would allow for as much ‘thrust’ as the energy you have to create the microwaves.

thoughts?

[GeronL]

If this drive system can be scaled up enough - like some articles suggest (Mars in weeks), humans most definitely will conquer the solar system I think.

We could retire to hollowed-out asteroids someday.

[2ndDivisionVet]

How the reactionless space drive could send nuclear subs into orbit
http://io9.com/how-the-reactionless-space-drive-could-send-nuclear-sub-1493423673

[SunkenCiv]

Thanks servo1969.

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[MHGinTN]

Maybe not, if ‘science’ will pay closer attention to the postulates of Haisch and Rueda.

[chaosagent]

Yeah, these kind of comments, like the well-known claim that Bumble Bee flight “violates the laws of aerodynamics” drive me nuts. The Chinese had rockets as far back as the 7th century, and rockets have been used in warfare for nearly a thousand years. Nobody thought Goddard’s ideas were kooky in the least.
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Yes, they did think he was kooky.

Everyone knew rockets would work - in the atmosphere.

But Goddard was talking about rockets into SPACE. And EVERYONE know rockets wouldn’t work in a vacuum because they needed something to push against.

It said so in the New York Times.

[InterceptPoint]

Like an Ion engine it probably takes forever to build up speed
++++
Assuming it works this is true. Ditto slowing down.

[InterceptPoint]

The increasing confinement of a narrowing waveguide (convergent) leads to a widening wavelength and a decrease of the group velocity (lower momentum transfer
++++
I don’t understand this statement. A narrowing waveguide will support higher frequencies in the lowest waveguide modes. You can argue that the bandwidth increases as a result. But widening wavelength? What does that mean?

[InterceptPoint]

They set the photons oscillating in a chamber which forces the wavelengths to change as the photon goes from one end to the other. This alters the group velocity of the photons, which changes the radiation pressure as the photons strike each end of the cavity.
++++
Someone needs to explain how you change the wavelength of a photon without some non-linear mechanism. Are we really talking about somehow filtering the AVERAGE wavelength of a broadband energy source as a function of the direction of travel in the cavity?

[tanknetter]

Assuming it works this is true. Ditto slowing down.

But could it be used in concert with traditional hydrogen/oxygen rocket engines, which would be used to boost the speed (and to decelerate)?

I know that in the vacuum of space there's no resistance, but as an imperfect analogy I'm thinking of how there are ships with both diesel and gas turbine engines. With the diesels used for cruising and the turbines for the extra kick to get up to max speed. IIRC the Russian Kirov class battlecruisers replace the diesels with a nuke plant.

[ckilmer]

The only way I can conceive of this working is if you could direct the microwave impacts to only hit the front side of the box. This would require catching any reflecting photons and redirecting them back at the front side, without letting them strike any other surface to impart their momentum. Some sort of non-physical system, like a magnetic containment field, might do the trick, but I have a feeling that there is a “catch” I am not thinking of that would make even that solution not work.
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I think you got it. True story here. My brother was reading the specs on an experiment his son was doing in his graduate program in rocket engineering. The experiment was designed to re-purpose a device meant to create electromagnetic waves into a device that creates a big electromagnetic funnel to funnel ions in space in one end of a device and spit them out the other.

My brother told his son. “Wait a minute. You could turn this into thrust to make an engine. I saw this in science fiction a couple decades back.”

“Yup.” Said his son.

When I heard this story over Christmas I told my brother he had some serious bragging rights. His son was doing some interesting work as well.