Propellant less space engine

[John Lowe]

20 minutes ago, Q-reeus said:

Look up Coriolis force - and think about that some. Oh, and that mass element is then 'pulled' back down to a lower speed - and so on cyclically. Nothing changes over a complete cycle.

If you think otherwise, try and prove using maths based on relativistic dynamics. Good luck!

I thought Coriolis force was fictitious? 

I'm not sure what you mean by ".. that mass element is then 'pulled' back down to a lower speed.." The extra mass is just extra relativistic mass and is always on the outside.

Each wheel has a fraction of relativistic mass due to its own rotation. This is equally spaced around the wheel. 

But also, each wheel has some extra relativistic mass due to the rotation of the carousel. It is this extra mass that is not equally spaced around the wheel. The outside edge of each wheel has more because it is travelling faster than the inside edge. Even though the wheel is spinning it is always the outside edge that has more "extra" mass.

[swansont]

3 hours ago, Q-reeus said:

See, from the start your diagrams vs commentary create confusion since in both diagrams the carousel axis is shown horizontal, whereas your commentary referencing 'up' only makes sense if 'up' is really 'sideways/horizontal' as per illustrations. Clarify that please. Also, your 'directions A' and 'directions B' are totally non-standard notation.

Regardless of which way your 'up' is relative to carousel axis, maximum 'relativistic mass' in each convected wheel rotating about the carousel axis, lies in the plane normal to that axis and which bisects each wheel. Thus any net momentum (for now ignoring my earlier input re role of stress!) in each convected wheel is directed along the carousel axis. There is zero net rate-of-change of momentum along that axis by reason of the symmetries of wheel circular motions. Hence no force along that axis. The symmetries of rim motions guarantees no net axial force can exist, given we are talking about a steady-state situation. Your whole thinking is that the carousel assembly will accelerate parallel to the carousel rotation axis - yes?
Which cannot happen. If that is not blindingly obvious by now, you have a real problem.

Consider a hamster wheel. The hamster is running along the wheel, so there is an excess of mass where the hamster is. But that mass isn't going anywhere. Therefore, it has no momentum, relative to the axis of motion, even though the wheel is turning.

Your excess mass (owing to relativity) is not moving with respect to the axis. It has no momentum. It is like the hamster.

 

 

[John Lowe]

23 minutes ago, swansont said:

Consider a hamster wheel. The hamster is running along the wheel, so there is an excess of mass where the hamster is. But that mass isn't going anywhere. Therefore, it has no momentum, relative to the axis of motion, even though the wheel is turning.

Your excess mass (owing to relativity) is not moving with respect to the axis. It has no momentum. It is like the hamster.

 

 

that sounds like a good point, let me ponder.

[J.C.MacSwell]

On 3/20/2019 at 11:00 AM, John Lowe said:

If you spin a balanced wheel is space it will stay spinning around it's centre. If it is imbalanced, there is more mass on one side  than the other, therefore, more momentum in one direction than the other. This will cause the wheel to oscillate, i.e. the axis will scribe a circle in space as the extra mass goes round with the wheel.

The extra momentum in my system is always going up. So why won't my system have a force upwards? 

It will. If...and only if...what accelerates the wheel has an equal downward force.

You are assuming (incorrectly) a symmetric (pure torque) input about a "balanced" wheel...and (correctly) seeing an asymmetric output...giving you a net force you do not get

For a non accelerating wheel see Swansont's hamster.

Edited March 21, 2019 by J.C.MacSwell

[Q-reeus]

7 hours ago, John Lowe said:

 I thought Coriolis force was fictitious?

Coriolis force is 'fictitious' in the sense that it is interpreted differently depending on one being in an accelerated or non-accelerated reference frame, but has very real dynamical effects regardless. However on thinking it over less reflexively, now realize it's not Coriolis but the centrifugal reaction forces generated by the carousel motion that 'pushes' and 'pulls' on any given mass element in a wheel. Which is experienced as periodically varying stresses in the wheel rims.

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I'm not sure what you mean by ".. that mass element is then 'pulled' back down to a lower speed.." The extra mass is just extra relativistic mass and is always on the outside.

Each wheel has a fraction of relativistic mass due to its own rotation. This is equally spaced around the wheel.

But also, each wheel has some extra relativistic mass due to the rotation of the carousel. It is this extra mass that is not equally spaced around the wheel. The outside edge of each wheel has more because it is travelling faster than the inside edge. Even though the wheel is spinning it is always the outside edge that has more "extra" mass.

This will cover for swansont's post also:
Place a paint spot on the rim of any given wheel. Does the spot remain stationary or move in an overall helical path? Obviously the latter. That paint spot is associated with a local element of wheel rim mass. Spot moves - so also a mass element adjacent to the spot. No brainer.

By analogy, consider a circular current loop, carried within a conducting wire. At any given fixed location along the wire, the current is unchanging. But that current is the result of individual charges in constant motion along the wire. Single out any given conduction charge and follow it. It's obviously not fixed at one location.
To sort of complete the analogy, imagine the conducting wire has a cross-sectional area that varies around the loop. Where the section is smallest, speed of charges there must be greater than where the section is larger, in order that the current remains constant in magnitude everywhere. So although the current is constant everywhere, individual charges, which collectively form the loop current, have to undergo acceleration and deceleration during a complete circuit around the loop.
The analogy is not perfect since in the wheels case, the wheel rim 'mass current' itself is not uniform but greatest at the outside of the rims (your speed A1's).
Moral - follow a given element of mass in a given wheel. It eventually traces out a closed helical path that simply keeps repeating.

In fact it's only necessary to consider the helical path through one complete wheel cycle. There is generally acceleration/deceleration along that path, but no change from one cycle to another. Always the velocity of a given mass element returns to the same value at a given angular location wrt the given wheel. Momentum circulates - hence no net dp/dt acting anywhere. In particular for you, there can be no net dp/dt along the carousel axis.

Rockets get round this via expulsion of mass.

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Edited March 21, 2019 by Q-reeus

[John Lowe]

Thank you all for explaining why this won't work, I think I get it now.

Can I just describe a slightly different version of my other method and see if you can help me with that one.

Imagine 2 cylindrical projectiles inside a linear accelerator (this is in space inside a space ship). We rotate the projectiles inside the accelerator in opposite directions. This rotation is to give them some relativistic mass. We accelerate the first one (while spinning) down the accelerator, followed by the second one. We give the second one slightly more speed so it catches up with the first one half way down the track. When they meet, they connect somehow and (via friction?) cancel each others rotation out (thus losing the relativistic mass). Then they are decelerated at the other end.

The act of decelerating a lighter mass should give us a net velocity gain with no propellant used.  

[Q-reeus]

21 minutes ago, John Lowe said:

Thank you all for explaining why this won't work, I think I get it now.

I truly hope so - good news if it stays that way!

21 minutes ago, John Lowe said:

Can I just describe a slightly different version of my other method and see if you can help me with that one.

Imagine 2 cylindrical projectiles inside a linear accelerator (this is in space inside a space ship). We rotate the projectiles inside the accelerator in opposite directions. This rotation is to give them some relativistic mass. We accelerate the first one (while spinning) down the accelerator, followed by the second one. We give the second one slightly more speed so it catches up with the first one half way down the track. When they meet, they connect somehow and (via friction?) cancel each others rotation out (thus losing the relativistic mass). Then they are decelerated at the other end.

The act of decelerating a lighter mass should give us a net velocity gain with no propellant used.

You deserve an A for ingenuity. but that doesn't translate into success. When the two projectiles mutually spin each other down, there is initially simply a conversion of rotational KE to thermal energy. So the total mass-energy hence also momentum is constant. Of course there follows radiation of heat into the surrounds, which owing to the forward motion, imparts a linear momentum to the surrounds via an overall Doppler shift enhancement of photon frequencies in the direction of motion.
So although the projectiles have lost mass, the combined momentum of cooling projectiles plus surrounds owing to radiated heat is constant. A final deceleration of projectiles merely net cancels out the initial impulse given to them at the start.
In summary, your system simply trades rotational KE for thermal energy, which partially 'leaks' into the environment, imparting just enough momentum there to fully account for the reduced momentum in the combined, non-rotating projectiles. Bottom line - still no propellantless propulsion. Bummer.

[John Lowe]

Bummer indeed. I'll leave you all alone for a bit now, until I have another brainwave. 

[Q-reeus]

7 hours ago, John Lowe said:

Bummer indeed. I'll leave you all alone for a bit now, until I have another brainwave. 

Very good. Imagination is necessary if anyone want's to be creative/innovative. However it needs partnering with a solid grasp of the established fundamentals in a chosen field.
Keep searching - and learning!