Propellantless Propulsion In Space Applications

There is already a CR4 blog (on Rodger's Equations) from this week on the subject.

http://cr4.globalspec.com/blogentry/26086/NASA-s-Investigation-Into-EM-Drives-What-if

Please study conservation of energy and momentum, and then ask again.

Tornado: OK; done that.

How is the conservation of momentum applied to the following? I have a handle on conservation of energy in the following but not the conservation of momentum.

A long electromagnet is fixed on a table top. It is in a demagnetized state.

A short cylindrical permanent magnet is placed near the fixed magnet aligned in such a manner so that when the electromagnet is energized it will be in repulsion.

The electromagnet is then energized.

The permanent magnet will begin to roll away from the fixed magnet.

How does the conservation of momentum apply here?

The needle of a small magnetic compass is mechanically forced into the opposite direction. It is then released. The needle is accelerated by earths magnetic field as it begins to align to the equilibrium position.

How does the conservation of momentum apply here?

What if there were some way to use the dipolar field of the Sun and planets as reaction fields?

http://cr4.globalspec.com/thread/11752

By the way - magnetic torque rods were first used in satellite attitude determination and control back in the late 60's. The engineers back then didn't seem to see it violating fundamental principles; it worked fine - perhaps complicating orbit stability problems; but working non the less.

The permanent magnet will begin to roll away from the fixed magnet.

How does the conservation of momentum apply here?

Believe it or not, when the permanent magnet moves away, the fixed magnet and the entire earth move in the opposite direction an extremely minute amount.

Got it. Thanks !

Do U mean to say that by 'say' propelling sufficient projectiles in the opposite of the earth's rotation U can actually reduce the speed of rotation of the earth?

Add conservation of angular momentum to your studies.

Yes, as long as the projectile is not stopped by the earth system.

It is known and measured that huge earthquakes have an influence on earth rotation as they release energy.

The only problem is that you have to throw it from the earth: rockets typically first leave the troposphere before accelerating to the enormous speeds, so the earth is not/little influenced by their launch.

A big cannon to "shoot" things in space would have the effect that is described.

An interesting reference here is the tidal friction between the Earth and Moon where I believe the rotational energy of the earth is slowly being translated to Earth relative Lunar gravitational potential.

"... After playing with bar magnets I have never understood why propulsion would require the expulsion of mass..."

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I'm curious: What exactly did you notice that made you think propellant-less propulsion in space would be possible?

If you have a smooth floor and a chair on rollers, or alternately a swimming pool and inflatable raft, bring as many magnets as you like onto the chair or raft and attempt to intentionally propellant yourself around using just the magnets with you and without touching the floor/water or any other objects.

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If you are successful, please video tape it and let us know.

"If you have a smooth floor and a chair on rollers, or alternately a swimming pool and inflatable raft, bring as many magnets as you like onto the chair or raft and attempt to intentionally propellant yourself around using just the magnets with you and without touching the floor/water or any other objects."

Simple.

Place your magnets around the side of the pool and use a electromagnet on your raft and a way you go!

Very slowly at first unless you have huge magnets by the pool and a large electromagnet on your raft.

Your magnets are your propellant. The magnets are necessary and you are leaving those behind.

What????

MY comment was in response to Tcmtech's response:

"... Place your magnets around the side of the pool and use a electromagnet on your raft and a way you go!..."

I was indicating that the magnets on the side of the pool (and any thing to which they are attached) are what feels the reaction force. Those magnets are being left behind, and so act as the propellant in a sense.

"I'm curious: What exactly did you notice that made you think propellant-less propulsion in space would be possible?" ---

The existence of significant solar and planetary dipolar field, the physics of a magnetic compass, the principles of electric motors, the process of induction (in the case of orbital braking), the tether experiments, the standard international definition of the ampere, and the applied technology of using magnetic torque rods for satellite attitude determination and control.

How is momentum conserved in a linear electric motor?

I forgot to mention the trigonometric relationships between relative field angle and force.

Momentum is conserved in a linear electric motor, you just don!t notice the change in velocity of 'stator' portion, because it is bolted down. If the normally stationary portion were as free to move it would be far easier to notice.

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The fact that induced force is at right angles to current and magnetic field does not mean there is not an equal force in the opposite direction. Check out the recoil in the videos of the Navy's new rail gun.

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If a linear motor did not conserve momentum, then building a reactionless drive for propulsion in space without propellant would be as simple as using a linear electric motor, i.e., railgun, to fire a mass that was tethered to the gun. If only the fired mass experienced a change in momentum, then a tether would allow that momentum to be transferred back to the system as a whole, gaining momentum with each firing.

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Unfortunately, it doesn't work like that.

It has been made quite clear that electro-magnetic propulsion using planetary dipolar field as a reaction field would not violate momentum conservation.

Again; electromagnetic field has been used in satellite attitude control for decades.

I agree that it has been made quite clear, repeatedly. I haven't taken a position against it.

What is not quite clear is why you feel compelled to repeat what has been made quite clear, when I have not taken a position to the contrary.

NASA has been trying to make electrodynamic tethers work for some time now.

http://aero.uc3m.es/ep2/docs/publicaciones/ahed92d.pdf

The theory is simple. A wire moving through a magnetic field (the earth's) generates a voltage. If a current is flowing through this wire, there is a force on this wire perpendicular to both the magnetic field and current flow. (It's the same principle as an electric motor.)

If you force the current to flow against the induced voltage, the force will cause the satellite to move to a higher orbit. (The circuit is apparently completed by the plasma that is still present at that altitude. The return current through the plasma would provide the opposite momentum to the charged particles in the plasma.)

So, you have thrust without using any propellant. Apparently, there are numerous practical problems that still need to be solved.

NASA has already used ion drives in their Dawn mission to Ceres. Not a magnetic drive but almost a no fuel system.

There is a profound difference between:

1.utilizing high propellant velocities to minimize mass required;

And...

Doing without propellant/reaction mass.

WRONG! it in fact does use fuel in the form of Xenon. I did a thread on this tech before, totally cool little enginehttp://en.wikipedia.org/wiki/Ion_thruster

That's why I said 'almost' no fuel.

Gavilan, you are right in this respect: some bodies (the sun and some planets) have magnetic fields and a spaceship with sufficient power could interact with these fields to move about without propellant. But I think it would be useful only very close to the bodies, as the field strength will decrease quickly with distance (I think it's by the inverse cube of the distance). Probably not gonna get us from planet to planet or to another star. But it's fun to speculate. And the BEM's probably used it and then found something better eons ago.

I believe magnetic force function is a square - not a cube.

This wise guy says inverse cube: http://www2.vernier.com/sample_labs/PWV-31-COMP-magnetic_field_permanent_magnet.pdf

Using magnetic forces may remove the need for expulsion of mass, but it has its own problems.

What is the power source of your electromagnet which you will use against the natural magnetic fields? How much mass does it require?

How are you going to regulate your velocity or acceleration? Consider that 1) the flux density you are working against decreases as you move away from its source, and 2) how variable is the natural magnetic field? The Sun has a nasty habit of throwing off a lot of ionized mass at odd intervals. These masses, being charged, might really screw up your magnetic drive systems as they stream by.

And conservation always applies. If your magnetic field is propelling you, the magnetic field it is working against is propelling its source in the opposite direction.

And even then, it technically may not be propellantless. Say the natural magnetic source is Earth. Your magnetic field imparts energy to the Earth's field, and therefore the Earth. Thus you are using Earth's mass as a propellant. Although you are not carrying it on board you are still throwing it away from you. That mv equation sneaks in there someplace: m_craftv_craft = m_Earthv_Earth, with v being a vector and the vectors in opposite directions.

1) Power source is cold fusion or a mini black hole, both (in Sci-Fi) staples.

2) There's an app for that.

I understand that deep space missions already use planet gravitational fields to move our
deep space probes without fuel. A "sling shot" approach using / passing through their gravity fields.

There is considerable research on other "drives" some are listed here:

http://www.newscientist.com/article/dn18283-engage-the-x-drive-ten-ways-to-traverse-deep-space.html#.VUqJCvBazTx

However, we have never (so far..) been able to use a force without a reaction,
at least as far as I am aware. If anyone "invents" one, they will make a fortune!
If the vehicle using that force (for propulsion) also has to contain/carry whatever
accepts the reaction (opposite force) then they cancel each other out.
i.e. the vehicle (space ship, chair, boat, whatever you wish) will go nowhere.

Dreamed about this many times.... but no answer. (so far....)

Hope this helps make it easy to understand.

jt.

A recent survey found that the three most sought after invisible objects were:
1)
2)
3)

There is reaction in electromagnetic acceleration of mass as pointed out numerous times above.

Electromagnetic torque rods have been used to generate field interaction between space craft and earths magnetic field for some number of decades. The process has is used to alter satellite attitude; for decades.

Those gravity assist maneuvers you refer to as "sling shot" are momentum exchange events. Where spacecraft energy is increased at the expense of the orbital energy of the "assisting" body.

For an assisting maneuver involving a planet with dipolar field, electro-magnetic propulsion could significantly add to the specific energy of the spacecraft as described in the original thread.

I am way too busy to sit down to run the actual numbers, but the concept of using a magnetic field as a mechanism of propulsion within the solar system seems fatally flawed on a number of accounts:

1. Not all planets harbor a magnetic field.

2. Solar and planetary flux densities at useful radii are going to be very, very small. To generate a meaningful reactive force would probably require massive amounts of energy on the part of the space vehicle (SV).

The greatest magnetic field ever created continuously is abut 45 T. The largest field ever made was 730 T and it was pulsed. That pulse destroyed the equipment used to generate it, so its a one-shot deal. I think someone created a field four times that, but it was done using explosives.

3. Field strengths about the SV would be tremendous. Current MRI diagnosis machines reach about 9.4 T. The Earth's magnetic field at its surface is only 35 to 50 µT. Obviously, flux densities diminish with the square of the radius, so once you get any meaningful distance you poop out. Again, massive energy is required to produce meaningful reaction.

The problem with this is that both man and machine are now subject to field strengths well beyond their operational safety limits.

Note: T = Tesla = Nw · A-1 · m-1 = kg · s-2 · A-1

Perhaps you have some insight to clarify this for me. In the OP's second link to the nasaflight.com article, there is this statement:

"Specifically, a useful EM Drive for space travel would need a nuclear power plant of 1.0 MWe (Megawatts-electric) to 100 MWe.

While that sounds significant, the U.S. Navy currently builds 220 MW-thermal reactors for its "Boomer" Ohio class ICBM vehicles."

"Ohio class" is a submarine, I think, not an ICBM. Is a submarine an ICBM vehicle? Strange phrasing. A submarine may need a 200MW power source, but an ICBM? Is a thermal reactor another name for a nuclear reactor? An ICBM might have a thermal battery, but that won't last long enough to be useful for space flight.

I served aboard an Ohio class beginning while it was still in construction.

Your assumption is correct, the reactor powers the sub. The missiles, technically SLBM are not powered by nuclear power. Warheads are a different story.

Something to note, to get 100 MWe requires far more than 100MWth.

Missiles are only powered by nuclear power after they get where they are going.

_{(That's kinda what I thought)}

Flux density diminishes with the cube of the distance one the distance is large relative to the size of the magnet. Closer, the Flux is heavily dependent on the shape of the magnet.

I think the magnetic intensity around a dipole source actually drops off as the cube of distance. But it's worse than that because the force between two dipoles would be proportional to the gradient of the field strength and would drop off at the fourth power of distance.

Like AH I think the available (space) fields would be too weak to support travel use
as you suggest. However:

What I think may work is to use the North-South "lines of field" somehow?

If we had a space map of them and could somehow "interlock" and then use their
directional flow for our own advantage. Like birds / gliders rising on thermals,
surfboards on waves, etc. Aligning / locking the space ship onto the required direction.

Similarly, if we could create a "bubble" of repulsion, or simply less dense air, then
the vehicle could rise (off the ground) without fuel. Like a bubble in water.

Just ideas.

jt.

A lady walked into a pharmacy and spoke to the pharmacist.
She asked , 'Do you have Viagra?'
'Yes , ' he answered.
She asked , 'Does it work?'
'Yes , ' he answered.
'Can I get it over the counter?' she asked.
'Only if I take two straight away........ ' he answered.

New idea! We'll use a magnetohydrodynamic drive working against the fabric of spacetime, or whatever stray particles are floating about in free space. OK, a few kinks to work out, but come back in a century or two.

Since gravity eminates from millions of exploding White Dwarfs and actually pushes objects to the surface of planets, etc., instead of pulling them in, the Gravity Bending Wedge could replace the nose cone of space rockets so that a cavity in front of the space ship could be created that would be devoid of resistance to forward motion of the ship.

The ship would then be pushed by the gravity from behind.

I have a question and it may be a bit off topic but I think it relates.

Once you get this "spaceship" to the speed you want or need, how do you slow it down to land or orbit what you were going after?

• You have no propellant.
• An incremental raise of speed that grows faster and faster that you used to travel through space isn't going to have the same reaction on slowing down as it did for speeding up?
• How long would it take you to slow the craft down with the same propellantless propulsion?

With the same force available, it would take as long to lose the velocity as it did to gain it. You could add speed up to the 1/2 way mark and then reduce speed for the other 1/2 of the trip (adjustments would be needed for difference in velocity of your origination and destination).....and the acceleration could provide a gravity like experience, as an added bonus.

Thank you,

I had a feeling that it would be like that but I just don't have the higher math or physics education that would be needed to calculate it out.

Actual propellantless drive sytems could be built if you could programmatically alter the mass of some object. Make it lighter, then toss it some distance away, then make it heavy, then pull yourself towards it. Rinse and repeat. Now, how can you alter the mass of an object? Spinning it? Heating it? Ideas?

E = MC^2

That should tell you how right there.

You can't change the speed of light, but does imposing rotational or thermal energy to a mass increase it energy? To me it seems the answer is yes. The math of proving it is way beyond me.

Rotating it increases its kinetic energy, but that does not change its mass.

The same thing applies to adding thermal energy. The molecules vibrate faster, but the mass remains static.

I guess it's that whole relativity thing that messes with the mind. You hear authorities say that acceleration increases mass and the reason you can't ever reach C is because you would be trying to push an infinite mass. Are not thermal of rotational vectors just movement of mass (one being group movement about the axis and the other being random jiggling)? I'm not saying the mass variance would be sufficient to do the push-pull in any practical scheme, I only wonder if the theory is utterly baseless.

The bit about having to move the energy forward is a good counter argument. Too bad. I guess we'll have to figure out a different means to all-electric space travel.

....and the energy needed to spin up or heat up? If it is stored aboard the mass to be heated or spun, does it not already contribute to the mass in its stored form? ...or alternately if it is to be shifted between the masses being alternately thrown and retrieved, wouldn't moving the energy forward cancel the momentum shift you were betting on gaining by reeling it back in?

Don a pair of boots, the kind with straps on the side. Reach down and pull up really hard. This is a far less expensive experiment, bound to bring you to the same conclusion as more convoluted 'push-me, pull-me' propulsion schemes.

Just one question: how do you program mass?

it has no USB connection or Wifi to upload the new firmware

Really: look for a scifi blog to amuse yourself

Nonsense I know (but we can dream) expanding on my #28.

If the "spaceship" had a "means" to make it's two ends as a north and south, at will,
i.e. as in a bar magnet, only being switchable at will, i.e. each end first North or south
pole and then reversed at the opportune time, in theory the ship could be attracted,
or repulsed, towards or from the required direction?

A facility would be needed to "map" (be aware of) the fields in space and use them
appropriately, probably computer aided, on a continuous basis to "trim" the ship.

i.e. A floating body able to "swim," to react with or against, the space magnetic flow.

Any good? jt.

(Sorry if you have heard it from me before, but it's a good space story.)

On July 20, 1969, as commander of the Apollo 11 lunar module, Neil Armstrong
was the first person to set foot on the moon.
His first words after stepping on the moon, "that's one small step for man,
one giant leap for mankind," were televised to earth and heard by millions.
But, just before he re-entered the lander, he made the enigmatic remark -
"good luck, Mr. Gorsky."
Many people at nasa thought it was a casual remark concerning some rival soviet cosmonaut.
however, upon checking, there was no Gorsky in either the Russian or American space programs .
Over the years, many people questioned Armstrong as to what the - 'good luck, Mr. Gorsky'
statement had meant, but Armstrong always just smiled.
On July 5, 1995, in Tampa bay, florida , while answering questions following a speech, a reporter
brought up the 26-year-old question about Mr Gorsky to Armstrong.
This time he finally responded because Mr. Gorsky had died, so Neil Armstrong felt he could
now answer the question. Here is the answer to "who was Mr Gorsky":
In 1938, when he was a kid in a small mid-western town , he was playing baseball with a friend in
the backyard. his friend hit the ball, which landed in his neighbor's yard by their bedroom window.
His neighbors were Mr. and Mrs. Gorsky. As he leaned down to pick up the ball, young Armstrong
heard Mrs. Gorsky shouting at Mr. Gorsky,....
"Sex! you want sex?! You'll get sex when the kid next door walks on the moon!"
(supplied as a true story)

I found this related information. Thought it was quite interesting.

http://ned.ipac.caltech.edu/level5/March03/Vallee2/Vallee2_3.html

I don't have time to devolve that in detail, but the supporting citations are so old (given how much has changed in the field of cosmology in the last few decades) that it raises a flag.

Also, correlation does not presume causation.

How does dipole length effect magnetic moment? What would be the approximate dipole length be of the Sun's dipolar field, and it is dipolar; as are the planetary fields and probably Galactic Fields.

Also; I had no idea that fundamental cosmology was evolving so rapidly as to nullify fundamental principles of electro physics.

Also; the decades of experience in using the Earth's dipolar magnetic field for satellite attitude determination and control clearly indicates adequate field for field reaction propulsion.

About the attitude of sattelites: it can be bad, really bad, and nobody up there to correct them

As a second thought.

Thinking more about this.

I believe space is not a complete vacuum; which presents the opportunity for collecting and funneling charged particles into an electromagnetic accelerating device. As long as the particles could be accelerated to a higher relative velocity than from which they were collected it is possible that the increased mechanical energy of the spacecraft could be increased and would approximate (.5*m* finalv^2) - (.5*m*initialv^2) where m is captured particle mass and finalv is the exhaust relative velocity and initialv is the initial relative velocity of the captured particles.

This would eliminate the need for the consumable ion fuel now used in ion propulsion.

Ion Propulsion is a Newtonian Propulsion Method; not a mass-less Field Reaction Propulsion Method.